1 //===- InstrRefBasedImpl.cpp - Tracking Debug Value MIs -------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 /// \file InstrRefBasedImpl.cpp
9 ///
10 /// This is a separate implementation of LiveDebugValues, see
11 /// LiveDebugValues.cpp and VarLocBasedImpl.cpp for more information.
12 ///
13 /// This pass propagates variable locations between basic blocks, resolving
14 /// control flow conflicts between them. The problem is much like SSA
15 /// construction, where each DBG_VALUE instruction assigns the *value* that
16 /// a variable has, and every instruction where the variable is in scope uses
17 /// that variable. The resulting map of instruction-to-value is then translated
18 /// into a register (or spill) location for each variable over each instruction.
19 ///
20 /// This pass determines which DBG_VALUE dominates which instructions, or if
21 /// none do, where values must be merged (like PHI nodes). The added
22 /// complication is that because codegen has already finished, a PHI node may
23 /// be needed for a variable location to be correct, but no register or spill
24 /// slot merges the necessary values. In these circumstances, the variable
25 /// location is dropped.
26 ///
27 /// What makes this analysis non-trivial is loops: we cannot tell in advance
28 /// whether a variable location is live throughout a loop, or whether its
29 /// location is clobbered (or redefined by another DBG_VALUE), without
30 /// exploring all the way through.
31 ///
32 /// To make this simpler we perform two kinds of analysis. First, we identify
33 /// every value defined by every instruction (ignoring those that only move
34 /// another value), then compute a map of which values are available for each
35 /// instruction. This is stronger than a reaching-def analysis, as we create
36 /// PHI values where other values merge.
37 ///
38 /// Secondly, for each variable, we effectively re-construct SSA using each
39 /// DBG_VALUE as a def. The DBG_VALUEs read a value-number computed by the
40 /// first analysis from the location they refer to. We can then compute the
41 /// dominance frontiers of where a variable has a value, and create PHI nodes
42 /// where they merge.
43 /// This isn't precisely SSA-construction though, because the function shape
44 /// is pre-defined. If a variable location requires a PHI node, but no
45 /// PHI for the relevant values is present in the function (as computed by the
46 /// first analysis), the location must be dropped.
47 ///
48 /// Once both are complete, we can pass back over all instructions knowing:
49 /// * What _value_ each variable should contain, either defined by an
50 /// instruction or where control flow merges
51 /// * What the location of that value is (if any).
52 /// Allowing us to create appropriate live-in DBG_VALUEs, and DBG_VALUEs when
53 /// a value moves location. After this pass runs, all variable locations within
54 /// a block should be specified by DBG_VALUEs within that block, allowing
55 /// DbgEntityHistoryCalculator to focus on individual blocks.
56 ///
57 /// This pass is able to go fast because the size of the first
58 /// reaching-definition analysis is proportional to the working-set size of
59 /// the function, which the compiler tries to keep small. (It's also
60 /// proportional to the number of blocks). Additionally, we repeatedly perform
61 /// the second reaching-definition analysis with only the variables and blocks
62 /// in a single lexical scope, exploiting their locality.
63 ///
64 /// Determining where PHIs happen is trickier with this approach, and it comes
65 /// to a head in the major problem for LiveDebugValues: is a value live-through
66 /// a loop, or not? Your garden-variety dataflow analysis aims to build a set of
67 /// facts about a function, however this analysis needs to generate new value
68 /// numbers at joins.
69 ///
70 /// To do this, consider a lattice of all definition values, from instructions
71 /// and from PHIs. Each PHI is characterised by the RPO number of the block it
72 /// occurs in. Each value pair A, B can be ordered by RPO(A) < RPO(B):
73 /// with non-PHI values at the top, and any PHI value in the last block (by RPO
74 /// order) at the bottom.
75 ///
76 /// (Awkwardly: lower-down-the _lattice_ means a greater RPO _number_. Below,
77 /// "rank" always refers to the former).
78 ///
79 /// At any join, for each register, we consider:
80 /// * All incoming values, and
81 /// * The PREVIOUS live-in value at this join.
82 /// If all incoming values agree: that's the live-in value. If they do not, the
83 /// incoming values are ranked according to the partial order, and the NEXT
84 /// LOWEST rank after the PREVIOUS live-in value is picked (multiple values of
85 /// the same rank are ignored as conflicting). If there are no candidate values,
86 /// or if the rank of the live-in would be lower than the rank of the current
87 /// blocks PHIs, create a new PHI value.
88 ///
89 /// Intuitively: if it's not immediately obvious what value a join should result
90 /// in, we iteratively descend from instruction-definitions down through PHI
91 /// values, getting closer to the current block each time. If the current block
92 /// is a loop head, this ordering is effectively searching outer levels of
93 /// loops, to find a value that's live-through the current loop.
94 ///
95 /// If there is no value that's live-through this loop, a PHI is created for
96 /// this location instead. We can't use a lower-ranked PHI because by definition
97 /// it doesn't dominate the current block. We can't create a PHI value any
98 /// earlier, because we risk creating a PHI value at a location where values do
99 /// not in fact merge, thus misrepresenting the truth, and not making the true
100 /// live-through value for variable locations.
101 ///
102 /// This algorithm applies to both calculating the availability of values in
103 /// the first analysis, and the location of variables in the second. However
104 /// for the second we add an extra dimension of pain: creating a variable
105 /// location PHI is only valid if, for each incoming edge,
106 /// * There is a value for the variable on the incoming edge, and
107 /// * All the edges have that value in the same register.
108 /// Or put another way: we can only create a variable-location PHI if there is
109 /// a matching machine-location PHI, each input to which is the variables value
110 /// in the predecessor block.
111 ///
112 /// To accommodate this difference, each point on the lattice is split in
113 /// two: a "proposed" PHI and "definite" PHI. Any PHI that can immediately
114 /// have a location determined are "definite" PHIs, and no further work is
115 /// needed. Otherwise, a location that all non-backedge predecessors agree
116 /// on is picked and propagated as a "proposed" PHI value. If that PHI value
117 /// is truly live-through, it'll appear on the loop backedges on the next
118 /// dataflow iteration, after which the block live-in moves to be a "definite"
119 /// PHI. If it's not truly live-through, the variable value will be downgraded
120 /// further as we explore the lattice, or remains "proposed" and is considered
121 /// invalid once dataflow completes.
122 ///
123 /// ### Terminology
124 ///
125 /// A machine location is a register or spill slot, a value is something that's
126 /// defined by an instruction or PHI node, while a variable value is the value
127 /// assigned to a variable. A variable location is a machine location, that must
128 /// contain the appropriate variable value. A value that is a PHI node is
129 /// occasionally called an mphi.
130 ///
131 /// The first dataflow problem is the "machine value location" problem,
132 /// because we're determining which machine locations contain which values.
133 /// The "locations" are constant: what's unknown is what value they contain.
134 ///
135 /// The second dataflow problem (the one for variables) is the "variable value
136 /// problem", because it's determining what values a variable has, rather than
137 /// what location those values are placed in. Unfortunately, it's not that
138 /// simple, because producing a PHI value always involves picking a location.
139 /// This is an imperfection that we just have to accept, at least for now.
140 ///
141 /// TODO:
142 /// Overlapping fragments
143 /// Entry values
144 /// Add back DEBUG statements for debugging this
145 /// Collect statistics
146 ///
147 //===----------------------------------------------------------------------===//
148
149 #include "llvm/ADT/DenseMap.h"
150 #include "llvm/ADT/PostOrderIterator.h"
151 #include "llvm/ADT/SmallPtrSet.h"
152 #include "llvm/ADT/SmallSet.h"
153 #include "llvm/ADT/SmallVector.h"
154 #include "llvm/ADT/Statistic.h"
155 #include "llvm/ADT/UniqueVector.h"
156 #include "llvm/CodeGen/LexicalScopes.h"
157 #include "llvm/CodeGen/MachineBasicBlock.h"
158 #include "llvm/CodeGen/MachineFrameInfo.h"
159 #include "llvm/CodeGen/MachineFunction.h"
160 #include "llvm/CodeGen/MachineFunctionPass.h"
161 #include "llvm/CodeGen/MachineInstr.h"
162 #include "llvm/CodeGen/MachineInstrBuilder.h"
163 #include "llvm/CodeGen/MachineMemOperand.h"
164 #include "llvm/CodeGen/MachineOperand.h"
165 #include "llvm/CodeGen/PseudoSourceValue.h"
166 #include "llvm/CodeGen/RegisterScavenging.h"
167 #include "llvm/CodeGen/TargetFrameLowering.h"
168 #include "llvm/CodeGen/TargetInstrInfo.h"
169 #include "llvm/CodeGen/TargetLowering.h"
170 #include "llvm/CodeGen/TargetPassConfig.h"
171 #include "llvm/CodeGen/TargetRegisterInfo.h"
172 #include "llvm/CodeGen/TargetSubtargetInfo.h"
173 #include "llvm/Config/llvm-config.h"
174 #include "llvm/IR/DIBuilder.h"
175 #include "llvm/IR/DebugInfoMetadata.h"
176 #include "llvm/IR/DebugLoc.h"
177 #include "llvm/IR/Function.h"
178 #include "llvm/IR/Module.h"
179 #include "llvm/InitializePasses.h"
180 #include "llvm/MC/MCRegisterInfo.h"
181 #include "llvm/Pass.h"
182 #include "llvm/Support/Casting.h"
183 #include "llvm/Support/Compiler.h"
184 #include "llvm/Support/Debug.h"
185 #include "llvm/Support/TypeSize.h"
186 #include "llvm/Support/raw_ostream.h"
187 #include <algorithm>
188 #include <cassert>
189 #include <cstdint>
190 #include <functional>
191 #include <queue>
192 #include <tuple>
193 #include <utility>
194 #include <vector>
195 #include <limits.h>
196 #include <limits>
197
198 #include "LiveDebugValues.h"
199
200 using namespace llvm;
201
202 #define DEBUG_TYPE "livedebugvalues"
203
204 // Act more like the VarLoc implementation, by propagating some locations too
205 // far and ignoring some transfers.
206 static cl::opt<bool> EmulateOldLDV("emulate-old-livedebugvalues", cl::Hidden,
207 cl::desc("Act like old LiveDebugValues did"),
208 cl::init(false));
209
210 // Rely on isStoreToStackSlotPostFE and similar to observe all stack spills.
211 static cl::opt<bool>
212 ObserveAllStackops("observe-all-stack-ops", cl::Hidden,
213 cl::desc("Allow non-kill spill and restores"),
214 cl::init(false));
215
216 namespace {
217
218 // The location at which a spilled value resides. It consists of a register and
219 // an offset.
220 struct SpillLoc {
221 unsigned SpillBase;
222 StackOffset SpillOffset;
operator ==__anon45b083930111::SpillLoc223 bool operator==(const SpillLoc &Other) const {
224 return std::make_pair(SpillBase, SpillOffset) ==
225 std::make_pair(Other.SpillBase, Other.SpillOffset);
226 }
operator <__anon45b083930111::SpillLoc227 bool operator<(const SpillLoc &Other) const {
228 return std::make_tuple(SpillBase, SpillOffset.getFixed(),
229 SpillOffset.getScalable()) <
230 std::make_tuple(Other.SpillBase, Other.SpillOffset.getFixed(),
231 Other.SpillOffset.getScalable());
232 }
233 };
234
235 class LocIdx {
236 unsigned Location;
237
238 // Default constructor is private, initializing to an illegal location number.
239 // Use only for "not an entry" elements in IndexedMaps.
LocIdx()240 LocIdx() : Location(UINT_MAX) { }
241
242 public:
243 #define NUM_LOC_BITS 24
LocIdx(unsigned L)244 LocIdx(unsigned L) : Location(L) {
245 assert(L < (1 << NUM_LOC_BITS) && "Machine locations must fit in 24 bits");
246 }
247
MakeIllegalLoc()248 static LocIdx MakeIllegalLoc() {
249 return LocIdx();
250 }
251
isIllegal() const252 bool isIllegal() const {
253 return Location == UINT_MAX;
254 }
255
asU64() const256 uint64_t asU64() const {
257 return Location;
258 }
259
operator ==(unsigned L) const260 bool operator==(unsigned L) const {
261 return Location == L;
262 }
263
operator ==(const LocIdx & L) const264 bool operator==(const LocIdx &L) const {
265 return Location == L.Location;
266 }
267
operator !=(unsigned L) const268 bool operator!=(unsigned L) const {
269 return !(*this == L);
270 }
271
operator !=(const LocIdx & L) const272 bool operator!=(const LocIdx &L) const {
273 return !(*this == L);
274 }
275
operator <(const LocIdx & Other) const276 bool operator<(const LocIdx &Other) const {
277 return Location < Other.Location;
278 }
279 };
280
281 class LocIdxToIndexFunctor {
282 public:
283 using argument_type = LocIdx;
operator ()(const LocIdx & L) const284 unsigned operator()(const LocIdx &L) const {
285 return L.asU64();
286 }
287 };
288
289 /// Unique identifier for a value defined by an instruction, as a value type.
290 /// Casts back and forth to a uint64_t. Probably replacable with something less
291 /// bit-constrained. Each value identifies the instruction and machine location
292 /// where the value is defined, although there may be no corresponding machine
293 /// operand for it (ex: regmasks clobbering values). The instructions are
294 /// one-based, and definitions that are PHIs have instruction number zero.
295 ///
296 /// The obvious limits of a 1M block function or 1M instruction blocks are
297 /// problematic; but by that point we should probably have bailed out of
298 /// trying to analyse the function.
299 class ValueIDNum {
300 uint64_t BlockNo : 20; /// The block where the def happens.
301 uint64_t InstNo : 20; /// The Instruction where the def happens.
302 /// One based, is distance from start of block.
303 uint64_t LocNo : NUM_LOC_BITS; /// The machine location where the def happens.
304
305 public:
306 // XXX -- temporarily enabled while the live-in / live-out tables are moved
307 // to something more type-y
ValueIDNum()308 ValueIDNum() : BlockNo(0xFFFFF),
309 InstNo(0xFFFFF),
310 LocNo(0xFFFFFF) { }
311
ValueIDNum(uint64_t Block,uint64_t Inst,uint64_t Loc)312 ValueIDNum(uint64_t Block, uint64_t Inst, uint64_t Loc)
313 : BlockNo(Block), InstNo(Inst), LocNo(Loc) { }
314
ValueIDNum(uint64_t Block,uint64_t Inst,LocIdx Loc)315 ValueIDNum(uint64_t Block, uint64_t Inst, LocIdx Loc)
316 : BlockNo(Block), InstNo(Inst), LocNo(Loc.asU64()) { }
317
getBlock() const318 uint64_t getBlock() const { return BlockNo; }
getInst() const319 uint64_t getInst() const { return InstNo; }
getLoc() const320 uint64_t getLoc() const { return LocNo; }
isPHI() const321 bool isPHI() const { return InstNo == 0; }
322
asU64() const323 uint64_t asU64() const {
324 uint64_t TmpBlock = BlockNo;
325 uint64_t TmpInst = InstNo;
326 return TmpBlock << 44ull | TmpInst << NUM_LOC_BITS | LocNo;
327 }
328
fromU64(uint64_t v)329 static ValueIDNum fromU64(uint64_t v) {
330 uint64_t L = (v & 0x3FFF);
331 return {v >> 44ull, ((v >> NUM_LOC_BITS) & 0xFFFFF), L};
332 }
333
operator <(const ValueIDNum & Other) const334 bool operator<(const ValueIDNum &Other) const {
335 return asU64() < Other.asU64();
336 }
337
operator ==(const ValueIDNum & Other) const338 bool operator==(const ValueIDNum &Other) const {
339 return std::tie(BlockNo, InstNo, LocNo) ==
340 std::tie(Other.BlockNo, Other.InstNo, Other.LocNo);
341 }
342
operator !=(const ValueIDNum & Other) const343 bool operator!=(const ValueIDNum &Other) const { return !(*this == Other); }
344
asString(const std::string & mlocname) const345 std::string asString(const std::string &mlocname) const {
346 return Twine("Value{bb: ")
347 .concat(Twine(BlockNo).concat(
348 Twine(", inst: ")
349 .concat((InstNo ? Twine(InstNo) : Twine("live-in"))
350 .concat(Twine(", loc: ").concat(Twine(mlocname)))
351 .concat(Twine("}")))))
352 .str();
353 }
354
355 static ValueIDNum EmptyValue;
356 };
357
358 } // end anonymous namespace
359
360 namespace {
361
362 /// Meta qualifiers for a value. Pair of whatever expression is used to qualify
363 /// the the value, and Boolean of whether or not it's indirect.
364 class DbgValueProperties {
365 public:
DbgValueProperties(const DIExpression * DIExpr,bool Indirect)366 DbgValueProperties(const DIExpression *DIExpr, bool Indirect)
367 : DIExpr(DIExpr), Indirect(Indirect) {}
368
369 /// Extract properties from an existing DBG_VALUE instruction.
DbgValueProperties(const MachineInstr & MI)370 DbgValueProperties(const MachineInstr &MI) {
371 assert(MI.isDebugValue());
372 DIExpr = MI.getDebugExpression();
373 Indirect = MI.getOperand(1).isImm();
374 }
375
operator ==(const DbgValueProperties & Other) const376 bool operator==(const DbgValueProperties &Other) const {
377 return std::tie(DIExpr, Indirect) == std::tie(Other.DIExpr, Other.Indirect);
378 }
379
operator !=(const DbgValueProperties & Other) const380 bool operator!=(const DbgValueProperties &Other) const {
381 return !(*this == Other);
382 }
383
384 const DIExpression *DIExpr;
385 bool Indirect;
386 };
387
388 /// Tracker for what values are in machine locations. Listens to the Things
389 /// being Done by various instructions, and maintains a table of what machine
390 /// locations have what values (as defined by a ValueIDNum).
391 ///
392 /// There are potentially a much larger number of machine locations on the
393 /// target machine than the actual working-set size of the function. On x86 for
394 /// example, we're extremely unlikely to want to track values through control
395 /// or debug registers. To avoid doing so, MLocTracker has several layers of
396 /// indirection going on, with two kinds of ``location'':
397 /// * A LocID uniquely identifies a register or spill location, with a
398 /// predictable value.
399 /// * A LocIdx is a key (in the database sense) for a LocID and a ValueIDNum.
400 /// Whenever a location is def'd or used by a MachineInstr, we automagically
401 /// create a new LocIdx for a location, but not otherwise. This ensures we only
402 /// account for locations that are actually used or defined. The cost is another
403 /// vector lookup (of LocID -> LocIdx) over any other implementation. This is
404 /// fairly cheap, and the compiler tries to reduce the working-set at any one
405 /// time in the function anyway.
406 ///
407 /// Register mask operands completely blow this out of the water; I've just
408 /// piled hacks on top of hacks to get around that.
409 class MLocTracker {
410 public:
411 MachineFunction &MF;
412 const TargetInstrInfo &TII;
413 const TargetRegisterInfo &TRI;
414 const TargetLowering &TLI;
415
416 /// IndexedMap type, mapping from LocIdx to ValueIDNum.
417 using LocToValueType = IndexedMap<ValueIDNum, LocIdxToIndexFunctor>;
418
419 /// Map of LocIdxes to the ValueIDNums that they store. This is tightly
420 /// packed, entries only exist for locations that are being tracked.
421 LocToValueType LocIdxToIDNum;
422
423 /// "Map" of machine location IDs (i.e., raw register or spill number) to the
424 /// LocIdx key / number for that location. There are always at least as many
425 /// as the number of registers on the target -- if the value in the register
426 /// is not being tracked, then the LocIdx value will be zero. New entries are
427 /// appended if a new spill slot begins being tracked.
428 /// This, and the corresponding reverse map persist for the analysis of the
429 /// whole function, and is necessarying for decoding various vectors of
430 /// values.
431 std::vector<LocIdx> LocIDToLocIdx;
432
433 /// Inverse map of LocIDToLocIdx.
434 IndexedMap<unsigned, LocIdxToIndexFunctor> LocIdxToLocID;
435
436 /// Unique-ification of spill slots. Used to number them -- their LocID
437 /// number is the index in SpillLocs minus one plus NumRegs.
