silence a release mode warning

llvm-svn: 23868
diff --git a/llvm/lib/Target/Alpha/AlphaISelPattern.cpp b/llvm/lib/Target/Alpha/AlphaISelPattern.cpp
index 2f04646..af9d29e 100644
--- a/llvm/lib/Target/Alpha/AlphaISelPattern.cpp
+++ b/llvm/lib/Target/Alpha/AlphaISelPattern.cpp
@@ -506,7 +506,7 @@
   unsigned Tmp1, Tmp2 = 0, Tmp3;
   unsigned Opc = 0;
   unsigned opcode = N.getOpcode();
-  int64_t SImm;
+  int64_t SImm = 0;
   uint64_t UImm;
 
   SDNode *Node = N.Val;