Add CHECK_INT64_EQ function to avoid operand size ambiguities.

src/checks.h

Index: src/checks.h
===================================================================
--- src/checks.h	(revision 3015)
+++ src/checks.h	(working copy)
@@ -80,17 +80,18 @@
   }
 }
 
-#if !V8_HOST_ARCH_64_BIT
-// Helper function used by the CHECK_EQ function when given int64_t
-// arguments.  Should not be called directly.
-static inline void CheckEqualsHelper(const char* file, int line,
-                                     const char* expected_source,
-                                     int64_t expected,
-                                     const char* value_source,
-                                     int64_t value) {
+// Helper function used by the CHECK_INT64_EQ function when given int64_t
+// arguments.  Should not be called directly.  We do not overload CHECK_EQ
+// with both 32-bit and 64-bit integers, because it causes ambiguity
+// with operands of mixed sizes.
+static inline void CheckInt64EqualsHelper(const char* file, int line,
+                                          const char* expected_source,
+                                          int64_t expected,
+                                          const char* value_source,
+                                          int64_t value) {
   if (expected != value) {
-    // Sorry, printing int64_t in a fanky hex way,
-    // that's our mother tongue after all :)
+    // Print int64_t values in hex, as two int32s,
+    // to avoid platform-dependencies.
     V8_Fatal(file, line,
              "CHECK_EQ(%s, %s) failed\n#"
              "   Expected: 0x%08x%08x\n#   Found: 0x%08x%08x",
@@ -99,7 +100,6 @@
              uint32_t(value >> 32), uint32_t(value));
   }
 }
-#endif
 
 
 // Helper function used by the CHECK_NE function when given int
@@ -233,7 +233,10 @@
 #define CHECK_GT(a, b) CHECK((a) > (b))
 #define CHECK_GE(a, b) CHECK((a) >= (b))
 
+#define CHECK_INT64_EQ(expected, value) CheckInt64EqualsHelper(__FILE__, \
+  __LINE__, #expected, expected, #value, value)
 
+
 // This is inspired by the static assertion facility in boost.  This
 // is pretty magical.  If it causes you trouble on a platform you may
 // find a fix in the boost code.