1 //===-- MipsConstantIslandPass.cpp - Emit Pc Relative loads----------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //
11 // This pass is used to make Pc relative loads of constants.
12 // For now, only Mips16 will use this.
13 //
14 // Loading constants inline is expensive on Mips16 and it's in general better
15 // to place the constant nearby in code space and then it can be loaded with a
16 // simple 16 bit load instruction.
17 //
18 // The constants can be not just numbers but addresses of functions and labels.
19 // This can be particularly helpful in static relocation mode for embedded
20 // non-linux targets.
21 //
22 //
23
24 #include "Mips.h"
25 #include "MCTargetDesc/MipsBaseInfo.h"
26 #include "Mips16InstrInfo.h"
27 #include "MipsMachineFunction.h"
28 #include "MipsTargetMachine.h"
29 #include "llvm/ADT/Statistic.h"
30 #include "llvm/CodeGen/MachineBasicBlock.h"
31 #include "llvm/CodeGen/MachineConstantPool.h"
32 #include "llvm/CodeGen/MachineFunctionPass.h"
33 #include "llvm/CodeGen/MachineInstrBuilder.h"
34 #include "llvm/CodeGen/MachineRegisterInfo.h"
35 #include "llvm/IR/Function.h"
36 #include "llvm/IR/InstIterator.h"
37 #include "llvm/Support/CommandLine.h"
38 #include "llvm/Support/Debug.h"
39 #include "llvm/Support/Format.h"
40 #include "llvm/Support/MathExtras.h"
41 #include "llvm/Support/raw_ostream.h"
42 #include "llvm/Target/TargetInstrInfo.h"
43 #include "llvm/Target/TargetMachine.h"
44 #include "llvm/Target/TargetRegisterInfo.h"
45 #include <algorithm>
46
47 using namespace llvm;
48
49 #define DEBUG_TYPE "mips-constant-islands"
50
51 STATISTIC(NumCPEs, "Number of constpool entries");
52 STATISTIC(NumSplit, "Number of uncond branches inserted");
53 STATISTIC(NumCBrFixed, "Number of cond branches fixed");
54 STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
55
56 // FIXME: This option should be removed once it has received sufficient testing.
57 static cl::opt<bool>
58 AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true),
59 cl::desc("Align constant islands in code"));
60
61
62 // Rather than do make check tests with huge amounts of code, we force
63 // the test to use this amount.
64 //
65 static cl::opt<int> ConstantIslandsSmallOffset(
66 "mips-constant-islands-small-offset",
67 cl::init(0),
68 cl::desc("Make small offsets be this amount for testing purposes"),
69 cl::Hidden);
70
71 //
72 // For testing purposes we tell it to not use relaxed load forms so that it
73 // will split blocks.
74 //
75 static cl::opt<bool> NoLoadRelaxation(
76 "mips-constant-islands-no-load-relaxation",
77 cl::init(false),
78 cl::desc("Don't relax loads to long loads - for testing purposes"),
79 cl::Hidden);
80
branchTargetOperand(MachineInstr * MI)81 static unsigned int branchTargetOperand(MachineInstr *MI) {
82 switch (MI->getOpcode()) {
83 case Mips::Bimm16:
84 case Mips::BimmX16:
85 case Mips::Bteqz16:
86 case Mips::BteqzX16:
87 case Mips::Btnez16:
88 case Mips::BtnezX16:
89 case Mips::JalB16:
90 return 0;
91 case Mips::BeqzRxImm16:
92 case Mips::BeqzRxImmX16:
93 case Mips::BnezRxImm16:
94 case Mips::BnezRxImmX16:
95 return 1;
96 }
97 llvm_unreachable("Unknown branch type");
98 }
99
isUnconditionalBranch(unsigned int Opcode)100 static bool isUnconditionalBranch(unsigned int Opcode) {
101 switch (Opcode) {
102 default: return false;
103 case Mips::Bimm16:
104 case Mips::BimmX16:
105 case Mips::JalB16:
106 return true;
107 }
108 }
109
longformBranchOpcode(unsigned int Opcode)110 static unsigned int longformBranchOpcode(unsigned int Opcode) {
111 switch (Opcode) {
112 case Mips::Bimm16:
113 case Mips::BimmX16:
114 return Mips::BimmX16;
115 case Mips::Bteqz16:
116 case Mips::BteqzX16:
117 return Mips::BteqzX16;
118 case Mips::Btnez16:
119 case Mips::BtnezX16:
120 return Mips::BtnezX16;
121 case Mips::JalB16:
122 return Mips::JalB16;
123 case Mips::BeqzRxImm16:
124 case Mips::BeqzRxImmX16:
125 return Mips::BeqzRxImmX16;
126 case Mips::BnezRxImm16:
127 case Mips::BnezRxImmX16:
128 return Mips::BnezRxImmX16;
129 }
130 llvm_unreachable("Unknown branch type");
131 }
132
133 //
134 // FIXME: need to go through this whole constant islands port and check the math
135 // for branch ranges and clean this up and make some functions to calculate things
136 // that are done many times identically.
137 // Need to refactor some of the code to call this routine.
138 //
branchMaxOffsets(unsigned int Opcode)139 static unsigned int branchMaxOffsets(unsigned int Opcode) {
140 unsigned Bits, Scale;
141 switch (Opcode) {
142 case Mips::Bimm16:
143 Bits = 11;
144 Scale = 2;
145 break;
146 case Mips::BimmX16:
147 Bits = 16;
148 Scale = 2;
149 break;
150 case Mips::BeqzRxImm16:
151 Bits = 8;
152 Scale = 2;
153 break;
154 case Mips::BeqzRxImmX16:
155 Bits = 16;
156 Scale = 2;
157 break;
158 case Mips::BnezRxImm16:
159 Bits = 8;
160 Scale = 2;
161 break;
162 case Mips::BnezRxImmX16:
163 Bits = 16;
164 Scale = 2;
165 break;
166 case Mips::Bteqz16:
167 Bits = 8;
168 Scale = 2;
169 break;
170 case Mips::BteqzX16:
171 Bits = 16;
172 Scale = 2;
173 break;
174 case Mips::Btnez16:
175 Bits = 8;
176 Scale = 2;
177 break;
178 case Mips::BtnezX16:
179 Bits = 16;
180 Scale = 2;
181 break;
182 default:
183 llvm_unreachable("Unknown branch type");
184 }
185 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
186 return MaxOffs;
187 }
188
189 namespace {
190
191
192 typedef MachineBasicBlock::iterator Iter;
193 typedef MachineBasicBlock::reverse_iterator ReverseIter;
194
195 /// MipsConstantIslands - Due to limited PC-relative displacements, Mips
196 /// requires constant pool entries to be scattered among the instructions
197 /// inside a function. To do this, it completely ignores the normal LLVM
198 /// constant pool; instead, it places constants wherever it feels like with
199 /// special instructions.
200 ///
201 /// The terminology used in this pass includes:
202 /// Islands - Clumps of constants placed in the function.
203 /// Water - Potential places where an island could be formed.
204 /// CPE - A constant pool entry that has been placed somewhere, which
205 /// tracks a list of users.
206
207 class MipsConstantIslands : public MachineFunctionPass {
208
209 /// BasicBlockInfo - Information about the offset and size of a single
210 /// basic block.
211 struct BasicBlockInfo {
212 /// Offset - Distance from the beginning of the function to the beginning
213 /// of this basic block.
214 ///
215 /// Offsets are computed assuming worst case padding before an aligned
216 /// block. This means that subtracting basic block offsets always gives a
217 /// conservative estimate of the real distance which may be smaller.
218 ///
219 /// Because worst case padding is used, the computed offset of an aligned
220 /// block may not actually be aligned.
221 unsigned Offset;
222
223 /// Size - Size of the basic block in bytes. If the block contains
224 /// inline assembly, this is a worst case estimate.
225 ///
226 /// The size does not include any alignment padding whether from the
227 /// beginning of the block, or from an aligned jump table at the end.
