1 //===-- llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp -------*- C++ -*--===//
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 //
9 // Common functionality for different debug information format backends.
10 // LLVM currently supports DWARF and CodeView.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "llvm/CodeGen/DebugHandlerBase.h"
15 #include "llvm/ADT/Optional.h"
16 #include "llvm/ADT/Twine.h"
17 #include "llvm/CodeGen/AsmPrinter.h"
18 #include "llvm/CodeGen/MachineFunction.h"
19 #include "llvm/CodeGen/MachineInstr.h"
20 #include "llvm/CodeGen/MachineModuleInfo.h"
21 #include "llvm/CodeGen/TargetSubtargetInfo.h"
22 #include "llvm/IR/DebugInfo.h"
23 #include "llvm/MC/MCStreamer.h"
24 #include "llvm/Support/CommandLine.h"
25
26 using namespace llvm;
27
28 #define DEBUG_TYPE "dwarfdebug"
29
30 /// If true, we drop variable location ranges which exist entirely outside the
31 /// variable's lexical scope instruction ranges.
32 static cl::opt<bool> TrimVarLocs("trim-var-locs", cl::Hidden, cl::init(true));
33
34 Optional<DbgVariableLocation>
extractFromMachineInstruction(const MachineInstr & Instruction)35 DbgVariableLocation::extractFromMachineInstruction(
36 const MachineInstr &Instruction) {
37 DbgVariableLocation Location;
38 // Variables calculated from multiple locations can't be represented here.
39 if (Instruction.getNumDebugOperands() != 1)
40 return None;
41 if (!Instruction.getDebugOperand(0).isReg())
42 return None;
43 Location.Register = Instruction.getDebugOperand(0).getReg();
44 Location.FragmentInfo.reset();
45 // We only handle expressions generated by DIExpression::appendOffset,
46 // which doesn't require a full stack machine.
47 int64_t Offset = 0;
48 const DIExpression *DIExpr = Instruction.getDebugExpression();
49 auto Op = DIExpr->expr_op_begin();
50 // We can handle a DBG_VALUE_LIST iff it has exactly one location operand that
51 // appears exactly once at the start of the expression.
52 if (Instruction.isDebugValueList()) {
53 if (Instruction.getNumDebugOperands() == 1 &&
54 Op->getOp() == dwarf::DW_OP_LLVM_arg)
55 ++Op;
56 else
57 return None;
58 }
59 while (Op != DIExpr->expr_op_end()) {
60 switch (Op->getOp()) {
61 case dwarf::DW_OP_constu: {
62 int Value = Op->getArg(0);
63 ++Op;
64 if (Op != DIExpr->expr_op_end()) {
65 switch (Op->getOp()) {
66 case dwarf::DW_OP_minus:
67 Offset -= Value;
68 break;
69 case dwarf::DW_OP_plus:
70 Offset += Value;
71 break;
72 default:
73 continue;
74 }
75 }
76 } break;
77 case dwarf::DW_OP_plus_uconst:
78 Offset += Op->getArg(0);
79 break;
80 case dwarf::DW_OP_LLVM_fragment:
81 Location.FragmentInfo = {Op->getArg(1), Op->getArg(0)};
82 break;
83 case dwarf::DW_OP_deref:
84 Location.LoadChain.push_back(Offset);
85 Offset = 0;
86 break;
87 default:
88 return None;
89 }
90 ++Op;
91 }
92
93 // Do one final implicit DW_OP_deref if this was an indirect DBG_VALUE
94 // instruction.
95 // FIXME: Replace these with DIExpression.
96 if (Instruction.isIndirectDebugValue())
97 Location.LoadChain.push_back(Offset);
98
99 return Location;
100 }
101
DebugHandlerBase(AsmPrinter * A)102 DebugHandlerBase::DebugHandlerBase(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {}
103
beginModule(Module * M)104 void DebugHandlerBase::beginModule(Module *M) {
105 if (M->debug_compile_units().empty())
106 Asm = nullptr;
107 }
108
109 // Each LexicalScope has first instruction and last instruction to mark
110 // beginning and end of a scope respectively. Create an inverse map that list
111 // scopes starts (and ends) with an instruction. One instruction may start (or
112 // end) multiple scopes. Ignore scopes that are not reachable.