438 UniqueVector<SpillLoc> SpillLocs;
439
440 // If we discover a new machine location, assign it an mphi with this
441 // block number.
442 unsigned CurBB;
443
444 /// Cached local copy of the number of registers the target has.
445 unsigned NumRegs;
446
447 /// Collection of register mask operands that have been observed. Second part
448 /// of pair indicates the instruction that they happened in. Used to
449 /// reconstruct where defs happened if we start tracking a location later
450 /// on.
451 SmallVector<std::pair<const MachineOperand *, unsigned>, 32> Masks;
452
453 /// Iterator for locations and the values they contain. Dereferencing
454 /// produces a struct/pair containing the LocIdx key for this location,
455 /// and a reference to the value currently stored. Simplifies the process
456 /// of seeking a particular location.
457 class MLocIterator {
458 LocToValueType &ValueMap;
459 LocIdx Idx;
460
461 public:
462 class value_type {
463 public:
value_type(LocIdx Idx,ValueIDNum & Value)464 value_type(LocIdx Idx, ValueIDNum &Value) : Idx(Idx), Value(Value) { }
465 const LocIdx Idx; /// Read-only index of this location.
466 ValueIDNum &Value; /// Reference to the stored value at this location.
467 };
468
MLocIterator(LocToValueType & ValueMap,LocIdx Idx)469 MLocIterator(LocToValueType &ValueMap, LocIdx Idx)
470 : ValueMap(ValueMap), Idx(Idx) { }
471
operator ==(const MLocIterator & Other) const472 bool operator==(const MLocIterator &Other) const {
473 assert(&ValueMap == &Other.ValueMap);
474 return Idx == Other.Idx;
475 }
476
operator !=(const MLocIterator & Other) const477 bool operator!=(const MLocIterator &Other) const {
478 return !(*this == Other);
479 }
480
operator ++()481 void operator++() {
482 Idx = LocIdx(Idx.asU64() + 1);
483 }
484
operator *()485 value_type operator*() {
486 return value_type(Idx, ValueMap[LocIdx(Idx)]);
487 }
488 };
489
MLocTracker(MachineFunction & MF,const TargetInstrInfo & TII,const TargetRegisterInfo & TRI,const TargetLowering & TLI)490 MLocTracker(MachineFunction &MF, const TargetInstrInfo &TII,
491 const TargetRegisterInfo &TRI, const TargetLowering &TLI)
492 : MF(MF), TII(TII), TRI(TRI), TLI(TLI),
493 LocIdxToIDNum(ValueIDNum::EmptyValue),
494 LocIdxToLocID(0) {
495 NumRegs = TRI.getNumRegs();
496 reset();
497 LocIDToLocIdx.resize(NumRegs, LocIdx::MakeIllegalLoc());
498 assert(NumRegs < (1u << NUM_LOC_BITS)); // Detect bit packing failure
499
500 // Always track SP. This avoids the implicit clobbering caused by regmasks
501 // from affectings its values. (LiveDebugValues disbelieves calls and
502 // regmasks that claim to clobber SP).
503 Register SP = TLI.getStackPointerRegisterToSaveRestore();
504 if (SP) {
505 unsigned ID = getLocID(SP, false);
506 (void)lookupOrTrackRegister(ID);
507 }
508 }
509
510 /// Produce location ID number for indexing LocIDToLocIdx. Takes the register
511 /// or spill number, and flag for whether it's a spill or not.
getLocID(Register RegOrSpill,bool isSpill)512 unsigned getLocID(Register RegOrSpill, bool isSpill) {
513 return (isSpill) ? RegOrSpill.id() + NumRegs - 1 : RegOrSpill.id();
514 }
515
516 /// Accessor for reading the value at Idx.
getNumAtPos(LocIdx Idx) const517 ValueIDNum getNumAtPos(LocIdx Idx) const {
518 assert(Idx.asU64() < LocIdxToIDNum.size());
519 return LocIdxToIDNum[Idx];
520 }
521
getNumLocs(void) const522 unsigned getNumLocs(void) const { return LocIdxToIDNum.size(); }
523
524 /// Reset all locations to contain a PHI value at the designated block. Used
525 /// sometimes for actual PHI values, othertimes to indicate the block entry
526 /// value (before any more information is known).
setMPhis(unsigned NewCurBB)527 void setMPhis(unsigned NewCurBB) {
528 CurBB = NewCurBB;
529 for (auto Location : locations())
530 Location.Value = {CurBB, 0, Location.Idx};
531 }
532
533 /// Load values for each location from array of ValueIDNums. Take current
534 /// bbnum just in case we read a value from a hitherto untouched register.
loadFromArray(ValueIDNum * Locs,unsigned NewCurBB)535 void loadFromArray(ValueIDNum *Locs, unsigned NewCurBB) {
536 CurBB = NewCurBB;
537 // Iterate over all tracked locations, and load each locations live-in
538 // value into our local index.
539 for (auto Location : locations())
540 Location.Value = Locs[Location.Idx.asU64()];
541 }
542
543 /// Wipe any un-necessary location records after traversing a block.
reset(void)544 void reset(void) {
545 // We could reset all the location values too; however either loadFromArray
546 // or setMPhis should be called before this object is re-used. Just
547 // clear Masks, they're definitely not needed.
548 Masks.clear();
549 }
550
551 /// Clear all data. Destroys the LocID <=> LocIdx map, which makes most of
552 /// the information in this pass uninterpretable.
clear(void)553 void clear(void) {
554 reset();
555 LocIDToLocIdx.clear();
556 LocIdxToLocID.clear();
557 LocIdxToIDNum.clear();
558 //SpillLocs.reset(); XXX UniqueVector::reset assumes a SpillLoc casts from 0
559 SpillLocs = decltype(SpillLocs)();
560
561 LocIDToLocIdx.resize(NumRegs, LocIdx::MakeIllegalLoc());
562 }
563
564 /// Set a locaiton to a certain value.
setMLoc(LocIdx L,ValueIDNum Num)565 void setMLoc(LocIdx L, ValueIDNum Num) {
566 assert(L.asU64() < LocIdxToIDNum.size());
567 LocIdxToIDNum[L] = Num;
568 }
569
570 /// Create a LocIdx for an untracked register ID. Initialize it to either an
571 /// mphi value representing a live-in, or a recent register mask clobber.
trackRegister(unsigned ID)572 LocIdx trackRegister(unsigned ID) {
573 assert(ID != 0);
574 LocIdx NewIdx = LocIdx(LocIdxToIDNum.size());
575 LocIdxToIDNum.grow(NewIdx);
576 LocIdxToLocID.grow(NewIdx);
577
578 // Default: it's an mphi.
579 ValueIDNum ValNum = {CurBB, 0, NewIdx};
580 // Was this reg ever touched by a regmask?
581 for (const auto &MaskPair : reverse(Masks)) {
582 if (MaskPair.first->clobbersPhysReg(ID)) {
583 // There was an earlier def we skipped.
584 ValNum = {CurBB, MaskPair.second, NewIdx};
585 break;
586 }
587 }
588
589 LocIdxToIDNum[NewIdx] = ValNum;
590 LocIdxToLocID[NewIdx] = ID;
591 return NewIdx;
592 }
593
lookupOrTrackRegister(unsigned ID)594 LocIdx lookupOrTrackRegister(unsigned ID) {
595 LocIdx &Index = LocIDToLocIdx[ID];
596 if (Index.isIllegal())
597 Index = trackRegister(ID);
598 return Index;
599 }
600
601 /// Record a definition of the specified register at the given block / inst.
602 /// This doesn't take a ValueIDNum, because the definition and its location
603 /// are synonymous.
defReg(Register R,unsigned BB,unsigned Inst)604 void defReg(Register R, unsigned BB, unsigned Inst) {
605 unsigned ID = getLocID(R, false);
606 LocIdx Idx = lookupOrTrackRegister(ID);
607 ValueIDNum ValueID = {BB, Inst, Idx};
608 LocIdxToIDNum[Idx] = ValueID;
609 }
610
611 /// Set a register to a value number. To be used if the value number is
612 /// known in advance.
setReg(Register R,ValueIDNum ValueID)613 void setReg(Register R, ValueIDNum ValueID) {
614 unsigned ID = getLocID(R, false);
615 LocIdx Idx = lookupOrTrackRegister(ID);
616 LocIdxToIDNum[Idx] = ValueID;
617 }
618
readReg(Register R)619 ValueIDNum readReg(Register R) {
620 unsigned ID = getLocID(R, false);
621 LocIdx Idx = lookupOrTrackRegister(ID);
622 return LocIdxToIDNum[Idx];
623 }
624
625 /// Reset a register value to zero / empty. Needed to replicate the
626 /// VarLoc implementation where a copy to/from a register effectively
627 /// clears the contents of the source register. (Values can only have one
628 /// machine location in VarLocBasedImpl).
wipeRegister(Register R)629 void wipeRegister(Register R) {
630 unsigned ID = getLocID(R, false);
631 LocIdx Idx = LocIDToLocIdx[ID];
632 LocIdxToIDNum[Idx] = ValueIDNum::EmptyValue;
633 }
634
635 /// Determine the LocIdx of an existing register.
getRegMLoc(Register R)636 LocIdx getRegMLoc(Register R) {
637 unsigned ID = getLocID(R, false);
638 return LocIDToLocIdx[ID];
639 }
640
641 /// Record a RegMask operand being executed. Defs any register we currently
642 /// track, stores a pointer to the mask in case we have to account for it
643 /// later.
writeRegMask(const MachineOperand * MO,unsigned CurBB,unsigned InstID)644 void writeRegMask(const MachineOperand *MO, unsigned CurBB, unsigned InstID) {
645 // Ensure SP exists, so that we don't override it later.
646 Register SP = TLI.getStackPointerRegisterToSaveRestore();
647
648 // Def any register we track have that isn't preserved. The regmask
649 // terminates the liveness of a register, meaning its value can't be
650 // relied upon -- we represent this by giving it a new value.
651 for (auto Location : locations()) {
652 unsigned ID = LocIdxToLocID[Location.Idx];
653 // Don't clobber SP, even if the mask says it's clobbered.
654 if (ID < NumRegs && ID != SP && MO->clobbersPhysReg(ID))
655 defReg(ID, CurBB, InstID);
656 }
657 Masks.push_back(std::make_pair(MO, InstID));
658 }
659
660 /// Find LocIdx for SpillLoc \p L, creating a new one if it's not tracked.
getOrTrackSpillLoc(SpillLoc L)661 LocIdx getOrTrackSpillLoc(SpillLoc L) {
662 unsigned SpillID = SpillLocs.idFor(L);
663 if (SpillID == 0) {
664 SpillID = SpillLocs.insert(L);
665 unsigned L = getLocID(SpillID, true);
666 LocIdx Idx = LocIdx(LocIdxToIDNum.size()); // New idx
667 LocIdxToIDNum.grow(Idx);
668 LocIdxToLocID.grow(Idx);
669 LocIDToLocIdx.push_back(Idx);
670 LocIdxToLocID[Idx] = L;
671 return Idx;
672 } else {
673 unsigned L = getLocID(SpillID, true);
674 LocIdx Idx = LocIDToLocIdx[L];
675 return Idx;
676 }
677 }
678
679 /// Set the value stored in a spill slot.
setSpill(SpillLoc L,ValueIDNum ValueID)680 void setSpill(SpillLoc L, ValueIDNum ValueID) {
681 LocIdx Idx = getOrTrackSpillLoc(L);
682 LocIdxToIDNum[Idx] = ValueID;
683 }
684
685 /// Read whatever value is in a spill slot, or None if it isn't tracked.
readSpill(SpillLoc L)686 Optional<ValueIDNum> readSpill(SpillLoc L) {
687 unsigned SpillID = SpillLocs.idFor(L);
688 if (SpillID == 0)
689 return None;
690
691 unsigned LocID = getLocID(SpillID, true);
692 LocIdx Idx = LocIDToLocIdx[LocID];
693 return LocIdxToIDNum[Idx];
694 }
695
696 /// Determine the LocIdx of a spill slot. Return None if it previously
697 /// hasn't had a value assigned.
getSpillMLoc(SpillLoc L)698 Optional<LocIdx> getSpillMLoc(SpillLoc L) {
699 unsigned SpillID = SpillLocs.idFor(L);
700 if (SpillID == 0)
701 return None;
702 unsigned LocNo = getLocID(SpillID, true);
703 return LocIDToLocIdx[LocNo];
704 }
705
706 /// Return true if Idx is a spill machine location.
isSpill(LocIdx Idx) const707 bool isSpill(LocIdx Idx) const {
708 return LocIdxToLocID[Idx] >= NumRegs;
709 }
710
begin()711 MLocIterator begin() {
712 return MLocIterator(LocIdxToIDNum, 0);
713 }
714
end()715 MLocIterator end() {
716 return MLocIterator(LocIdxToIDNum, LocIdxToIDNum.size());
717 }
718
719 /// Return a range over all locations currently tracked.
locations()720 iterator_range<MLocIterator> locations() {
721 return llvm::make_range(begin(), end());
722 }
723
LocIdxToName(LocIdx Idx) const724 std::string LocIdxToName(LocIdx Idx) const {
725 unsigned ID = LocIdxToLocID[Idx];
726 if (ID >= NumRegs)
727 return Twine("slot ").concat(Twine(ID - NumRegs)).str();
728 else
729 return TRI.getRegAsmName(ID).str();
730 }
731
IDAsString(const ValueIDNum & Num) const732 std::string IDAsString(const ValueIDNum &Num) const {
733 std::string DefName = LocIdxToName(Num.getLoc());
734 return Num.asString(DefName);
735 }
736
737 LLVM_DUMP_METHOD
dump()738 void dump() {
739 for (auto Location : locations()) {
740 std::string MLocName = LocIdxToName(Location.Value.getLoc());
741 std::string DefName = Location.Value.asString(MLocName);
742 dbgs() << LocIdxToName(Location.Idx) << " --> " << DefName << "\n";
743 }
744 }
745
746 LLVM_DUMP_METHOD
dump_mloc_map()747 void dump_mloc_map() {
748 for (auto Location : locations()) {
749 std::string foo = LocIdxToName(Location.Idx);
750 dbgs() << "Idx " << Location.Idx.asU64() << " " << foo << "\n";
751 }
752 }
753
754 /// Create a DBG_VALUE based on machine location \p MLoc. Qualify it with the
755 /// information in \pProperties, for variable Var. Don't insert it anywhere,
756 /// just return the builder for it.
emitLoc(Optional<LocIdx> MLoc,const DebugVariable & Var,const DbgValueProperties & Properties)757 MachineInstrBuilder emitLoc(Optional<LocIdx> MLoc, const DebugVariable &Var,
758 const DbgValueProperties &Properties) {
759 DebugLoc DL = DILocation::get(Var.getVariable()->getContext(), 0, 0,
760 Var.getVariable()->getScope(),
761 const_cast<DILocation *>(Var.getInlinedAt()));
762 auto MIB = BuildMI(MF, DL, TII.get(TargetOpcode::DBG_VALUE));
763
764 const DIExpression *Expr = Properties.DIExpr;
765 if (!MLoc) {
766 // No location -> DBG_VALUE $noreg
767 MIB.addReg(0, RegState::Debug);
768 MIB.addReg(0, RegState::Debug);
769 } else if (LocIdxToLocID[*MLoc] >= NumRegs) {
770 unsigned LocID = LocIdxToLocID[*MLoc];
771 const SpillLoc &Spill = SpillLocs[LocID - NumRegs + 1];
772
773 auto *TRI = MF.getSubtarget().getRegisterInfo();
774 Expr = TRI->prependOffsetExpression(Expr, DIExpression::ApplyOffset,
775 Spill.SpillOffset);
776 unsigned Base = Spill.SpillBase;
777 MIB.addReg(Base, RegState::Debug);
778 MIB.addImm(0);
779 } else {
780 unsigned LocID = LocIdxToLocID[*MLoc];
781 MIB.addReg(LocID, RegState::Debug);
782 if (Properties.Indirect)
783 MIB.addImm(0);
784 else
785 MIB.addReg(0, RegState::Debug);
786 }
787
788 MIB.addMetadata(Var.getVariable());
789 MIB.addMetadata(Expr);
790 return MIB;
791 }
792 };
793
794 /// Class recording the (high level) _value_ of a variable. Identifies either
795 /// the value of the variable as a ValueIDNum, or a constant MachineOperand.
796 /// This class also stores meta-information about how the value is qualified.
797 /// Used to reason about variable values when performing the second
798 /// (DebugVariable specific) dataflow analysis.
799 class DbgValue {
800 public:
801 union {
802 /// If Kind is Def, the value number that this value is based on.
803 ValueIDNum ID;
804 /// If Kind is Const, the MachineOperand defining this value.
805 MachineOperand MO;
806 /// For a NoVal DbgValue, which block it was generated in.
807 unsigned BlockNo;
808 };
809 /// Qualifiers for the ValueIDNum above.
810 DbgValueProperties Properties;
811
812 typedef enum {
813 Undef, // Represents a DBG_VALUE $noreg in the transfer function only.
814 Def, // This value is defined by an inst, or is a PHI value.
815 Const, // A constant value contained in the MachineOperand field.
816 Proposed, // This is a tentative PHI value, which may be confirmed or
817 // invalidated later.
818 NoVal // Empty DbgValue, generated during dataflow. BlockNo stores
819 // which block this was generated in.
820 } KindT;
821 /// Discriminator for whether this is a constant or an in-program value.
822 KindT Kind;
823
DbgValue(const ValueIDNum & Val,const DbgValueProperties & Prop,KindT Kind)824 DbgValue(const ValueIDNum &Val, const DbgValueProperties &Prop, KindT Kind)
825 : ID(Val), Properties(Prop), Kind(Kind) {
826 assert(Kind == Def || Kind == Proposed);
827 }
828
DbgValue(unsigned BlockNo,const DbgValueProperties & Prop,KindT Kind)829 DbgValue(unsigned BlockNo, const DbgValueProperties &Prop, KindT Kind)
830 : BlockNo(BlockNo), Properties(Prop), Kind(Kind) {
831 assert(Kind == NoVal);
832 }
833
DbgValue(const MachineOperand & MO,const DbgValueProperties & Prop,KindT Kind)834 DbgValue(const MachineOperand &MO, const DbgValueProperties &Prop, KindT Kind)
835 : MO(MO), Properties(Prop), Kind(Kind) {
836 assert(Kind == Const);
837 }
838
DbgValue(const DbgValueProperties & Prop,KindT Kind)839 DbgValue(const DbgValueProperties &Prop, KindT Kind)
840 : Properties(Prop), Kind(Kind) {
841 assert(Kind == Undef &&
842 "Empty DbgValue constructor must pass in Undef kind");
843 }
844
dump(const MLocTracker * MTrack) const845 void dump(const MLocTracker *MTrack) const {
846 if (Kind == Const) {
847 MO.dump();
848 } else if (Kind == NoVal) {
849 dbgs() << "NoVal(" << BlockNo << ")";
850 } else if (Kind == Proposed) {
851 dbgs() << "VPHI(" << MTrack->IDAsString(ID) << ")";
852 } else {
853 assert(Kind == Def);
854 dbgs() << MTrack->IDAsString(ID);
855 }
856 if (Properties.Indirect)
857 dbgs() << " indir";
858 if (Properties.DIExpr)
859 dbgs() << " " << *Properties.DIExpr;
860 }
861
operator ==(const DbgValue & Other) const862 bool operator==(const DbgValue &Other) const {
863 if (std::tie(Kind, Properties) != std::tie(Other.Kind, Other.Properties))
864 return false;
865 else if (Kind == Proposed && ID != Other.ID)
866 return false;
867 else if (Kind == Def && ID != Other.ID)
868 return false;
869 else if (Kind == NoVal && BlockNo != Other.BlockNo)
870 return false;
871 else if (Kind == Const)
872 return MO.isIdenticalTo(Other.MO);
873
874 return true;
875 }
876
operator !=(const DbgValue & Other) const877 bool operator!=(const DbgValue &Other) const { return !(*this == Other); }
878 };
879
880 /// Types for recording sets of variable fragments that overlap. For a given
881 /// local variable, we record all other fragments of that variable that could
882 /// overlap it, to reduce search time.
