[llvm] r372142 - Reland "[SLC] Preserve attrs for strncpy(x, "", y) -> memset(align 1 x, '\0', y)"

[David Bolvansky via llvm-commits]

Author: xbolva00
Date: Tue Sep 17 10:12:24 2019
New Revision: 372142

URL: http://llvm.org/viewvc/llvm-project?rev=372142&view=rev
Log:
Reland "[SLC] Preserve attrs for strncpy(x, "", y) -> memset(align 1 x, '\0', y)"

Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp
    llvm/trunk/test/Transforms/InstCombine/strncpy-1.ll

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp?rev=372142&r1=372141&r2=372142&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp Tue Sep 17 10:12:24 2019
@@ -610,7 +610,10 @@ Value *LibCallSimplifier::optimizeStrNCp
 
   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;
   }
 

Modified: llvm/trunk/test/Transforms/InstCombine/strncpy-1.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/strncpy-1.ll?rev=372142&r1=372141&r2=372142&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/strncpy-1.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/strncpy-1.ll Tue Sep 17 10:12:24 2019
@@ -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() {