void LineNumberAnnotatedWriter::emitInstructionAnnot( const Instruction *I, formatted_raw_ostream &Out) { DILocation *NewInstrLoc = I->getDebugLoc(); if (!NewInstrLoc) { auto Loc = DebugLoc.find(I); if (Loc != DebugLoc.end()) NewInstrLoc = Loc->second; } if (!NewInstrLoc || NewInstrLoc == InstrLoc) return; InstrLoc = NewInstrLoc; std::vector<DILineInfo> DIvec; do { DIvec.emplace_back(); DILineInfo &DI = DIvec.back(); DIScope *scope = NewInstrLoc->getScope(); if (scope) DI.FunctionName = scope->getName(); DI.FileName = NewInstrLoc->getFilename(); DI.Line = NewInstrLoc->getLine(); NewInstrLoc = NewInstrLoc->getInlinedAt(); } while (NewInstrLoc); LinePrinter.emit_lineinfo(Out, DIvec); }
const DILocation *DILocation::getMergedLocation(const DILocation *LocA, const DILocation *LocB) { if (!LocA || !LocB) return nullptr; if (LocA == LocB) return LocA; SmallPtrSet<DILocation *, 5> InlinedLocationsA; for (DILocation *L = LocA->getInlinedAt(); L; L = L->getInlinedAt()) InlinedLocationsA.insert(L); SmallSet<std::pair<DIScope *, DILocation *>, 5> Locations; DIScope *S = LocA->getScope(); DILocation *L = LocA->getInlinedAt(); while (S) { Locations.insert(std::make_pair(S, L)); S = S->getScope().resolve(); if (!S && L) { S = L->getScope(); L = L->getInlinedAt(); } } const DILocation *Result = LocB; S = LocB->getScope(); L = LocB->getInlinedAt(); while (S) { if (Locations.count(std::make_pair(S, L))) break; S = S->getScope().resolve(); if (!S && L) { S = L->getScope(); L = L->getInlinedAt(); } } // If the two locations are irreconsilable, just pick one. This is misleading, // but on the other hand, it's a "line 0" location. if (!S || !isa<DILocalScope>(S)) S = LocA->getScope(); return DILocation::get(Result->getContext(), 0, 0, S, L); }
const DILocation *DILocation::getMergedLocation(const DILocation *LocA, const DILocation *LocB, bool GenerateLocation) { if (!LocA || !LocB) return nullptr; if (LocA == LocB || !LocA->canDiscriminate(*LocB)) return LocA; if (!GenerateLocation) return nullptr; SmallPtrSet<DILocation *, 5> InlinedLocationsA; for (DILocation *L = LocA->getInlinedAt(); L; L = L->getInlinedAt()) InlinedLocationsA.insert(L); const DILocation *Result = LocB; for (DILocation *L = LocB->getInlinedAt(); L; L = L->getInlinedAt()) { Result = L; if (InlinedLocationsA.count(L)) break; } return DILocation::get(Result->getContext(), 0, 0, Result->getScope(), Result->getInlinedAt()); }
/// \brief Assign DWARF discriminators. /// /// To assign discriminators, we examine the boundaries of every /// basic block and its successors. Suppose there is a basic block B1 /// with successor B2. The last instruction I1 in B1 and the first /// instruction I2 in B2 are located at the same file and line number. /// This situation is illustrated in the following code snippet: /// /// if (i < 10) x = i; /// /// entry: /// br i1 %cmp, label %if.then, label %if.end, !dbg !10 /// if.then: /// %1 = load i32* %i.addr, align 4, !dbg !10 /// store i32 %1, i32* %x, align 4, !dbg !10 /// br label %if.end, !dbg !10 /// if.end: /// ret void, !dbg !12 /// /// Notice how the branch instruction in block 'entry' and all the /// instructions in block 'if.then' have the exact same debug location /// information (!dbg !10). /// /// To distinguish instructions in block 'entry' from instructions in /// block 'if.then', we generate a new lexical block for all the /// instruction in block 'if.then' that share the same file and line /// location with the last instruction of block 'entry'. /// /// This new lexical block will have the same location information as /// the previous one, but with a new DWARF discriminator value. /// /// One of the main uses of this discriminator value is in runtime /// sample profilers. It allows the profiler to distinguish instructions /// at location !dbg !10 that execute on different basic blocks. This is /// important because while the predicate 'if (x < 10)' may have been /// executed millions of times, the assignment 'x = i' may have only /// executed a handful of times (meaning that the entry->if.then edge is /// seldom taken). /// /// If we did not have discriminator information, the profiler would /// assign the same weight to both blocks 'entry' and 'if.then', which /// in turn will make it conclude that the entry->if.then edge is very /// hot. /// /// To decide where to create new discriminator