Implement Red Zone utilization on x86-64. This is currently

disabled by default; I'll enable it when I hook it up with
the llvm-gcc flag which controls it.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63056 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetOptions.h

@@ -107,6 +107,10 @@ namespace llvm {
   /// wth earlier copy coalescing.
   extern bool StrongPHIElim;
 
+  /// DisableRedZone - This flag disables use of the "Red Zone" on
+  /// targets which would otherwise have one.
+  extern bool DisableRedZone;
+
 } // End llvm namespace
 
 #endif