228 unsigned Size;
229
230 // FIXME: ignore LogAlign for this patch
231 //
postOffset__anonb36f20960111::MipsConstantIslands::BasicBlockInfo232 unsigned postOffset(unsigned LogAlign = 0) const {
233 unsigned PO = Offset + Size;
234 return PO;
235 }
236
BasicBlockInfo__anonb36f20960111::MipsConstantIslands::BasicBlockInfo237 BasicBlockInfo() : Offset(0), Size(0) {}
238
239 };
240
241 std::vector<BasicBlockInfo> BBInfo;
242
243 /// WaterList - A sorted list of basic blocks where islands could be placed
244 /// (i.e. blocks that don't fall through to the following block, due
245 /// to a return, unreachable, or unconditional branch).
246 std::vector<MachineBasicBlock*> WaterList;
247
248 /// NewWaterList - The subset of WaterList that was created since the
249 /// previous iteration by inserting unconditional branches.
250 SmallSet<MachineBasicBlock*, 4> NewWaterList;
251
252 typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
253
254 /// CPUser - One user of a constant pool, keeping the machine instruction
255 /// pointer, the constant pool being referenced, and the max displacement
256 /// allowed from the instruction to the CP. The HighWaterMark records the
257 /// highest basic block where a new CPEntry can be placed. To ensure this
258 /// pass terminates, the CP entries are initially placed at the end of the
259 /// function and then move monotonically to lower addresses. The
260 /// exception to this rule is when the current CP entry for a particular
261 /// CPUser is out of range, but there is another CP entry for the same
262 /// constant value in range. We want to use the existing in-range CP
263 /// entry, but if it later moves out of range, the search for new water
264 /// should resume where it left off. The HighWaterMark is used to record
265 /// that point.
266 struct CPUser {
267 MachineInstr *MI;
268 MachineInstr *CPEMI;
269 MachineBasicBlock *HighWaterMark;
270 private:
271 unsigned MaxDisp;
272 unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
273 // with different displacements
274 unsigned LongFormOpcode;
275 public:
276 bool NegOk;
CPUser__anonb36f20960111::MipsConstantIslands::CPUser277 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
278 bool neg,
279 unsigned longformmaxdisp, unsigned longformopcode)
280 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
281 LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
282 NegOk(neg){
283 HighWaterMark = CPEMI->getParent();
284 }
285 /// getMaxDisp - Returns the maximum displacement supported by MI.
getMaxDisp__anonb36f20960111::MipsConstantIslands::CPUser286 unsigned getMaxDisp() const {
287 unsigned xMaxDisp = ConstantIslandsSmallOffset?
288 ConstantIslandsSmallOffset: MaxDisp;
289 return xMaxDisp;
290 }
setMaxDisp__anonb36f20960111::MipsConstantIslands::CPUser291 void setMaxDisp(unsigned val) {
292 MaxDisp = val;
293 }
getLongFormMaxDisp__anonb36f20960111::MipsConstantIslands::CPUser294 unsigned getLongFormMaxDisp() const {
295 return LongFormMaxDisp;
296 }
getLongFormOpcode__anonb36f20960111::MipsConstantIslands::CPUser297 unsigned getLongFormOpcode() const {
298 return LongFormOpcode;
299 }
300 };
301
302 /// CPUsers - Keep track of all of the machine instructions that use various
303 /// constant pools and their max displacement.
304 std::vector<CPUser> CPUsers;
305
306 /// CPEntry - One per constant pool entry, keeping the machine instruction
307 /// pointer, the constpool index, and the number of CPUser's which
308 /// reference this entry.
309 struct CPEntry {
310 MachineInstr *CPEMI;
311 unsigned CPI;
312 unsigned RefCount;
CPEntry__anonb36f20960111::MipsConstantIslands::CPEntry313 CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
314 : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
315 };
316
317 /// CPEntries - Keep track of all of the constant pool entry machine
318 /// instructions. For each original constpool index (i.e. those that
319 /// existed upon entry to this pass), it keeps a vector of entries.
320 /// Original elements are cloned as we go along; the clones are
321 /// put in the vector of the original element, but have distinct CPIs.
322 std::vector<std::vector<CPEntry> > CPEntries;
323
324 /// ImmBranch - One per immediate branch, keeping the machine instruction
325 /// pointer, conditional or unconditional, the max displacement,
326 /// and (if isCond is true) the corresponding unconditional branch
327 /// opcode.
328 struct ImmBranch {
329 MachineInstr *MI;
330 unsigned MaxDisp : 31;
331 bool isCond : 1;
332 int UncondBr;
ImmBranch__anonb36f20960111::MipsConstantIslands::ImmBranch333 ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
334 : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
335 };
336
337 /// ImmBranches - Keep track of all the immediate branch instructions.
338 ///
339 std::vector<ImmBranch> ImmBranches;
340
341 /// HasFarJump - True if any far jump instruction has been emitted during
342 /// the branch fix up pass.
343 bool HasFarJump;
344
345 const TargetMachine &TM;
346 bool IsPIC;
347 const MipsSubtarget *STI;
348 const Mips16InstrInfo *TII;
349 MipsFunctionInfo *MFI;
350 MachineFunction *MF;
351 MachineConstantPool *MCP;
352
353 unsigned PICLabelUId;
354 bool PrescannedForConstants;
355
initPICLabelUId(unsigned UId)356 void initPICLabelUId(unsigned UId) {
357 PICLabelUId = UId;
358 }
359
360
createPICLabelUId()361 unsigned createPICLabelUId() {
362 return PICLabelUId++;
363 }
364
365 public:
366 static char ID;
MipsConstantIslands(TargetMachine & tm)367 MipsConstantIslands(TargetMachine &tm)
368 : MachineFunctionPass(ID), TM(tm),
369 IsPIC(TM.getRelocationModel() == Reloc::PIC_), STI(nullptr),
370 MF(nullptr), MCP(nullptr), PrescannedForConstants(false) {}
371
getPassName() const372 const char *getPassName() const override {
373 return "Mips Constant Islands";
374 }
375
376 bool runOnMachineFunction(MachineFunction &F) override;
377
378 void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
379 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
380 unsigned getCPELogAlign(const MachineInstr *CPEMI);
381 void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
382 unsigned getOffsetOf(MachineInstr *MI) const;
383 unsigned getUserOffset(CPUser&) const;
384 void dumpBBs();
385
386 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
387 unsigned Disp, bool NegativeOK);
388 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
389 const CPUser &U);
390
391 void computeBlockSize(MachineBasicBlock *MBB);
392 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
393 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
394 void adjustBBOffsetsAfter(MachineBasicBlock *BB);
395 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
396 int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
397 int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
398 bool findAvailableWater(CPUser&U, unsigned UserOffset,
399 water_iterator &WaterIter);
400 void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
401 MachineBasicBlock *&NewMBB);
402 bool handleConstantPoolUser(unsigned CPUserIndex);
403 void removeDeadCPEMI(MachineInstr *CPEMI);
404 bool removeUnusedCPEntries();
405 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
406 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
407 bool DoDump = false);
408 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
409 CPUser &U, unsigned &Growth);
410 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
411 bool fixupImmediateBr(ImmBranch &Br);
412 bool fixupConditionalBr(ImmBranch &Br);
413 bool fixupUnconditionalBr(ImmBranch &Br);
414
415 void prescanForConstants();
416
417 private:
418
419 };
420
421 char MipsConstantIslands::ID = 0;
422 } // end of anonymous namespace
423
isOffsetInRange(unsigned UserOffset,unsigned TrialOffset,const CPUser & U)424 bool MipsConstantIslands::isOffsetInRange
425 (unsigned UserOffset, unsigned TrialOffset,
426 const CPUser &U) {
427 return isOffsetInRange(UserOffset, TrialOffset,
428 U.getMaxDisp(), U.NegOk);
429 }
430 /// print block size and offset information - debugging
dumpBBs()431 void MipsConstantIslands::dumpBBs() {
432 DEBUG({
433 for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
434 const BasicBlockInfo &BBI = BBInfo[J];
435 dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
436 << format(" size=%#x\n", BBInfo[J].Size);
437 }
438 });
439 }
440 /// createMipsLongBranchPass - Returns a pass that converts branches to long
441 /// branches.
createMipsConstantIslandPass(MipsTargetMachine & tm)442 FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
443 return new MipsConstantIslands(tm);
444 }
445
runOnMachineFunction(MachineFunction & mf)446 bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
447 // The intention is for this to be a mips16 only pass for now
448 // FIXME:
449 MF = &mf;
450 MCP = mf.getConstantPool();
451 STI = &mf.getTarget().getSubtarget<MipsSubtarget>();
452 DEBUG(dbgs() << "constant island machine function " << "\n");
453 if (!STI->inMips16Mode() || !MipsSubtarget::useConstantIslands()) {
454 return false;
455 }
456 TII = (const Mips16InstrInfo *)MF->getTarget()
457 .getSubtargetImpl()
458 ->getInstrInfo();
459 MFI = MF->getInfo<MipsFunctionInfo>();
460 DEBUG(dbgs() << "constant island processing " << "\n");
461 //
462 // will need to make predermination if there is any constants we need to
463 // put in constant islands. TBD.
