Add const qualifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90918 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 74651c1..851e6c0 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -5870,7 +5870,7 @@
 
 /// InferPtrAlignment - Infer alignment of a load / store address. Return 0 if
 /// it cannot be inferred.
-unsigned SelectionDAG::InferPtrAlignment(SDValue Ptr) {
+unsigned SelectionDAG::InferPtrAlignment(SDValue Ptr) const {
   // If this is a direct reference to a stack slot, use information about the
   // stack slot's alignment.
   int FrameIdx = 1 << 31;