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/PowerPC/PPCTargetTransformInfo.cpp b/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
index 5559cdc..3dbd5f5 100644
--- a/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
@@ -230,7 +230,7 @@
   return ST->hasVSX() ? 64 : 32;
 }
 
-unsigned PPCTTIImpl::getRegisterBitWidth(bool Vector) {
+unsigned PPCTTIImpl::getRegisterBitWidth(bool Vector) const {
   if (Vector) {
     if (ST->hasQPX()) return 256;
     if (ST->hasAltivec()) return 128;