identifyScopeMarkers()113 void DebugHandlerBase::identifyScopeMarkers() {
114 SmallVector<LexicalScope *, 4> WorkList;
115 WorkList.push_back(LScopes.getCurrentFunctionScope());
116 while (!WorkList.empty()) {
117 LexicalScope *S = WorkList.pop_back_val();
118
119 const SmallVectorImpl<LexicalScope *> &Children = S->getChildren();
120 if (!Children.empty())
121 WorkList.append(Children.begin(), Children.end());
122
123 if (S->isAbstractScope())
124 continue;
125
126 for (const InsnRange &R : S->getRanges()) {
127 assert(R.first && "InsnRange does not have first instruction!");
128 assert(R.second && "InsnRange does not have second instruction!");
129 requestLabelBeforeInsn(R.first);
130 requestLabelAfterInsn(R.second);
131 }
132 }
133 }
134
135 // Return Label preceding the instruction.
getLabelBeforeInsn(const MachineInstr * MI)136 MCSymbol *DebugHandlerBase::getLabelBeforeInsn(const MachineInstr *MI) {
137 MCSymbol *Label = LabelsBeforeInsn.lookup(MI);
138 assert(Label && "Didn't insert label before instruction");
139 return Label;
140 }
141
142 // Return Label immediately following the instruction.
getLabelAfterInsn(const MachineInstr * MI)143 MCSymbol *DebugHandlerBase::getLabelAfterInsn(const MachineInstr *MI) {
144 return LabelsAfterInsn.lookup(MI);
145 }
146
147 /// If this type is derived from a base type then return base type size.
getBaseTypeSize(const DIType * Ty)148 uint64_t DebugHandlerBase::getBaseTypeSize(const DIType *Ty) {
149 assert(Ty);
150 const DIDerivedType *DDTy = dyn_cast<DIDerivedType>(Ty);
151 if (!DDTy)
152 return Ty->getSizeInBits();
153
154 unsigned Tag = DDTy->getTag();
155
156 if (Tag != dwarf::DW_TAG_member && Tag != dwarf::DW_TAG_typedef &&
157 Tag != dwarf::DW_TAG_const_type && Tag != dwarf::DW_TAG_volatile_type &&
158 Tag != dwarf::DW_TAG_restrict_type && Tag != dwarf::DW_TAG_atomic_type)
159 return DDTy->getSizeInBits();
160
161 DIType *BaseType = DDTy->getBaseType();
162
163 if (!BaseType)
164 return 0;
165
166 // If this is a derived type, go ahead and get the base type, unless it's a
167 // reference then it's just the size of the field. Pointer types have no need
168 // of this since they're a different type of qualification on the type.
169 if (BaseType->getTag() == dwarf::DW_TAG_reference_type ||
170 BaseType->getTag() == dwarf::DW_TAG_rvalue_reference_type)
171 return Ty->getSizeInBits();
172
173 return getBaseTypeSize(BaseType);
174 }
175
isUnsignedDIType(const DIType * Ty)176 bool DebugHandlerBase::isUnsignedDIType(const DIType *Ty) {
177 // SROA may generate dbg value intrinsics to assign an unsigned value to a
178 // Fortran CHARACTER(1) type variables. Make them as unsigned.
179 if (isa<DIStringType>(Ty)) {
180 assert((Ty->getSizeInBits()) == 8 && "Not a valid unsigned type!");
181 return true;
182 }
183 if (auto *CTy = dyn_cast<DICompositeType>(Ty)) {
184 // FIXME: Enums without a fixed underlying type have unknown signedness
185 // here, leading to incorrectly emitted constants.
186 if (CTy->getTag() == dwarf::DW_TAG_enumeration_type)
187 return false;
188
189 // (Pieces of) aggregate types that get hacked apart by SROA may be
190 // represented by a constant. Encode them as unsigned bytes.
191 return true;
192 }
193
194 if (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
195 dwarf::Tag T = (dwarf::Tag)Ty->getTag();
196 // Encode pointer constants as unsigned bytes. This is used at least for
197 // null pointer constant emission.
198 // FIXME: reference and rvalue_reference /probably/ shouldn't be allowed
199 // here, but accept them for now due to a bug in SROA producing bogus
200 // dbg.values.