464 //
465 if (!PrescannedForConstants) prescanForConstants();
466
467 HasFarJump = false;
468 // This pass invalidates liveness information when it splits basic blocks.
469 MF->getRegInfo().invalidateLiveness();
470
471 // Renumber all of the machine basic blocks in the function, guaranteeing that
472 // the numbers agree with the position of the block in the function.
473 MF->RenumberBlocks();
474
475 bool MadeChange = false;
476
477 // Perform the initial placement of the constant pool entries. To start with,
478 // we put them all at the end of the function.
479 std::vector<MachineInstr*> CPEMIs;
480 if (!MCP->isEmpty())
481 doInitialPlacement(CPEMIs);
482
483 /// The next UID to take is the first unused one.
484 initPICLabelUId(CPEMIs.size());
485
486 // Do the initial scan of the function, building up information about the
487 // sizes of each block, the location of all the water, and finding all of the
488 // constant pool users.
489 initializeFunctionInfo(CPEMIs);
490 CPEMIs.clear();
491 DEBUG(dumpBBs());
492
493 /// Remove dead constant pool entries.
494 MadeChange |= removeUnusedCPEntries();
495
496 // Iteratively place constant pool entries and fix up branches until there
497 // is no change.
498 unsigned NoCPIters = 0, NoBRIters = 0;
499 (void)NoBRIters;
500 while (true) {
501 DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
502 bool CPChange = false;
503 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
504 CPChange |= handleConstantPoolUser(i);
505 if (CPChange && ++NoCPIters > 30)
506 report_fatal_error("Constant Island pass failed to converge!");
507 DEBUG(dumpBBs());
508
509 // Clear NewWaterList now. If we split a block for branches, it should
510 // appear as "new water" for the next iteration of constant pool placement.
511 NewWaterList.clear();
512
513 DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
514 bool BRChange = false;
515 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
516 BRChange |= fixupImmediateBr(ImmBranches[i]);
517 if (BRChange && ++NoBRIters > 30)
518 report_fatal_error("Branch Fix Up pass failed to converge!");
519 DEBUG(dumpBBs());
520 if (!CPChange && !BRChange)
521 break;
522 MadeChange = true;
523 }
524
525 DEBUG(dbgs() << '\n'; dumpBBs());
526
527 BBInfo.clear();
528 WaterList.clear();
529 CPUsers.clear();
530 CPEntries.clear();
531 ImmBranches.clear();
532 return MadeChange;
533 }
534
535 /// doInitialPlacement - Perform the initial placement of the constant pool
536 /// entries. To start with, we put them all at the end of the function.
537 void
doInitialPlacement(std::vector<MachineInstr * > & CPEMIs)538 MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
539 // Create the basic block to hold the CPE's.
540 MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
541 MF->push_back(BB);
542
543
544 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
545 unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
546
547 // Mark the basic block as required by the const-pool.
548 // If AlignConstantIslands isn't set, use 4-byte alignment for everything.
549 BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
550
551 // The function needs to be as aligned as the basic blocks. The linker may
552 // move functions around based on their alignment.
553 MF->ensureAlignment(BB->getAlignment());
554
555 // Order the entries in BB by descending alignment. That ensures correct
556 // alignment of all entries as long as BB is sufficiently aligned. Keep
557 // track of the insertion point for each alignment. We are going to bucket
558 // sort the entries as they are created.
559 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
560
561 // Add all of the constants from the constant pool to the end block, use an
562 // identity mapping of CPI's to CPE's.
563 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
564
565 const DataLayout &TD = *MF->getSubtarget().getDataLayout();
566 for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
567 unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
568 assert(Size >= 4 && "Too small constant pool entry");
569 unsigned Align = CPs[i].getAlignment();
570 assert(isPowerOf2_32(Align) && "Invalid alignment");
571 // Verify that all constant pool entries are a multiple of their alignment.
572 // If not, we would have to pad them out so that instructions stay aligned.
573 assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
574
575 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
576 unsigned LogAlign = Log2_32(Align);
577 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
578
579 MachineInstr *CPEMI =
580 BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
581 .addImm(i).addConstantPoolIndex(i).addImm(Size);
582
583 CPEMIs.push_back(CPEMI);
584
585 // Ensure that future entries with higher alignment get inserted before
586 // CPEMI. This is bucket sort with iterators.
587 for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
588 if (InsPoint[a] == InsAt)
589 InsPoint[a] = CPEMI;
590 // Add a new CPEntry, but no corresponding CPUser yet.
591 CPEntries.emplace_back(1, CPEntry(CPEMI, i));
592 ++NumCPEs;
593 DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
594 << Size << ", align = " << Align <<'\n');
595 }
596 DEBUG(BB->dump());
597 }
598
599 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
600 /// into the block immediately after it.
BBHasFallthrough(MachineBasicBlock * MBB)601 static bool BBHasFallthrough(MachineBasicBlock *MBB) {
602 // Get the next machine basic block in the function.
603 MachineFunction::iterator MBBI = MBB;
604 // Can't fall off end of function.
605 if (std::next(MBBI) == MBB->getParent()->end())
606 return false;
607
608 MachineBasicBlock *NextBB = std::next(MBBI);
609 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
610 E = MBB->succ_end(); I != E; ++I)
611 if (*I == NextBB)
612 return true;
613
614 return false;
615 }
616
617 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
618 /// look up the corresponding CPEntry.
619 MipsConstantIslands::CPEntry
findConstPoolEntry(unsigned CPI,const MachineInstr * CPEMI)620 *MipsConstantIslands::findConstPoolEntry(unsigned CPI,
621 const MachineInstr *CPEMI) {
622 std::vector<CPEntry> &CPEs = CPEntries[CPI];
623 // Number of entries per constpool index should be small, just do a
624 // linear search.
625 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
626 if (CPEs[i].CPEMI == CPEMI)
627 return &CPEs[i];
628 }
629 return nullptr;
630 }
631
632 /// getCPELogAlign - Returns the required alignment of the constant pool entry
633 /// represented by CPEMI. Alignment is measured in log2(bytes) units.
getCPELogAlign(const MachineInstr * CPEMI)634 unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
635 assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY);
636
637 // Everything is 4-byte aligned unless AlignConstantIslands is set.
638 if (!AlignConstantIslands)
639 return 2;
640
641 unsigned CPI = CPEMI->getOperand(1).getIndex();
642 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
643 unsigned Align = MCP->getConstants()[CPI].getAlignment();
644 assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
645 return Log2_32(Align);
646 }
647
648 /// initializeFunctionInfo - Do the initial scan of the function, building up
649 /// information about the sizes of each block, the location of all the water,
650 /// and finding all of the constant pool users.
651 void MipsConstantIslands::
initializeFunctionInfo(const std::vector<MachineInstr * > & CPEMIs)652 initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
653 BBInfo.clear();
654 BBInfo.resize(MF->getNumBlockIDs());
655
656 // First thing, compute the size of all basic blocks, and see if the function
657 // has any inline assembly in it. If so, we have to be conservative about
658 // alignment assumptions, as we don't know for sure the size of any
659 // instructions in the inline assembly.
660 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
661 computeBlockSize(I);
662
663
664 // Compute block offsets.
