Implement the NoBuiltin attribute.

The 'nobuiltin' attribute is applied to call sites to indicate that LLVM should
not treat the callee function as a built-in function. I.e., it shouldn't try to
replace that function with different code.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175835 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/SimplifyLibCalls.cpp

@@ -1889,6 +1889,7 @@ LibCallSimplifier::~LibCallSimplifier() {
 }
 
 Value *LibCallSimplifier::optimizeCall(CallInst *CI) {
+  if (CI->hasFnAttr(Attribute::NoBuiltin)) return 0;
   return Impl->optimizeCall(CI);
 }