From 18b02bbf441660683df7f3925946984203d49bab Mon Sep 17 00:00:00 2001 From: DianQK Date: Wed, 20 Nov 2024 19:52:51 +0800 Subject: [PATCH] [LICM] allow MemoryAccess creation failure (#116813) Fixes #116809. After running some passes (SimpleLoopUnswitch, LoopInstSimplify, etc.), MemorySSA might be outdated, and the instruction `I` may have become a non-memory touching instruction. LICM has already handled this, but it does not pass `CreationMustSucceed=false` to `createDefinedAccess`. --- llvm/include/llvm/Analysis/MemorySSAUpdater.h | 3 +- llvm/lib/Analysis/MemorySSAUpdater.cpp | 8 +-- llvm/lib/Transforms/Scalar/LICM.cpp | 5 +- .../LICM/PR116813-memoryssa-outdated.ll | 50 +++++++++++++++++++ 4 files changed, 61 insertions(+), 5 deletions(-) create mode 100644 llvm/test/Transforms/LICM/PR116813-memoryssa-outdated.ll diff --git a/llvm/include/llvm/Analysis/MemorySSAUpdater.h b/llvm/include/llvm/Analysis/MemorySSAUpdater.h index d4da3ef1146db7..055feceefb0546 100644 --- a/llvm/include/llvm/Analysis/MemorySSAUpdater.h +++ b/llvm/include/llvm/Analysis/MemorySSAUpdater.h @@ -190,7 +190,8 @@ class MemorySSAUpdater { /// inaccessible and it *must* have removeMemoryAccess called on it. MemoryAccess *createMemoryAccessInBB(Instruction *I, MemoryAccess *Definition, const BasicBlock *BB, - MemorySSA::InsertionPlace Point); + MemorySSA::InsertionPlace Point, + bool CreationMustSucceed = true); /// Create a MemoryAccess in MemorySSA before an existing MemoryAccess. /// diff --git a/llvm/lib/Analysis/MemorySSAUpdater.cpp b/llvm/lib/Analysis/MemorySSAUpdater.cpp index aa550f0b6a7bfd..f672bd0e1e133e 100644 --- a/llvm/lib/Analysis/MemorySSAUpdater.cpp +++ b/llvm/lib/Analysis/MemorySSAUpdater.cpp @@ -1403,9 +1403,11 @@ void MemorySSAUpdater::changeToUnreachable(const Instruction *I) { MemoryAccess *MemorySSAUpdater::createMemoryAccessInBB( Instruction *I, MemoryAccess *Definition, const BasicBlock *BB, - MemorySSA::InsertionPlace Point) { - MemoryUseOrDef *NewAccess = MSSA->createDefinedAccess(I, Definition); - MSSA->insertIntoListsForBlock(NewAccess, BB, Point); + MemorySSA::InsertionPlace Point, bool CreationMustSucceed) { + MemoryUseOrDef *NewAccess = MSSA->createDefinedAccess( + I, Definition, /*Template=*/nullptr, CreationMustSucceed); + if (NewAccess) + MSSA->insertIntoListsForBlock(NewAccess, BB, Point); return NewAccess; } diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp index fa04ced7182dc7..94bfe44a847a37 100644 --- a/llvm/lib/Transforms/Scalar/LICM.cpp +++ b/llvm/lib/Transforms/Scalar/LICM.cpp @@ -1465,8 +1465,11 @@ static Instruction *cloneInstructionInExitBlock( if (MSSAU.getMemorySSA()->getMemoryAccess(&I)) { // Create a new MemoryAccess and let MemorySSA set its defining access. + // After running some passes, MemorySSA might be outdated, and the + // instruction `I` may have become a non-memory touching instruction. MemoryAccess *NewMemAcc = MSSAU.createMemoryAccessInBB( - New, nullptr, New->getParent(), MemorySSA::Beginning); + New, nullptr, New->getParent(), MemorySSA::Beginning, + /*CreationMustSucceed=*/false); if (NewMemAcc) { if (auto *MemDef = dyn_cast(NewMemAcc)) MSSAU.insertDef(MemDef, /*RenameUses=*/true); diff --git a/llvm/test/Transforms/LICM/PR116813-memoryssa-outdated.ll b/llvm/test/Transforms/LICM/PR116813-memoryssa-outdated.ll new file mode 100644 index 00000000000000..a040c3cc6947c6 --- /dev/null +++ b/llvm/test/Transforms/LICM/PR116813-memoryssa-outdated.ll @@ -0,0 +1,50 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5 +; RUN: opt -passes='loop-mssa(simple-loop-unswitch,licm)' -verify-memoryssa -S < %s | FileCheck %s + +; Check that running LICM after SimpleLoopUnswitch does not result in a crash. + +define i32 @foo(i1 %arg, ptr %arg1) { +; CHECK-LABEL: define i32 @foo( +; CHECK-SAME: i1 [[ARG:%.*]], ptr [[ARG1:%.*]]) { +; CHECK-NEXT: [[START:.*:]] +; CHECK-NEXT: [[ARG_FR:%.*]] = freeze i1 [[ARG]] +; CHECK-NEXT: br i1 [[ARG_FR]], label %[[START_SPLIT_US:.*]], label %[[START_SPLIT:.*]] +; CHECK: [[START_SPLIT_US]]: +; CHECK-NEXT: br label %[[LOOP_US:.*]] +; CHECK: [[LOOP_US]]: +; CHECK-NEXT: br label %[[BB0:.*]] +; CHECK: [[BB0]]: +; CHECK-NEXT: br label %[[BB1:.*]] +; CHECK: [[BB1]]: +; CHECK-NEXT: [[UNSWITCHED_SELECT_US:%.*]] = phi ptr [ [[ARG1]], %[[BB0]] ] +; CHECK-NEXT: [[I3_US:%.*]] = call i32 [[UNSWITCHED_SELECT_US]]() +; CHECK-NEXT: br i1 true, label %[[LOOP_US]], label %[[RET_SPLIT_US:.*]] +; CHECK: [[RET_SPLIT_US]]: +; CHECK-NEXT: [[I3_LCSSA_US:%.*]] = phi i32 [ [[I3_US]], %[[BB1]] ] +; CHECK-NEXT: br label %[[RET:.*]] +; CHECK: [[START_SPLIT]]: +; CHECK-NEXT: br label %[[LOOP:.*]] +; CHECK: [[LOOP]]: +; CHECK-NEXT: br label %[[BB2:.*]] +; CHECK: [[BB2]]: +; CHECK-NEXT: br i1 false, label %[[LOOP]], label %[[RET_SPLIT:.*]] +; CHECK: [[RET_SPLIT]]: +; CHECK-NEXT: [[I3_LE:%.*]] = call i32 @bar() +; CHECK-NEXT: br label %[[RET]] +; CHECK: [[RET]]: +; CHECK-NEXT: [[DOTUS_PHI:%.*]] = phi i32 [ [[I3_LE]], %[[RET_SPLIT]] ], [ [[I3_LCSSA_US]], %[[RET_SPLIT_US]] ] +; CHECK-NEXT: ret i32 [[DOTUS_PHI]] +; +start: + br label %loop + +loop: ; preds = %loop, %bb + %i = select i1 %arg, ptr %arg1, ptr @bar + %i3 = call i32 %i() + br i1 %arg, label %loop, label %ret + +ret: ; preds = %loop + ret i32 %i3 +} + +declare i32 @bar() nounwind willreturn memory(none)