665 adjustBBOffsetsAfter(MF->begin());
666
667 // Now go back through the instructions and build up our data structures.
668 for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
669 MBBI != E; ++MBBI) {
670 MachineBasicBlock &MBB = *MBBI;
671
672 // If this block doesn't fall through into the next MBB, then this is
673 // 'water' that a constant pool island could be placed.
674 if (!BBHasFallthrough(&MBB))
675 WaterList.push_back(&MBB);
676 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
677 I != E; ++I) {
678 if (I->isDebugValue())
679 continue;
680
681 int Opc = I->getOpcode();
682 if (I->isBranch()) {
683 bool isCond = false;
684 unsigned Bits = 0;
685 unsigned Scale = 1;
686 int UOpc = Opc;
687 switch (Opc) {
688 default:
689 continue; // Ignore other branches for now
690 case Mips::Bimm16:
691 Bits = 11;
692 Scale = 2;
693 isCond = false;
694 break;
695 case Mips::BimmX16:
696 Bits = 16;
697 Scale = 2;
698 isCond = false;
699 break;
700 case Mips::BeqzRxImm16:
701 UOpc=Mips::Bimm16;
702 Bits = 8;
703 Scale = 2;
704 isCond = true;
705 break;
706 case Mips::BeqzRxImmX16:
707 UOpc=Mips::Bimm16;
708 Bits = 16;
709 Scale = 2;
710 isCond = true;
711 break;
712 case Mips::BnezRxImm16:
713 UOpc=Mips::Bimm16;
714 Bits = 8;
715 Scale = 2;
716 isCond = true;
717 break;
718 case Mips::BnezRxImmX16:
719 UOpc=Mips::Bimm16;
720 Bits = 16;
721 Scale = 2;
722 isCond = true;
723 break;
724 case Mips::Bteqz16:
725 UOpc=Mips::Bimm16;
726 Bits = 8;
727 Scale = 2;
728 isCond = true;
729 break;
730 case Mips::BteqzX16:
731 UOpc=Mips::Bimm16;
732 Bits = 16;
733 Scale = 2;
734 isCond = true;
735 break;
736 case Mips::Btnez16:
737 UOpc=Mips::Bimm16;
738 Bits = 8;
739 Scale = 2;
740 isCond = true;
741 break;
742 case Mips::BtnezX16:
743 UOpc=Mips::Bimm16;
744 Bits = 16;
745 Scale = 2;
746 isCond = true;
747 break;
748 }
749 // Record this immediate branch.
750 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
751 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
752 }
753
754 if (Opc == Mips::CONSTPOOL_ENTRY)
755 continue;
756
757
758 // Scan the instructions for constant pool operands.
759 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
760 if (I->getOperand(op).isCPI()) {
761
762 // We found one. The addressing mode tells us the max displacement
763 // from the PC that this instruction permits.
764
765 // Basic size info comes from the TSFlags field.
766 unsigned Bits = 0;
767 unsigned Scale = 1;
768 bool NegOk = false;
769 unsigned LongFormBits = 0;
770 unsigned LongFormScale = 0;
771 unsigned LongFormOpcode = 0;
772 switch (Opc) {
773 default:
774 llvm_unreachable("Unknown addressing mode for CP reference!");
775 case Mips::LwRxPcTcp16:
776 Bits = 8;
777 Scale = 4;
778 LongFormOpcode = Mips::LwRxPcTcpX16;
779 LongFormBits = 14;
780 LongFormScale = 1;
781 break;
782 case Mips::LwRxPcTcpX16:
783 Bits = 14;
784 Scale = 1;
785 NegOk = true;
786 break;
787 }
788 // Remember that this is a user of a CP entry.
789 unsigned CPI = I->getOperand(op).getIndex();
790 MachineInstr *CPEMI = CPEMIs[CPI];
791 unsigned MaxOffs = ((1 << Bits)-1) * Scale;
792 unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
793 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk,
794 LongFormMaxOffs, LongFormOpcode));
795
796 // Increment corresponding CPEntry reference count.
797 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
798 assert(CPE && "Cannot find a corresponding CPEntry!");
799 CPE->RefCount++;
800
801 // Instructions can only use one CP entry, don't bother scanning the
802 // rest of the operands.
803 break;
804
805 }
806
807 }
808 }
809
810 }
811
812 /// computeBlockSize - Compute the size and some alignment information for MBB.
813 /// This function updates BBInfo directly.
computeBlockSize(MachineBasicBlock * MBB)814 void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
815 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
816 BBI.Size = 0;
817
818 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
819 ++I)
820 BBI.Size += TII->GetInstSizeInBytes(I);
821
822 }
823
824 /// getOffsetOf - Return the current offset of the specified machine instruction
825 /// from the start of the function. This offset changes as stuff is moved
826 /// around inside the function.
getOffsetOf(MachineInstr * MI) const827 unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
828 MachineBasicBlock *MBB = MI->getParent();
829
830 // The offset is composed of two things: the sum of the sizes of all MBB's
831 // before this instruction's block, and the offset from the start of the block
832 // it is in.
833 unsigned Offset = BBInfo[MBB->getNumber()].Offset;
834
835 // Sum instructions before MI in MBB.
836 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
837 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
838 Offset += TII->GetInstSizeInBytes(I);
839 }
840 return Offset;
841 }
842
843 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
844 /// ID.
CompareMBBNumbers(const MachineBasicBlock * LHS,const MachineBasicBlock * RHS)845 static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
846 const MachineBasicBlock *RHS) {
847 return LHS->getNumber() < RHS->getNumber();
848 }
849
850 /// updateForInsertedWaterBlock - When a block is newly inserted into the
851 /// machine function, it upsets all of the block numbers. Renumber the blocks
852 /// and update the arrays that parallel this numbering.
updateForInsertedWaterBlock(MachineBasicBlock * NewBB)853 void MipsConstantIslands::updateForInsertedWaterBlock
854 (MachineBasicBlock *NewBB) {
855 // Renumber the MBB's to keep them consecutive.
856 NewBB->getParent()->RenumberBlocks(NewBB);
857
858 // Insert an entry into BBInfo to align it properly with the (newly
859 // renumbered) block numbers.
860 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
861
862 // Next, update WaterList. Specifically, we need to add NewMBB as having
863 // available water after it.
864 water_iterator IP =
865 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
866 CompareMBBNumbers);
867 WaterList.insert(IP, NewBB);
868 }
869
getUserOffset(CPUser & U) const870 unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
871 return getOffsetOf(U.MI);
872 }
873
874 /// Split the basic block containing MI into two blocks, which are joined by
875 /// an unconditional branch. Update data structures and renumber blocks to
876 /// account for this change and returns the newly created block.
splitBlockBeforeInstr(MachineInstr * MI)877 MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr
878 (MachineInstr *MI) {
879 MachineBasicBlock *OrigBB = MI->getParent();
880
881 // Create a new MBB for the code after the OrigBB.
882 MachineBasicBlock *NewBB =
883 MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
884 MachineFunction::iterator MBBI = OrigBB; ++MBBI;
885 MF->insert(MBBI, NewBB);
886
887 // Splice the instructions starting with MI over to NewBB.
888 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
889
890 // Add an unconditional branch from OrigBB to NewBB.
891 // Note the new unconditional branch is not being recorded.
892 // There doesn't seem to be meaningful DebugInfo available; this doesn't
893 // correspond to anything in the source.
894 BuildMI(OrigBB, DebugLoc(), TII->get(Mips::Bimm16)).addMBB(NewBB);
895 ++NumSplit;
896
897 // Update the CFG. All succs of OrigBB are now succs of NewBB.
898 NewBB->transferSuccessors(OrigBB);
899
900 // OrigBB branches to NewBB.
901 OrigBB->addSuccessor(NewBB);
902
903 // Update internal data structures to account for the newly inserted MBB.
904 // This is almost the same as updateForInsertedWaterBlock, except that
905 // the Water goes after OrigBB, not NewBB.
906 MF->RenumberBlocks(NewBB);
907
908 // Insert an entry into BBInfo to align it properly with the (newly
909 // renumbered) block numbers.