883 using FragmentOfVar =
884 std::pair<const DILocalVariable *, DIExpression::FragmentInfo>;
885 using OverlapMap =
886 DenseMap<FragmentOfVar, SmallVector<DIExpression::FragmentInfo, 1>>;
887
888 /// Collection of DBG_VALUEs observed when traversing a block. Records each
889 /// variable and the value the DBG_VALUE refers to. Requires the machine value
890 /// location dataflow algorithm to have run already, so that values can be
891 /// identified.
892 class VLocTracker {
893 public:
894 /// Map DebugVariable to the latest Value it's defined to have.
895 /// Needs to be a MapVector because we determine order-in-the-input-MIR from
896 /// the order in this container.
897 /// We only retain the last DbgValue in each block for each variable, to
898 /// determine the blocks live-out variable value. The Vars container forms the
899 /// transfer function for this block, as part of the dataflow analysis. The
900 /// movement of values between locations inside of a block is handled at a
901 /// much later stage, in the TransferTracker class.
902 MapVector<DebugVariable, DbgValue> Vars;
903 DenseMap<DebugVariable, const DILocation *> Scopes;
904 MachineBasicBlock *MBB;
905
906 public:
VLocTracker()907 VLocTracker() {}
908
defVar(const MachineInstr & MI,const DbgValueProperties & Properties,Optional<ValueIDNum> ID)909 void defVar(const MachineInstr &MI, const DbgValueProperties &Properties,
910 Optional<ValueIDNum> ID) {
911 assert(MI.isDebugValue() || MI.isDebugRef());
912 DebugVariable Var(MI.getDebugVariable(), MI.getDebugExpression(),
913 MI.getDebugLoc()->getInlinedAt());
914 DbgValue Rec = (ID) ? DbgValue(*ID, Properties, DbgValue::Def)
915 : DbgValue(Properties, DbgValue::Undef);
916
917 // Attempt insertion; overwrite if it's already mapped.
918 auto Result = Vars.insert(std::make_pair(Var, Rec));
919 if (!Result.second)
920 Result.first->second = Rec;
921 Scopes[Var] = MI.getDebugLoc().get();
922 }
923
defVar(const MachineInstr & MI,const MachineOperand & MO)924 void defVar(const MachineInstr &MI, const MachineOperand &MO) {
925 // Only DBG_VALUEs can define constant-valued variables.
926 assert(MI.isDebugValue());
927 DebugVariable Var(MI.getDebugVariable(), MI.getDebugExpression(),
928 MI.getDebugLoc()->getInlinedAt());
929 DbgValueProperties Properties(MI);
930 DbgValue Rec = DbgValue(MO, Properties, DbgValue::Const);
931
932 // Attempt insertion; overwrite if it's already mapped.
933 auto Result = Vars.insert(std::make_pair(Var, Rec));
934 if (!Result.second)
935 Result.first->second = Rec;
936 Scopes[Var] = MI.getDebugLoc().get();
937 }
938 };
939
940 /// Tracker for converting machine value locations and variable values into
941 /// variable locations (the output of LiveDebugValues), recorded as DBG_VALUEs
942 /// specifying block live-in locations and transfers within blocks.
943 ///
944 /// Operating on a per-block basis, this class takes a (pre-loaded) MLocTracker
945 /// and must be initialized with the set of variable values that are live-in to
946 /// the block. The caller then repeatedly calls process(). TransferTracker picks
947 /// out variable locations for the live-in variable values (if there _is_ a
948 /// location) and creates the corresponding DBG_VALUEs. Then, as the block is
949 /// stepped through, transfers of values between machine locations are
950 /// identified and if profitable, a DBG_VALUE created.
951 ///
952 /// This is where debug use-before-defs would be resolved: a variable with an
953 /// unavailable value could materialize in the middle of a block, when the
954 /// value becomes available. Or, we could detect clobbers and re-specify the
955 /// variable in a backup location. (XXX these are unimplemented).
956 class TransferTracker {
957 public:
958 const TargetInstrInfo *TII;
959 /// This machine location tracker is assumed to always contain the up-to-date
960 /// value mapping for all machine locations. TransferTracker only reads
961 /// information from it. (XXX make it const?)
962 MLocTracker *MTracker;
963 MachineFunction &MF;
964
965 /// Record of all changes in variable locations at a block position. Awkwardly
966 /// we allow inserting either before or after the point: MBB != nullptr
967 /// indicates it's before, otherwise after.
968 struct Transfer {
969 MachineBasicBlock::iterator Pos; /// Position to insert DBG_VALUes
970 MachineBasicBlock *MBB; /// non-null if we should insert after.
971 SmallVector<MachineInstr *, 4> Insts; /// Vector of DBG_VALUEs to insert.
972 };
973
974 typedef struct {
975 LocIdx Loc;
976 DbgValueProperties Properties;
977 } LocAndProperties;
978
979 /// Collection of transfers (DBG_VALUEs) to be inserted.
980 SmallVector<Transfer, 32> Transfers;
981
982 /// Local cache of what-value-is-in-what-LocIdx. Used to identify differences
983 /// between TransferTrackers view of variable locations and MLocTrackers. For
984 /// example, MLocTracker observes all clobbers, but TransferTracker lazily
985 /// does not.
986 std::vector<ValueIDNum> VarLocs;
987
988 /// Map from LocIdxes to which DebugVariables are based that location.
989 /// Mantained while stepping through the block. Not accurate if
990 /// VarLocs[Idx] != MTracker->LocIdxToIDNum[Idx].
991 std::map<LocIdx, SmallSet<DebugVariable, 4>> ActiveMLocs;
992
993 /// Map from DebugVariable to it's current location and qualifying meta
994 /// information. To be used in conjunction with ActiveMLocs to construct
995 /// enough information for the DBG_VALUEs for a particular LocIdx.
996 DenseMap<DebugVariable, LocAndProperties> ActiveVLocs;
997
998 /// Temporary cache of DBG_VALUEs to be entered into the Transfers collection.
999 SmallVector<MachineInstr *, 4> PendingDbgValues;
1000
1001 /// Record of a use-before-def: created when a value that's live-in to the
1002 /// current block isn't available in any machine location, but it will be
1003 /// defined in this block.
1004 struct UseBeforeDef {
1005 /// Value of this variable, def'd in block.
1006 ValueIDNum ID;
1007 /// Identity of this variable.
1008 DebugVariable Var;
1009 /// Additional variable properties.
1010 DbgValueProperties Properties;
1011 };
1012
1013 /// Map from instruction index (within the block) to the set of UseBeforeDefs
1014 /// that become defined at that instruction.
1015 DenseMap<unsigned, SmallVector<UseBeforeDef, 1>> UseBeforeDefs;
1016
1017 /// The set of variables that are in UseBeforeDefs and can become a location
1018 /// once the relevant value is defined. An element being erased from this
1019 /// collection prevents the use-before-def materializing.
1020 DenseSet<DebugVariable> UseBeforeDefVariables;
1021
1022 const TargetRegisterInfo &TRI;
1023 const BitVector &CalleeSavedRegs;
1024
TransferTracker(const TargetInstrInfo * TII,MLocTracker * MTracker,MachineFunction & MF,const TargetRegisterInfo & TRI,const BitVector & CalleeSavedRegs)1025 TransferTracker(const TargetInstrInfo *TII, MLocTracker *MTracker,
1026 MachineFunction &MF, const TargetRegisterInfo &TRI,
1027 const BitVector &CalleeSavedRegs)
1028 : TII(TII), MTracker(MTracker), MF(MF), TRI(TRI),
1029 CalleeSavedRegs(CalleeSavedRegs) {}
1030
1031 /// Load object with live-in variable values. \p mlocs contains the live-in
1032 /// values in each machine location, while \p vlocs the live-in variable
1033 /// values. This method picks variable locations for the live-in variables,
1034 /// creates DBG_VALUEs and puts them in #Transfers, then prepares the other
1035 /// object fields to track variable locations as we step through the block.
1036 /// FIXME: could just examine mloctracker instead of passing in \p mlocs?
loadInlocs(MachineBasicBlock & MBB,ValueIDNum * MLocs,SmallVectorImpl<std::pair<DebugVariable,DbgValue>> & VLocs,unsigned NumLocs)1037 void loadInlocs(MachineBasicBlock &MBB, ValueIDNum *MLocs,
1038 SmallVectorImpl<std::pair<DebugVariable, DbgValue>> &VLocs,
1039 unsigned NumLocs) {
1040 ActiveMLocs.clear();
1041 ActiveVLocs.clear();
1042 VarLocs.clear();
1043 VarLocs.reserve(NumLocs);
1044 UseBeforeDefs.clear();
1045 UseBeforeDefVariables.clear();
1046
1047 auto isCalleeSaved = [&](LocIdx L) {
1048 unsigned Reg = MTracker->LocIdxToLocID[L];
1049 if (Reg >= MTracker->NumRegs)
1050 return false;
1051 for (MCRegAliasIterator RAI(Reg, &TRI, true); RAI.isValid(); ++RAI)
1052 if (CalleeSavedRegs.test(*RAI))
1053 return true;
1054 return false;
1055 };
1056
1057 // Map of the preferred location for each value.
1058 std::map<ValueIDNum, LocIdx> ValueToLoc;
1059
1060 // Produce a map of value numbers to the current machine locs they live
1061 // in. When emulating VarLocBasedImpl, there should only be one
1062 // location; when not, we get to pick.
1063 for (auto Location : MTracker->locations()) {
1064 LocIdx Idx = Location.Idx;
1065 ValueIDNum &VNum = MLocs[Idx.asU64()];
1066 VarLocs.push_back(VNum);
1067 auto it = ValueToLoc.find(VNum);
1068 // In order of preference, pick:
1069 // * Callee saved registers,
1070 // * Other registers,
1071 // * Spill slots.
1072 if (it == ValueToLoc.end() || MTracker->isSpill(it->second) ||
1073 (!isCalleeSaved(it->second) && isCalleeSaved(Idx.asU64()))) {
1074 // Insert, or overwrite if insertion failed.
1075 auto PrefLocRes = ValueToLoc.insert(std::make_pair(VNum, Idx));
1076 if (!PrefLocRes.second)
1077 PrefLocRes.first->second = Idx;
1078 }
1079 }
1080
1081 // Now map variables to their picked LocIdxes.
1082 for (auto Var : VLocs) {
1083 if (Var.second.Kind == DbgValue::Const) {
1084 PendingDbgValues.push_back(
1085 emitMOLoc(Var.second.MO, Var.first, Var.second.Properties));
1086 continue;
1087 }
1088
1089 // If the value has no location, we can't make a variable location.
1090 const ValueIDNum &Num = Var.second.ID;
1091 auto ValuesPreferredLoc = ValueToLoc.find(Num);
1092 if (ValuesPreferredLoc == ValueToLoc.end()) {
1093 // If it's a def that occurs in this block, register it as a
1094 // use-before-def to be resolved as we step through the block.
1095 if (Num.getBlock() == (unsigned)MBB.getNumber() && !Num.isPHI())
1096 addUseBeforeDef(Var.first, Var.second.Properties, Num);
1097 continue;
1098 }
1099
1100 LocIdx M = ValuesPreferredLoc->second;
1101 auto NewValue = LocAndProperties{M, Var.second.Properties};
1102 auto Result = ActiveVLocs.insert(std::make_pair(Var.first, NewValue));
1103 if (!Result.second)
1104 Result.first->second = NewValue;
1105 ActiveMLocs[M].insert(Var.first);
1106 PendingDbgValues.push_back(
1107 MTracker->emitLoc(M, Var.first, Var.second.Properties));
1108 }
1109 flushDbgValues(MBB.begin(), &MBB);
1110 }
1111
1112 /// Record that \p Var has value \p ID, a value that becomes available
1113 /// later in the function.
addUseBeforeDef(const DebugVariable & Var,const DbgValueProperties & Properties,ValueIDNum ID)1114 void addUseBeforeDef(const DebugVariable &Var,
1115 const DbgValueProperties &Properties, ValueIDNum ID) {
1116 UseBeforeDef UBD = {ID, Var, Properties};
1117 UseBeforeDefs[ID.getInst()].push_back(UBD);
1118 UseBeforeDefVariables.insert(Var);
1119 }
1120
1121 /// After the instruction at index \p Inst and position \p pos has been
1122 /// processed, check whether it defines a variable value in a use-before-def.
1123 /// If so, and the variable value hasn't changed since the start of the
1124 /// block, create a DBG_VALUE.
checkInstForNewValues(unsigned Inst,MachineBasicBlock::iterator pos)1125 void checkInstForNewValues(unsigned Inst, MachineBasicBlock::iterator pos) {
1126 auto MIt = UseBeforeDefs.find(Inst);
1127 if (MIt == UseBeforeDefs.end())
1128 return;
1129
1130 for (auto &Use : MIt->second) {
1131 LocIdx L = Use.ID.getLoc();
1132
1133 // If something goes very wrong, we might end up labelling a COPY
1134 // instruction or similar with an instruction number, where it doesn't
1135 // actually define a new value, instead it moves a value. In case this
1136 // happens, discard.
1137 if (MTracker->LocIdxToIDNum[L] != Use.ID)
1138 continue;
1139
1140 // If a different debug instruction defined the variable value / location
1141 // since the start of the block, don't materialize this use-before-def.
1142 if (!UseBeforeDefVariables.count(Use.Var))
1143 continue;
1144
1145 PendingDbgValues.push_back(MTracker->emitLoc(L, Use.Var, Use.Properties));
1146 }
1147 flushDbgValues(pos, nullptr);
1148 }
1149
1150 /// Helper to move created DBG_VALUEs into Transfers collection.
flushDbgValues(MachineBasicBlock::iterator Pos,MachineBasicBlock * MBB)1151 void flushDbgValues(MachineBasicBlock::iterator Pos, MachineBasicBlock *MBB) {
1152 if (PendingDbgValues.size() > 0) {
1153 Transfers.push_back({Pos, MBB, PendingDbgValues});
1154 PendingDbgValues.clear();
1155 }
1156 }
1157
1158 /// Change a variable value after encountering a DBG_VALUE inside a block.
redefVar(const MachineInstr & MI)1159 void redefVar(const MachineInstr &MI) {
1160 DebugVariable Var(MI.getDebugVariable(), MI.getDebugExpression(),
1161 MI.getDebugLoc()->getInlinedAt());
1162 DbgValueProperties Properties(MI);
1163
1164 const MachineOperand &MO = MI.getOperand(0);
1165
1166 // Ignore non-register locations, we don't transfer those.
1167 if (!MO.isReg() || MO.getReg() == 0) {
1168 auto It = ActiveVLocs.find(Var);
1169 if (It != ActiveVLocs.end()) {
1170 ActiveMLocs[It->second.Loc].erase(Var);
1171 ActiveVLocs.erase(It);
1172 }
1173 // Any use-before-defs no longer apply.
1174 UseBeforeDefVariables.erase(Var);
1175 return;
1176 }
1177
1178 Register Reg = MO.getReg();
1179 LocIdx NewLoc = MTracker->getRegMLoc(Reg);
1180 redefVar(MI, Properties, NewLoc);
1181 }
1182
1183 /// Handle a change in variable location within a block. Terminate the
1184 /// variables current location, and record the value it now refers to, so
1185 /// that we can detect location transfers later on.
redefVar(const MachineInstr & MI,const DbgValueProperties & Properties,Optional<LocIdx> OptNewLoc)1186 void redefVar(const MachineInstr &MI, const DbgValueProperties &Properties,
1187 Optional<LocIdx> OptNewLoc) {
1188 DebugVariable Var(MI.getDebugVariable(), MI.getDebugExpression(),
1189 MI.getDebugLoc()->getInlinedAt());
1190 // Any use-before-defs no longer apply.
1191 UseBeforeDefVariables.erase(Var);
1192
1193 // Erase any previous location,
1194 auto It = ActiveVLocs.find(Var);
1195 if (It != ActiveVLocs.end())
1196 ActiveMLocs[It->second.Loc].erase(Var);
1197
1198 // If there _is_ no new location, all we had to do was erase.
1199 if (!OptNewLoc)
1200 return;
1201 LocIdx NewLoc = *OptNewLoc;
1202
1203 // Check whether our local copy of values-by-location in #VarLocs is out of
1204 // date. Wipe old tracking data for the location if it's been clobbered in
1205 // the meantime.
1206 if (MTracker->getNumAtPos(NewLoc) != VarLocs[NewLoc.asU64()]) {
1207 for (auto &P : ActiveMLocs[NewLoc]) {
1208 ActiveVLocs.erase(P);
1209 }
1210 ActiveMLocs[NewLoc.asU64()].clear();
1211 VarLocs[NewLoc.asU64()] = MTracker->getNumAtPos(NewLoc);
1212 }
1213
1214 ActiveMLocs[NewLoc].insert(Var);
1215 if (It == ActiveVLocs.end()) {
1216 ActiveVLocs.insert(
1217 std::make_pair(Var, LocAndProperties{NewLoc, Properties}));
1218 } else {
1219 It->second.Loc = NewLoc;
1220 It->second.Properties = Properties;
1221 }
1222 }
1223
1224 /// Explicitly terminate variable locations based on \p mloc. Creates undef
1225 /// DBG_VALUEs for any variables that were located there, and clears
1226 /// #ActiveMLoc / #ActiveVLoc tracking information for that location.
clobberMloc(LocIdx MLoc,MachineBasicBlock::iterator Pos)1227 void clobberMloc(LocIdx MLoc, MachineBasicBlock::iterator Pos) {
1228 assert(MTracker->isSpill(MLoc));
1229 auto ActiveMLocIt = ActiveMLocs.find(MLoc);
1230 if (ActiveMLocIt == ActiveMLocs.end())
1231 return;
1232
1233 VarLocs[MLoc.asU64()] = ValueIDNum::EmptyValue;
1234
1235 for (auto &Var : ActiveMLocIt->second) {
1236 auto ActiveVLocIt = ActiveVLocs.find(Var);
1237 // Create an undef. We can't feed in a nullptr DIExpression alas,
1238 // so use the variables last expression. Pass None as the location.
1239 const DIExpression *Expr = ActiveVLocIt->second.Properties.DIExpr;
1240 DbgValueProperties Properties(Expr, false);
1241 PendingDbgValues.push_back(MTracker->emitLoc(None, Var, Properties));
1242 ActiveVLocs.erase(ActiveVLocIt);
1243 }
1244 flushDbgValues(Pos, nullptr);
1245
1246 ActiveMLocIt->second.clear();
1247 }
1248
1249 /// Transfer variables based on \p Src to be based on \p Dst. This handles
1250 /// both register copies as well as spills and restores. Creates DBG_VALUEs
1251 /// describing the movement.
transferMlocs(LocIdx Src,LocIdx Dst,MachineBasicBlock::iterator Pos)1252 void transferMlocs(LocIdx Src, LocIdx Dst, MachineBasicBlock::iterator Pos) {
1253 // Does Src still contain the value num we expect? If not, it's been
1254 // clobbered in the meantime, and our variable locations are stale.
1255 if (VarLocs[Src.asU64()] != MTracker->getNumAtPos(Src))
1256 return;
1257
1258 // assert(ActiveMLocs[Dst].size() == 0);
1259 //^^^ Legitimate scenario on account of un-clobbered slot being assigned to?
1260 ActiveMLocs[Dst] = ActiveMLocs[Src];
1261 VarLocs[Dst.asU64()] = VarLocs[Src.asU64()];
1262
1263 // For each variable based on Src; create a location at Dst.
