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[InstCombine] Fix miscompile on GEP+load to icmp fold #628

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[InstCombine] Fix miscompile on GEP+load to icmp fold #628

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b410b31
[InstCombine] Add pre-commit test for Fix miscompile on GEP+load to i…
vladimirradosavljevic Jun 18, 2024
95a8b42
[InstCombine] Fix miscompile on GEP+load to icmp fold
vladimirradosavljevic Jun 18, 2024
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4 changes: 3 additions & 1 deletion llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -305,7 +305,9 @@ Instruction *InstCombinerImpl::foldCmpLoadFromIndexedGlobal(
DL.getTypeAllocSize(Init->getType()->getArrayElementType());
auto MaskIdx = [&](Value *Idx) {
if (!GEP->isInBounds() && llvm::countr_zero(ElementSize) != 0) {
Value *Mask = ConstantInt::get(Idx->getType(), -1);
// EraVM local begin
Value *Mask = ConstantInt::get(Idx->getType(), -1, true);
// EraVM local end
Mask = Builder.CreateLShr(Mask, llvm::countr_zero(ElementSize));
Idx = Builder.CreateAnd(Idx, Mask);
}
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20 changes: 20 additions & 0 deletions llvm/test/Transforms/InstCombine/load-cmp-bug.ll
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@@ -0,0 +1,20 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
; RUN: opt -passes=instcombine -S < %s | FileCheck %s

target datalayout = "E-p:256:256-i256:256:256-S32-a:256:256"

@G16 = internal constant [10 x i256] [i256 35, i256 82, i256 69, i256 81, i256 85,
i256 73, i256 82, i256 69, i256 68, i256 0]

define i1 @test_noinbounds(i256 %X) {
; CHECK-LABEL: define i1 @test_noinbounds
; CHECK-SAME: (i256 [[X:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = and i256 [[X]], 3618502788666131106986593281521497120414687020801267626233049500247285301247
; CHECK-NEXT: [[R:%.*]] = icmp eq i256 [[TMP1]], 9
; CHECK-NEXT: ret i1 [[R]]
;
%P = getelementptr [10 x i256], ptr @G16, i256 0, i256 %X
%Q = load i256, ptr %P
%R = icmp eq i256 %Q, 0
ret i1 %R
}