910 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
911
912 // Next, update WaterList. Specifically, we need to add OrigMBB as having
913 // available water after it (but not if it's already there, which happens
914 // when splitting before a conditional branch that is followed by an
915 // unconditional branch - in that case we want to insert NewBB).
916 water_iterator IP =
917 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
918 CompareMBBNumbers);
919 MachineBasicBlock* WaterBB = *IP;
920 if (WaterBB == OrigBB)
921 WaterList.insert(std::next(IP), NewBB);
922 else
923 WaterList.insert(IP, OrigBB);
924 NewWaterList.insert(OrigBB);
925
926 // Figure out how large the OrigBB is. As the first half of the original
927 // block, it cannot contain a tablejump. The size includes
928 // the new jump we added. (It should be possible to do this without
929 // recounting everything, but it's very confusing, and this is rarely
930 // executed.)
931 computeBlockSize(OrigBB);
932
933 // Figure out how large the NewMBB is. As the second half of the original
934 // block, it may contain a tablejump.
935 computeBlockSize(NewBB);
936
937 // All BBOffsets following these blocks must be modified.
938 adjustBBOffsetsAfter(OrigBB);
939
940 return NewBB;
941 }
942
943
944
945 /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
946 /// reference) is within MaxDisp of TrialOffset (a proposed location of a
947 /// constant pool entry).
isOffsetInRange(unsigned UserOffset,unsigned TrialOffset,unsigned MaxDisp,bool NegativeOK)948 bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
949 unsigned TrialOffset, unsigned MaxDisp,
950 bool NegativeOK) {
951 if (UserOffset <= TrialOffset) {
952 // User before the Trial.
953 if (TrialOffset - UserOffset <= MaxDisp)
954 return true;
955 } else if (NegativeOK) {
956 if (UserOffset - TrialOffset <= MaxDisp)
957 return true;
958 }
959 return false;
960 }
961
962 /// isWaterInRange - Returns true if a CPE placed after the specified
963 /// Water (a basic block) will be in range for the specific MI.
964 ///
965 /// Compute how much the function will grow by inserting a CPE after Water.
isWaterInRange(unsigned UserOffset,MachineBasicBlock * Water,CPUser & U,unsigned & Growth)966 bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
967 MachineBasicBlock* Water, CPUser &U,
968 unsigned &Growth) {
969 unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
970 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
971 unsigned NextBlockOffset, NextBlockAlignment;
972 MachineFunction::const_iterator NextBlock = Water;
973 if (++NextBlock == MF->end()) {
974 NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
975 NextBlockAlignment = 0;
976 } else {
977 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
978 NextBlockAlignment = NextBlock->getAlignment();
979 }
980 unsigned Size = U.CPEMI->getOperand(2).getImm();
981 unsigned CPEEnd = CPEOffset + Size;
982
983 // The CPE may be able to hide in the alignment padding before the next
984 // block. It may also cause more padding to be required if it is more aligned
985 // that the next block.
986 if (CPEEnd > NextBlockOffset) {
987 Growth = CPEEnd - NextBlockOffset;
988 // Compute the padding that would go at the end of the CPE to align the next
989 // block.
990 Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment);
991
992 // If the CPE is to be inserted before the instruction, that will raise
993 // the offset of the instruction. Also account for unknown alignment padding
994 // in blocks between CPE and the user.
995 if (CPEOffset < UserOffset)
996 UserOffset += Growth;
997 } else
998 // CPE fits in existing padding.
999 Growth = 0;
1000
1001 return isOffsetInRange(UserOffset, CPEOffset, U);
1002 }
1003
1004 /// isCPEntryInRange - Returns true if the distance between specific MI and
1005 /// specific ConstPool entry instruction can fit in MI's displacement field.
isCPEntryInRange(MachineInstr * MI,unsigned UserOffset,MachineInstr * CPEMI,unsigned MaxDisp,bool NegOk,bool DoDump)1006 bool MipsConstantIslands::isCPEntryInRange
1007 (MachineInstr *MI, unsigned UserOffset,
1008 MachineInstr *CPEMI, unsigned MaxDisp,
1009 bool NegOk, bool DoDump) {
1010 unsigned CPEOffset = getOffsetOf(CPEMI);
1011
1012 if (DoDump) {
1013 DEBUG({
1014 unsigned Block = MI->getParent()->getNumber();
1015 const BasicBlockInfo &BBI = BBInfo[Block];
1016 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
1017 << " max delta=" << MaxDisp
1018 << format(" insn address=%#x", UserOffset)
1019 << " in BB#" << Block << ": "
1020 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
1021 << format("CPE address=%#x offset=%+d: ", CPEOffset,
1022 int(CPEOffset-UserOffset));
1023 });
1024 }
1025
1026 return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
1027 }
1028
1029 #ifndef NDEBUG
1030 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor
1031 /// unconditionally branches to its only successor.
BBIsJumpedOver(MachineBasicBlock * MBB)1032 static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
1033 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
1034 return false;
1035 MachineBasicBlock *Succ = *MBB->succ_begin();
1036 MachineBasicBlock *Pred = *MBB->pred_begin();
1037 MachineInstr *PredMI = &Pred->back();
1038 if (PredMI->getOpcode() == Mips::Bimm16)
1039 return PredMI->getOperand(0).getMBB() == Succ;
1040 return false;
1041 }
1042 #endif
1043
adjustBBOffsetsAfter(MachineBasicBlock * BB)1044 void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
1045 unsigned BBNum = BB->getNumber();
1046 for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
1047 // Get the offset and known bits at the end of the layout predecessor.
1048 // Include the alignment of the current block.
1049 unsigned Offset = BBInfo[i - 1].Offset + BBInfo[i - 1].Size;
1050 BBInfo[i].Offset = Offset;
1051 }
1052 }
1053
1054 /// decrementCPEReferenceCount - find the constant pool entry with index CPI
1055 /// and instruction CPEMI, and decrement its refcount. If the refcount
1056 /// becomes 0 remove the entry and instruction. Returns true if we removed
1057 /// the entry, false if we didn't.
1058
decrementCPEReferenceCount(unsigned CPI,MachineInstr * CPEMI)1059 bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
1060 MachineInstr *CPEMI) {
1061 // Find the old entry. Eliminate it if it is no longer used.
1062 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
1063 assert(CPE && "Unexpected!");
1064 if (--CPE->RefCount == 0) {
1065 removeDeadCPEMI(CPEMI);
1066 CPE->CPEMI = nullptr;
1067 --NumCPEs;
1068 return true;
1069 }
1070 return false;
1071 }
1072
1073 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1074 /// if not, see if an in-range clone of the CPE is in range, and if so,
1075 /// change the data structures so the user references the clone. Returns:
1076 /// 0 = no existing entry found
1077 /// 1 = entry found, and there were no code insertions or deletions
1078 /// 2 = entry found, and there were code insertions or deletions
findInRangeCPEntry(CPUser & U,unsigned UserOffset)1079 int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
1080 {
1081 MachineInstr *UserMI = U.MI;
1082 MachineInstr *CPEMI = U.CPEMI;
1083
1084 // Check to see if the CPE is already in-range.
1085 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
1086 true)) {
1087 DEBUG(dbgs() << "In range\n");
1088 return 1;
1089 }
1090
1091 // No. Look for previously created clones of the CPE that are in range.
1092 unsigned CPI = CPEMI->getOperand(1).getIndex();
1093 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1094 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1095 // We already tried this one
1096 if (CPEs[i].CPEMI == CPEMI)
1097 continue;
1098 // Removing CPEs can leave empty entries, skip
1099 if (CPEs[i].CPEMI == nullptr)
1100 continue;
1101 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
1102 U.NegOk)) {
1103 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1104 << CPEs[i].CPI << "\n");
1105 // Point the CPUser node to the replacement
1106 U.CPEMI = CPEs[i].CPEMI;
1107 // Change the CPI in the instruction operand to refer to the clone.
1108 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1109 if (UserMI->getOperand(j).isCPI()) {
1110 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1111 break;
1112 }
1113 // Adjust the refcount of the clone...
