Fix cast warning on Win32

src/ia32/code-stubs-ia32.cc

Index: src/ia32/code-stubs-ia32.cc
diff --git a/src/ia32/code-stubs-ia32.cc b/src/ia32/code-stubs-ia32.cc
index f16c807a5ab88fe3d1b864c9de670eb7d411bef9..a52685bf6563d598f383f0b4e27f36a09714058f 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -6913,14 +6913,14 @@ void ICCompareStub::GenerateUniqueNames(MacroAssembler* masm) {
   Label succeed1;
   __ test(tmp1, Immediate(kIsInternalizedMask));
   __ j(not_zero, &succeed1);
-  __ cmpb(tmp1, static_cast<int8_t>(SYMBOL_TYPE));
+  __ cmpb(tmp1, static_cast<uint8_t>(SYMBOL_TYPE));
   __ j(not_equal, &miss);
   __ bind(&succeed1);
 
   Label succeed2;
   __ test(tmp2, Immediate(kIsInternalizedMask));
   __ j(not_zero, &succeed2);
-  __ cmpb(tmp2, static_cast<int8_t>(SYMBOL_TYPE));
+  __ cmpb(tmp2, static_cast<uint8_t>(SYMBOL_TYPE));
   __ j(not_equal, &miss);
   __ bind(&succeed2);