Add a method to TargetRegisterInfo to get the register number that the Win64 EH

scheme uses internally. Implement it for x86 (the only architecture that LLVM
supports for which this matters right now).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131969 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetRegisterInfo.h

@@ -809,6 +809,12 @@ public:
   /// getRARegister - This method should return the register where the return
   /// address can be found.
   virtual unsigned getRARegister() const = 0;
+
+  /// getSEHRegNum - Map a target register to an equivalent SEH register
+  /// number.  Returns -1 if there is no equivalent value.
+  virtual int getSEHRegNum(unsigned i) const {
+    return i;
+  }
 };