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[SimplifyLibCalls] Don't change alignment when creating memset

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Fix for PR49984
This was discovered during Attributor testing.
Memset was always created with alignment of 1
and in case when strncpy alignment was changed
it triggered an assertion in the AttrBuilder.
Memset will now be created with appropriate alignment.

Differential Revision: https://reviews.llvm.org/D100875
This commit is contained in:
sstefan1 2021-04-20 19:55:11 +02:00
parent b3bc645e79
commit b6d664ee22
2 changed files with 14 additions and 2 deletions
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6
lib/Transforms/Utils/SimplifyLibCalls.cpp
View File

@ -575,8 +575,10 @@ Value *LibCallSimplifier::optimizeStrNCpy(CallInst *CI, IRBuilderBase &B) {
}
if (SrcLen == 0) {
// strncpy(x, "", y) -> memset(align 1 x, '\0', y)
CallInst *NewCI = B.CreateMemSet(Dst, B.getInt8('\0'), Size, Align(1));
// strncpy(x, "", y) -> memset(x, '\0', y)
Align MemSetAlign =
CI->getAttributes().getParamAttributes(0).getAlignment().valueOrOne();
CallInst *NewCI = B.CreateMemSet(Dst, B.getInt8('\0'), Size, MemSetAlign);
AttrBuilder ArgAttrs(CI->getAttributes().getParamAttributes(0));
NewCI->setAttributes(NewCI->getAttributes().addParamAttributes(
CI->getContext(), 0, ArgAttrs));

10
test/Transforms/InstCombine/strncpy-1.ll
View File

@ -144,6 +144,16 @@ define i8* @test3(i8* %dst, i32 %n) {
ret i8* %ret
}
define i8* @test4(i8* %dst, i32 %n) {
; CHECK-LABEL: @test4(
; CHECK-NEXT: call void @llvm.memset.p0i8.i32(i8* noalias noundef nonnull align 16 dereferenceable(5) [[DST:%.*]], i8 0, i32 5, i1 false)
; CHECK-NEXT: ret i8* [[DST]]
;
%src = getelementptr [1 x i8], [1 x i8]* @null, i32 0, i32 0
%ret = call i8* @strncpy(i8* align(16) noalias nonnull %dst, i8* nonnull %src, i32 5);
ret i8* %ret
}
; Check cases that shouldn't be simplified.
define void @test_no_simplify1() {