Use a signed value for this enum to avoid spuriuos warnings from gcc.

llvm-svn: 153184
diff --git a/llvm/lib/Target/X86/InstPrinter/X86InstComments.cpp b/llvm/lib/Target/X86/InstPrinter/X86InstComments.cpp
index 19909cb..f532019 100644
--- a/llvm/lib/Target/X86/InstPrinter/X86InstComments.cpp
+++ b/llvm/lib/Target/X86/InstPrinter/X86InstComments.cpp
@@ -511,7 +511,7 @@
     for (unsigned i = 0, e = ShuffleMask.size(); i != e; ++i) {
       if (i != 0)
         OS << ',';
-      if (ShuffleMask[i] == (int)SM_SentinelZero) {
+      if (ShuffleMask[i] == SM_SentinelZero) {
         OS << "zero";
         continue;
       }