[LibCalls] Added returned attribute to libcalls

[efriedma]

LGTM with nits.

lib/Transforms/Utils/BuildLibCalls.cpp

162

Please explicitly mark fallthrough using LLVM_FALLTHROUGH.

276

Please explicitly mark fallthrough using LLVM_FALLTHROUGH.

[xbolva00]

• Added LLVM_FALLTHROUGH

lib/Transforms/Utils/BuildLibCalls.cpp

 STATISTIC(NumReadNone, "Number of functions inferred as readnone");
 STATISTIC(NumReadOnly, "Number of functions inferred as readonly");
 STATISTIC(NumArgMemOnly, "Number of functions inferred as argmemonly");
 STATISTIC(NumNoUnwind, "Number of functions inferred as nounwind");
 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())
     return false;
   F.setDoesNotAccessMemory();
   ++NumReadNone;
   return true;
 }
assert(F.getReturnType()->isPointerTy() &&
          "nonnull applies only to pointers");
   if (F.hasAttribute(AttributeList::ReturnIndex, Attribute::NonNull))
     return false;
   F.addAttribute(AttributeList::ReturnIndex, Attribute::NonNull);
   ++NumNonNull;
   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;
   F.addFnAttr(Attribute::NonLazyBind);
   return true;
 }
 
 bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
   case LibFunc_strtoll:
   case LibFunc_strtold:
   case LibFunc_strtoull:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 1);
     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);
+  case LibFunc_stpcpy:
   case LibFunc_stpncpy:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
     return Changed;
   case LibFunc_strxfrm:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 0);
case LibFunc_memrchr:
     return Changed;
   case LibFunc_modf:
   case LibFunc_modff:
   case LibFunc_modfl:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 1);
     return Changed;
   case LibFunc_memcpy:
+  case LibFunc_memmove:
+    Changed |= setReturnedArg(F, 0);
   case LibFunc_mempcpy:
   case LibFunc_memccpy:
-  case LibFunc_memmove:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
     return Changed;
   case LibFunc_memcpy_chk:
     Changed |= setDoesNotThrow(F);
     return Changed;
   case LibFunc_memalign:

test/Transforms/InferFunctionAttrs/annotate.ll

 declare i8* @memccpy(i8*, i8*, i32, i64)
 
 ; CHECK: declare i8* @memchr(i8*, i32, i64) [[G1]]
 declare i8* @memchr(i8*, i32, i64)
 
 ; CHECK: declare i32 @memcmp(i8* nocapture, i8* nocapture, i64) [[G1]]
 declare i32 @memcmp(i8*, i8*, i64)
 
-; CHECK: declare i8* @memcpy(i8*, i8* nocapture readonly, i64) [[G0]]
+; CHECK: declare i8* @memcpy(i8* returned, i8* nocapture readonly, i64) [[G0]]
 declare i8* @memcpy(i8*, i8*, i64)
 
 ; CHECK: declare i8* @mempcpy(i8*, i8* nocapture readonly, i64) [[G0]]
 declare i8* @mempcpy(i8*, i8*, i64)
 
-; CHECK: declare i8* @memmove(i8*, i8* nocapture readonly, i64) [[G0]]
+; CHECK: declare i8* @memmove(i8* returned, i8* nocapture readonly, i64) [[G0]]
 declare i8* @memmove(i8*, i8*, i64)
 
 ; CHECK: declare i8* @memset(i8*, i32, i64)
 declare i8* @memset(i8*, i32, i64)
 
 ; CHECK: declare i32 @mkdir(i8* nocapture readonly, i16 zeroext) [[G0]]
 declare i32 @mkdir(i8*, i16 zeroext)
 

 declare i8* @stpcpy(i8*, i8*)
 
 ; CHECK: declare i8* @stpncpy(i8*, i8* nocapture readonly, i64) [[G0]]
 declare i8* @stpncpy(i8*, i8*, i64)
 
 ; CHECK: declare i32 @strcasecmp(i8* nocapture, i8* nocapture) [[G1]]
 declare i32 @strcasecmp(i8*, i8*)
 
-; CHECK: declare i8* @strcat(i8*, i8* nocapture readonly) [[G0]]
+; CHECK: declare i8* @strcat(i8* returned, i8* nocapture readonly) [[G0]]
 declare i8* @strcat(i8*, i8*)
 
 ; CHECK: declare i8* @strchr(i8*, i32) [[G1]]
 declare i8* @strchr(i8*, i32)
 
 ; CHECK: declare i32 @strcmp(i8* nocapture, i8* nocapture) [[G1]]
 declare i32 @strcmp(i8*, i8*)
 
 ; CHECK: declare i32 @strcoll(i8* nocapture, i8* nocapture) [[G1]]
 declare i32 @strcoll(i8*, i8*)
 
-; CHECK: declare i8* @strcpy(i8*, i8* nocapture readonly) [[G0]]
+; CHECK: declare i8* @strcpy(i8* returned, i8* nocapture readonly) [[G0]]
 declare i8* @strcpy(i8*, i8*)
 
 ; CHECK: declare i64 @strcspn(i8* nocapture, i8* nocapture) [[G1]]
 declare i64 @strcspn(i8*, i8*)
 
 ; CHECK: declare noalias i8* @strdup(i8* nocapture readonly) [[G0]]
 declare i8* @strdup(i8*)
 
 ; CHECK: declare i64 @strlen(i8* nocapture) [[G2:#[0-9]+]]
 declare i64 @strlen(i8*)
 
 ; CHECK: declare i32 @strncasecmp(i8* nocapture, i8* nocapture, i64) [[G1]]
 declare i32 @strncasecmp(i8*, i8*, i64)
 
-; CHECK: declare i8* @strncat(i8*, i8* nocapture readonly, i64) [[G0]]
+; CHECK: declare i8* @strncat(i8* returned, i8* nocapture readonly, i64) [[G0]]
 declare i8* @strncat(i8*, i8*, i64)
 
 ; CHECK: declare i32 @strncmp(i8* nocapture, i8* nocapture, i64) [[G1]]
 declare i32 @strncmp(i8*, i8*, i64)
 
-; CHECK: declare i8* @strncpy(i8*, i8* nocapture readonly, i64) [[G0]]
+; CHECK: declare i8* @strncpy(i8* returned, i8* nocapture readonly, i64) [[G0]]
 declare i8* @strncpy(i8*, i8*, i64)
 
 ; CHECK: declare noalias i8* @strndup(i8* nocapture readonly, i64) [[G0]]
 declare i8* @strndup(i8*, i64)
 
 ; CHECK: declare i64 @strnlen(i8*, i64)
 declare i64 @strnlen(i8*, i64)