1264 for (auto &Var : ActiveMLocs[Src]) {
1265 auto ActiveVLocIt = ActiveVLocs.find(Var);
1266 assert(ActiveVLocIt != ActiveVLocs.end());
1267 ActiveVLocIt->second.Loc = Dst;
1268
1269 assert(Dst != 0);
1270 MachineInstr *MI =
1271 MTracker->emitLoc(Dst, Var, ActiveVLocIt->second.Properties);
1272 PendingDbgValues.push_back(MI);
1273 }
1274 ActiveMLocs[Src].clear();
1275 flushDbgValues(Pos, nullptr);
1276
1277 // XXX XXX XXX "pretend to be old LDV" means dropping all tracking data
1278 // about the old location.
1279 if (EmulateOldLDV)
1280 VarLocs[Src.asU64()] = ValueIDNum::EmptyValue;
1281 }
1282
emitMOLoc(const MachineOperand & MO,const DebugVariable & Var,const DbgValueProperties & Properties)1283 MachineInstrBuilder emitMOLoc(const MachineOperand &MO,
1284 const DebugVariable &Var,
1285 const DbgValueProperties &Properties) {
1286 DebugLoc DL = DILocation::get(Var.getVariable()->getContext(), 0, 0,
1287 Var.getVariable()->getScope(),
1288 const_cast<DILocation *>(Var.getInlinedAt()));
1289 auto MIB = BuildMI(MF, DL, TII->get(TargetOpcode::DBG_VALUE));
1290 MIB.add(MO);
1291 if (Properties.Indirect)
1292 MIB.addImm(0);
1293 else
1294 MIB.addReg(0);
1295 MIB.addMetadata(Var.getVariable());
1296 MIB.addMetadata(Properties.DIExpr);
1297 return MIB;
1298 }
1299 };
1300
1301 class InstrRefBasedLDV : public LDVImpl {
1302 private:
1303 using FragmentInfo = DIExpression::FragmentInfo;
1304 using OptFragmentInfo = Optional<DIExpression::FragmentInfo>;
1305
1306 // Helper while building OverlapMap, a map of all fragments seen for a given
1307 // DILocalVariable.
1308 using VarToFragments =
1309 DenseMap<const DILocalVariable *, SmallSet<FragmentInfo, 4>>;
1310
1311 /// Machine location/value transfer function, a mapping of which locations
1312 /// are assigned which new values.
1313 using MLocTransferMap = std::map<LocIdx, ValueIDNum>;
1314
1315 /// Live in/out structure for the variable values: a per-block map of
1316 /// variables to their values. XXX, better name?
1317 using LiveIdxT =
1318 DenseMap<const MachineBasicBlock *, DenseMap<DebugVariable, DbgValue> *>;
1319
1320 using VarAndLoc = std::pair<DebugVariable, DbgValue>;
1321
1322 /// Type for a live-in value: the predecessor block, and its value.
1323 using InValueT = std::pair<MachineBasicBlock *, DbgValue *>;
1324
1325 /// Vector (per block) of a collection (inner smallvector) of live-ins.
1326 /// Used as the result type for the variable value dataflow problem.
1327 using LiveInsT = SmallVector<SmallVector<VarAndLoc, 8>, 8>;
1328
1329 const TargetRegisterInfo *TRI;
1330 const TargetInstrInfo *TII;
1331 const TargetFrameLowering *TFI;
1332 BitVector CalleeSavedRegs;
1333 LexicalScopes LS;
1334 TargetPassConfig *TPC;
1335
1336 /// Object to track machine locations as we step through a block. Could
1337 /// probably be a field rather than a pointer, as it's always used.
1338 MLocTracker *MTracker;
1339
1340 /// Number of the current block LiveDebugValues is stepping through.
1341 unsigned CurBB;
1342
1343 /// Number of the current instruction LiveDebugValues is evaluating.
1344 unsigned CurInst;
1345
1346 /// Variable tracker -- listens to DBG_VALUEs occurring as InstrRefBasedImpl
1347 /// steps through a block. Reads the values at each location from the
1348 /// MLocTracker object.
1349 VLocTracker *VTracker;
1350
1351 /// Tracker for transfers, listens to DBG_VALUEs and transfers of values
1352 /// between locations during stepping, creates new DBG_VALUEs when values move
1353 /// location.
1354 TransferTracker *TTracker;
1355
1356 /// Blocks which are artificial, i.e. blocks which exclusively contain
1357 /// instructions without DebugLocs, or with line 0 locations.
1358 SmallPtrSet<const MachineBasicBlock *, 16> ArtificialBlocks;
1359
1360 // Mapping of blocks to and from their RPOT order.
1361 DenseMap<unsigned int, MachineBasicBlock *> OrderToBB;
1362 DenseMap<MachineBasicBlock *, unsigned int> BBToOrder;
1363 DenseMap<unsigned, unsigned> BBNumToRPO;
1364
1365 /// Pair of MachineInstr, and its 1-based offset into the containing block.
1366 using InstAndNum = std::pair<const MachineInstr *, unsigned>;
1367 /// Map from debug instruction number to the MachineInstr labelled with that
1368 /// number, and its location within the function. Used to transform
1369 /// instruction numbers in DBG_INSTR_REFs into machine value numbers.
1370 std::map<uint64_t, InstAndNum> DebugInstrNumToInstr;
1371
1372 // Map of overlapping variable fragments.
1373 OverlapMap OverlapFragments;
1374 VarToFragments SeenFragments;
1375
1376 /// Tests whether this instruction is a spill to a stack slot.
1377 bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF);
1378
1379 /// Decide if @MI is a spill instruction and return true if it is. We use 2
1380 /// criteria to make this decision:
1381 /// - Is this instruction a store to a spill slot?
1382 /// - Is there a register operand that is both used and killed?
1383 /// TODO: Store optimization can fold spills into other stores (including
1384 /// other spills). We do not handle this yet (more than one memory operand).
1385 bool isLocationSpill(const MachineInstr &MI, MachineFunction *MF,
1386 unsigned &Reg);
1387
1388 /// If a given instruction is identified as a spill, return the spill slot
1389 /// and set \p Reg to the spilled register.
1390 Optional<SpillLoc> isRestoreInstruction(const MachineInstr &MI,
1391 MachineFunction *MF, unsigned &Reg);
1392
1393 /// Given a spill instruction, extract the register and offset used to
1394 /// address the spill slot in a target independent way.
1395 SpillLoc extractSpillBaseRegAndOffset(const MachineInstr &MI);
1396
1397 /// Observe a single instruction while stepping through a block.
1398 void process(MachineInstr &MI);
1399
1400 /// Examines whether \p MI is a DBG_VALUE and notifies trackers.
1401 /// \returns true if MI was recognized and processed.
1402 bool transferDebugValue(const MachineInstr &MI);
1403
1404 /// Examines whether \p MI is a DBG_INSTR_REF and notifies trackers.
1405 /// \returns true if MI was recognized and processed.
1406 bool transferDebugInstrRef(MachineInstr &MI);
1407
1408 /// Examines whether \p MI is copy instruction, and notifies trackers.
1409 /// \returns true if MI was recognized and processed.
1410 bool transferRegisterCopy(MachineInstr &MI);
1411
1412 /// Examines whether \p MI is stack spill or restore instruction, and
1413 /// notifies trackers. \returns true if MI was recognized and processed.
1414 bool transferSpillOrRestoreInst(MachineInstr &MI);
1415
1416 /// Examines \p MI for any registers that it defines, and notifies trackers.
1417 void transferRegisterDef(MachineInstr &MI);
1418
1419 /// Copy one location to the other, accounting for movement of subregisters
1420 /// too.
1421 void performCopy(Register Src, Register Dst);
1422
1423 void accumulateFragmentMap(MachineInstr &MI);
1424
1425 /// Step through the function, recording register definitions and movements
1426 /// in an MLocTracker. Convert the observations into a per-block transfer
1427 /// function in \p MLocTransfer, suitable for using with the machine value
1428 /// location dataflow problem.
1429 void
1430 produceMLocTransferFunction(MachineFunction &MF,
1431 SmallVectorImpl<MLocTransferMap> &MLocTransfer,
1432 unsigned MaxNumBlocks);
1433
1434 /// Solve the machine value location dataflow problem. Takes as input the
1435 /// transfer functions in \p MLocTransfer. Writes the output live-in and
1436 /// live-out arrays to the (initialized to zero) multidimensional arrays in
1437 /// \p MInLocs and \p MOutLocs. The outer dimension is indexed by block
1438 /// number, the inner by LocIdx.
1439 void mlocDataflow(ValueIDNum **MInLocs, ValueIDNum **MOutLocs,
1440 SmallVectorImpl<MLocTransferMap> &MLocTransfer);
1441
1442 /// Perform a control flow join (lattice value meet) of the values in machine
1443 /// locations at \p MBB. Follows the algorithm described in the file-comment,
1444 /// reading live-outs of predecessors from \p OutLocs, the current live ins
1445 /// from \p InLocs, and assigning the newly computed live ins back into
1446 /// \p InLocs. \returns two bools -- the first indicates whether a change
1447 /// was made, the second whether a lattice downgrade occurred. If the latter
1448 /// is true, revisiting this block is necessary.
1449 std::tuple<bool, bool>
1450 mlocJoin(MachineBasicBlock &MBB,
1451 SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
1452 ValueIDNum **OutLocs, ValueIDNum *InLocs);
1453
1454 /// Solve the variable value dataflow problem, for a single lexical scope.
1455 /// Uses the algorithm from the file comment to resolve control flow joins,
1456 /// although there are extra hacks, see vlocJoin. Reads the
1457 /// locations of values from the \p MInLocs and \p MOutLocs arrays (see
1458 /// mlocDataflow) and reads the variable values transfer function from
1459 /// \p AllTheVlocs. Live-in and Live-out variable values are stored locally,
1460 /// with the live-ins permanently stored to \p Output once the fixedpoint is
1461 /// reached.
1462 /// \p VarsWeCareAbout contains a collection of the variables in \p Scope
1463 /// that we should be tracking.
1464 /// \p AssignBlocks contains the set of blocks that aren't in \p Scope, but
1465 /// which do contain DBG_VALUEs, which VarLocBasedImpl tracks locations
1466 /// through.
1467 void vlocDataflow(const LexicalScope *Scope, const DILocation *DILoc,
1468 const SmallSet<DebugVariable, 4> &VarsWeCareAbout,
1469 SmallPtrSetImpl<MachineBasicBlock *> &AssignBlocks,
1470 LiveInsT &Output, ValueIDNum **MOutLocs,
1471 ValueIDNum **MInLocs,
1472 SmallVectorImpl<VLocTracker> &AllTheVLocs);
1473
1474 /// Compute the live-ins to a block, considering control flow merges according
1475 /// to the method in the file comment. Live out and live in variable values
1476 /// are stored in \p VLOCOutLocs and \p VLOCInLocs. The live-ins for \p MBB
1477 /// are computed and stored into \p VLOCInLocs. \returns true if the live-ins
1478 /// are modified.
1479 /// \p InLocsT Output argument, storage for calculated live-ins.
1480 /// \returns two bools -- the first indicates whether a change
1481 /// was made, the second whether a lattice downgrade occurred. If the latter
1482 /// is true, revisiting this block is necessary.
1483 std::tuple<bool, bool>
1484 vlocJoin(MachineBasicBlock &MBB, LiveIdxT &VLOCOutLocs, LiveIdxT &VLOCInLocs,
1485 SmallPtrSet<const MachineBasicBlock *, 16> *VLOCVisited,
1486 unsigned BBNum, const SmallSet<DebugVariable, 4> &AllVars,
1487 ValueIDNum **MOutLocs, ValueIDNum **MInLocs,
1488 SmallPtrSet<const MachineBasicBlock *, 8> &InScopeBlocks,
1489 SmallPtrSet<const MachineBasicBlock *, 8> &BlocksToExplore,
1490 DenseMap<DebugVariable, DbgValue> &InLocsT);
1491
1492 /// Continue exploration of the variable-value lattice, as explained in the
1493 /// file-level comment. \p OldLiveInLocation contains the current
1494 /// exploration position, from which we need to descend further. \p Values
1495 /// contains the set of live-in values, \p CurBlockRPONum the RPO number of
1496 /// the current block, and \p CandidateLocations a set of locations that
1497 /// should be considered as PHI locations, if we reach the bottom of the
1498 /// lattice. \returns true if we should downgrade; the value is the agreeing
1499 /// value number in a non-backedge predecessor.
1500 bool vlocDowngradeLattice(const MachineBasicBlock &MBB,
1501 const DbgValue &OldLiveInLocation,
1502 const SmallVectorImpl<InValueT> &Values,
1503 unsigned CurBlockRPONum);
1504
1505 /// For the given block and live-outs feeding into it, try to find a
1506 /// machine location where they all join. If a solution for all predecessors
1507 /// can't be found, a location where all non-backedge-predecessors join
1508 /// will be returned instead. While this method finds a join location, this
1509 /// says nothing as to whether it should be used.
1510 /// \returns Pair of value ID if found, and true when the correct value
1511 /// is available on all predecessor edges, or false if it's only available
1512 /// for non-backedge predecessors.
1513 std::tuple<Optional<ValueIDNum>, bool>
1514 pickVPHILoc(MachineBasicBlock &MBB, const DebugVariable &Var,
1515 const LiveIdxT &LiveOuts, ValueIDNum **MOutLocs,
1516 ValueIDNum **MInLocs,
1517 const SmallVectorImpl<MachineBasicBlock *> &BlockOrders);
1518
1519 /// Given the solutions to the two dataflow problems, machine value locations
1520 /// in \p MInLocs and live-in variable values in \p SavedLiveIns, runs the
1521 /// TransferTracker class over the function to produce live-in and transfer
1522 /// DBG_VALUEs, then inserts them. Groups of DBG_VALUEs are inserted in the
1523 /// order given by AllVarsNumbering -- this could be any stable order, but
1524 /// right now "order of appearence in function, when explored in RPO", so
1525 /// that we can compare explictly against VarLocBasedImpl.
1526 void emitLocations(MachineFunction &MF, LiveInsT SavedLiveIns,
1527 ValueIDNum **MInLocs,
1528 DenseMap<DebugVariable, unsigned> &AllVarsNumbering);
1529
1530 /// Boilerplate computation of some initial sets, artifical blocks and
1531 /// RPOT block ordering.
1532 void initialSetup(MachineFunction &MF);
1533
1534 bool ExtendRanges(MachineFunction &MF, TargetPassConfig *TPC) override;
1535
1536 public:
1537 /// Default construct and initialize the pass.
1538 InstrRefBasedLDV();
1539
1540 LLVM_DUMP_METHOD
1541 void dump_mloc_transfer(const MLocTransferMap &mloc_transfer) const;
1542
isCalleeSaved(LocIdx L)1543 bool isCalleeSaved(LocIdx L) {
1544 unsigned Reg = MTracker->LocIdxToLocID[L];
1545 for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI)
1546 if (CalleeSavedRegs.test(*RAI))
1547 return true;
1548 return false;
1549 }
1550 };
1551
1552 } // end anonymous namespace
1553
1554 //===----------------------------------------------------------------------===//
1555 // Implementation
1556 //===----------------------------------------------------------------------===//
1557
1558 ValueIDNum ValueIDNum::EmptyValue = {UINT_MAX, UINT_MAX, UINT_MAX};
1559
1560 /// Default construct and initialize the pass.
InstrRefBasedLDV()1561 InstrRefBasedLDV::InstrRefBasedLDV() {}
1562
1563 //===----------------------------------------------------------------------===//
1564 // Debug Range Extension Implementation
1565 //===----------------------------------------------------------------------===//
1566
1567 #ifndef NDEBUG
1568 // Something to restore in the future.
1569 // void InstrRefBasedLDV::printVarLocInMBB(..)
1570 #endif
1571
1572 SpillLoc
extractSpillBaseRegAndOffset(const MachineInstr & MI)1573 InstrRefBasedLDV::extractSpillBaseRegAndOffset(const MachineInstr &MI) {
1574 assert(MI.hasOneMemOperand() &&
1575 "Spill instruction does not have exactly one memory operand?");
1576 auto MMOI = MI.memoperands_begin();
1577 const PseudoSourceValue *PVal = (*MMOI)->getPseudoValue();
1578 assert(PVal->kind() == PseudoSourceValue::FixedStack &&
1579 "Inconsistent memory operand in spill instruction");
1580 int FI = cast<FixedStackPseudoSourceValue>(PVal)->getFrameIndex();
1581 const MachineBasicBlock *MBB = MI.getParent();
1582 Register Reg;
1583 StackOffset Offset = TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg);
1584 return {Reg, Offset};
1585 }
1586
1587 /// End all previous ranges related to @MI and start a new range from @MI
1588 /// if it is a DBG_VALUE instr.
transferDebugValue(const MachineInstr & MI)1589 bool InstrRefBasedLDV::transferDebugValue(const MachineInstr &MI) {
1590 if (!MI.isDebugValue())
1591 return false;
1592
1593 const DILocalVariable *Var = MI.getDebugVariable();
1594 const DIExpression *Expr = MI.getDebugExpression();
1595 const DILocation *DebugLoc = MI.getDebugLoc();
1596 const DILocation *InlinedAt = DebugLoc->getInlinedAt();
1597 assert(Var->isValidLocationForIntrinsic(DebugLoc) &&
1598 "Expected inlined-at fields to agree");
1599
1600 DebugVariable V(Var, Expr, InlinedAt);
1601 DbgValueProperties Properties(MI);
1602
1603 // If there are no instructions in this lexical scope, do no location tracking
1604 // at all, this variable shouldn't get a legitimate location range.
1605 auto *Scope = LS.findLexicalScope(MI.getDebugLoc().get());
1606 if (Scope == nullptr)
1607 return true; // handled it; by doing nothing
1608
1609 const MachineOperand &MO = MI.getOperand(0);
1610
1611 // MLocTracker needs to know that this register is read, even if it's only
1612 // read by a debug inst.
1613 if (MO.isReg() && MO.getReg() != 0)
1614 (void)MTracker->readReg(MO.getReg());
1615
1616 // If we're preparing for the second analysis (variables), the machine value
1617 // locations are already solved, and we report this DBG_VALUE and the value
1618 // it refers to to VLocTracker.
1619 if (VTracker) {
1620 if (MO.isReg()) {
1621 // Feed defVar the new variable location, or if this is a
1622 // DBG_VALUE $noreg, feed defVar None.
1623 if (MO.getReg())
1624 VTracker->defVar(MI, Properties, MTracker->readReg(MO.getReg()));
1625 else
1626 VTracker->defVar(MI, Properties, None);
1627 } else if (MI.getOperand(0).isImm() || MI.getOperand(0).isFPImm() ||
1628 MI.getOperand(0).isCImm()) {
1629 VTracker->defVar(MI, MI.getOperand(0));
1630 }
1631 }
1632
1633 // If performing final tracking of transfers, report this variable definition
1634 // to the TransferTracker too.
1635 if (TTracker)
1636 TTracker->redefVar(MI);
1637 return true;
1638 }
1639
transferDebugInstrRef(MachineInstr & MI)1640 bool InstrRefBasedLDV::transferDebugInstrRef(MachineInstr &MI) {
1641 if (!MI.isDebugRef())
1642 return false;
1643
1644 // Only handle this instruction when we are building the variable value
1645 // transfer function.
1646 if (!VTracker)
1647 return false;
1648
1649 unsigned InstNo = MI.getOperand(0).getImm();
1650 unsigned OpNo = MI.getOperand(1).getImm();
1651
1652 const DILocalVariable *Var = MI.getDebugVariable();
1653 const DIExpression *Expr = MI.getDebugExpression();
1654 const DILocation *DebugLoc = MI.getDebugLoc();
1655 const DILocation *InlinedAt = DebugLoc->getInlinedAt();
1656 assert(Var->isValidLocationForIntrinsic(DebugLoc) &&
1657 "Expected inlined-at fields to agree");
1658
1659 DebugVariable V(Var, Expr, InlinedAt);
1660
1661 auto *Scope = LS.findLexicalScope(MI.getDebugLoc().get());
1662 if (Scope == nullptr)
1663 return true; // Handled by doing nothing. This variable is never in scope.
1664
1665 const MachineFunction &MF = *MI.getParent()->getParent();
1666
1667 // Various optimizations may have happened to the value during codegen,
1668 // recorded in the value substitution table. Apply any substitutions to
1669 // the instruction / operand number in this DBG_INSTR_REF.