201 if (T == dwarf::DW_TAG_pointer_type ||
202 T == dwarf::DW_TAG_ptr_to_member_type ||
203 T == dwarf::DW_TAG_reference_type ||
204 T == dwarf::DW_TAG_rvalue_reference_type)
205 return true;
206 assert(T == dwarf::DW_TAG_typedef || T == dwarf::DW_TAG_const_type ||
207 T == dwarf::DW_TAG_volatile_type ||
208 T == dwarf::DW_TAG_restrict_type || T == dwarf::DW_TAG_atomic_type);
209 assert(DTy->getBaseType() && "Expected valid base type");
210 return isUnsignedDIType(DTy->getBaseType());
211 }
212
213 auto *BTy = cast<DIBasicType>(Ty);
214 unsigned Encoding = BTy->getEncoding();
215 assert((Encoding == dwarf::DW_ATE_unsigned ||
216 Encoding == dwarf::DW_ATE_unsigned_char ||
217 Encoding == dwarf::DW_ATE_signed ||
218 Encoding == dwarf::DW_ATE_signed_char ||
219 Encoding == dwarf::DW_ATE_float || Encoding == dwarf::DW_ATE_UTF ||
220 Encoding == dwarf::DW_ATE_boolean ||
221 (Ty->getTag() == dwarf::DW_TAG_unspecified_type &&
222 Ty->getName() == "decltype(nullptr)")) &&
223 "Unsupported encoding");
224 return Encoding == dwarf::DW_ATE_unsigned ||
225 Encoding == dwarf::DW_ATE_unsigned_char ||
226 Encoding == dwarf::DW_ATE_UTF || Encoding == dwarf::DW_ATE_boolean ||
227 Ty->getTag() == dwarf::DW_TAG_unspecified_type;
228 }
229
hasDebugInfo(const MachineModuleInfo * MMI,const MachineFunction * MF)230 static bool hasDebugInfo(const MachineModuleInfo *MMI,
231 const MachineFunction *MF) {
232 if (!MMI->hasDebugInfo())
233 return false;
234 auto *SP = MF->getFunction().getSubprogram();
235 if (!SP)
236 return false;
237 assert(SP->getUnit());
238 auto EK = SP->getUnit()->getEmissionKind();
239 if (EK == DICompileUnit::NoDebug)
240 return false;
241 return true;
242 }
243
beginFunction(const MachineFunction * MF)244 void DebugHandlerBase::beginFunction(const MachineFunction *MF) {
245 PrevInstBB = nullptr;
246
247 if (!Asm || !hasDebugInfo(MMI, MF)) {
248 skippedNonDebugFunction();
249 return;
250 }
251
252 // Grab the lexical scopes for the function, if we don't have any of those
253 // then we're not going to be able to do anything.
254 LScopes.initialize(*MF);
255 if (LScopes.empty()) {
256 beginFunctionImpl(MF);
257 return;
258 }
259
260 // Make sure that each lexical scope will have a begin/end label.
261 identifyScopeMarkers();
262
263 // Calculate history for local variables.
264 assert(DbgValues.empty() && "DbgValues map wasn't cleaned!");
265 assert(DbgLabels.empty() && "DbgLabels map wasn't cleaned!");
266 calculateDbgEntityHistory(MF, Asm->MF->getSubtarget().getRegisterInfo(),
267 DbgValues, DbgLabels);
268 InstOrdering.initialize(*MF);
269 if (TrimVarLocs)
270 DbgValues.trimLocationRanges(*MF, LScopes, InstOrdering);
271 LLVM_DEBUG(DbgValues.dump());
272
273 // Request labels for the full history.
274 for (const auto &I : DbgValues) {
275 const auto &Entries = I.second;
276 if (Entries.empty())
277 continue;
278
279 auto IsDescribedByReg = [](const MachineInstr *MI) {
280 return any_of(MI->debug_operands(),
281 [](auto &MO) { return MO.isReg() && MO.getReg(); });
282 };
283
284 // The first mention of a function argument gets the CurrentFnBegin label,
285 // so arguments are visible when breaking at function entry.
286 //
287 // We do not change the label for values that are described by registers,
288 // as that could place them above their defining instructions. We should
289 // ideally not change the labels for constant debug values either, since
290 // doing that violates the ranges that are calculated in the history map.
291 // However, we currently do not emit debug values for constant arguments
292 // directly at the start of the function, so this code is still useful.
293 // FIXME: If the first mention of an argument is in a unique section basic
294 // block, we cannot always assign the CurrentFnBeginLabel as it lies in a
295 // different section. Temporarily, we disable generating loc list
296 // information or DW_AT_const_value when the block is in a different
297 // section.
298 const DILocalVariable *DIVar =
299 Entries.front().getInstr()->getDebugVariable();
300 if (DIVar->isParameter() &&
301 getDISubprogram(DIVar->getScope())->describes(&MF->getFunction()) &&
302 Entries.front().getInstr()->getParent()->sameSection(&MF->front())) {
303 if (!IsDescribedByReg(Entries.front().getInstr()))
304 LabelsBeforeInsn[Entries.front().getInstr()] = Asm->getFunctionBegin();
305 if (Entries.front().getInstr()->getDebugExpression()->isFragment()) {
306 // Mark all non-overlapping initial fragments.
