[mips] Forbid the use of registers t6, t7 and t8 if the target is NaCl.

Differential Revision: http://llvm-reviews.chandlerc.com/D2694

llvm-svn: 200978
diff --git a/llvm/lib/Target/Mips/MipsSubtarget.h b/llvm/lib/Target/Mips/MipsSubtarget.h
index f8fcef4..ba1e145 100644
--- a/llvm/lib/Target/Mips/MipsSubtarget.h
+++ b/llvm/lib/Target/Mips/MipsSubtarget.h
@@ -209,6 +209,7 @@
   bool os16() const { return Os16;};
 
   bool isTargetNaCl() const { return TargetTriple.isOSNaCl(); }
+  bool isNotTargetNaCl() const { return !TargetTriple.isOSNaCl(); }
 
 // for now constant islands are on for the whole compilation unit but we only
 // really use them if in addition we are in mips16 mode