1670 auto Sub = MF.DebugValueSubstitutions.find(std::make_pair(InstNo, OpNo));
1671 while (Sub != MF.DebugValueSubstitutions.end()) {
1672 InstNo = Sub->second.first;
1673 OpNo = Sub->second.second;
1674 Sub = MF.DebugValueSubstitutions.find(std::make_pair(InstNo, OpNo));
1675 }
1676
1677 // Default machine value number is <None> -- if no instruction defines
1678 // the corresponding value, it must have been optimized out.
1679 Optional<ValueIDNum> NewID = None;
1680
1681 // Try to lookup the instruction number, and find the machine value number
1682 // that it defines.
1683 auto InstrIt = DebugInstrNumToInstr.find(InstNo);
1684 if (InstrIt != DebugInstrNumToInstr.end()) {
1685 const MachineInstr &TargetInstr = *InstrIt->second.first;
1686 uint64_t BlockNo = TargetInstr.getParent()->getNumber();
1687
1688 // Pick out the designated operand.
1689 assert(OpNo < TargetInstr.getNumOperands());
1690 const MachineOperand &MO = TargetInstr.getOperand(OpNo);
1691
1692 // Today, this can only be a register.
1693 assert(MO.isReg() && MO.isDef());
1694
1695 unsigned LocID = MTracker->getLocID(MO.getReg(), false);
1696 LocIdx L = MTracker->LocIDToLocIdx[LocID];
1697 NewID = ValueIDNum(BlockNo, InstrIt->second.second, L);
1698 }
1699
1700 // We, we have a value number or None. Tell the variable value tracker about
1701 // it. The rest of this LiveDebugValues implementation acts exactly the same
1702 // for DBG_INSTR_REFs as DBG_VALUEs (just, the former can refer to values that
1703 // aren't immediately available).
1704 DbgValueProperties Properties(Expr, false);
1705 VTracker->defVar(MI, Properties, NewID);
1706
1707 // If we're on the final pass through the function, decompose this INSTR_REF
1708 // into a plain DBG_VALUE.
1709 if (!TTracker)
1710 return true;
1711
1712 // Pick a location for the machine value number, if such a location exists.
1713 // (This information could be stored in TransferTracker to make it faster).
1714 Optional<LocIdx> FoundLoc = None;
1715 for (auto Location : MTracker->locations()) {
1716 LocIdx CurL = Location.Idx;
1717 ValueIDNum ID = MTracker->LocIdxToIDNum[CurL];
1718 if (NewID && ID == NewID) {
1719 // If this is the first location with that value, pick it. Otherwise,
1720 // consider whether it's a "longer term" location.
1721 if (!FoundLoc) {
1722 FoundLoc = CurL;
1723 continue;
1724 }
1725
1726 if (MTracker->isSpill(CurL))
1727 FoundLoc = CurL; // Spills are a longer term location.
1728 else if (!MTracker->isSpill(*FoundLoc) &&
1729 !MTracker->isSpill(CurL) &&
1730 !isCalleeSaved(*FoundLoc) &&
1731 isCalleeSaved(CurL))
1732 FoundLoc = CurL; // Callee saved regs are longer term than normal.
1733 }
1734 }
1735
1736 // Tell transfer tracker that the variable value has changed.
1737 TTracker->redefVar(MI, Properties, FoundLoc);
1738
1739 // If there was a value with no location; but the value is defined in a
1740 // later instruction in this block, this is a block-local use-before-def.
1741 if (!FoundLoc && NewID && NewID->getBlock() == CurBB &&
1742 NewID->getInst() > CurInst)
1743 TTracker->addUseBeforeDef(V, {MI.getDebugExpression(), false}, *NewID);
1744
1745 // Produce a DBG_VALUE representing what this DBG_INSTR_REF meant.
1746 // This DBG_VALUE is potentially a $noreg / undefined location, if
1747 // FoundLoc is None.
1748 // (XXX -- could morph the DBG_INSTR_REF in the future).
1749 MachineInstr *DbgMI = MTracker->emitLoc(FoundLoc, V, Properties);
1750 TTracker->PendingDbgValues.push_back(DbgMI);
1751 TTracker->flushDbgValues(MI.getIterator(), nullptr);
1752
1753 return true;
1754 }
1755
transferRegisterDef(MachineInstr & MI)1756 void InstrRefBasedLDV::transferRegisterDef(MachineInstr &MI) {
1757 // Meta Instructions do not affect the debug liveness of any register they
1758 // define.
1759 if (MI.isImplicitDef()) {
1760 // Except when there's an implicit def, and the location it's defining has
1761 // no value number. The whole point of an implicit def is to announce that
1762 // the register is live, without be specific about it's value. So define
1763 // a value if there isn't one already.
1764 ValueIDNum Num = MTracker->readReg(MI.getOperand(0).getReg());
1765 // Has a legitimate value -> ignore the implicit def.
1766 if (Num.getLoc() != 0)
1767 return;
1768 // Otherwise, def it here.
1769 } else if (MI.isMetaInstruction())
1770 return;
1771
1772 MachineFunction *MF = MI.getMF();
1773 const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
1774 Register SP = TLI->getStackPointerRegisterToSaveRestore();
1775
1776 // Find the regs killed by MI, and find regmasks of preserved regs.
1777 // Max out the number of statically allocated elements in `DeadRegs`, as this
1778 // prevents fallback to std::set::count() operations.
1779 SmallSet<uint32_t, 32> DeadRegs;
1780 SmallVector<const uint32_t *, 4> RegMasks;
1781 SmallVector<const MachineOperand *, 4> RegMaskPtrs;
1782 for (const MachineOperand &MO : MI.operands()) {
1783 // Determine whether the operand is a register def.
1784 if (MO.isReg() && MO.isDef() && MO.getReg() &&
1785 Register::isPhysicalRegister(MO.getReg()) &&
1786 !(MI.isCall() && MO.getReg() == SP)) {
1787 // Remove ranges of all aliased registers.
1788 for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI)
1789 // FIXME: Can we break out of this loop early if no insertion occurs?
1790 DeadRegs.insert(*RAI);
1791 } else if (MO.isRegMask()) {
1792 RegMasks.push_back(MO.getRegMask());
1793 RegMaskPtrs.push_back(&MO);
1794 }
1795 }
1796
1797 // Tell MLocTracker about all definitions, of regmasks and otherwise.
1798 for (uint32_t DeadReg : DeadRegs)
1799 MTracker->defReg(DeadReg, CurBB, CurInst);
1800
1801 for (auto *MO : RegMaskPtrs)
1802 MTracker->writeRegMask(MO, CurBB, CurInst);
1803 }
1804
performCopy(Register SrcRegNum,Register DstRegNum)1805 void InstrRefBasedLDV::performCopy(Register SrcRegNum, Register DstRegNum) {
1806 ValueIDNum SrcValue = MTracker->readReg(SrcRegNum);
1807
1808 MTracker->setReg(DstRegNum, SrcValue);
1809
1810 // In all circumstances, re-def the super registers. It's definitely a new
1811 // value now. This doesn't uniquely identify the composition of subregs, for
1812 // example, two identical values in subregisters composed in different
1813 // places would not get equal value numbers.
1814 for (MCSuperRegIterator SRI(DstRegNum, TRI); SRI.isValid(); ++SRI)
1815 MTracker->defReg(*SRI, CurBB, CurInst);
1816
1817 // If we're emulating VarLocBasedImpl, just define all the subregisters.
1818 // DBG_VALUEs of them will expect to be tracked from the DBG_VALUE, not
1819 // through prior copies.
1820 if (EmulateOldLDV) {
1821 for (MCSubRegIndexIterator DRI(DstRegNum, TRI); DRI.isValid(); ++DRI)
1822 MTracker->defReg(DRI.getSubReg(), CurBB, CurInst);
1823 return;
1824 }
1825
1826 // Otherwise, actually copy subregisters from one location to another.
1827 // XXX: in addition, any subregisters of DstRegNum that don't line up with
1828 // the source register should be def'd.
1829 for (MCSubRegIndexIterator SRI(SrcRegNum, TRI); SRI.isValid(); ++SRI) {
1830 unsigned SrcSubReg = SRI.getSubReg();
1831 unsigned SubRegIdx = SRI.getSubRegIndex();
1832 unsigned DstSubReg = TRI->getSubReg(DstRegNum, SubRegIdx);
1833 if (!DstSubReg)
1834 continue;
1835
1836 // Do copy. There are two matching subregisters, the source value should
1837 // have been def'd when the super-reg was, the latter might not be tracked
1838 // yet.
1839 // This will force SrcSubReg to be tracked, if it isn't yet.
1840 (void)MTracker->readReg(SrcSubReg);
1841 LocIdx SrcL = MTracker->getRegMLoc(SrcSubReg);
1842 assert(SrcL.asU64());
1843 (void)MTracker->readReg(DstSubReg);
1844 LocIdx DstL = MTracker->getRegMLoc(DstSubReg);
1845 assert(DstL.asU64());
1846 (void)DstL;
1847 ValueIDNum CpyValue = {SrcValue.getBlock(), SrcValue.getInst(), SrcL};
1848
1849 MTracker->setReg(DstSubReg, CpyValue);
1850 }
1851 }
1852
isSpillInstruction(const MachineInstr & MI,MachineFunction * MF)1853 bool InstrRefBasedLDV::isSpillInstruction(const MachineInstr &MI,
1854 MachineFunction *MF) {
1855 // TODO: Handle multiple stores folded into one.
1856 if (!MI.hasOneMemOperand())
1857 return false;
1858
1859 if (!MI.getSpillSize(TII) && !MI.getFoldedSpillSize(TII))
1860 return false; // This is not a spill instruction, since no valid size was
1861 // returned from either function.
1862
1863 return true;
1864 }
1865
isLocationSpill(const MachineInstr & MI,MachineFunction * MF,unsigned & Reg)1866 bool InstrRefBasedLDV::isLocationSpill(const MachineInstr &MI,
1867 MachineFunction *MF, unsigned &Reg) {
1868 if (!isSpillInstruction(MI, MF))
1869 return false;
1870
1871 // XXX FIXME: On x86, isStoreToStackSlotPostFE returns '1' instead of an
1872 // actual register number.
1873 if (ObserveAllStackops) {
1874 int FI;
1875 Reg = TII->isStoreToStackSlotPostFE(MI, FI);
1876 return Reg != 0;
1877 }
1878
1879 auto isKilledReg = [&](const MachineOperand MO, unsigned &Reg) {
1880 if (!MO.isReg() || !MO.isUse()) {
1881 Reg = 0;
1882 return false;
1883 }
1884 Reg = MO.getReg();
1885 return MO.isKill();
1886 };
1887
1888 for (const MachineOperand &MO : MI.operands()) {
1889 // In a spill instruction generated by the InlineSpiller the spilled
1890 // register has its kill flag set.
1891 if (isKilledReg(MO, Reg))
1892 return true;
1893 if (Reg != 0) {
1894 // Check whether next instruction kills the spilled register.
1895 // FIXME: Current solution does not cover search for killed register in
1896 // bundles and instructions further down the chain.
1897 auto NextI = std::next(MI.getIterator());
1898 // Skip next instruction that points to basic block end iterator.
1899 if (MI.getParent()->end() == NextI)
1900 continue;
1901 unsigned RegNext;
1902 for (const MachineOperand &MONext : NextI->operands()) {
1903 // Return true if we came across the register from the
1904 // previous spill instruction that is killed in NextI.
1905 if (isKilledReg(MONext, RegNext) && RegNext == Reg)
1906 return true;
1907 }
1908 }
1909 }
1910 // Return false if we didn't find spilled register.
1911 return false;
1912 }
1913
1914 Optional<SpillLoc>
isRestoreInstruction(const MachineInstr & MI,MachineFunction * MF,unsigned & Reg)1915 InstrRefBasedLDV::isRestoreInstruction(const MachineInstr &MI,
1916 MachineFunction *MF, unsigned &Reg) {
1917 if (!MI.hasOneMemOperand())
1918 return None;
1919
1920 // FIXME: Handle folded restore instructions with more than one memory
1921 // operand.
1922 if (MI.getRestoreSize(TII)) {
1923 Reg = MI.getOperand(0).getReg();
1924 return extractSpillBaseRegAndOffset(MI);
1925 }
1926 return None;
1927 }
1928
transferSpillOrRestoreInst(MachineInstr & MI)1929 bool InstrRefBasedLDV::transferSpillOrRestoreInst(MachineInstr &MI) {
1930 // XXX -- it's too difficult to implement VarLocBasedImpl's stack location
1931 // limitations under the new model. Therefore, when comparing them, compare
1932 // versions that don't attempt spills or restores at all.
1933 if (EmulateOldLDV)
1934 return false;
1935
1936 MachineFunction *MF = MI.getMF();
1937 unsigned Reg;
1938 Optional<SpillLoc> Loc;
1939
1940 LLVM_DEBUG(dbgs() << "Examining instruction: "; MI.dump(););
1941
1942 // First, if there are any DBG_VALUEs pointing at a spill slot that is
1943 // written to, terminate that variable location. The value in memory
1944 // will have changed. DbgEntityHistoryCalculator doesn't try to detect this.
1945 if (isSpillInstruction(MI, MF)) {
1946 Loc = extractSpillBaseRegAndOffset(MI);
1947
1948 if (TTracker) {
1949 Optional<LocIdx> MLoc = MTracker->getSpillMLoc(*Loc);
1950 if (MLoc)
1951 TTracker->clobberMloc(*MLoc, MI.getIterator());
1952 }
1953 }
1954
1955 // Try to recognise spill and restore instructions that may transfer a value.
1956 if (isLocationSpill(MI, MF, Reg)) {
1957 Loc = extractSpillBaseRegAndOffset(MI);
1958 auto ValueID = MTracker->readReg(Reg);
1959
1960 // If the location is empty, produce a phi, signify it's the live-in value.
1961 if (ValueID.getLoc() == 0)
1962 ValueID = {CurBB, 0, MTracker->getRegMLoc(Reg)};
1963
1964 MTracker->setSpill(*Loc, ValueID);
1965 auto OptSpillLocIdx = MTracker->getSpillMLoc(*Loc);
1966 assert(OptSpillLocIdx && "Spill slot set but has no LocIdx?");
1967 LocIdx SpillLocIdx = *OptSpillLocIdx;
1968
1969 // Tell TransferTracker about this spill, produce DBG_VALUEs for it.
1970 if (TTracker)
1971 TTracker->transferMlocs(MTracker->getRegMLoc(Reg), SpillLocIdx,
1972 MI.getIterator());
1973 } else {
1974 if (!(Loc = isRestoreInstruction(MI, MF, Reg)))
1975 return false;
1976
1977 // Is there a value to be restored?
1978 auto OptValueID = MTracker->readSpill(*Loc);
1979 if (OptValueID) {
1980 ValueIDNum ValueID = *OptValueID;
1981 LocIdx SpillLocIdx = *MTracker->getSpillMLoc(*Loc);
1982 // XXX -- can we recover sub-registers of this value? Until we can, first
1983 // overwrite all defs of the register being restored to.
1984 for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI)
1985 MTracker->defReg(*RAI, CurBB, CurInst);
1986
1987 // Now override the reg we're restoring to.
1988 MTracker->setReg(Reg, ValueID);
1989
1990 // Report this restore to the transfer tracker too.
1991 if (TTracker)
1992 TTracker->transferMlocs(SpillLocIdx, MTracker->getRegMLoc(Reg),
1993 MI.getIterator());
1994 } else {
1995 // There isn't anything in the location; not clear if this is a code path
1996 // that still runs. Def this register anyway just in case.
1997 for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI)
1998 MTracker->defReg(*RAI, CurBB, CurInst);
1999
2000 // Force the spill slot to be tracked.
2001 LocIdx L = MTracker->getOrTrackSpillLoc(*Loc);
2002
2003 // Set the restored value to be a machine phi number, signifying that it's
2004 // whatever the spills live-in value is in this block. Definitely has
2005 // a LocIdx due to the setSpill above.
2006 ValueIDNum ValueID = {CurBB, 0, L};
2007 MTracker->setReg(Reg, ValueID);
2008 MTracker->setSpill(*Loc, ValueID);
2009 }
2010 }
2011 return true;
2012 }
2013
transferRegisterCopy(MachineInstr & MI)2014 bool InstrRefBasedLDV::transferRegisterCopy(MachineInstr &MI) {
2015 auto DestSrc = TII->isCopyInstr(MI);
2016 if (!DestSrc)
2017 return false;
2018
2019 const MachineOperand *DestRegOp = DestSrc->Destination;
2020 const MachineOperand *SrcRegOp = DestSrc->Source;
2021
2022 auto isCalleeSavedReg = [&](unsigned Reg) {
2023 for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI)
2024 if (CalleeSavedRegs.test(*RAI))
2025 return true;
2026 return false;
2027 };
2028
2029 Register SrcReg = SrcRegOp->getReg();
2030 Register DestReg = DestRegOp->getReg();
2031
2032 // Ignore identity copies. Yep, these make it as far as LiveDebugValues.
2033 if (SrcReg == DestReg)
2034 return true;
2035
2036 // For emulating VarLocBasedImpl:
2037 // We want to recognize instructions where destination register is callee
2038 // saved register. If register that could be clobbered by the call is
2039 // included, there would be a great chance that it is going to be clobbered
2040 // soon. It is more likely that previous register, which is callee saved, is
2041 // going to stay unclobbered longer, even if it is killed.
2042 //
2043 // For InstrRefBasedImpl, we can track multiple locations per value, so
2044 // ignore this condition.
2045 if (EmulateOldLDV && !isCalleeSavedReg(DestReg))
2046 return false;
2047
2048 // InstrRefBasedImpl only followed killing copies.
2049 if (EmulateOldLDV && !SrcRegOp->isKill())
2050 return false;
2051
2052 // Copy MTracker info, including subregs if available.
2053 InstrRefBasedLDV::performCopy(SrcReg, DestReg);
2054
2055 // Only produce a transfer of DBG_VALUE within a block where old LDV
2056 // would have. We might make use of the additional value tracking in some
2057 // other way, later.
2058 if (TTracker && isCalleeSavedReg(DestReg) && SrcRegOp->isKill())
2059 TTracker->transferMlocs(MTracker->getRegMLoc(SrcReg),
2060 MTracker->getRegMLoc(DestReg), MI.getIterator());
2061
2062 // VarLocBasedImpl would quit tracking the old location after copying.
2063 if (EmulateOldLDV && SrcReg != DestReg)
2064 MTracker->defReg(SrcReg, CurBB, CurInst);
2065
2066 return true;
2067 }
2068
2069 /// Accumulate a mapping between each DILocalVariable fragment and other
2070 /// fragments of that DILocalVariable which overlap. This reduces work during
2071 /// the data-flow stage from "Find any overlapping fragments" to "Check if the
2072 /// known-to-overlap fragments are present".
2073 /// \param MI A previously unprocessed DEBUG_VALUE instruction to analyze for
2074 /// fragment usage.
accumulateFragmentMap(MachineInstr & MI)2075 void InstrRefBasedLDV::accumulateFragmentMap(MachineInstr &MI) {
2076 DebugVariable MIVar(MI.getDebugVariable(), MI.getDebugExpression(),
2077 MI.getDebugLoc()->getInlinedAt());
2078 FragmentInfo ThisFragment = MIVar.getFragmentOrDefault();
2079
2080 // If this is the first sighting of this variable, then we are guaranteed
2081 // there are currently no overlapping fragments either. Initialize the set
2082 // of seen fragments, record no overlaps for the current one, and return.
2083 auto SeenIt = SeenFragments.find(MIVar.getVariable());
2084 if (SeenIt == SeenFragments.end()) {
2085 SmallSet<FragmentInfo, 4> OneFragment;
2086 OneFragment.insert(ThisFragment);
2087 SeenFragments.insert({MIVar.getVariable(), OneFragment});
2088
2089 OverlapFragments.insert({{MIVar.getVariable(), ThisFragment}, {}});
2090 return;
2091 }
2092
2093 // If this particular Variable/Fragment pair already exists in the overlap
2094 // map, it has already been accounted for.