1114 CPEs[i].RefCount++;
1115 // ...and the original. If we didn't remove the old entry, none of the
1116 // addresses changed, so we don't need another pass.
1117 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1118 }
1119 }
1120 return 0;
1121 }
1122
1123 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1124 /// This version checks if the longer form of the instruction can be used to
1125 /// to satisfy things.
1126 /// if not, see if an in-range clone of the CPE is in range, and if so,
1127 /// change the data structures so the user references the clone. Returns:
1128 /// 0 = no existing entry found
1129 /// 1 = entry found, and there were no code insertions or deletions
1130 /// 2 = entry found, and there were code insertions or deletions
findLongFormInRangeCPEntry(CPUser & U,unsigned UserOffset)1131 int MipsConstantIslands::findLongFormInRangeCPEntry
1132 (CPUser& U, unsigned UserOffset)
1133 {
1134 MachineInstr *UserMI = U.MI;
1135 MachineInstr *CPEMI = U.CPEMI;
1136
1137 // Check to see if the CPE is already in-range.
1138 if (isCPEntryInRange(UserMI, UserOffset, CPEMI,
1139 U.getLongFormMaxDisp(), U.NegOk,
1140 true)) {
1141 DEBUG(dbgs() << "In range\n");
1142 UserMI->setDesc(TII->get(U.getLongFormOpcode()));
1143 U.setMaxDisp(U.getLongFormMaxDisp());
1144 return 2; // instruction is longer length now
1145 }
1146
1147 // No. Look for previously created clones of the CPE that are in range.
1148 unsigned CPI = CPEMI->getOperand(1).getIndex();
1149 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1150 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1151 // We already tried this one
1152 if (CPEs[i].CPEMI == CPEMI)
1153 continue;
1154 // Removing CPEs can leave empty entries, skip
1155 if (CPEs[i].CPEMI == nullptr)
1156 continue;
1157 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI,
1158 U.getLongFormMaxDisp(), U.NegOk)) {
1159 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1160 << CPEs[i].CPI << "\n");
1161 // Point the CPUser node to the replacement
1162 U.CPEMI = CPEs[i].CPEMI;
1163 // Change the CPI in the instruction operand to refer to the clone.
1164 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1165 if (UserMI->getOperand(j).isCPI()) {
1166 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1167 break;
1168 }
1169 // Adjust the refcount of the clone...
1170 CPEs[i].RefCount++;
1171 // ...and the original. If we didn't remove the old entry, none of the
1172 // addresses changed, so we don't need another pass.
1173 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1174 }
1175 }
1176 return 0;
1177 }
1178
1179 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1180 /// the specific unconditional branch instruction.
getUnconditionalBrDisp(int Opc)1181 static inline unsigned getUnconditionalBrDisp(int Opc) {
1182 switch (Opc) {
1183 case Mips::Bimm16:
1184 return ((1<<10)-1)*2;
1185 case Mips::BimmX16:
1186 return ((1<<16)-1)*2;
1187 default:
1188 break;
1189 }
1190 return ((1<<16)-1)*2;
1191 }
1192
1193 /// findAvailableWater - Look for an existing entry in the WaterList in which
1194 /// we can place the CPE referenced from U so it's within range of U's MI.
1195 /// Returns true if found, false if not. If it returns true, WaterIter
1196 /// is set to the WaterList entry.
1197 /// To ensure that this pass
1198 /// terminates, the CPE location for a particular CPUser is only allowed to
1199 /// move to a lower address, so search backward from the end of the list and
1200 /// prefer the first water that is in range.
findAvailableWater(CPUser & U,unsigned UserOffset,water_iterator & WaterIter)1201 bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
1202 water_iterator &WaterIter) {
1203 if (WaterList.empty())
1204 return false;
1205
1206 unsigned BestGrowth = ~0u;
1207 for (water_iterator IP = std::prev(WaterList.end()), B = WaterList.begin();;
1208 --IP) {
1209 MachineBasicBlock* WaterBB = *IP;
1210 // Check if water is in range and is either at a lower address than the
1211 // current "high water mark" or a new water block that was created since
1212 // the previous iteration by inserting an unconditional branch. In the
1213 // latter case, we want to allow resetting the high water mark back to
1214 // this new water since we haven't seen it before. Inserting branches
1215 // should be relatively uncommon and when it does happen, we want to be
1216 // sure to take advantage of it for all the CPEs near that block, so that
1217 // we don't insert more branches than necessary.
1218 unsigned Growth;
1219 if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
1220 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1221 NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
1222 // This is the least amount of required padding seen so far.
1223 BestGrowth = Growth;
1224 WaterIter = IP;
1225 DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
1226 << " Growth=" << Growth << '\n');
1227
1228 // Keep looking unless it is perfect.
1229 if (BestGrowth == 0)
1230 return true;
1231 }
1232 if (IP == B)
1233 break;
1234 }
1235 return BestGrowth != ~0u;
1236 }
1237
1238 /// createNewWater - No existing WaterList entry will work for
1239 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1240 /// block is used if in range, and the conditional branch munged so control
1241 /// flow is correct. Otherwise the block is split to create a hole with an
1242 /// unconditional branch around it. In either case NewMBB is set to a
1243 /// block following which the new island can be inserted (the WaterList
1244 /// is not adjusted).
createNewWater(unsigned CPUserIndex,unsigned UserOffset,MachineBasicBlock * & NewMBB)1245 void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
1246 unsigned UserOffset,
1247 MachineBasicBlock *&NewMBB) {
1248 CPUser &U = CPUsers[CPUserIndex];
1249 MachineInstr *UserMI = U.MI;
1250 MachineInstr *CPEMI = U.CPEMI;
1251 unsigned CPELogAlign = getCPELogAlign(CPEMI);
1252 MachineBasicBlock *UserMBB = UserMI->getParent();
1253 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
1254
1255 // If the block does not end in an unconditional branch already, and if the
1256 // end of the block is within range, make new water there.
1257 if (BBHasFallthrough(UserMBB)) {
1258 // Size of branch to insert.
1259 unsigned Delta = 2;
1260 // Compute the offset where the CPE will begin.
1261 unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
1262
1263 if (isOffsetInRange(UserOffset, CPEOffset, U)) {
1264 DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
1265 << format(", expected CPE offset %#x\n", CPEOffset));
1266 NewMBB = std::next(MachineFunction::iterator(UserMBB));
1267 // Add an unconditional branch from UserMBB to fallthrough block. Record
1268 // it for branch lengthening; this new branch will not get out of range,
1269 // but if the preceding conditional branch is out of range, the targets
1270 // will be exchanged, and the altered branch may be out of range, so the
1271 // machinery has to know about it.
1272 int UncondBr = Mips::Bimm16;
1273 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
1274 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1275 ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1276 MaxDisp, false, UncondBr));
1277 BBInfo[UserMBB->getNumber()].Size += Delta;
1278 adjustBBOffsetsAfter(UserMBB);
1279 return;
1280 }
1281 }
1282
1283 // What a big block. Find a place within the block to split it.
1284
1285 // Try to split the block so it's fully aligned. Compute the latest split
1286 // point where we can add a 4-byte branch instruction, and then align to
1287 // LogAlign which is the largest possible alignment in the function.
1288 unsigned LogAlign = MF->getAlignment();
1289 assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
1290 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp();
1291 DEBUG(dbgs() << format("Split in middle of big block before %#x",
1292 BaseInsertOffset));
1293
1294 // The 4 in the following is for the unconditional branch we'll be inserting
1295 // Alignment of the island is handled
1296 // inside isOffsetInRange.
1297 BaseInsertOffset -= 4;
1298
1299 DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
1300 << " la=" << LogAlign << '\n');
1301
1302 // This could point off the end of the block if we've already got constant
1303 // pool entries following this block; only the last one is in the water list.
1304 // Back past any possible branches (allow for a conditional and a maximally
1305 // long unconditional).
