[BuildLibCalls] Noalias annotation

Summary: I think this is better solution than annotating callsites in IC/SLC.

Reviewers: jdoerfert

Reviewed By: jdoerfert

Subscribers: MaskRay, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66217

llvm-svn: 368875

2 files changed, 16 insertions, 9 deletions

diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index bab4d38ae5c..ea1fbc9e73b 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -88,6 +88,14 @@ static bool setDoesNotCapture(Function &F, unsigned ArgNo) {
   return true;
 }
 
+static bool setDoesNotAlias(Function &F, unsigned ArgNo) {
+  if (F.hasParamAttribute(ArgNo, Attribute::NoAlias))
+    return false;
+  F.addParamAttr(ArgNo, Attribute::NoAlias);
+  ++NumNoAlias;
+  return true;
+}
+
 static bool setOnlyReadsMemory(Function &F, unsigned ArgNo) {
   if (F.hasParamAttribute(ArgNo, Attribute::ReadOnly))
     return false;
@@ -175,6 +183,9 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
     return Changed;
   case LibFunc_strcpy:
   case LibFunc_strncpy:
+    Changed |= setDoesNotAlias(F, 0);
+    Changed |= setDoesNotAlias(F, 1);
+    LLVM_FALLTHROUGH;
   case LibFunc_strcat:
   case LibFunc_strncat:
     Changed |= setReturnedArg(F, 0);
@@ -249,12 +260,14 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
   case LibFunc_sprintf:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 0);
+    Changed |= setDoesNotAlias(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
     return Changed;
   case LibFunc_snprintf:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 0);
+    Changed |= setDoesNotAlias(F, 0);
     Changed |= setDoesNotCapture(F, 2);
     Changed |= setOnlyReadsMemory(F, 2);
     return Changed;
@@ -291,6 +304,9 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
     Changed |= setDoesNotCapture(F, 1);
     return Changed;
   case LibFunc_memcpy:
+    Changed |= setDoesNotAlias(F, 0);
+    Changed |= setDoesNotAlias(F, 1);
+    LLVM_FALLTHROUGH;
   case LibFunc_memmove:
     Changed |= setReturnedArg(F, 0);
     LLVM_FALLTHROUGH;
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index cb1021dae33..ef4cc227222 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -460,9 +460,6 @@ 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)
@@ -505,9 +502,6 @@ 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)
@@ -989,9 +983,6 @@ 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;