Added support for the Builtin attribute.

The Builtin attribute is an attribute that can be placed on function call site that signal that even though a function is declared as being a builtin,

rdar://problem/13727199

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185049 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/IR/Attributes.cpp b/lib/IR/Attributes.cpp
index e48ebb1..2160ea2 100644
--- a/lib/IR/Attributes.cpp
+++ b/lib/IR/Attributes.cpp
@@ -157,6 +157,8 @@
     return "sanitize_address";
   if (hasAttribute(Attribute::AlwaysInline))
     return "alwaysinline";
+  if (hasAttribute(Attribute::Builtin))
+    return "builtin";
   if (hasAttribute(Attribute::ByVal))
     return "byval";
   if (hasAttribute(Attribute::InlineHint))
@@ -399,6 +401,7 @@
   case Attribute::NoBuiltin:       return 1ULL << 38;
   case Attribute::Returned:        return 1ULL << 39;
   case Attribute::Cold:            return 1ULL << 40;
+  case Attribute::Builtin:         return 1ULL << 41;
   }
   llvm_unreachable("Unsupported attribute type");
 }