1306 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
1307 BaseInsertOffset = UserBBI.postOffset() - 8;
1308 DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1309 }
1310 unsigned EndInsertOffset = BaseInsertOffset + 4 +
1311 CPEMI->getOperand(2).getImm();
1312 MachineBasicBlock::iterator MI = UserMI;
1313 ++MI;
1314 unsigned CPUIndex = CPUserIndex+1;
1315 unsigned NumCPUsers = CPUsers.size();
1316 //MachineInstr *LastIT = 0;
1317 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
1318 Offset < BaseInsertOffset;
1319 Offset += TII->GetInstSizeInBytes(MI), MI = std::next(MI)) {
1320 assert(MI != UserMBB->end() && "Fell off end of block");
1321 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1322 CPUser &U = CPUsers[CPUIndex];
1323 if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
1324 // Shift intertion point by one unit of alignment so it is within reach.
1325 BaseInsertOffset -= 1u << LogAlign;
1326 EndInsertOffset -= 1u << LogAlign;
1327 }
1328 // This is overly conservative, as we don't account for CPEMIs being
1329 // reused within the block, but it doesn't matter much. Also assume CPEs
1330 // are added in order with alignment padding. We may eventually be able
1331 // to pack the aligned CPEs better.
1332 EndInsertOffset += U.CPEMI->getOperand(2).getImm();
1333 CPUIndex++;
1334 }
1335 }
1336
1337 --MI;
1338 NewMBB = splitBlockBeforeInstr(MI);
1339 }
1340
1341 /// handleConstantPoolUser - Analyze the specified user, checking to see if it
1342 /// is out-of-range. If so, pick up the constant pool value and move it some
1343 /// place in-range. Return true if we changed any addresses (thus must run
1344 /// another pass of branch lengthening), false otherwise.
handleConstantPoolUser(unsigned CPUserIndex)1345 bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1346 CPUser &U = CPUsers[CPUserIndex];
1347 MachineInstr *UserMI = U.MI;
1348 MachineInstr *CPEMI = U.CPEMI;
1349 unsigned CPI = CPEMI->getOperand(1).getIndex();
1350 unsigned Size = CPEMI->getOperand(2).getImm();
1351 // Compute this only once, it's expensive.
1352 unsigned UserOffset = getUserOffset(U);
1353
1354 // See if the current entry is within range, or there is a clone of it
1355 // in range.
1356 int result = findInRangeCPEntry(U, UserOffset);
1357 if (result==1) return false;
1358 else if (result==2) return true;
1359
1360
1361 // Look for water where we can place this CPE.
1362 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1363 MachineBasicBlock *NewMBB;
1364 water_iterator IP;
1365 if (findAvailableWater(U, UserOffset, IP)) {
1366 DEBUG(dbgs() << "Found water in range\n");
1367 MachineBasicBlock *WaterBB = *IP;
1368
1369 // If the original WaterList entry was "new water" on this iteration,
1370 // propagate that to the new island. This is just keeping NewWaterList
1371 // updated to match the WaterList, which will be updated below.
1372 if (NewWaterList.erase(WaterBB))
1373 NewWaterList.insert(NewIsland);
1374
1375 // The new CPE goes before the following block (NewMBB).
1376 NewMBB = std::next(MachineFunction::iterator(WaterBB));
1377
1378 } else {
1379 // No water found.
1380 // we first see if a longer form of the instrucion could have reached
1381 // the constant. in that case we won't bother to split
1382 if (!NoLoadRelaxation) {
1383 result = findLongFormInRangeCPEntry(U, UserOffset);
1384 if (result != 0) return true;
1385 }
1386 DEBUG(dbgs() << "No water found\n");
1387 createNewWater(CPUserIndex, UserOffset, NewMBB);
1388
1389 // splitBlockBeforeInstr adds to WaterList, which is important when it is
1390 // called while handling branches so that the water will be seen on the
1391 // next iteration for constant pools, but in this context, we don't want
1392 // it. Check for this so it will be removed from the WaterList.
1393 // Also remove any entry from NewWaterList.
1394 MachineBasicBlock *WaterBB = std::prev(MachineFunction::iterator(NewMBB));
1395 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
1396 if (IP != WaterList.end())
1397 NewWaterList.erase(WaterBB);
1398
1399 // We are adding new water. Update NewWaterList.
1400 NewWaterList.insert(NewIsland);
1401 }
1402
1403 // Remove the original WaterList entry; we want subsequent insertions in
1404 // this vicinity to go after the one we're about to insert. This
1405 // considerably reduces the number of times we have to move the same CPE
1406 // more than once and is also important to ensure the algorithm terminates.
1407 if (IP != WaterList.end())
1408 WaterList.erase(IP);
1409
1410 // Okay, we know we can put an island before NewMBB now, do it!
1411 MF->insert(NewMBB, NewIsland);
1412
1413 // Update internal data structures to account for the newly inserted MBB.
1414 updateForInsertedWaterBlock(NewIsland);
1415
1416 // Decrement the old entry, and remove it if refcount becomes 0.
1417 decrementCPEReferenceCount(CPI, CPEMI);
1418
1419 // No existing clone of this CPE is within range.
1420 // We will be generating a new clone. Get a UID for it.
1421 unsigned ID = createPICLabelUId();
1422
1423 // Now that we have an island to add the CPE to, clone the original CPE and
1424 // add it to the island.
1425 U.HighWaterMark = NewIsland;
1426 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
1427 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1428 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1429 ++NumCPEs;
1430
1431 // Mark the basic block as aligned as required by the const-pool entry.
1432 NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
1433
1434 // Increase the size of the island block to account for the new entry.
1435 BBInfo[NewIsland->getNumber()].Size += Size;
1436 adjustBBOffsetsAfter(std::prev(MachineFunction::iterator(NewIsland)));
1437
1438
1439
1440 // Finally, change the CPI in the instruction operand to be ID.
1441 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1442 if (UserMI->getOperand(i).isCPI()) {
1443 UserMI->getOperand(i).setIndex(ID);
1444 break;
1445 }
1446
1447 DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1448 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1449
1450 return true;
1451 }
1452
1453 /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1454 /// sizes and offsets of impacted basic blocks.
removeDeadCPEMI(MachineInstr * CPEMI)1455 void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1456 MachineBasicBlock *CPEBB = CPEMI->getParent();
1457 unsigned Size = CPEMI->getOperand(2).getImm();
1458 CPEMI->eraseFromParent();
1459 BBInfo[CPEBB->getNumber()].Size -= Size;
1460 // All succeeding offsets have the current size value added in, fix this.
1461 if (CPEBB->empty()) {
1462 BBInfo[CPEBB->getNumber()].Size = 0;
1463
1464 // This block no longer needs to be aligned.
1465 CPEBB->setAlignment(0);
1466 } else
1467 // Entries are sorted by descending alignment, so realign from the front.
1468 CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
1469
1470 adjustBBOffsetsAfter(CPEBB);
1471 // An island has only one predecessor BB and one successor BB. Check if
1472 // this BB's predecessor jumps directly to this BB's successor. This
1473 // shouldn't happen currently.
1474 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1475 // FIXME: remove the empty blocks after all the work is done?
1476 }
1477
1478 /// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1479 /// are zero.
removeUnusedCPEntries()1480 bool MipsConstantIslands::removeUnusedCPEntries() {
1481 unsigned MadeChange = false;
1482 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1483 std::vector<CPEntry> &CPEs = CPEntries[i];
1484 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1485 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1486 removeDeadCPEMI(CPEs[j].CPEMI);
1487 CPEs[j].CPEMI = nullptr;
1488 MadeChange = true;
1489 }
1490 }
1491 }
1492 return MadeChange;
1493 }
1494
1495 /// isBBInRange - Returns true if the distance between specific MI and
1496 /// specific BB can fit in MI's displacement field.
isBBInRange(MachineInstr * MI,MachineBasicBlock * DestBB,unsigned MaxDisp)1497 bool MipsConstantIslands::isBBInRange
1498 (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) {
1499
1500 unsigned PCAdj = 4;
1501
1502 unsigned BrOffset = getOffsetOf(MI) + PCAdj;
1503 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1504
1505 DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
1506 << " from BB#" << MI->getParent()->getNumber()
1507 << " max delta=" << MaxDisp
1508 << " from " << getOffsetOf(MI) << " to " << DestOffset
1509 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1510
1511 if (BrOffset <= DestOffset) {
1512 // Branch before the Dest.