307 for (auto I = Entries.begin(); I != Entries.end(); ++I) {
308 if (!I->isDbgValue())
309 continue;
310 const DIExpression *Fragment = I->getInstr()->getDebugExpression();
311 if (std::any_of(Entries.begin(), I,
312 [&](DbgValueHistoryMap::Entry Pred) {
313 return Pred.isDbgValue() &&
314 Fragment->fragmentsOverlap(
315 Pred.getInstr()->getDebugExpression());
316 }))
317 break;
318 // The code that generates location lists for DWARF assumes that the
319 // entries' start labels are monotonically increasing, and since we
320 // don't change the label for fragments that are described by
321 // registers, we must bail out when encountering such a fragment.
322 if (IsDescribedByReg(I->getInstr()))
323 break;
324 LabelsBeforeInsn[I->getInstr()] = Asm->getFunctionBegin();
325 }
326 }
327 }
328
329 for (const auto &Entry : Entries) {
330 if (Entry.isDbgValue())
331 requestLabelBeforeInsn(Entry.getInstr());
332 else
333 requestLabelAfterInsn(Entry.getInstr());
334 }
335 }
336
337 // Ensure there is a symbol before DBG_LABEL.
338 for (const auto &I : DbgLabels) {
339 const MachineInstr *MI = I.second;
340 requestLabelBeforeInsn(MI);
341 }
342
343 PrevInstLoc = DebugLoc();
344 PrevLabel = Asm->getFunctionBegin();
345 beginFunctionImpl(MF);
346 }
347
beginInstruction(const MachineInstr * MI)348 void DebugHandlerBase::beginInstruction(const MachineInstr *MI) {
349 if (!Asm || !MMI->hasDebugInfo())
350 return;
351
352 assert(CurMI == nullptr);
353 CurMI = MI;
354
355 // Insert labels where requested.
356 DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
357 LabelsBeforeInsn.find(MI);
358
359 // No label needed.
360 if (I == LabelsBeforeInsn.end())
361 return;
362
363 // Label already assigned.
364 if (I->second)
365 return;
366
367 if (!PrevLabel) {
368 PrevLabel = MMI->getContext().createTempSymbol();
369 Asm->OutStreamer->emitLabel(PrevLabel);
370 }
371 I->second = PrevLabel;
372 }
373
endInstruction()374 void DebugHandlerBase::endInstruction() {
375 if (!Asm || !MMI->hasDebugInfo())
376 return;
377
378 assert(CurMI != nullptr);
379 // Don't create a new label after DBG_VALUE and other instructions that don't
380 // generate code.
381 if (!CurMI->isMetaInstruction()) {
382 PrevLabel = nullptr;
383 PrevInstBB = CurMI->getParent();
384 }
385
386 DenseMap<const MachineInstr *, MCSymbol *>::iterator I =
387 LabelsAfterInsn.find(CurMI);
388 CurMI = nullptr;
389
390 // No label needed.
391 if (I == LabelsAfterInsn.end())
392 return;
393
394 // Label already assigned.
395 if (I->second)
396 return;
397
398 // We need a label after this instruction.
399 if (!PrevLabel) {
400 PrevLabel = MMI->getContext().createTempSymbol();
401 Asm->OutStreamer->emitLabel(PrevLabel);
402 }
403 I->second = PrevLabel;
404 }
405
endFunction(const MachineFunction * MF)406 void DebugHandlerBase::endFunction(const MachineFunction *MF) {
407 if (Asm && hasDebugInfo(MMI, MF))
408 endFunctionImpl(MF);
409 DbgValues.clear();
410 DbgLabels.clear();
411 LabelsBeforeInsn.clear();
412 LabelsAfterInsn.clear();
413 InstOrdering.clear();
414 }
415
beginBasicBlock(const MachineBasicBlock & MBB)416 void DebugHandlerBase::beginBasicBlock(const MachineBasicBlock &MBB) {
417 if (!MBB.isBeginSection())
418 return;
419
420 PrevLabel = MBB.getSymbol();
421 }
422
endBasicBlock(const MachineBasicBlock & MBB)423 void DebugHandlerBase::endBasicBlock(const MachineBasicBlock &MBB) {
424 if (!MBB.isEndSection())
425 return;
426
427 PrevLabel = nullptr;
428 }
429