Const correctness for TTI::getRegisterBitWidth

Summary: The method TargetTransformInfo::getRegisterBitWidth() is declared const, but the type erasing implementation classes (TargetTransformInfo::Concept & TargetTransformInfo::Model) that were introduced by Chandler in https://reviews.llvm.org/D7293 do not have the method declared const. This is an NFC to tidy up the const consistency between TTI and its implementation.

Reviewers: chandlerc, rnk, reames

Reviewed By: reames

Subscribers: reames, jfb, arsenm, dschuff, nemanjai, nhaehnle, javed.absar, sbc100, jgravelle-google, llvm-commits

Differential Revision: https://reviews.llvm.org/D33903

llvm-svn: 305189
diff --git a/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp b/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
index 6a3dc67..422c16b 100644
--- a/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
@@ -302,7 +302,7 @@
   return 0;
 }
 
-unsigned SystemZTTIImpl::getRegisterBitWidth(bool Vector) {
+unsigned SystemZTTIImpl::getRegisterBitWidth(bool Vector) const {
   if (!Vector)
     return 64;
   if (ST->hasVector())