isMarkedForSpill() should be const.

llvm-svn: 7155
diff --git a/llvm/lib/CodeGen/RegAlloc/LiveRange.h b/llvm/lib/CodeGen/RegAlloc/LiveRange.h
index 588b7b5..c3caa29 100644
--- a/llvm/lib/CodeGen/RegAlloc/LiveRange.h
+++ b/llvm/lib/CodeGen/RegAlloc/LiveRange.h
@@ -101,7 +101,7 @@
 
   inline void markForSpill() { mustSpill = true; }
 
-  inline bool isMarkedForSpill() { return mustSpill; }
+  inline bool isMarkedForSpill() const { return mustSpill; }
 
   inline void setSpillOffFromFP(int StackOffset) {
     assert(mustSpill && "This LR is not spilled");