444 lines · cpp
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-exception6//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/CodeGen/AsmPrinter.h"16#include "llvm/CodeGen/MachineFunction.h"17#include "llvm/CodeGen/MachineInstr.h"18#include "llvm/CodeGen/MachineModuleInfo.h"19#include "llvm/CodeGen/TargetSubtargetInfo.h"20#include "llvm/IR/DebugInfo.h"21#include "llvm/IR/Module.h"22#include "llvm/MC/MCStreamer.h"23#include "llvm/Support/CommandLine.h"24 25using namespace llvm;26 27#define DEBUG_TYPE "dwarfdebug"28 29/// If true, we drop variable location ranges which exist entirely outside the30/// variable's lexical scope instruction ranges.31static cl::opt<bool> TrimVarLocs("trim-var-locs", cl::Hidden, cl::init(true));32 33std::optional<DbgVariableLocation>34DbgVariableLocation::extractFromMachineInstruction(35 const MachineInstr &Instruction) {36 DbgVariableLocation Location;37 // Variables calculated from multiple locations can't be represented here.38 if (Instruction.getNumDebugOperands() != 1)39 return std::nullopt;40 if (!Instruction.getDebugOperand(0).isReg())41 return std::nullopt;42 Location.Register = Instruction.getDebugOperand(0).getReg().asMCReg();43 Location.FragmentInfo.reset();44 // We only handle expressions generated by DIExpression::appendOffset,45 // which doesn't require a full stack machine.46 int64_t Offset = 0;47 const DIExpression *DIExpr = Instruction.getDebugExpression();48 auto Op = DIExpr->expr_op_begin();49 // We can handle a DBG_VALUE_LIST iff it has exactly one location operand that50 // appears exactly once at the start of the expression.51 if (Instruction.isDebugValueList()) {52 if (Instruction.getNumDebugOperands() == 1 &&53 Op->getOp() == dwarf::DW_OP_LLVM_arg)54 ++Op;55 else56 return std::nullopt;57 }58 while (Op != DIExpr->expr_op_end()) {59 switch (Op->getOp()) {60 case dwarf::DW_OP_constu: {61 int Value = Op->getArg(0);62 ++Op;63 if (Op != DIExpr->expr_op_end()) {64 switch (Op->getOp()) {65 case dwarf::DW_OP_minus:66 Offset -= Value;67 break;68 case dwarf::DW_OP_plus:69 Offset += Value;70 break;71 default:72 continue;73 }74 }75 } break;76 case dwarf::DW_OP_plus_uconst:77 Offset += Op->getArg(0);78 break;79 case dwarf::DW_OP_LLVM_fragment:80 Location.FragmentInfo = {Op->getArg(1), Op->getArg(0)};81 break;82 case dwarf::DW_OP_deref:83 Location.LoadChain.push_back(Offset);84 Offset = 0;85 break;86 default:87 return std::nullopt;88 }89 ++Op;90 }91 92 // Do one final implicit DW_OP_deref if this was an indirect DBG_VALUE93 // instruction.94 // FIXME: Replace these with DIExpression.95 if (Instruction.isIndirectDebugValue())96 Location.LoadChain.push_back(Offset);97 98 return Location;99}100 101DebugHandlerBase::DebugHandlerBase(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {}102 103DebugHandlerBase::~DebugHandlerBase() = default;104 105void DebugHandlerBase::beginModule(Module *M) {106 if (M->debug_compile_units().empty())107 Asm = nullptr;108 else109 LScopes.initialize(*M);110}111 112// Each LexicalScope has first instruction and last instruction to mark113// beginning and end of a scope respectively. Create an inverse map that list114// scopes starts (and ends) with an instruction. One instruction may start (or115// end) multiple scopes. Ignore scopes that are not reachable.116void DebugHandlerBase::identifyScopeMarkers() {117 SmallVector<LexicalScope *, 4> WorkList;118 WorkList.push_back(LScopes.getCurrentFunctionScope());119 while (!WorkList.empty()) {120 LexicalScope *S = WorkList.pop_back_val();121 122 const SmallVectorImpl<LexicalScope *> &Children = S->getChildren();123 if (!Children.empty())124 WorkList.append(Children.begin(), Children.end());125 