[SimplifyLibCalls] Add noalias from known callsites

Summary:
Should be fine for memcpy, strcpy, strncpy.


Reviewers: jdoerfert, efriedma

Reviewed By: jdoerfert

Subscribers: uenoku, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66135

llvm-svn: 368724

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index ef4cc227222..cb1021dae33 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -460,6 +460,9 @@ Value *LibCallSimplifier::optimizeStrCpy(CallInst *CI, IRBuilder<> &B) {
   if (Dst == Src) // strcpy(x,x)  -> x
     return Src;
 
+  CI->addParamAttr(0, Attribute::NoAlias);
+  CI->addParamAttr(1, Attribute::NoAlias);
+
   // See if we can get the length of the input string.
   uint64_t Len = GetStringLength(Src);
   if (Len == 0)
@@ -502,6 +505,9 @@ Value *LibCallSimplifier::optimizeStrNCpy(CallInst *CI, IRBuilder<> &B) {
   Value *Src = CI->getArgOperand(1);
   Value *LenOp = CI->getArgOperand(2);
 
+  CI->addParamAttr(0, Attribute::NoAlias);
+  CI->addParamAttr(1, Attribute::NoAlias);
+
   // See if we can get the length of the input string.
   uint64_t SrcLen = GetStringLength(Src);
   if (SrcLen == 0)
@@ -983,6 +989,9 @@ Value *LibCallSimplifier::optimizeMemCpy(CallInst *CI, IRBuilder<> &B,
   if (ConstantInt *LenC = dyn_cast<ConstantInt>(Size))
     annotateDereferenceableBytes(CI, {0, 1}, LenC->getZExtValue());
 
+  CI->addParamAttr(0, Attribute::NoAlias);
+  CI->addParamAttr(1, Attribute::NoAlias);
+
   if (isIntrinsic)
     return nullptr;