2095 auto IsInOLapMap =
2096 OverlapFragments.insert({{MIVar.getVariable(), ThisFragment}, {}});
2097 if (!IsInOLapMap.second)
2098 return;
2099
2100 auto &ThisFragmentsOverlaps = IsInOLapMap.first->second;
2101 auto &AllSeenFragments = SeenIt->second;
2102
2103 // Otherwise, examine all other seen fragments for this variable, with "this"
2104 // fragment being a previously unseen fragment. Record any pair of
2105 // overlapping fragments.
2106 for (auto &ASeenFragment : AllSeenFragments) {
2107 // Does this previously seen fragment overlap?
2108 if (DIExpression::fragmentsOverlap(ThisFragment, ASeenFragment)) {
2109 // Yes: Mark the current fragment as being overlapped.
2110 ThisFragmentsOverlaps.push_back(ASeenFragment);
2111 // Mark the previously seen fragment as being overlapped by the current
2112 // one.
2113 auto ASeenFragmentsOverlaps =
2114 OverlapFragments.find({MIVar.getVariable(), ASeenFragment});
2115 assert(ASeenFragmentsOverlaps != OverlapFragments.end() &&
2116 "Previously seen var fragment has no vector of overlaps");
2117 ASeenFragmentsOverlaps->second.push_back(ThisFragment);
2118 }
2119 }
2120
2121 AllSeenFragments.insert(ThisFragment);
2122 }
2123
process(MachineInstr & MI)2124 void InstrRefBasedLDV::process(MachineInstr &MI) {
2125 // Try to interpret an MI as a debug or transfer instruction. Only if it's
2126 // none of these should we interpret it's register defs as new value
2127 // definitions.
2128 if (transferDebugValue(MI))
2129 return;
2130 if (transferDebugInstrRef(MI))
2131 return;
2132 if (transferRegisterCopy(MI))
2133 return;
2134 if (transferSpillOrRestoreInst(MI))
2135 return;
2136 transferRegisterDef(MI);
2137 }
2138
produceMLocTransferFunction(MachineFunction & MF,SmallVectorImpl<MLocTransferMap> & MLocTransfer,unsigned MaxNumBlocks)2139 void InstrRefBasedLDV::produceMLocTransferFunction(
2140 MachineFunction &MF, SmallVectorImpl<MLocTransferMap> &MLocTransfer,
2141 unsigned MaxNumBlocks) {
2142 // Because we try to optimize around register mask operands by ignoring regs
2143 // that aren't currently tracked, we set up something ugly for later: RegMask
2144 // operands that are seen earlier than the first use of a register, still need
2145 // to clobber that register in the transfer function. But this information
2146 // isn't actively recorded. Instead, we track each RegMask used in each block,
2147 // and accumulated the clobbered but untracked registers in each block into
2148 // the following bitvector. Later, if new values are tracked, we can add
2149 // appropriate clobbers.
2150 SmallVector<BitVector, 32> BlockMasks;
2151 BlockMasks.resize(MaxNumBlocks);
2152
2153 // Reserve one bit per register for the masks described above.
2154 unsigned BVWords = MachineOperand::getRegMaskSize(TRI->getNumRegs());
2155 for (auto &BV : BlockMasks)
2156 BV.resize(TRI->getNumRegs(), true);
2157
2158 // Step through all instructions and inhale the transfer function.
2159 for (auto &MBB : MF) {
2160 // Object fields that are read by trackers to know where we are in the
2161 // function.
2162 CurBB = MBB.getNumber();
2163 CurInst = 1;
2164
2165 // Set all machine locations to a PHI value. For transfer function
2166 // production only, this signifies the live-in value to the block.
2167 MTracker->reset();
2168 MTracker->setMPhis(CurBB);
2169
2170 // Step through each instruction in this block.
2171 for (auto &MI : MBB) {
2172 process(MI);
2173 // Also accumulate fragment map.
2174 if (MI.isDebugValue())
2175 accumulateFragmentMap(MI);
2176
2177 // Create a map from the instruction number (if present) to the
2178 // MachineInstr and its position.
2179 if (uint64_t InstrNo = MI.peekDebugInstrNum()) {
2180 auto InstrAndPos = std::make_pair(&MI, CurInst);
2181 auto InsertResult =
2182 DebugInstrNumToInstr.insert(std::make_pair(InstrNo, InstrAndPos));
2183
2184 // There should never be duplicate instruction numbers.
2185 assert(InsertResult.second);
2186 (void)InsertResult;
2187 }
2188
2189 ++CurInst;
2190 }
2191
2192 // Produce the transfer function, a map of machine location to new value. If
2193 // any machine location has the live-in phi value from the start of the
2194 // block, it's live-through and doesn't need recording in the transfer
2195 // function.
2196 for (auto Location : MTracker->locations()) {
2197 LocIdx Idx = Location.Idx;
2198 ValueIDNum &P = Location.Value;
2199 if (P.isPHI() && P.getLoc() == Idx.asU64())
2200 continue;
2201
2202 // Insert-or-update.
2203 auto &TransferMap = MLocTransfer[CurBB];
2204 auto Result = TransferMap.insert(std::make_pair(Idx.asU64(), P));
2205 if (!Result.second)
2206 Result.first->second = P;
2207 }
2208
2209 // Accumulate any bitmask operands into the clobberred reg mask for this
2210 // block.
2211 for (auto &P : MTracker->Masks) {
2212 BlockMasks[CurBB].clearBitsNotInMask(P.first->getRegMask(), BVWords);
2213 }
2214 }
2215
2216 // Compute a bitvector of all the registers that are tracked in this block.
2217 const TargetLowering *TLI = MF.getSubtarget().getTargetLowering();
2218 Register SP = TLI->getStackPointerRegisterToSaveRestore();
2219 BitVector UsedRegs(TRI->getNumRegs());
2220 for (auto Location : MTracker->locations()) {
2221 unsigned ID = MTracker->LocIdxToLocID[Location.Idx];
2222 if (ID >= TRI->getNumRegs() || ID == SP)
2223 continue;
2224 UsedRegs.set(ID);
2225 }
2226
2227 // Check that any regmask-clobber of a register that gets tracked, is not
2228 // live-through in the transfer function. It needs to be clobbered at the
2229 // very least.
2230 for (unsigned int I = 0; I < MaxNumBlocks; ++I) {
2231 BitVector &BV = BlockMasks[I];
2232 BV.flip();
2233 BV &= UsedRegs;
2234 // This produces all the bits that we clobber, but also use. Check that
2235 // they're all clobbered or at least set in the designated transfer
2236 // elem.
2237 for (unsigned Bit : BV.set_bits()) {
2238 unsigned ID = MTracker->getLocID(Bit, false);
2239 LocIdx Idx = MTracker->LocIDToLocIdx[ID];
2240 auto &TransferMap = MLocTransfer[I];
2241
2242 // Install a value representing the fact that this location is effectively
2243 // written to in this block. As there's no reserved value, instead use
2244 // a value number that is never generated. Pick the value number for the
2245 // first instruction in the block, def'ing this location, which we know
2246 // this block never used anyway.
2247 ValueIDNum NotGeneratedNum = ValueIDNum(I, 1, Idx);
2248 auto Result =
2249 TransferMap.insert(std::make_pair(Idx.asU64(), NotGeneratedNum));
2250 if (!Result.second) {
2251 ValueIDNum &ValueID = Result.first->second;
2252 if (ValueID.getBlock() == I && ValueID.isPHI())
2253 // It was left as live-through. Set it to clobbered.
2254 ValueID = NotGeneratedNum;
2255 }
2256 }
2257 }
2258 }
2259
2260 std::tuple<bool, bool>
mlocJoin(MachineBasicBlock & MBB,SmallPtrSet<const MachineBasicBlock *,16> & Visited,ValueIDNum ** OutLocs,ValueIDNum * InLocs)2261 InstrRefBasedLDV::mlocJoin(MachineBasicBlock &MBB,
2262 SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
2263 ValueIDNum **OutLocs, ValueIDNum *InLocs) {
2264 LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n");
2265 bool Changed = false;
2266 bool DowngradeOccurred = false;
2267
2268 // Collect predecessors that have been visited. Anything that hasn't been
2269 // visited yet is a backedge on the first iteration, and the meet of it's
2270 // lattice value for all locations will be unaffected.
2271 SmallVector<const MachineBasicBlock *, 8> BlockOrders;
2272 for (auto Pred : MBB.predecessors()) {
2273 if (Visited.count(Pred)) {
2274 BlockOrders.push_back(Pred);
2275 }
2276 }
2277
2278 // Visit predecessors in RPOT order.
2279 auto Cmp = [&](const MachineBasicBlock *A, const MachineBasicBlock *B) {
2280 return BBToOrder.find(A)->second < BBToOrder.find(B)->second;
2281 };
2282 llvm::sort(BlockOrders, Cmp);
2283
2284 // Skip entry block.
2285 if (BlockOrders.size() == 0)
2286 return std::tuple<bool, bool>(false, false);
2287
2288 // Step through all machine locations, then look at each predecessor and
2289 // detect disagreements.
2290 unsigned ThisBlockRPO = BBToOrder.find(&MBB)->second;
2291 for (auto Location : MTracker->locations()) {
2292 LocIdx Idx = Location.Idx;
2293 // Pick out the first predecessors live-out value for this location. It's
2294 // guaranteed to be not a backedge, as we order by RPO.
2295 ValueIDNum BaseVal = OutLocs[BlockOrders[0]->getNumber()][Idx.asU64()];
2296
2297 // Some flags for whether there's a disagreement, and whether it's a
2298 // disagreement with a backedge or not.
2299 bool Disagree = false;
2300 bool NonBackEdgeDisagree = false;
2301
2302 // Loop around everything that wasn't 'base'.
2303 for (unsigned int I = 1; I < BlockOrders.size(); ++I) {
2304 auto *MBB = BlockOrders[I];
2305 if (BaseVal != OutLocs[MBB->getNumber()][Idx.asU64()]) {
2306 // Live-out of a predecessor disagrees with the first predecessor.
2307 Disagree = true;
2308
2309 // Test whether it's a disagreemnt in the backedges or not.
2310 if (BBToOrder.find(MBB)->second < ThisBlockRPO) // might be self b/e
2311 NonBackEdgeDisagree = true;
2312 }
2313 }
2314
2315 bool OverRide = false;
2316 if (Disagree && !NonBackEdgeDisagree) {
2317 // Only the backedges disagree. Consider demoting the livein
2318 // lattice value, as per the file level comment. The value we consider
2319 // demoting to is the value that the non-backedge predecessors agree on.
2320 // The order of values is that non-PHIs are \top, a PHI at this block
2321 // \bot, and phis between the two are ordered by their RPO number.
2322 // If there's no agreement, or we've already demoted to this PHI value
2323 // before, replace with a PHI value at this block.
2324
2325 // Calculate order numbers: zero means normal def, nonzero means RPO
2326 // number.
2327 unsigned BaseBlockRPONum = BBNumToRPO[BaseVal.getBlock()] + 1;
2328 if (!BaseVal.isPHI())
2329 BaseBlockRPONum = 0;
2330
2331 ValueIDNum &InLocID = InLocs[Idx.asU64()];
2332 unsigned InLocRPONum = BBNumToRPO[InLocID.getBlock()] + 1;
2333 if (!InLocID.isPHI())
2334 InLocRPONum = 0;
2335
2336 // Should we ignore the disagreeing backedges, and override with the
2337 // value the other predecessors agree on (in "base")?
2338 unsigned ThisBlockRPONum = BBNumToRPO[MBB.getNumber()] + 1;
2339 if (BaseBlockRPONum > InLocRPONum && BaseBlockRPONum < ThisBlockRPONum) {
2340 // Override.
2341 OverRide = true;
2342 DowngradeOccurred = true;
2343 }
2344 }
2345 // else: if we disagree in the non-backedges, then this is definitely
2346 // a control flow merge where different values merge. Make it a PHI.
2347
2348 // Generate a phi...
2349 ValueIDNum PHI = {(uint64_t)MBB.getNumber(), 0, Idx};
2350 ValueIDNum NewVal = (Disagree && !OverRide) ? PHI : BaseVal;
2351 if (InLocs[Idx.asU64()] != NewVal) {
2352 Changed |= true;
2353 InLocs[Idx.asU64()] = NewVal;
2354 }
2355 }
2356
2357 // TODO: Reimplement NumInserted and NumRemoved.
2358 return std::tuple<bool, bool>(Changed, DowngradeOccurred);
2359 }
2360
mlocDataflow(ValueIDNum ** MInLocs,ValueIDNum ** MOutLocs,SmallVectorImpl<MLocTransferMap> & MLocTransfer)2361 void InstrRefBasedLDV::mlocDataflow(
2362 ValueIDNum **MInLocs, ValueIDNum **MOutLocs,
2363 SmallVectorImpl<MLocTransferMap> &MLocTransfer) {
2364 std::priority_queue<unsigned int, std::vector<unsigned int>,
2365 std::greater<unsigned int>>
2366 Worklist, Pending;
2367
2368 // We track what is on the current and pending worklist to avoid inserting
2369 // the same thing twice. We could avoid this with a custom priority queue,
2370 // but this is probably not worth it.
2371 SmallPtrSet<MachineBasicBlock *, 16> OnPending, OnWorklist;
2372
2373 // Initialize worklist with every block to be visited.
2374 for (unsigned int I = 0; I < BBToOrder.size(); ++I) {
2375 Worklist.push(I);
2376 OnWorklist.insert(OrderToBB[I]);
2377 }
2378
2379 MTracker->reset();
2380
2381 // Set inlocs for entry block -- each as a PHI at the entry block. Represents
2382 // the incoming value to the function.
2383 MTracker->setMPhis(0);
2384 for (auto Location : MTracker->locations())
2385 MInLocs[0][Location.Idx.asU64()] = Location.Value;
2386
2387 SmallPtrSet<const MachineBasicBlock *, 16> Visited;
2388 while (!Worklist.empty() || !Pending.empty()) {
2389 // Vector for storing the evaluated block transfer function.
2390 SmallVector<std::pair<LocIdx, ValueIDNum>, 32> ToRemap;
2391
2392 while (!Worklist.empty()) {
2393 MachineBasicBlock *MBB = OrderToBB[Worklist.top()];
2394 CurBB = MBB->getNumber();
2395 Worklist.pop();
2396
2397 // Join the values in all predecessor blocks.
2398 bool InLocsChanged, DowngradeOccurred;
2399 std::tie(InLocsChanged, DowngradeOccurred) =
2400 mlocJoin(*MBB, Visited, MOutLocs, MInLocs[CurBB]);
2401 InLocsChanged |= Visited.insert(MBB).second;
2402
2403 // If a downgrade occurred, book us in for re-examination on the next
2404 // iteration.
2405 if (DowngradeOccurred && OnPending.insert(MBB).second)
2406 Pending.push(BBToOrder[MBB]);
2407
2408 // Don't examine transfer function if we've visited this loc at least
2409 // once, and inlocs haven't changed.
2410 if (!InLocsChanged)
2411 continue;
2412
2413 // Load the current set of live-ins into MLocTracker.
2414 MTracker->loadFromArray(MInLocs[CurBB], CurBB);
2415
2416 // Each element of the transfer function can be a new def, or a read of
2417 // a live-in value. Evaluate each element, and store to "ToRemap".
2418 ToRemap.clear();
2419 for (auto &P : MLocTransfer[CurBB]) {
2420 if (P.second.getBlock() == CurBB && P.second.isPHI()) {
2421 // This is a movement of whatever was live in. Read it.
2422 ValueIDNum NewID = MTracker->getNumAtPos(P.second.getLoc());
2423 ToRemap.push_back(std::make_pair(P.first, NewID));
2424 } else {
2425 // It's a def. Just set it.
2426 assert(P.second.getBlock() == CurBB);
2427 ToRemap.push_back(std::make_pair(P.first, P.second));
2428 }
2429 }
2430
2431 // Commit the transfer function changes into mloc tracker, which
2432 // transforms the contents of the MLocTracker into the live-outs.
2433 for (auto &P : ToRemap)
2434 MTracker->setMLoc(P.first, P.second);
2435
2436 // Now copy out-locs from mloc tracker into out-loc vector, checking
2437 // whether changes have occurred. These changes can have come from both
2438 // the transfer function, and mlocJoin.
2439 bool OLChanged = false;
2440 for (auto Location : MTracker->locations()) {
2441 OLChanged |= MOutLocs[CurBB][Location.Idx.asU64()] != Location.Value;
2442 MOutLocs[CurBB][Location.Idx.asU64()] = Location.Value;
2443 }
2444
2445 MTracker->reset();
2446
2447 // No need to examine successors again if out-locs didn't change.
2448 if (!OLChanged)
2449 continue;
2450
2451 // All successors should be visited: put any back-edges on the pending
2452 // list for the next dataflow iteration, and any other successors to be
2453 // visited this iteration, if they're not going to be already.
2454 for (auto s : MBB->successors()) {
2455 // Does branching to this successor represent a back-edge?
2456 if (BBToOrder[s] > BBToOrder[MBB]) {
2457 // No: visit it during this dataflow iteration.
2458 if (OnWorklist.insert(s).second)
2459 Worklist.push(BBToOrder[s]);
2460 } else {
2461 // Yes: visit it on the next iteration.
2462 if (OnPending.insert(s).second)
2463 Pending.push(BBToOrder[s]);
2464 }
2465 }
2466 }
2467
2468 Worklist.swap(Pending);
2469 std::swap(OnPending, OnWorklist);
2470 OnPending.clear();
2471 // At this point, pending must be empty, since it was just the empty
2472 // worklist
2473 assert(Pending.empty() && "Pending should be empty");
2474 }
2475
2476 // Once all the live-ins don't change on mlocJoin(), we've reached a
2477 // fixedpoint.
2478 }
2479
vlocDowngradeLattice(const MachineBasicBlock & MBB,const DbgValue & OldLiveInLocation,const SmallVectorImpl<InValueT> & Values,unsigned CurBlockRPONum)2480 bool InstrRefBasedLDV::vlocDowngradeLattice(
2481 const MachineBasicBlock &MBB, const DbgValue &OldLiveInLocation,
2482 const SmallVectorImpl<InValueT> &Values, unsigned CurBlockRPONum) {
2483 // Ranking value preference: see file level comment, the highest rank is
2484 // a plain def, followed by PHI values in reverse post-order. Numerically,
2485 // we assign all defs the rank '0', all PHIs their blocks RPO number plus
2486 // one, and consider the lowest value the highest ranked.
2487 int OldLiveInRank = BBNumToRPO[OldLiveInLocation.ID.getBlock()] + 1;
2488 if (!OldLiveInLocation.ID.isPHI())
2489 OldLiveInRank = 0;
2490
2491 // Allow any unresolvable conflict to be over-ridden.
2492 if (OldLiveInLocation.Kind == DbgValue::NoVal) {
2493 // Although if it was an unresolvable conflict from _this_ block, then
2494 // all other seeking of downgrades and PHIs must have failed before hand.
2495 if (OldLiveInLocation.BlockNo == (unsigned)MBB.getNumber())
2496 return false;
2497 OldLiveInRank = INT_MIN;
2498 }
2499
2500 auto &InValue = *Values[0].second;
2501
2502 if (InValue.Kind == DbgValue::Const || InValue.Kind == DbgValue::NoVal)
2503 return false;
2504
2505 unsigned ThisRPO = BBNumToRPO[InValue.ID.getBlock()];
2506 int ThisRank = ThisRPO + 1;
2507 if (!InValue.ID.isPHI())
2508 ThisRank = 0;
2509
2510 // Too far down the lattice?
2511 if (ThisRPO >= CurBlockRPONum)
2512 return false;
2513
2514 // Higher in the lattice than what we've already explored?
