Add more const qualifiers on TargetMachine and friends.

llvm-svn: 101977
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 5c3992e..33c8d1a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -480,7 +480,8 @@
 }
 
 /// NOTE: The constructor takes ownership of TLOF.
-TargetLowering::TargetLowering(TargetMachine &tm,TargetLoweringObjectFile *tlof)
+TargetLowering::TargetLowering(const TargetMachine &tm,
+                               const TargetLoweringObjectFile *tlof)
   : TM(tm), TD(TM.getTargetData()), TLOF(*tlof) {
   // All operations default to being supported.
   memset(OpActions, 0, sizeof(OpActions));