From 9e66c4ec127ef6e73f1bafe06fe3fba45d59feee Mon Sep 17 00:00:00 2001 From: Alina Sbirlea Date: Thu, 23 Jan 2020 14:21:08 -0800 Subject: [PATCH] [Utils] Use WeakTrackingVH in vector used as scratch storage. The utility method RecursivelyDeleteTriviallyDeadInstructions receives as input a vector of Instructions, where all inputs are valid instructions. This same vector is used as a scratch storage (per the header comment) to recursively delete instructions. If an instruction is added as an operand of multiple other instructions, it may be added twice, then deleted once, then the second reference in the vector is invalid. Switch to using a Vector. This change facilitates a clean-up in LoopStrengthReduction. --- llvm/include/llvm/Transforms/Utils/Local.h | 2 +- llvm/lib/Transforms/IPO/Attributor.cpp | 2 +- llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp | 2 +- llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp | 2 +- llvm/lib/Transforms/Utils/Local.cpp | 21 ++++++++++++--------- 5 files changed, 16 insertions(+), 13 deletions(-) diff --git a/llvm/include/llvm/Transforms/Utils/Local.h b/llvm/include/llvm/Transforms/Utils/Local.h index be619d74da3..79b743d6752 100644 --- a/llvm/include/llvm/Transforms/Utils/Local.h +++ b/llvm/include/llvm/Transforms/Utils/Local.h @@ -153,7 +153,7 @@ bool RecursivelyDeleteTriviallyDeadInstructions( /// `DeadInsts` will be used as scratch storage for this routine and will be /// empty afterward. void RecursivelyDeleteTriviallyDeadInstructions( - SmallVectorImpl &DeadInsts, + SmallVectorImpl &DeadInsts, const TargetLibraryInfo *TLI = nullptr, MemorySSAUpdater *MSSAU = nullptr); /// If the specified value is an effectively dead PHI node, due to being a diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp index f2995817eaf..baa1cb125d7 100644 --- a/llvm/lib/Transforms/IPO/Attributor.cpp +++ b/llvm/lib/Transforms/IPO/Attributor.cpp @@ -6041,7 +6041,7 @@ ChangeStatus Attributor::run(Module &M) { << ToBeDeletedInsts.size() << " instructions and " << ToBeChangedUses.size() << " uses\n"); - SmallVector DeadInsts; + SmallVector DeadInsts; SmallVector TerminatorsToFold; for (auto &It : ToBeChangedUses) { diff --git a/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp b/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp index e8bbf2936da..e87b622ab19 100644 --- a/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp +++ b/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp @@ -40,7 +40,7 @@ static bool runImpl(Function &F, const SimplifyQuery &SQ, if (!SQ.DT->isReachableFromEntry(&BB)) continue; - SmallVector DeadInstsInBB; + SmallVector DeadInstsInBB; for (Instruction &I : BB) { // The first time through the loop, ToSimplify is empty and we try to // simplify all instructions. On later iterations, ToSimplify is not diff --git a/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp b/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp index 901204181a7..3153a872119 100644 --- a/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp +++ b/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp @@ -68,7 +68,7 @@ static bool simplifyLoopInst(Loop &L, DominatorTree &DT, LoopInfo &LI, // While simplifying we may discover dead code or cause code to become dead. // Keep track of all such instructions and we will delete them at the end. - SmallVector DeadInsts; + SmallVector DeadInsts; // First we want to create an RPO traversal of the loop body. By processing in // RPO we can ensure that definitions are processed prior to uses (for non PHI diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp index 5b188fc4385..10afed34718 100644 --- a/llvm/lib/Transforms/Utils/Local.cpp +++ b/llvm/lib/Transforms/Utils/Local.cpp @@ -443,7 +443,7 @@ bool llvm::RecursivelyDeleteTriviallyDeadInstructions( if (!I || !isInstructionTriviallyDead(I, TLI)) return false; - SmallVector DeadInsts; + SmallVector DeadInsts; DeadInsts.push_back(I); RecursivelyDeleteTriviallyDeadInstructions(DeadInsts, TLI, MSSAU); @@ -451,21 +451,24 @@ bool llvm::RecursivelyDeleteTriviallyDeadInstructions( } void llvm::RecursivelyDeleteTriviallyDeadInstructions( - SmallVectorImpl &DeadInsts, const TargetLibraryInfo *TLI, + SmallVectorImpl &DeadInsts, const TargetLibraryInfo *TLI, MemorySSAUpdater *MSSAU) { // Process the dead instruction list until empty. while (!DeadInsts.empty()) { - Instruction &I = *DeadInsts.pop_back_val(); - assert(I.use_empty() && "Instructions with uses are not dead."); - assert(isInstructionTriviallyDead(&I, TLI) && + Value *V = DeadInsts.pop_back_val(); + Instruction *I = cast_or_null(V); + if (!I) + continue; + assert(isInstructionTriviallyDead(I, TLI) && "Live instruction found in dead worklist!"); + assert(I->use_empty() && "Instructions with uses are not dead."); // Don't lose the debug info while deleting the instructions. - salvageDebugInfo(I); + salvageDebugInfo(*I); // Null out all of the instruction's operands to see if any operand becomes // dead as we go. - for (Use &OpU : I.operands()) { + for (Use &OpU : I->operands()) { Value *OpV = OpU.get(); OpU.set(nullptr); @@ -480,9 +483,9 @@ void llvm::RecursivelyDeleteTriviallyDeadInstructions( DeadInsts.push_back(OpI); } if (MSSAU) - MSSAU->removeMemoryAccess(&I); + MSSAU->removeMemoryAccess(I); - I.eraseFromParent(); + I->eraseFromParent(); } } -- 2.11.0