1513 if (DestOffset-BrOffset <= MaxDisp)
1514 return true;
1515 } else {
1516 if (BrOffset-DestOffset <= MaxDisp)
1517 return true;
1518 }
1519 return false;
1520 }
1521
1522 /// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1523 /// away to fit in its displacement field.
fixupImmediateBr(ImmBranch & Br)1524 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1525 MachineInstr *MI = Br.MI;
1526 unsigned TargetOperand = branchTargetOperand(MI);
1527 MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
1528
1529 // Check to see if the DestBB is already in-range.
1530 if (isBBInRange(MI, DestBB, Br.MaxDisp))
1531 return false;
1532
1533 if (!Br.isCond)
1534 return fixupUnconditionalBr(Br);
1535 return fixupConditionalBr(Br);
1536 }
1537
1538 /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1539 /// too far away to fit in its displacement field. If the LR register has been
1540 /// spilled in the epilogue, then we can use BL to implement a far jump.
1541 /// Otherwise, add an intermediate branch instruction to a branch.
1542 bool
fixupUnconditionalBr(ImmBranch & Br)1543 MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1544 MachineInstr *MI = Br.MI;
1545 MachineBasicBlock *MBB = MI->getParent();
1546 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1547 // Use BL to implement far jump.
1548 unsigned BimmX16MaxDisp = ((1 << 16)-1) * 2;
1549 if (isBBInRange(MI, DestBB, BimmX16MaxDisp)) {
1550 Br.MaxDisp = BimmX16MaxDisp;
1551 MI->setDesc(TII->get(Mips::BimmX16));
1552 }
1553 else {
1554 // need to give the math a more careful look here
1555 // this is really a segment address and not
1556 // a PC relative address. FIXME. But I think that
1557 // just reducing the bits by 1 as I've done is correct.
1558 // The basic block we are branching too much be longword aligned.
1559 // we know that RA is saved because we always save it right now.
1560 // this requirement will be relaxed later but we also have an alternate
1561 // way to implement this that I will implement that does not need jal.
1562 // We should have a way to back out this alignment restriction if we "can" later.
1563 // but it is not harmful.
1564 //
1565 DestBB->setAlignment(2);
1566 Br.MaxDisp = ((1<<24)-1) * 2;
1567 MI->setDesc(TII->get(Mips::JalB16));
1568 }
1569 BBInfo[MBB->getNumber()].Size += 2;
1570 adjustBBOffsetsAfter(MBB);
1571 HasFarJump = true;
1572 ++NumUBrFixed;
1573
1574 DEBUG(dbgs() << " Changed B to long jump " << *MI);
1575
1576 return true;
1577 }
1578
1579
1580 /// fixupConditionalBr - Fix up a conditional branch whose destination is too
1581 /// far away to fit in its displacement field. It is converted to an inverse
1582 /// conditional branch + an unconditional branch to the destination.
1583 bool
fixupConditionalBr(ImmBranch & Br)1584 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1585 MachineInstr *MI = Br.MI;
1586 unsigned TargetOperand = branchTargetOperand(MI);
1587 MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
1588 unsigned Opcode = MI->getOpcode();
1589 unsigned LongFormOpcode = longformBranchOpcode(Opcode);
1590 unsigned LongFormMaxOff = branchMaxOffsets(LongFormOpcode);
1591
1592 // Check to see if the DestBB is already in-range.
1593 if (isBBInRange(MI, DestBB, LongFormMaxOff)) {
1594 Br.MaxDisp = LongFormMaxOff;
1595 MI->setDesc(TII->get(LongFormOpcode));
1596 return true;
1597 }
1598
1599 // Add an unconditional branch to the destination and invert the branch
1600 // condition to jump over it:
1601 // bteqz L1
1602 // =>
1603 // bnez L2
1604 // b L1
1605 // L2:
1606
1607 // If the branch is at the end of its MBB and that has a fall-through block,
1608 // direct the updated conditional branch to the fall-through block. Otherwise,
1609 // split the MBB before the next instruction.
1610 MachineBasicBlock *MBB = MI->getParent();
1611 MachineInstr *BMI = &MBB->back();
1612 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
1613 unsigned OppositeBranchOpcode = TII->getOppositeBranchOpc(Opcode);
1614
1615 ++NumCBrFixed;
1616 if (BMI != MI) {
1617 if (std::next(MachineBasicBlock::iterator(MI)) == std::prev(MBB->end()) &&
1618 isUnconditionalBranch(BMI->getOpcode())) {
1619 // Last MI in the BB is an unconditional branch. Can we simply invert the
1620 // condition and swap destinations:
1621 // beqz L1
1622 // b L2
1623 // =>
1624 // bnez L2
1625 // b L1
1626 unsigned BMITargetOperand = branchTargetOperand(BMI);
1627 MachineBasicBlock *NewDest =
1628 BMI->getOperand(BMITargetOperand).getMBB();
1629 if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
1630 DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
1631 << *BMI);
1632 MI->setDesc(TII->get(OppositeBranchOpcode));
1633 BMI->getOperand(BMITargetOperand).setMBB(DestBB);
1634 MI->getOperand(TargetOperand).setMBB(NewDest);
1635 return true;
1636 }
1637 }
1638 }
1639
1640
1641 if (NeedSplit) {
1642 splitBlockBeforeInstr(MI);
1643 // No need for the branch to the next block. We're adding an unconditional
1644 // branch to the destination.
1645 int delta = TII->GetInstSizeInBytes(&MBB->back());
1646 BBInfo[MBB->getNumber()].Size -= delta;
1647 MBB->back().eraseFromParent();
1648 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1649 }
1650 MachineBasicBlock *NextBB = std::next(MachineFunction::iterator(MBB));
1651
1652 DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
1653 << " also invert condition and change dest. to BB#"
1654 << NextBB->getNumber() << "\n");
1655
1656 // Insert a new conditional branch and a new unconditional branch.
1657 // Also update the ImmBranch as well as adding a new entry for the new branch.
1658 if (MI->getNumExplicitOperands() == 2) {
1659 BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
1660 .addReg(MI->getOperand(0).getReg())
1661 .addMBB(NextBB);
1662 } else {
1663 BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
1664 .addMBB(NextBB);
1665 }
1666 Br.MI = &MBB->back();
1667 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1668 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1669 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1670 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1671 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1672
1673 // Remove the old conditional branch. It may or may not still be in MBB.
1674 BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
1675 MI->eraseFromParent();
1676 adjustBBOffsetsAfter(MBB);
1677 return true;
1678 }
1679
1680
prescanForConstants()1681 void MipsConstantIslands::prescanForConstants() {
1682 unsigned J = 0;
1683 (void)J;
1684 for (MachineFunction::iterator B =
1685 MF->begin(), E = MF->end(); B != E; ++B) {
1686 for (MachineBasicBlock::instr_iterator I =
1687 B->instr_begin(), EB = B->instr_end(); I != EB; ++I) {
1688 switch(I->getDesc().getOpcode()) {
1689 case Mips::LwConstant32: {
1690 PrescannedForConstants = true;
1691 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1692 J = I->getNumOperands();
1693 DEBUG(dbgs() << "num operands " << J << "\n");
1694 MachineOperand& Literal = I->getOperand(1);
1695 if (Literal.isImm()) {
1696 int64_t V = Literal.getImm();
1697 DEBUG(dbgs() << "literal " << V << "\n");
1698 Type *Int32Ty =
1699 Type::getInt32Ty(MF->getFunction()->getContext());
1700 const Constant *C = ConstantInt::get(Int32Ty, V);
1701 unsigned index = MCP->getConstantPoolIndex(C, 4);
1702 I->getOperand(2).ChangeToImmediate(index);
1703 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1704 I->setDesc(TII->get(Mips::LwRxPcTcp16));
1705 I->RemoveOperand(1);
1706 I->RemoveOperand(1);
1707 I->addOperand(MachineOperand::CreateCPI(index, 0));
1708 I->addOperand(MachineOperand::CreateImm(4));
1709 }
1710 break;
1711 }
1712 default:
1713 break;
1714 }
1715 }
1716 }
1717 }
1718
1719