values, this function /// traverses the CFG and examines instruction at basic block boundaries. /// If the last instruction I1 of a block B1 is at the same file and line /// location as instruction I2 of successor B2, then it creates a new /// lexical block for I2 and all the instruction in B2 that share the same /// file and line location as I2. This new lexical block will have a /// different discriminator number than I1. bool AddDiscriminators::runOnFunction(Function &F) { // If the function has debug information, but the user has disabled // discriminators, do nothing. // Simlarly, if the function has no debug info, do nothing. // Finally, if this module is built with dwarf versions earlier than 4, // do nothing (discriminator support is a DWARF 4 feature). if (NoDiscriminators || !hasDebugInfo(F) || F.getParent()->getDwarfVersion() < 4) return false; bool Changed = false; Module *M = F.getParent(); LLVMContext &Ctx = M->getContext(); DIBuilder Builder(*M, /*AllowUnresolved*/ false); typedef std::pair<StringRef, unsigned> Location; typedef DenseMap<const BasicBlock *, Metadata *> BBScopeMap; typedef DenseMap<Location, BBScopeMap> LocationBBMap; typedef DenseMap<Location, unsigned> LocationDiscriminatorMap; LocationBBMap LBM; LocationDiscriminatorMap LDM; // Traverse all instructions in the function. If the source line location // of the instruction appears in other basic block, assign a new // discriminator for this instruction. for (BasicBlock &B : F) { for (auto &I : B.getInstList()) { if (isa<DbgInfoIntrinsic>(&I)) continue; const DILocation *DIL = I.getDebugLoc(); if (!DIL) continue; Location L = std::make_pair(DIL->getFilename(), DIL->getLine()); auto &BBMap = LBM[L]; auto R = BBMap.insert(std::make_pair(&B, (Metadata *)nullptr)); if (BBMap.size() == 1) continue; bool InsertSuccess = R.second; Metadata *&NewScope = R.first->second; // If we could insert a different block in the same location, a // discriminator is needed to distinguish both instructions. if (InsertSuccess) { auto *Scope = DIL->getScope(); auto *File = Builder.createFile(DIL->getFilename(), Scope->getDirectory()); NewScope = Builder.createLexicalBlockFile(Scope, File, ++LDM[L]); } I.setDebugLoc(DILocation::get(Ctx, DIL->getLine(), DIL->getColumn(), NewScope, DIL->getInlinedAt())); DEBUG(dbgs() << DIL->getFilename() << ":" << DIL->getLine() << ":" << DIL->getColumn() << ":" << dyn_cast<DILexicalBlockFile>(NewScope)->getDiscriminator() << I << "\n"); Changed = true; } } // Traverse all instructions and assign new discriminators to call // instructions with the same lineno that are in the same basic block. // Sample base profile needs to distinguish different function calls within // a same source line for correct profile annotation. for (BasicBlock &B : F) { const DILocation *FirstDIL = nullptr; for (auto &I : B.getInstList()) { CallInst *Current = dyn_cast<CallInst>(&I); if (!Current || isa<DbgInfoIntrinsic>(&I)) continue; DILocation *CurrentDIL = Current->getDebugLoc(); if (FirstDIL) { if (CurrentDIL && CurrentDIL->getLine() == FirstDIL->getLine() && CurrentDIL->getFilename() == FirstDIL->getFilename()) { auto *Scope = FirstDIL->getScope(); auto *File = Builder.createFile(FirstDIL->getFilename(), Scope->getDirectory()); Location L = std::make_pair(FirstDIL->getFilename(), FirstDIL->getLine()); auto *NewScope = Builder.createLexicalBlockFile(Scope, File, ++LDM[L]); Current->setDebugLoc(DILocation::get( Ctx, CurrentDIL->getLine(), CurrentDIL->getColumn(), NewScope, CurrentDIL->getInlinedAt())); Changed = true; } else { FirstDIL = CurrentDIL; } } else { FirstDIL = CurrentDIL; } } } return Changed; }
/// \brief Assign DWARF discriminators. /// /// To assign discriminators, we examine the boundaries of every /// basic block and its successors. Suppose there is a basic block B1 /// with successor B2. The last instruction I1 in B1 and the first /// instruction I2 in B2 are located at the same file and line number. /// This situation is illustrated in the following code snippet: /// /// if (i < 10) x = i; /// /// entry: /// br i1 %cmp, label %if.then, label %if.end, !dbg !10 /// if.then: /// %1 = load i32* %i.addr, align 4, !dbg !10 /// store i32 %1, i32* %x, align 4, !dbg !10 /// br label %if.end, !dbg !10 /// if.end: /// ret void, !dbg !12 /// /// Notice how the branch instruction in block 'entry' and all the /// instructions in block 'if.then' have the exact same debug location /// information (!dbg !10). /// /// To distinguish instructions in block 'entry' from instructions in /// block 'if.then', we generate a new lexical block for all the /// instruction in block 'if.then' that share the same file and line /// location with the last instruction of block 'entry'. /// /// This new lexical block will have the same location information as /// the previous one, but with a new DWARF discriminator value. /// /// One of the main uses of this discriminator value is in runtime /// sample profilers. It allows the profiler to distinguish instructions /// at location !dbg !10 that execute on different basic blocks. This is /// important because while the predicate 'if (x < 10)' may have been /// executed millions of times, the assignment 'x = i' may have only /// executed a handful of times (meaning that the entry->if.then edge is /// seldom taken). /// /// If we did not have discriminator information, the profiler would /// assign the same weight to both blocks 'entry' and 'if.then', which /// in turn will make it conclude that the entry->if.then edge is very /// hot. /// /// To decide where to create new discriminator values, this function /// traverses the CFG and examines instruction at basic block boundaries. /// If the last instruction I1 of a block B1 is at the same file and line /// location as instruction I2 of successor B2, then it creates a new /// lexical block for I2 and all the instruction in B2 that share the same /// file and line location as I2. This new lexical block will have a /// different discriminator number than I1. bool AddDiscriminators::runOnFunction(Function &F) { // If the function has debug information, but the user has disabled // discriminators, do nothing. // Simlarly, if the function has no debug info, do nothing. // Finally, if this module is built with dwarf versions earlier than 4, // do nothing (discriminator support is a DWARF 4 feature). if (NoDiscriminators || !hasDebugInfo(F) || F.getParent()->getDwarfVersion() < 4) return false; bool Changed = false; Module *M = F.getParent(); LLVMContext &Ctx = M->getContext(); DIBuilder Builder(*M, /*AllowUnresolved*/ false); // Traverse all the blocks looking for instructions in different // blocks that are at the same file:line location. for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) { BasicBlock *B = I; TerminatorInst *Last = B->getTerminator(); DILocation LastDIL = Last->getDebugLoc().get(); if (!LastDIL) continue; for (unsigned I = 0; I < Last->getNumSuccessors(); ++I) { BasicBlock *Succ = Last->getSuccessor(I); Instruction *First = Succ->getFirstNonPHIOrDbgOrLifetime(); DILocation FirstDIL = First->getDebugLoc().get(); if (!FirstDIL) continue; // If the first instruction (First) of Succ is at the same file // location as B's last instruction (Last), add a new // discriminator for First's location and all the instructions // in Succ that share the same location with First. if (!FirstDIL->canDiscriminate(*LastDIL)) { // Create a new lexical scope and compute a new discriminator // number for it. StringRef Filename = FirstDIL->getFilename(); auto *Scope = FirstDIL->getScope(); auto *File = Builder.createFile(Filename, Scope->getDirectory()); // FIXME: Calculate the discriminator here, based on local information, // and delete MDLocation::computeNewDiscriminator(). The current // solution gives different results depending on other modules in the // same context. All we really need is to discriminate between // FirstDIL and LastDIL -- a local map would suffice. unsigned Discriminator = FirstDIL->computeNewDiscriminator(); auto *NewScope = Builder.createLexicalBlockFile(Scope, File, Discriminator); auto *NewDIL = MDLocation::get(Ctx, FirstDIL->getLine(), FirstDIL->getColumn(), NewScope, FirstDIL->getInlinedAt()); DebugLoc newDebugLoc = NewDIL; // Attach this new debug location to First and every // instruction following First that shares the same location. for (BasicBlock::iterator I1(*First), E1 = Succ->end(); I1 != E1; ++I1) { if (I1->getDebugLoc().get() != FirstDIL) break; I1->setDebugLoc(newDebugLoc); DEBUG(dbgs() << NewDIL->getFilename() << ":" << NewDIL->getLine() << ":" << NewDIL->getColumn() << ":" << NewDIL->getDiscriminator() << *I1 << "\n"); } DEBUG(dbgs() << "\n"); Changed = true; } } } return Changed; }