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[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
This commit is contained in:
Nikita Popov 2020-01-13 23:54:42 +01:00
parent fa63234093
commit 652cd7c100
2 changed files with 9 additions and 9 deletions
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5
llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -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<StoreInst>(V)) {
assert(SI->isSimple() && SI->getOperand(0) == OldPN);
Builder.SetInsertPoint(SI);

13
llvm/test/Transforms/InstCombine/bitcast-phi-uselistorder.ll
View File

@ -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