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Reland "[SLC] Preserve attrs for strncpy(x, "", y) -> memset(align 1 x, '\0', y)"

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llvm-svn: 372142
This commit is contained in:
David Bolvansky 2019-09-17 17:12:24 +00:00
parent 416a79594b
commit 5b5fcd24ff
2 changed files with 14 additions and 1 deletions
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5
lib/Transforms/Utils/SimplifyLibCalls.cpp
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@ -610,7 +610,10 @@ Value *LibCallSimplifier::optimizeStrNCpy(CallInst *CI, IRBuilder<> &B) {
if (SrcLen == 0) {
// strncpy(x, "", y) -> memset(align 1 x, '\0', y)
B.CreateMemSet(Dst, B.getInt8('\0'), Size, 1);
CallInst *NewCI = B.CreateMemSet(Dst, B.getInt8('\0'), Size, 1);
AttrBuilder ArgAttrs(CI->getAttributes().getParamAttributes(0));
NewCI->setAttributes(NewCI->getAttributes().addParamAttributes(
CI->getContext(), 0, ArgAttrs));
return Dst;
}

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

@ -134,6 +134,16 @@ define i8* @test2(i8* %dst) {
ret i8* %ret
}
define i8* @test3(i8* %dst, i32 %n) {
; CHECK-LABEL: @test3(
; CHECK-NEXT: call void @llvm.memset.p0i8.i32(i8* noalias nonnull align 1 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* noalias nonnull %dst, i8* nonnull %src, i32 5);
ret i8* %ret
}
; Check cases that shouldn't be simplified.
define void @test_no_simplify1() {