2515 if (ThisRank <= OldLiveInRank)
2516 return false;
2517
2518 return true;
2519 }
2520
pickVPHILoc(MachineBasicBlock & MBB,const DebugVariable & Var,const LiveIdxT & LiveOuts,ValueIDNum ** MOutLocs,ValueIDNum ** MInLocs,const SmallVectorImpl<MachineBasicBlock * > & BlockOrders)2521 std::tuple<Optional<ValueIDNum>, bool> InstrRefBasedLDV::pickVPHILoc(
2522 MachineBasicBlock &MBB, const DebugVariable &Var, const LiveIdxT &LiveOuts,
2523 ValueIDNum **MOutLocs, ValueIDNum **MInLocs,
2524 const SmallVectorImpl<MachineBasicBlock *> &BlockOrders) {
2525 // Collect a set of locations from predecessor where its live-out value can
2526 // be found.
2527 SmallVector<SmallVector<LocIdx, 4>, 8> Locs;
2528 unsigned NumLocs = MTracker->getNumLocs();
2529 unsigned BackEdgesStart = 0;
2530
2531 for (auto p : BlockOrders) {
2532 // Pick out where backedges start in the list of predecessors. Relies on
2533 // BlockOrders being sorted by RPO.
2534 if (BBToOrder[p] < BBToOrder[&MBB])
2535 ++BackEdgesStart;
2536
2537 // For each predecessor, create a new set of locations.
2538 Locs.resize(Locs.size() + 1);
2539 unsigned ThisBBNum = p->getNumber();
2540 auto LiveOutMap = LiveOuts.find(p);
2541 if (LiveOutMap == LiveOuts.end())
2542 // This predecessor isn't in scope, it must have no live-in/live-out
2543 // locations.
2544 continue;
2545
2546 auto It = LiveOutMap->second->find(Var);
2547 if (It == LiveOutMap->second->end())
2548 // There's no value recorded for this variable in this predecessor,
2549 // leave an empty set of locations.
2550 continue;
2551
2552 const DbgValue &OutVal = It->second;
2553
2554 if (OutVal.Kind == DbgValue::Const || OutVal.Kind == DbgValue::NoVal)
2555 // Consts and no-values cannot have locations we can join on.
2556 continue;
2557
2558 assert(OutVal.Kind == DbgValue::Proposed || OutVal.Kind == DbgValue::Def);
2559 ValueIDNum ValToLookFor = OutVal.ID;
2560
2561 // Search the live-outs of the predecessor for the specified value.
2562 for (unsigned int I = 0; I < NumLocs; ++I) {
2563 if (MOutLocs[ThisBBNum][I] == ValToLookFor)
2564 Locs.back().push_back(LocIdx(I));
2565 }
2566 }
2567
2568 // If there were no locations at all, return an empty result.
2569 if (Locs.empty())
2570 return std::tuple<Optional<ValueIDNum>, bool>(None, false);
2571
2572 // Lambda for seeking a common location within a range of location-sets.
2573 using LocsIt = SmallVector<SmallVector<LocIdx, 4>, 8>::iterator;
2574 auto SeekLocation =
2575 [&Locs](llvm::iterator_range<LocsIt> SearchRange) -> Optional<LocIdx> {
2576 // Starting with the first set of locations, take the intersection with
2577 // subsequent sets.
2578 SmallVector<LocIdx, 4> base = Locs[0];
2579 for (auto &S : SearchRange) {
2580 SmallVector<LocIdx, 4> new_base;
2581 std::set_intersection(base.begin(), base.end(), S.begin(), S.end(),
2582 std::inserter(new_base, new_base.begin()));
2583 base = new_base;
2584 }
2585 if (base.empty())
2586 return None;
2587
2588 // We now have a set of LocIdxes that contain the right output value in
2589 // each of the predecessors. Pick the lowest; if there's a register loc,
2590 // that'll be it.
2591 return *base.begin();
2592 };
2593
2594 // Search for a common location for all predecessors. If we can't, then fall
2595 // back to only finding a common location between non-backedge predecessors.
2596 bool ValidForAllLocs = true;
2597 auto TheLoc = SeekLocation(Locs);
2598 if (!TheLoc) {
2599 ValidForAllLocs = false;
2600 TheLoc =
2601 SeekLocation(make_range(Locs.begin(), Locs.begin() + BackEdgesStart));
2602 }
2603
2604 if (!TheLoc)
2605 return std::tuple<Optional<ValueIDNum>, bool>(None, false);
2606
2607 // Return a PHI-value-number for the found location.
2608 LocIdx L = *TheLoc;
2609 ValueIDNum PHIVal = {(unsigned)MBB.getNumber(), 0, L};
2610 return std::tuple<Optional<ValueIDNum>, bool>(PHIVal, ValidForAllLocs);
2611 }
2612
vlocJoin(MachineBasicBlock & MBB,LiveIdxT & VLOCOutLocs,LiveIdxT & VLOCInLocs,SmallPtrSet<const MachineBasicBlock *,16> * VLOCVisited,unsigned BBNum,const SmallSet<DebugVariable,4> & AllVars,ValueIDNum ** MOutLocs,ValueIDNum ** MInLocs,SmallPtrSet<const MachineBasicBlock *,8> & InScopeBlocks,SmallPtrSet<const MachineBasicBlock *,8> & BlocksToExplore,DenseMap<DebugVariable,DbgValue> & InLocsT)2613 std::tuple<bool, bool> InstrRefBasedLDV::vlocJoin(
2614 MachineBasicBlock &MBB, LiveIdxT &VLOCOutLocs, LiveIdxT &VLOCInLocs,
2615 SmallPtrSet<const MachineBasicBlock *, 16> *VLOCVisited, unsigned BBNum,
2616 const SmallSet<DebugVariable, 4> &AllVars, ValueIDNum **MOutLocs,
2617 ValueIDNum **MInLocs,
2618 SmallPtrSet<const MachineBasicBlock *, 8> &InScopeBlocks,
2619 SmallPtrSet<const MachineBasicBlock *, 8> &BlocksToExplore,
2620 DenseMap<DebugVariable, DbgValue> &InLocsT) {
2621 bool DowngradeOccurred = false;
2622
2623 // To emulate VarLocBasedImpl, process this block if it's not in scope but
2624 // _does_ assign a variable value. No live-ins for this scope are transferred
2625 // in though, so we can return immediately.
2626 if (InScopeBlocks.count(&MBB) == 0 && !ArtificialBlocks.count(&MBB)) {
2627 if (VLOCVisited)
2628 return std::tuple<bool, bool>(true, false);
2629 return std::tuple<bool, bool>(false, false);
2630 }
2631
2632 LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n");
2633 bool Changed = false;
2634
2635 // Find any live-ins computed in a prior iteration.
2636 auto ILSIt = VLOCInLocs.find(&MBB);
2637 assert(ILSIt != VLOCInLocs.end());
2638 auto &ILS = *ILSIt->second;
2639
2640 // Order predecessors by RPOT order, for exploring them in that order.
2641 SmallVector<MachineBasicBlock *, 8> BlockOrders(MBB.predecessors());
2642
2643 auto Cmp = [&](MachineBasicBlock *A, MachineBasicBlock *B) {
2644 return BBToOrder[A] < BBToOrder[B];
2645 };
2646
2647 llvm::sort(BlockOrders, Cmp);
2648
2649 unsigned CurBlockRPONum = BBToOrder[&MBB];
2650
2651 // Force a re-visit to loop heads in the first dataflow iteration.
2652 // FIXME: if we could "propose" Const values this wouldn't be needed,
2653 // because they'd need to be confirmed before being emitted.
2654 if (!BlockOrders.empty() &&
2655 BBToOrder[BlockOrders[BlockOrders.size() - 1]] >= CurBlockRPONum &&
2656 VLOCVisited)
2657 DowngradeOccurred = true;
2658
2659 auto ConfirmValue = [&InLocsT](const DebugVariable &DV, DbgValue VR) {
2660 auto Result = InLocsT.insert(std::make_pair(DV, VR));
2661 (void)Result;
2662 assert(Result.second);
2663 };
2664
2665 auto ConfirmNoVal = [&ConfirmValue, &MBB](const DebugVariable &Var, const DbgValueProperties &Properties) {
2666 DbgValue NoLocPHIVal(MBB.getNumber(), Properties, DbgValue::NoVal);
2667
2668 ConfirmValue(Var, NoLocPHIVal);
2669 };
2670
2671 // Attempt to join the values for each variable.
2672 for (auto &Var : AllVars) {
2673 // Collect all the DbgValues for this variable.
2674 SmallVector<InValueT, 8> Values;
2675 bool Bail = false;
2676 unsigned BackEdgesStart = 0;
2677 for (auto p : BlockOrders) {
2678 // If the predecessor isn't in scope / to be explored, we'll never be
2679 // able to join any locations.
2680 if (!BlocksToExplore.contains(p)) {
2681 Bail = true;
2682 break;
2683 }
2684
2685 // Don't attempt to handle unvisited predecessors: they're implicitly
2686 // "unknown"s in the lattice.
2687 if (VLOCVisited && !VLOCVisited->count(p))
2688 continue;
2689
2690 // If the predecessors OutLocs is absent, there's not much we can do.
2691 auto OL = VLOCOutLocs.find(p);
2692 if (OL == VLOCOutLocs.end()) {
2693 Bail = true;
2694 break;
2695 }
2696
2697 // No live-out value for this predecessor also means we can't produce
2698 // a joined value.
2699 auto VIt = OL->second->find(Var);
2700 if (VIt == OL->second->end()) {
2701 Bail = true;
2702 break;
2703 }
2704
2705 // Keep track of where back-edges begin in the Values vector. Relies on
2706 // BlockOrders being sorted by RPO.
2707 unsigned ThisBBRPONum = BBToOrder[p];
2708 if (ThisBBRPONum < CurBlockRPONum)
2709 ++BackEdgesStart;
2710
2711 Values.push_back(std::make_pair(p, &VIt->second));
2712 }
2713
2714 // If there were no values, or one of the predecessors couldn't have a
2715 // value, then give up immediately. It's not safe to produce a live-in
2716 // value.
2717 if (Bail || Values.size() == 0)
2718 continue;
2719
2720 // Enumeration identifying the current state of the predecessors values.
2721 enum {
2722 Unset = 0,
2723 Agreed, // All preds agree on the variable value.
2724 PropDisagree, // All preds agree, but the value kind is Proposed in some.
2725 BEDisagree, // Only back-edges disagree on variable value.
2726 PHINeeded, // Non-back-edge predecessors have conflicing values.
2727 NoSolution // Conflicting Value metadata makes solution impossible.
2728 } OurState = Unset;
2729
2730 // All (non-entry) blocks have at least one non-backedge predecessor.
2731 // Pick the variable value from the first of these, to compare against
2732 // all others.
2733 const DbgValue &FirstVal = *Values[0].second;
2734 const ValueIDNum &FirstID = FirstVal.ID;
2735
2736 // Scan for variable values that can't be resolved: if they have different
2737 // DIExpressions, different indirectness, or are mixed constants /
2738 // non-constants.
2739 for (auto &V : Values) {
2740 if (V.second->Properties != FirstVal.Properties)
2741 OurState = NoSolution;
2742 if (V.second->Kind == DbgValue::Const && FirstVal.Kind != DbgValue::Const)
2743 OurState = NoSolution;
2744 }
2745
2746 // Flags diagnosing _how_ the values disagree.
2747 bool NonBackEdgeDisagree = false;
2748 bool DisagreeOnPHINess = false;
2749 bool IDDisagree = false;
2750 bool Disagree = false;
2751 if (OurState == Unset) {
2752 for (auto &V : Values) {
2753 if (*V.second == FirstVal)
2754 continue; // No disagreement.
2755
2756 Disagree = true;
2757
2758 // Flag whether the value number actually diagrees.
2759 if (V.second->ID != FirstID)
2760 IDDisagree = true;
2761
2762 // Distinguish whether disagreement happens in backedges or not.
2763 // Relies on Values (and BlockOrders) being sorted by RPO.
2764 unsigned ThisBBRPONum = BBToOrder[V.first];
2765 if (ThisBBRPONum < CurBlockRPONum)
2766 NonBackEdgeDisagree = true;
2767
2768 // Is there a difference in whether the value is definite or only
2769 // proposed?
2770 if (V.second->Kind != FirstVal.Kind &&
2771 (V.second->Kind == DbgValue::Proposed ||
2772 V.second->Kind == DbgValue::Def) &&
2773 (FirstVal.Kind == DbgValue::Proposed ||
2774 FirstVal.Kind == DbgValue::Def))
2775 DisagreeOnPHINess = true;
2776 }
2777
2778 // Collect those flags together and determine an overall state for
2779 // what extend the predecessors agree on a live-in value.
2780 if (!Disagree)
2781 OurState = Agreed;
2782 else if (!IDDisagree && DisagreeOnPHINess)
2783 OurState = PropDisagree;
2784 else if (!NonBackEdgeDisagree)
2785 OurState = BEDisagree;
2786 else
2787 OurState = PHINeeded;
2788 }
2789
2790 // An extra indicator: if we only disagree on whether the value is a
2791 // Def, or proposed, then also flag whether that disagreement happens
2792 // in backedges only.
2793 bool PropOnlyInBEs = Disagree && !IDDisagree && DisagreeOnPHINess &&
2794 !NonBackEdgeDisagree && FirstVal.Kind == DbgValue::Def;
2795
2796 const auto &Properties = FirstVal.Properties;
2797
2798 auto OldLiveInIt = ILS.find(Var);
2799 const DbgValue *OldLiveInLocation =
2800 (OldLiveInIt != ILS.end()) ? &OldLiveInIt->second : nullptr;
2801
2802 bool OverRide = false;
2803 if (OurState == BEDisagree && OldLiveInLocation) {
2804 // Only backedges disagree: we can consider downgrading. If there was a
2805 // previous live-in value, use it to work out whether the current
2806 // incoming value represents a lattice downgrade or not.
2807 OverRide =
2808 vlocDowngradeLattice(MBB, *OldLiveInLocation, Values, CurBlockRPONum);
2809 }
2810
2811 // Use the current state of predecessor agreement and other flags to work
2812 // out what to do next. Possibilities include:
2813 // * Accept a value all predecessors agree on, or accept one that
2814 // represents a step down the exploration lattice,
2815 // * Use a PHI value number, if one can be found,
2816 // * Propose a PHI value number, and see if it gets confirmed later,
2817 // * Emit a 'NoVal' value, indicating we couldn't resolve anything.
2818 if (OurState == Agreed) {
2819 // Easiest solution: all predecessors agree on the variable value.
2820 ConfirmValue(Var, FirstVal);
2821 } else if (OurState == BEDisagree && OverRide) {
2822 // Only backedges disagree, and the other predecessors have produced
2823 // a new live-in value further down the exploration lattice.
2824 DowngradeOccurred = true;
2825 ConfirmValue(Var, FirstVal);
2826 } else if (OurState == PropDisagree) {
2827 // Predecessors agree on value, but some say it's only a proposed value.
2828 // Propagate it as proposed: unless it was proposed in this block, in
2829 // which case we're able to confirm the value.
2830 if (FirstID.getBlock() == (uint64_t)MBB.getNumber() && FirstID.isPHI()) {
2831 ConfirmValue(Var, DbgValue(FirstID, Properties, DbgValue::Def));
2832 } else if (PropOnlyInBEs) {
2833 // If only backedges disagree, a higher (in RPO) block confirmed this
2834 // location, and we need to propagate it into this loop.
2835 ConfirmValue(Var, DbgValue(FirstID, Properties, DbgValue::Def));
2836 } else {
2837 // Otherwise; a Def meeting a Proposed is still a Proposed.
2838 ConfirmValue(Var, DbgValue(FirstID, Properties, DbgValue::Proposed));
2839 }
2840 } else if ((OurState == PHINeeded || OurState == BEDisagree)) {
2841 // Predecessors disagree and can't be downgraded: this can only be
2842 // solved with a PHI. Use pickVPHILoc to go look for one.
2843 Optional<ValueIDNum> VPHI;
2844 bool AllEdgesVPHI = false;
2845 std::tie(VPHI, AllEdgesVPHI) =
2846 pickVPHILoc(MBB, Var, VLOCOutLocs, MOutLocs, MInLocs, BlockOrders);
2847
2848 if (VPHI && AllEdgesVPHI) {
2849 // There's a PHI value that's valid for all predecessors -- we can use
2850 // it. If any of the non-backedge predecessors have proposed values
2851 // though, this PHI is also only proposed, until the predecessors are
2852 // confirmed.
2853 DbgValue::KindT K = DbgValue::Def;
2854 for (unsigned int I = 0; I < BackEdgesStart; ++I)
2855 if (Values[I].second->Kind == DbgValue::Proposed)
2856 K = DbgValue::Proposed;
2857
2858 ConfirmValue(Var, DbgValue(*VPHI, Properties, K));
2859 } else if (VPHI) {
2860 // There's a PHI value, but it's only legal for backedges. Leave this
2861 // as a proposed PHI value: it might come back on the backedges,
2862 // and allow us to confirm it in the future.
2863 DbgValue NoBEValue = DbgValue(*VPHI, Properties, DbgValue::Proposed);
2864 ConfirmValue(Var, NoBEValue);
2865 } else {
2866 ConfirmNoVal(Var, Properties);
2867 }
2868 } else {
2869 // Otherwise: we don't know. Emit a "phi but no real loc" phi.
2870 ConfirmNoVal(Var, Properties);
2871 }
2872 }
2873
2874 // Store newly calculated in-locs into VLOCInLocs, if they've changed.
2875 Changed = ILS != InLocsT;
2876 if (Changed)
2877 ILS = InLocsT;
2878
2879 return std::tuple<bool, bool>(Changed, DowngradeOccurred);
2880 }
2881
vlocDataflow(const LexicalScope * Scope,const DILocation * DILoc,const SmallSet<DebugVariable,4> & VarsWeCareAbout,SmallPtrSetImpl<MachineBasicBlock * > & AssignBlocks,LiveInsT & Output,ValueIDNum ** MOutLocs,ValueIDNum ** MInLocs,SmallVectorImpl<VLocTracker> & AllTheVLocs)2882 void InstrRefBasedLDV::vlocDataflow(
2883 const LexicalScope *Scope, const DILocation *DILoc,
2884 const SmallSet<DebugVariable, 4> &VarsWeCareAbout,
2885 SmallPtrSetImpl<MachineBasicBlock *> &AssignBlocks, LiveInsT &Output,
2886 ValueIDNum **MOutLocs, ValueIDNum **MInLocs,
2887 SmallVectorImpl<VLocTracker> &AllTheVLocs) {
2888 // This method is much like mlocDataflow: but focuses on a single
2889 // LexicalScope at a time. Pick out a set of blocks and variables that are
2890 // to have their value assignments solved, then run our dataflow algorithm
2891 // until a fixedpoint is reached.
2892 std::priority_queue<unsigned int, std::vector<unsigned int>,
2893 std::greater<unsigned int>>
2894 Worklist, Pending;
2895 SmallPtrSet<MachineBasicBlock *, 16> OnWorklist, OnPending;
2896
2897 // The set of blocks we'll be examining.
2898 SmallPtrSet<const MachineBasicBlock *, 8> BlocksToExplore;
2899
2900 // The order in which to examine them (RPO).
2901 SmallVector<MachineBasicBlock *, 8> BlockOrders;
2902
2903 // RPO ordering function.
2904 auto Cmp = [&](MachineBasicBlock *A, MachineBasicBlock *B) {
2905 return BBToOrder[A] < BBToOrder[B];
2906 };
2907
2908 LS.getMachineBasicBlocks(DILoc, BlocksToExplore);
2909
2910 // A separate container to distinguish "blocks we're exploring" versus
2911 // "blocks that are potentially in scope. See comment at start of vlocJoin.
2912 SmallPtrSet<const MachineBasicBlock *, 8> InScopeBlocks = BlocksToExplore;
2913
2914 // Old LiveDebugValues tracks variable locations that come out of blocks
2915 // not in scope, where DBG_VALUEs occur. This is something we could
2916 // legitimately ignore, but lets allow it for now.
2917 if (EmulateOldLDV)
2918 BlocksToExplore.insert(AssignBlocks.begin(), AssignBlocks.end());
2919
2920 // We also need to propagate variable values through any artificial blocks
2921 // that immediately follow blocks in scope.
