diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp index 2e440511d6fde..ab181be20964d 100644 --- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp @@ -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)); diff --git a/llvm/test/Transforms/InstCombine/strncpy-1.ll b/llvm/test/Transforms/InstCombine/strncpy-1.ll index bc104cab081ae..210df0e7c1ea4 100644 --- a/llvm/test/Transforms/InstCombine/strncpy-1.ll +++ b/llvm/test/Transforms/InstCombine/strncpy-1.ll @@ -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() {