From 652cd7c1007aa5a13ad9864fadc939c5710c5199 Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Mon, 13 Jan 2020 23:54:42 +0100 Subject: [PATCH] [InstCombine] Fix user iterator invalidation in bitcast of phi transform This fixes the issue encountered in D71164. Instead of using a range-based for, manually iterate over the users and advance the iterator beforehand, so we do not skip any users due to iterator invalidation. Differential Revision: https://reviews.llvm.org/D72657 --- .../lib/Transforms/InstCombine/InstCombineCasts.cpp | 5 ++++- .../InstCombine/bitcast-phi-uselistorder.ll | 13 +++++-------- 2 files changed, 9 insertions(+), 9 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp index 3ba56bbe53e0..f6c7bb5d4479 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp @@ -2344,7 +2344,10 @@ Instruction *InstCombiner::optimizeBitCastFromPhi(CastInst &CI, PHINode *PN) { Instruction *RetVal = nullptr; for (auto *OldPN : OldPhiNodes) { PHINode *NewPN = NewPNodes[OldPN]; - for (User *V : OldPN->users()) { + for (auto It = OldPN->user_begin(), End = OldPN->user_end(); It != End; ) { + User *V = *It; + // We may remove this user, advance to avoid iterator invalidation. + ++It; if (auto *SI = dyn_cast(V)) { assert(SI->isSimple() && SI->getOperand(0) == OldPN); Builder.SetInsertPoint(SI); diff --git a/llvm/test/Transforms/InstCombine/bitcast-phi-uselistorder.ll b/llvm/test/Transforms/InstCombine/bitcast-phi-uselistorder.ll index d1af21f6c4d5..d5489484bddf 100644 --- a/llvm/test/Transforms/InstCombine/bitcast-phi-uselistorder.ll +++ b/llvm/test/Transforms/InstCombine/bitcast-phi-uselistorder.ll @@ -8,16 +8,13 @@ define double @test(i1 %c, i64* %p) { ; CHECK-NEXT: entry: ; CHECK-NEXT: br i1 [[C:%.*]], label [[IF:%.*]], label [[END:%.*]] ; CHECK: if: -; CHECK-NEXT: [[LOAD:%.*]] = load i64, i64* bitcast (double* @Q to i64*), align 8 -; CHECK-NEXT: [[TMP0:%.*]] = bitcast i64 [[LOAD]] to double -; CHECK-NEXT: [[PHITMP:%.*]] = bitcast i64 [[LOAD]] to double +; CHECK-NEXT: [[LOAD1:%.*]] = load double, double* @Q, align 8 ; CHECK-NEXT: br label [[END]] ; CHECK: end: -; CHECK-NEXT: [[TMP1:%.*]] = phi double [ 0.000000e+00, [[ENTRY:%.*]] ], [ [[TMP0]], [[IF]] ] -; CHECK-NEXT: [[PHI:%.*]] = phi double [ 0.000000e+00, [[ENTRY]] ], [ [[PHITMP]], [[IF]] ] -; CHECK-NEXT: [[TMP2:%.*]] = bitcast i64* [[P:%.*]] to double* -; CHECK-NEXT: store double [[TMP1]], double* [[TMP2]], align 8 -; CHECK-NEXT: ret double [[PHI]] +; CHECK-NEXT: [[TMP0:%.*]] = phi double [ 0.000000e+00, [[ENTRY:%.*]] ], [ [[LOAD1]], [[IF]] ] +; CHECK-NEXT: [[TMP1:%.*]] = bitcast i64* [[P:%.*]] to double* +; CHECK-NEXT: store double [[TMP0]], double* [[TMP1]], align 8 +; CHECK-NEXT: ret double [[TMP0]] ; entry: br i1 %c, label %if, label %end