Author: Florian Hahn Date: 2021-01-04T09:51:20Z New Revision: e0905553b424afe94938e2cc010fcecd0822eaba
URL: https://github.com/llvm/llvm-project/commit/e0905553b424afe94938e2cc010fcecd0822eaba DIFF: https://github.com/llvm/llvm-project/commit/e0905553b424afe94938e2cc010fcecd0822eaba.diff LOG: [ArgPromotion] Delay dead GEP removal until doPromotion. Currently ArgPromotion removes dead GEPs as part of the legality check in isSafeToPromoteArgument. If no promotion happens, this means the pass claims no modifications happened, even though GEPs were removed. This patch fixes the issue by delaying removal of dead GEPs until doPromotion: isSafeToPromoteArgument can simply skips dead GEPs and the code in doPromotion dealing with GEPs is updated to account for dead GEPs. Once we committed to promotion, it should be safe to remove dead GEPs. Alternatively isSafeToPromoteArgument could return an additional boolean to indicate whether it made changes, but this is quite cumbersome and there should be no real benefit of weeding out some dead GEPs here if we do not perform promotion. I added a test for the case where dead GEPs need to be removed when promotion happens in 578c5a0c6e71. Fixes PR47477. Reviewed By: jdoerfert Differential Revision: https://reviews.llvm.org/D93991 Added: llvm/test/Transforms/ArgumentPromotion/dead-gep-no-promotion.ll Modified: llvm/lib/Transforms/IPO/ArgumentPromotion.cpp Removed: ################################################################################ diff --git a/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp b/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp index 11c8d3b7a8d6..eaaee9a520ab 100644 --- a/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp +++ b/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp @@ -160,13 +160,19 @@ doPromotion(Function *F, SmallPtrSetImpl<Argument *> &ArgsToPromote, // In this table, we will track which indices are loaded from the argument // (where direct loads are tracked as no indices). ScalarizeTable &ArgIndices = ScalarizedElements[&*I]; - for (User *U : I->users()) { - Instruction *UI = cast<Instruction>(U); + for (auto Iter = I->user_begin(), End = I->user_end(); Iter != End;) { + Instruction *UI = cast<Instruction>(*Iter++); Type *SrcTy; if (LoadInst *L = dyn_cast<LoadInst>(UI)) SrcTy = L->getType(); else SrcTy = cast<GetElementPtrInst>(UI)->getSourceElementType(); + // Skip dead GEPs and remove them. + if (isa<GetElementPtrInst>(UI) && UI->use_empty()) { + UI->eraseFromParent(); + continue; + } + IndicesVector Indices; Indices.reserve(UI->getNumOperands() - 1); // Since loads will only have a single operand, and GEPs only a single @@ -436,6 +442,8 @@ doPromotion(Function *F, SmallPtrSetImpl<Argument *> &ArgsToPromote, << "' in function '" << F->getName() << "'\n"); } else { GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->user_back()); + assert(!GEP->use_empty() && + "GEPs without uses should be cleaned up already"); IndicesVector Operands; Operands.reserve(GEP->getNumIndices()); for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end(); @@ -674,11 +682,7 @@ static bool isSafeToPromoteArgument(Argument *Arg, Type *ByValTy, AAResults &AAR if (GEP->use_empty()) { // Dead GEP's cause trouble later. Just remove them if we run into // them. - GEP->eraseFromParent(); - // TODO: This runs the above loop over and over again for dead GEPs - // Couldn't we just do increment the UI iterator earlier and erase the - // use? - return isSafeToPromoteArgument(Arg, ByValTy, AAR, MaxElements); + continue; } if (!UpdateBaseTy(GEP->getSourceElementType())) diff --git a/llvm/test/Transforms/ArgumentPromotion/dead-gep-no-promotion.ll b/llvm/test/Transforms/ArgumentPromotion/dead-gep-no-promotion.ll new file mode 100644 index 000000000000..72431a43ae6f --- /dev/null +++ b/llvm/test/Transforms/ArgumentPromotion/dead-gep-no-promotion.ll @@ -0,0 +1,30 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py +; RUN: opt -argpromotion -S %s | FileCheck %s + +@glob = external global i32* + +; No arguments in @callee can be promoted, but it contains a dead GEP. Make +; sure it is not removed, as we do not perform any promotion. +define i32 @caller(i32* %ptr) { +; CHECK-LABEL: @caller( +; CHECK-NEXT: call void @callee(i32* [[PTR:%.*]], i32* [[PTR]], i32* [[PTR]]) +; CHECK-NEXT: ret i32 0 +; + call void @callee(i32* %ptr, i32* %ptr, i32* %ptr) + ret i32 0 +} + +define internal void @callee(i32* %arg, i32* %arg1, i32* %arg2) { +; CHECK-LABEL: define internal void @callee( +; CHECK-NEXT: call void @external_fn(i32* [[ARG:%.*]], i32* [[ARG1:%.*]]) +; CHECK-NEXT: [[DEAD_GEP:%.*]] = getelementptr inbounds i32, i32* [[ARG1]], i32 17 +; CHECK-NEXT: store i32* [[ARG2:%.*]], i32** @glob, align 8 +; CHECK-NEXT: ret void +; + call void @external_fn(i32* %arg, i32* %arg1) + %dead.gep = getelementptr inbounds i32, i32* %arg1, i32 17 + store i32* %arg2, i32** @glob, align 8 + ret void +} + +declare void @external_fn(i32*, i32*) _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
