[LibCalls] Added returned attribute to libcalls

Reviewers: efriedma

Reviewed By: efriedma

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D51092

llvm-svn: 340512

1 files changed, 16 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index d0396e6ce47..b782641383a 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -38,6 +38,7 @@ STATISTIC(NumNoCapture, "Number of arguments inferred as nocapture");
 STATISTIC(NumReadOnlyArg, "Number of arguments inferred as readonly");
 STATISTIC(NumNoAlias, "Number of function returns inferred as noalias");
 STATISTIC(NumNonNull, "Number of function returns inferred as nonnull returns");
+STATISTIC(NumReturnedArg, "Number of arguments inferred as returned");
 
 static bool setDoesNotAccessMemory(Function &F) {
   if (F.doesNotAccessMemory())
@@ -105,6 +106,14 @@ static bool setRetNonNull(Function &F) {
   return true;
 }
 
+static bool setReturnedArg(Function &F, unsigned ArgNo) {
+  if (F.hasParamAttribute(ArgNo, Attribute::Returned))
+    return false;
+  F.addParamAttr(ArgNo, Attribute::Returned);
+  ++NumReturnedArg;
+  return true;
+}
+
 static bool setNonLazyBind(Function &F) {
   if (F.hasFnAttribute(Attribute::NonLazyBind))
     return false;
@@ -147,10 +156,12 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
     Changed |= setOnlyReadsMemory(F, 0);
     return Changed;
   case LibFunc_strcpy:
-  case LibFunc_stpcpy:
+  case LibFunc_strncpy:
   case LibFunc_strcat:
   case LibFunc_strncat:
-  case LibFunc_strncpy:
+    Changed |= setReturnedArg(F, 0);
+    LLVM_FALLTHROUGH;
+  case LibFunc_stpcpy:
   case LibFunc_stpncpy:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 1);
@@ -262,9 +273,11 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
     Changed |= setDoesNotCapture(F, 1);
     return Changed;
   case LibFunc_memcpy:
+  case LibFunc_memmove:
+    Changed |= setReturnedArg(F, 0);
+    LLVM_FALLTHROUGH;
   case LibFunc_mempcpy:
   case LibFunc_memccpy:
-  case LibFunc_memmove:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);