126 if (S->isAbstractScope())127 continue;128 129 for (const InsnRange &R : S->getRanges()) {130 assert(R.first && "InsnRange does not have first instruction!");131 assert(R.second && "InsnRange does not have second instruction!");132 requestLabelBeforeInsn(R.first);133 requestLabelAfterInsn(R.second);134 }135 }136}137 138// Return Label preceding the instruction.139MCSymbol *DebugHandlerBase::getLabelBeforeInsn(const MachineInstr *MI) {140 MCSymbol *Label = LabelsBeforeInsn.lookup(MI);141 assert(Label && "Didn't insert label before instruction");142 return Label;143}144 145// Return Label immediately following the instruction.146MCSymbol *DebugHandlerBase::getLabelAfterInsn(const MachineInstr *MI) {147 return LabelsAfterInsn.lookup(MI);148}149 150/// If this type is derived from a base type then return base type size.151uint64_t DebugHandlerBase::getBaseTypeSize(const DIType *Ty) {152 assert(Ty);153 154 unsigned Tag = Ty->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 Tag != dwarf::DW_TAG_immutable_type &&160 Tag != dwarf::DW_TAG_template_alias)161 return Ty->getSizeInBits();162 163 DIType *BaseType = nullptr;164 if (const DIDerivedType *DDTy = dyn_cast<DIDerivedType>(Ty))165 BaseType = DDTy->getBaseType();166 else if (const DISubrangeType *SRTy = dyn_cast<DISubrangeType>(Ty))167 BaseType = SRTy->getBaseType();168 169 if (!BaseType)170 return 0;171 172 // If this is a derived type, go ahead and get the base type, unless it's a173 // reference then it's just the size of the field. Pointer types have no need174 // of this since they're a different type of qualification on the type.175 if (BaseType->getTag() == dwarf::DW_TAG_reference_type ||176 BaseType->getTag() == dwarf::DW_TAG_rvalue_reference_type)177 return Ty->getSizeInBits();178 179 return getBaseTypeSize(BaseType);180}181 182bool DebugHandlerBase::isUnsignedDIType(const DIType *Ty) {183 if (isa<DIStringType>(Ty)) {184 // Some transformations (e.g. instcombine) may decide to turn a Fortran185 // character object into an integer, and later ones (e.g. SROA) may186 // further inject a constant integer in a llvm.dbg.value call to track187 // the object's value. Here we trust the transformations are doing the188 // right thing, and treat the constant as unsigned to preserve that value189 // (i.e. avoid sign extension).190 return true;191 }192 193 if (auto *SRTy = dyn_cast<DISubrangeType>(Ty)) {194 Ty = SRTy->getBaseType();195 if (!Ty)196 return false;197 }198 199 if (auto *CTy = dyn_cast<DICompositeType>(Ty)) {200 if (CTy->getTag() == dwarf::DW_TAG_enumeration_type) {201 if (!(Ty = CTy->getBaseType()))202 // FIXME: Enums without a fixed underlying type have unknown signedness203 // here, leading to incorrectly emitted constants.204 return false;205 } else206 // (Pieces of) aggregate types that get hacked apart by SROA may be207 // represented by a constant. Encode them as unsigned bytes.208 return true;209 }210 211 if (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {212 dwarf::Tag T = (dwarf::Tag)Ty->getTag();213 // Encode pointer constants as unsigned bytes. This is used at least for214 // null pointer constant emission.215 // FIXME: reference and rvalue_reference /probably/ shouldn't be allowed216 // here, but accept them for now due to a bug in SROA producing bogus217 // dbg.values.218 if (T == dwarf::DW_TAG_pointer_type ||219 T == dwarf::DW_TAG_ptr_to_member_type ||220 T == dwarf::DW_TAG_reference_type ||221 T == dwarf::DW_TAG_rvalue_reference_type)222 return true;223 assert(T == dwarf::DW_TAG_typedef || T == dwarf::DW_TAG_const_type ||224 T == dwarf::DW_TAG_volatile_type ||225 T == dwarf::DW_TAG_restrict_type || T == dwarf::DW_TAG_atomic_type ||226 T == dwarf::DW_TAG_immutable_type ||227 T == dwarf::DW_TAG_template_alias);228 assert(DTy->getBaseType() && "Expected valid base type");229 return isUnsignedDIType(DTy->getBaseType());230 }231 232 auto *BTy = cast<DIBasicType>(Ty);233 unsigned Encoding = BTy->getEncoding();234 assert((Encoding == dwarf::DW_ATE_unsigned ||235 Encoding == dwarf::DW_ATE_unsigned_char ||236 Encoding == dwarf::DW_ATE_signed ||237 Encoding == dwarf::DW_ATE_signed_char ||238 Encoding == dwarf::DW_ATE_float || Encoding == dwarf::DW_ATE_UTF ||239 Encoding == dwarf::DW_ATE_boolean ||240 Encoding == dwarf::DW_ATE_complex_float ||241 Encoding == dwarf::DW_ATE_signed_fixed ||242 Encoding == dwarf::DW_ATE_unsigned_fixed ||243 (Encoding >= dwarf::DW_ATE_lo_user &&244 Encoding <= dwarf::DW_ATE_hi_user) ||245 (Ty->getTag() == dwarf::DW_TAG_unspecified_type &&246 Ty->getName() == "decltype(nullptr)")) &&247 "Unsupported encoding");248 return Encoding == dwarf::DW_ATE_unsigned ||249 Encoding == dwarf::DW_ATE_unsigned_char ||250 Encoding == dwarf::DW_ATE_UTF || Encoding == dwarf::DW_ATE_boolean ||251 Encoding == llvm::dwarf::DW_ATE_unsigned_fixed ||252 Ty->getTag() == dwarf::DW_TAG_unspecified_type;253}254 255static bool hasDebugInfo(const MachineFunction *MF) {256 auto *SP = MF->getFunction().getSubprogram();257 if (!SP)258 return false;259 assert(SP->getUnit());260 auto EK = SP->getUnit()->getEmissionKind();261 if (EK == DICompileUnit::NoDebug)262 return false;263 return true;264}265 266void DebugHandlerBase::beginFunction(const MachineFunction *MF) {267 PrevInstBB = nullptr;268 269 if (!Asm || !hasDebugInfo(MF)) {270 skippedNonDebugFunction();271 return;272 }273 274 // Grab the lexical scopes for the function, if we don't have any of those275 // then we're not going to be able to do anything.276 LScopes.scanFunction(*MF);277 if (LScopes.empty()) {278 beginFunctionImpl(MF);279 return;280 }281 282 // Make sure that each lexical scope will have a begin/end label.283 identifyScopeMarkers();284 285 // Calculate history for local variables.286 assert(DbgValues.empty() && "DbgValues map wasn't cleaned!");287 assert(DbgLabels.empty() && "DbgLabels map wasn't cleaned!");288 calculateDbgEntityHistory(MF, Asm->MF->getSubtarget().getRegisterInfo(),289 DbgValues, DbgLabels);290 InstOrdering.initialize(*MF);291 if (TrimVarLocs)292 DbgValues.trimLocationRanges(*MF, LScopes, InstOrdering);293 LLVM_DEBUG(DbgValues.dump(MF->getName()));294 295 // Request labels for the full history.296 for (const auto &I : DbgValues) {297 const auto &Entries = I.second;298 if (Entries.empty())299 continue;300 301 auto IsDescribedByReg = [](const MachineInstr *MI) {302 return any_of(MI->debug_operands(),303 [](auto &MO) { return MO.isReg() && MO.getReg(); });304 };305 306 // The first mention of a function argument gets the CurrentFnBegin label,307 // so arguments are visible when breaking at function entry.308 //309 // We do not change the label for values that are described by registers,310 // as that could place them above their defining instructions. We should311 // ideally not change the labels for constant debug values either, since312 // doing that violates the ranges that are calculated in the history map.313 // However, we currently do not emit debug values for constant arguments314 // directly at the start of the function, so this code is still useful.315 const DILocalVariable *DIVar =316 Entries.front().getInstr()->getDebugVariable();317 if (DIVar->isParameter() &&318 getDISubprogram(DIVar->getScope())->describes(&MF->getFunction())) {319 if (!IsDescribedByReg(Entries.front().getInstr()))320 