Added support in FunctionAttrs for adding relevant function/argument attributes for the posix call gettimeofday.

This implies annotating it as nounwind and its arguments as nocapture. To be
conservative, we do not annotate the arguments with noalias since some platforms
do not have restrict on the declaration for gettimeofday.

llvm-svn: 185502

llvm/lib/Transforms/IPO/FunctionAttrs.cpp

@@ -1310,6 +1310,16 @@ bool FunctionAttrs::inferPrototypeAttributes(Function &F) {
     // May throw; "open" is a valid pthread cancellation point.
     setDoesNotCapture(F, 1);
     break;
+  case LibFunc::gettimeofday:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    // Currently some platforms have the restrict keyword on the arguments to
+    // gettimeofday. To be conservative, do not add noalias to gettimeofday's
+    // arguments.
+    setDoesNotThrow(F);
+    setDoesNotCapture(F, 1);
+    setDoesNotCapture(F, 2);
   default:
     // Didn't mark any attributes.
     return false;

llvm/test/Transforms/FunctionAttrs/annotate-1.ll

@@ -14,5 +14,8 @@ declare i32* @realloc(i32*, i32)
 declare i32 @strcpy(...)
 ; CHECK: declare i32 @strcpy(...)
 
+declare i32 @gettimeofday(i8*, i8*)
+; CHECK: declare i32 @gettimeofday(i8* nocapture, i8* nocapture) [[G0]]
+
 ; CHECK: attributes [[G0]] = { nounwind }
 ; CHECK: attributes [[G1]] = { nounwind readonly }