2922 DenseSet<const MachineBasicBlock *> ToAdd;
2923
2924 // Helper lambda: For a given block in scope, perform a depth first search
2925 // of all the artificial successors, adding them to the ToAdd collection.
2926 auto AccumulateArtificialBlocks =
2927 [this, &ToAdd, &BlocksToExplore,
2928 &InScopeBlocks](const MachineBasicBlock *MBB) {
2929 // Depth-first-search state: each node is a block and which successor
2930 // we're currently exploring.
2931 SmallVector<std::pair<const MachineBasicBlock *,
2932 MachineBasicBlock::const_succ_iterator>,
2933 8>
2934 DFS;
2935
2936 // Find any artificial successors not already tracked.
2937 for (auto *succ : MBB->successors()) {
2938 if (BlocksToExplore.count(succ) || InScopeBlocks.count(succ))
2939 continue;
2940 if (!ArtificialBlocks.count(succ))
2941 continue;
2942 DFS.push_back(std::make_pair(succ, succ->succ_begin()));
2943 ToAdd.insert(succ);
2944 }
2945
2946 // Search all those blocks, depth first.
2947 while (!DFS.empty()) {
2948 const MachineBasicBlock *CurBB = DFS.back().first;
2949 MachineBasicBlock::const_succ_iterator &CurSucc = DFS.back().second;
2950 // Walk back if we've explored this blocks successors to the end.
2951 if (CurSucc == CurBB->succ_end()) {
2952 DFS.pop_back();
2953 continue;
2954 }
2955
2956 // If the current successor is artificial and unexplored, descend into
2957 // it.
2958 if (!ToAdd.count(*CurSucc) && ArtificialBlocks.count(*CurSucc)) {
2959 DFS.push_back(std::make_pair(*CurSucc, (*CurSucc)->succ_begin()));
2960 ToAdd.insert(*CurSucc);
2961 continue;
2962 }
2963
2964 ++CurSucc;
2965 }
2966 };
2967
2968 // Search in-scope blocks and those containing a DBG_VALUE from this scope
2969 // for artificial successors.
2970 for (auto *MBB : BlocksToExplore)
2971 AccumulateArtificialBlocks(MBB);
2972 for (auto *MBB : InScopeBlocks)
2973 AccumulateArtificialBlocks(MBB);
2974
2975 BlocksToExplore.insert(ToAdd.begin(), ToAdd.end());
2976 InScopeBlocks.insert(ToAdd.begin(), ToAdd.end());
2977
2978 // Single block scope: not interesting! No propagation at all. Note that
2979 // this could probably go above ArtificialBlocks without damage, but
2980 // that then produces output differences from original-live-debug-values,
2981 // which propagates from a single block into many artificial ones.
2982 if (BlocksToExplore.size() == 1)
2983 return;
2984
2985 // Picks out relevants blocks RPO order and sort them.
2986 for (auto *MBB : BlocksToExplore)
2987 BlockOrders.push_back(const_cast<MachineBasicBlock *>(MBB));
2988
2989 llvm::sort(BlockOrders, Cmp);
2990 unsigned NumBlocks = BlockOrders.size();
2991
2992 // Allocate some vectors for storing the live ins and live outs. Large.
2993 SmallVector<DenseMap<DebugVariable, DbgValue>, 32> LiveIns, LiveOuts;
2994 LiveIns.resize(NumBlocks);
2995 LiveOuts.resize(NumBlocks);
2996
2997 // Produce by-MBB indexes of live-in/live-outs, to ease lookup within
2998 // vlocJoin.
2999 LiveIdxT LiveOutIdx, LiveInIdx;
3000 LiveOutIdx.reserve(NumBlocks);
3001 LiveInIdx.reserve(NumBlocks);
3002 for (unsigned I = 0; I < NumBlocks; ++I) {
3003 LiveOutIdx[BlockOrders[I]] = &LiveOuts[I];
3004 LiveInIdx[BlockOrders[I]] = &LiveIns[I];
3005 }
3006
3007 for (auto *MBB : BlockOrders) {
3008 Worklist.push(BBToOrder[MBB]);
3009 OnWorklist.insert(MBB);
3010 }
3011
3012 // Iterate over all the blocks we selected, propagating variable values.
3013 bool FirstTrip = true;
3014 SmallPtrSet<const MachineBasicBlock *, 16> VLOCVisited;
3015 while (!Worklist.empty() || !Pending.empty()) {
3016 while (!Worklist.empty()) {
3017 auto *MBB = OrderToBB[Worklist.top()];
3018 CurBB = MBB->getNumber();
3019 Worklist.pop();
3020
3021 DenseMap<DebugVariable, DbgValue> JoinedInLocs;
3022
3023 // Join values from predecessors. Updates LiveInIdx, and writes output
3024 // into JoinedInLocs.
3025 bool InLocsChanged, DowngradeOccurred;
3026 std::tie(InLocsChanged, DowngradeOccurred) = vlocJoin(
3027 *MBB, LiveOutIdx, LiveInIdx, (FirstTrip) ? &VLOCVisited : nullptr,
3028 CurBB, VarsWeCareAbout, MOutLocs, MInLocs, InScopeBlocks,
3029 BlocksToExplore, JoinedInLocs);
3030
3031 bool FirstVisit = VLOCVisited.insert(MBB).second;
3032
3033 // Always explore transfer function if inlocs changed, or if we've not
3034 // visited this block before.
3035 InLocsChanged |= FirstVisit;
3036
3037 // If a downgrade occurred, book us in for re-examination on the next
3038 // iteration.
3039 if (DowngradeOccurred && OnPending.insert(MBB).second)
3040 Pending.push(BBToOrder[MBB]);
3041
3042 if (!InLocsChanged)
3043 continue;
3044
3045 // Do transfer function.
3046 auto &VTracker = AllTheVLocs[MBB->getNumber()];
3047 for (auto &Transfer : VTracker.Vars) {
3048 // Is this var we're mangling in this scope?
3049 if (VarsWeCareAbout.count(Transfer.first)) {
3050 // Erase on empty transfer (DBG_VALUE $noreg).
3051 if (Transfer.second.Kind == DbgValue::Undef) {
3052 JoinedInLocs.erase(Transfer.first);
3053 } else {
3054 // Insert new variable value; or overwrite.
3055 auto NewValuePair = std::make_pair(Transfer.first, Transfer.second);
3056 auto Result = JoinedInLocs.insert(NewValuePair);
3057 if (!Result.second)
3058 Result.first->second = Transfer.second;
3059 }
3060 }
3061 }
3062
3063 // Did the live-out locations change?
3064 bool OLChanged = JoinedInLocs != *LiveOutIdx[MBB];
3065
3066 // If they haven't changed, there's no need to explore further.
3067 if (!OLChanged)
3068 continue;
3069
3070 // Commit to the live-out record.
3071 *LiveOutIdx[MBB] = JoinedInLocs;
3072
3073 // We should visit all successors. Ensure we'll visit any non-backedge
3074 // successors during this dataflow iteration; book backedge successors
3075 // to be visited next time around.
3076 for (auto s : MBB->successors()) {
3077 // Ignore out of scope / not-to-be-explored successors.
3078 if (LiveInIdx.find(s) == LiveInIdx.end())
3079 continue;
3080
3081 if (BBToOrder[s] > BBToOrder[MBB]) {
3082 if (OnWorklist.insert(s).second)
3083 Worklist.push(BBToOrder[s]);
3084 } else if (OnPending.insert(s).second && (FirstTrip || OLChanged)) {
3085 Pending.push(BBToOrder[s]);
3086 }
3087 }
3088 }
3089 Worklist.swap(Pending);
3090 std::swap(OnWorklist, OnPending);
3091 OnPending.clear();
3092 assert(Pending.empty());
3093 FirstTrip = false;
3094 }
3095
3096 // Dataflow done. Now what? Save live-ins. Ignore any that are still marked
3097 // as being variable-PHIs, because those did not have their machine-PHI
3098 // value confirmed. Such variable values are places that could have been
3099 // PHIs, but are not.
3100 for (auto *MBB : BlockOrders) {
3101 auto &VarMap = *LiveInIdx[MBB];
3102 for (auto &P : VarMap) {
3103 if (P.second.Kind == DbgValue::Proposed ||
3104 P.second.Kind == DbgValue::NoVal)
3105 continue;
3106 Output[MBB->getNumber()].push_back(P);
3107 }
3108 }
3109
3110 BlockOrders.clear();
3111 BlocksToExplore.clear();
3112 }
3113
3114 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump_mloc_transfer(const MLocTransferMap & mloc_transfer) const3115 void InstrRefBasedLDV::dump_mloc_transfer(
3116 const MLocTransferMap &mloc_transfer) const {
3117 for (auto &P : mloc_transfer) {
3118 std::string foo = MTracker->LocIdxToName(P.first);
3119 std::string bar = MTracker->IDAsString(P.second);
3120 dbgs() << "Loc " << foo << " --> " << bar << "\n";
3121 }
3122 }
3123 #endif
3124
emitLocations(MachineFunction & MF,LiveInsT SavedLiveIns,ValueIDNum ** MInLocs,DenseMap<DebugVariable,unsigned> & AllVarsNumbering)3125 void InstrRefBasedLDV::emitLocations(
3126 MachineFunction &MF, LiveInsT SavedLiveIns, ValueIDNum **MInLocs,
3127 DenseMap<DebugVariable, unsigned> &AllVarsNumbering) {
3128 TTracker = new TransferTracker(TII, MTracker, MF, *TRI, CalleeSavedRegs);
3129 unsigned NumLocs = MTracker->getNumLocs();
3130
3131 // For each block, load in the machine value locations and variable value
3132 // live-ins, then step through each instruction in the block. New DBG_VALUEs
3133 // to be inserted will be created along the way.
3134 for (MachineBasicBlock &MBB : MF) {
3135 unsigned bbnum = MBB.getNumber();
3136 MTracker->reset();
3137 MTracker->loadFromArray(MInLocs[bbnum], bbnum);
3138 TTracker->loadInlocs(MBB, MInLocs[bbnum], SavedLiveIns[MBB.getNumber()],
3139 NumLocs);
3140
3141 CurBB = bbnum;
3142 CurInst = 1;
3143 for (auto &MI : MBB) {
3144 process(MI);
3145 TTracker->checkInstForNewValues(CurInst, MI.getIterator());
3146 ++CurInst;
3147 }
3148 }
3149
3150 // We have to insert DBG_VALUEs in a consistent order, otherwise they appeaer
3151 // in DWARF in different orders. Use the order that they appear when walking
3152 // through each block / each instruction, stored in AllVarsNumbering.
3153 auto OrderDbgValues = [&](const MachineInstr *A,
3154 const MachineInstr *B) -> bool {
3155 DebugVariable VarA(A->getDebugVariable(), A->getDebugExpression(),
3156 A->getDebugLoc()->getInlinedAt());
3157 DebugVariable VarB(B->getDebugVariable(), B->getDebugExpression(),
3158 B->getDebugLoc()->getInlinedAt());
3159 return AllVarsNumbering.find(VarA)->second <
3160 AllVarsNumbering.find(VarB)->second;
3161 };
3162
3163 // Go through all the transfers recorded in the TransferTracker -- this is
3164 // both the live-ins to a block, and any movements of values that happen
3165 // in the middle.
3166 for (auto &P : TTracker->Transfers) {
3167 // Sort them according to appearance order.
3168 llvm::sort(P.Insts, OrderDbgValues);
3169 // Insert either before or after the designated point...
3170 if (P.MBB) {
3171 MachineBasicBlock &MBB = *P.MBB;
3172 for (auto *MI : P.Insts) {
3173 MBB.insert(P.Pos, MI);
3174 }
3175 } else {
3176 MachineBasicBlock &MBB = *P.Pos->getParent();
3177 for (auto *MI : P.Insts) {
3178 MBB.insertAfter(P.Pos, MI);
3179 }
3180 }
3181 }
3182 }
3183
initialSetup(MachineFunction & MF)3184 void InstrRefBasedLDV::initialSetup(MachineFunction &MF) {
3185 // Build some useful data structures.
3186 auto hasNonArtificialLocation = [](const MachineInstr &MI) -> bool {
3187 if (const DebugLoc &DL = MI.getDebugLoc())
3188 return DL.getLine() != 0;
3189 return false;
3190 };
3191 // Collect a set of all the artificial blocks.
3192 for (auto &MBB : MF)
3193 if (none_of(MBB.instrs(), hasNonArtificialLocation))
3194 ArtificialBlocks.insert(&MBB);
3195
3196 // Compute mappings of block <=> RPO order.
3197 ReversePostOrderTraversal<MachineFunction *> RPOT(&MF);
3198 unsigned int RPONumber = 0;
3199 for (MachineBasicBlock *MBB : RPOT) {
3200 OrderToBB[RPONumber] = MBB;
3201 BBToOrder[MBB] = RPONumber;
3202 BBNumToRPO[MBB->getNumber()] = RPONumber;
3203 ++RPONumber;
3204 }
3205 }
3206
3207 /// Calculate the liveness information for the given machine function and
3208 /// extend ranges across basic blocks.
ExtendRanges(MachineFunction & MF,TargetPassConfig * TPC)3209 bool InstrRefBasedLDV::ExtendRanges(MachineFunction &MF,
3210 TargetPassConfig *TPC) {
3211 // No subprogram means this function contains no debuginfo.
3212 if (!MF.getFunction().getSubprogram())
3213 return false;
3214
3215 LLVM_DEBUG(dbgs() << "\nDebug Range Extension\n");
3216 this->TPC = TPC;
3217
3218 TRI = MF.getSubtarget().getRegisterInfo();
3219 TII = MF.getSubtarget().getInstrInfo();
3220 TFI = MF.getSubtarget().getFrameLowering();
3221 TFI->getCalleeSaves(MF, CalleeSavedRegs);
3222 LS.initialize(MF);
3223
3224 MTracker =
3225 new MLocTracker(MF, *TII, *TRI, *MF.getSubtarget().getTargetLowering());
3226 VTracker = nullptr;
3227 TTracker = nullptr;
3228
3229 SmallVector<MLocTransferMap, 32> MLocTransfer;
3230 SmallVector<VLocTracker, 8> vlocs;
3231 LiveInsT SavedLiveIns;
3232
3233 int MaxNumBlocks = -1;
3234 for (auto &MBB : MF)
3235 MaxNumBlocks = std::max(MBB.getNumber(), MaxNumBlocks);
3236 assert(MaxNumBlocks >= 0);
3237 ++MaxNumBlocks;
3238
3239 MLocTransfer.resize(MaxNumBlocks);
3240 vlocs.resize(MaxNumBlocks);
3241 SavedLiveIns.resize(MaxNumBlocks);
3242
3243 initialSetup(MF);
3244
3245 produceMLocTransferFunction(MF, MLocTransfer, MaxNumBlocks);
3246
3247 // Allocate and initialize two array-of-arrays for the live-in and live-out
3248 // machine values. The outer dimension is the block number; while the inner
3249 // dimension is a LocIdx from MLocTracker.
3250 ValueIDNum **MOutLocs = new ValueIDNum *[MaxNumBlocks];
3251 ValueIDNum **MInLocs = new ValueIDNum *[MaxNumBlocks];
3252 unsigned NumLocs = MTracker->getNumLocs();
3253 for (int i = 0; i < MaxNumBlocks; ++i) {
3254 MOutLocs[i] = new ValueIDNum[NumLocs];
3255 MInLocs[i] = new ValueIDNum[NumLocs];
3256 }
3257
3258 // Solve the machine value dataflow problem using the MLocTransfer function,
3259 // storing the computed live-ins / live-outs into the array-of-arrays. We use
3260 // both live-ins and live-outs for decision making in the variable value
3261 // dataflow problem.
3262 mlocDataflow(MInLocs, MOutLocs, MLocTransfer);
3263
3264 // Walk back through each block / instruction, collecting DBG_VALUE
3265 // instructions and recording what machine value their operands refer to.
3266 for (auto &OrderPair : OrderToBB) {
3267 MachineBasicBlock &MBB = *OrderPair.second;
3268 CurBB = MBB.getNumber();
3269 VTracker = &vlocs[CurBB];
3270 VTracker->MBB = &MBB;
3271 MTracker->loadFromArray(MInLocs[CurBB], CurBB);
3272 CurInst = 1;
3273 for (auto &MI : MBB) {
3274 process(MI);
3275 ++CurInst;
3276 }
3277 MTracker->reset();
3278 }
3279
3280 // Number all variables in the order that they appear, to be used as a stable
3281 // insertion order later.
3282 DenseMap<DebugVariable, unsigned> AllVarsNumbering;
3283
3284 // Map from one LexicalScope to all the variables in that scope.
3285 DenseMap<const LexicalScope *, SmallSet<DebugVariable, 4>> ScopeToVars;
3286
3287 // Map from One lexical scope to all blocks in that scope.
3288 DenseMap<const LexicalScope *, SmallPtrSet<MachineBasicBlock *, 4>>
3289 ScopeToBlocks;
3290
3291 // Store a DILocation that describes a scope.
3292 DenseMap<const LexicalScope *, const DILocation *> ScopeToDILocation;
3293
3294 // To mirror old LiveDebugValues, enumerate variables in RPOT order. Otherwise
3295 // the order is unimportant, it just has to be stable.
3296 for (unsigned int I = 0; I < OrderToBB.size(); ++I) {
3297 auto *MBB = OrderToBB[I];
3298 auto *VTracker = &vlocs[MBB->getNumber()];
3299 // Collect each variable with a DBG_VALUE in this block.
3300 for (auto &idx : VTracker->Vars) {
3301 const auto &Var = idx.first;
3302 const DILocation *ScopeLoc = VTracker->Scopes[Var];
3303 assert(ScopeLoc != nullptr);
3304 auto *Scope = LS.findLexicalScope(ScopeLoc);
3305
3306 // No insts in scope -> shouldn't have been recorded.
3307 assert(Scope != nullptr);
3308
3309 AllVarsNumbering.insert(std::make_pair(Var, AllVarsNumbering.size()));
3310 ScopeToVars[Scope].insert(Var);
3311 ScopeToBlocks[Scope].insert(VTracker->MBB);
3312 ScopeToDILocation[Scope] = ScopeLoc;
3313 }
3314 }
3315
3316 // OK. Iterate over scopes: there might be something to be said for
3317 // ordering them by size/locality, but that's for the future. For each scope,
3318 // solve the variable value problem, producing a map of variables to values
3319 // in SavedLiveIns.
3320 for (auto &P : ScopeToVars) {
3321 vlocDataflow(P.first, ScopeToDILocation[P.first], P.second,
3322 ScopeToBlocks[P.first], SavedLiveIns, MOutLocs, MInLocs,
3323 vlocs);
3324 }
3325
3326 // Using the computed value locations and variable values for each block,
3327 // create the DBG_VALUE instructions representing the extended variable
3328 // locations.
3329 emitLocations(MF, SavedLiveIns, MInLocs, AllVarsNumbering);
3330
3331 for (int Idx = 0; Idx < MaxNumBlocks; ++Idx) {
3332 delete[] MOutLocs[Idx];
3333 delete[] MInLocs[Idx];
3334 }
3335 delete[] MOutLocs;
3336 delete[] MInLocs;
3337
3338 // Did we actually make any changes? If we created any DBG_VALUEs, then yes.
3339 bool Changed = TTracker->Transfers.size() != 0;
3340
3341 delete MTracker;
3342 delete TTracker;
3343 MTracker = nullptr;
3344 VTracker = nullptr;
3345 TTracker = nullptr;
3346
3347 ArtificialBlocks.clear();
3348 OrderToBB.clear();
3349 BBToOrder.clear();
3350 BBNumToRPO.clear();
3351 DebugInstrNumToInstr.clear();
3352
3353 return Changed;
3354 }
3355
makeInstrRefBasedLiveDebugValues()3356 LDVImpl *llvm::makeInstrRefBasedLiveDebugValues() {
3357 return new InstrRefBasedLDV();
3358 }
3359