LabelsBeforeInsn[Entries.front().getInstr()] = Asm->getFunctionBegin();321 if (Entries.front().getInstr()->getDebugExpression()->isFragment()) {322 // Mark all non-overlapping initial fragments.323 for (const auto *I = Entries.begin(); I != Entries.end(); ++I) {324 if (!I->isDbgValue())325 continue;326 const DIExpression *Fragment = I->getInstr()->getDebugExpression();327 if (std::any_of(Entries.begin(), I,328 [&](DbgValueHistoryMap::Entry Pred) {329 return Pred.isDbgValue() &&330 Fragment->fragmentsOverlap(331 Pred.getInstr()->getDebugExpression());332 }))333 break;334 // The code that generates location lists for DWARF assumes that the335 // entries' start labels are monotonically increasing, and since we336 // don't change the label for fragments that are described by337 // registers, we must bail out when encountering such a fragment.338 if (IsDescribedByReg(I->getInstr()))339 break;340 LabelsBeforeInsn[I->getInstr()] = Asm->getFunctionBegin();341 }342 }343 }344 345 for (const auto &Entry : Entries) {346 if (Entry.isDbgValue())347 requestLabelBeforeInsn(Entry.getInstr());348 else349 requestLabelAfterInsn(Entry.getInstr());350 }351 }352 353 // Ensure there is a symbol before DBG_LABEL.354 for (const auto &I : DbgLabels) {355 const MachineInstr *MI = I.second;356 requestLabelBeforeInsn(MI);357 }358 359 PrevInstLoc = DebugLoc();360 PrevLabel = Asm->getFunctionBegin();361 beginFunctionImpl(MF);362}363 364void DebugHandlerBase::beginInstruction(const MachineInstr *MI) {365 if (!Asm || !Asm->hasDebugInfo())366 return;367 368 assert(CurMI == nullptr);369 CurMI = MI;370 371 // Insert labels where requested.372 DenseMap<const MachineInstr *, MCSymbol *>::iterator I =373 LabelsBeforeInsn.find(MI);374 375 // No label needed.376 if (I == LabelsBeforeInsn.end())377 return;378 379 // Label already assigned.380 if (I->second)381 return;382 383 if (!PrevLabel) {384 PrevLabel = MMI->getContext().createTempSymbol();385 Asm->OutStreamer->emitLabel(PrevLabel);386 }387 I->second = PrevLabel;388}389 390void DebugHandlerBase::endInstruction() {391 if (!Asm || !Asm->hasDebugInfo())392 return;393 394 assert(CurMI != nullptr);395 // Don't create a new label after DBG_VALUE and other instructions that don't396 // generate code.397 if (!CurMI->isMetaInstruction()) {398 PrevLabel = nullptr;399 PrevInstBB = CurMI->getParent();400 }401 402 DenseMap<const MachineInstr *, MCSymbol *>::iterator I =403 LabelsAfterInsn.find(CurMI);404 405 // No label needed or label already assigned.406 if (I == LabelsAfterInsn.end() || I->second) {407 CurMI = nullptr;408 return;409 }410 411 // We need a label after this instruction. With basic block sections, just412 // use the end symbol of the section if this is the last instruction of the413 // section. This reduces the need for an additional label and also helps414 // merging ranges.415 if (CurMI->getParent()->isEndSection() && CurMI->getNextNode() == nullptr) {416 PrevLabel = CurMI->getParent()->getEndSymbol();417 } else if (!PrevLabel) {418 PrevLabel = MMI->getContext().createTempSymbol();419 Asm->OutStreamer->emitLabel(PrevLabel);420 }421 I->second = PrevLabel;422 CurMI = nullptr;423}424 425void DebugHandlerBase::endFunction(const MachineFunction *MF) {426 if (Asm && hasDebugInfo(MF))427 endFunctionImpl(MF);428 DbgValues.clear();429 DbgLabels.clear();430 LabelsBeforeInsn.clear();431 LabelsAfterInsn.clear();432 InstOrdering.clear();433}434 435void DebugHandlerBase::beginBasicBlockSection(const MachineBasicBlock &MBB) {436 EpilogBeginBlock = nullptr;437 if (!MBB.isEntryBlock())438 PrevLabel = MBB.getSymbol();439}440 441void DebugHandlerBase::endBasicBlockSection(const MachineBasicBlock &MBB) {442 PrevLabel = nullptr;443}444