From 3dc191b56de30fd9d9042742178434f086afb91c Mon Sep 17 00:00:00 2001
From: Mike Hommey <mh+mozilla@glandium.org>
Date: Mon, 11 Jul 2011 07:57:35 +0200
Subject: [PATCH] Bug 654664 - Optimize JSDOUBLE_IS_NEGZERO after bug 640494.
 r=jimb

---
 js/src/jsvalue.h | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/js/src/jsvalue.h b/js/src/jsvalue.h
index ebe6cc987779..75064bd38670 100644
--- a/js/src/jsvalue.h
+++ b/js/src/jsvalue.h
@@ -92,16 +92,25 @@
 #define JSDOUBLE_SIGNBIT (((uint64) 1) << 63)
 #define JSDOUBLE_EXPMASK (((uint64) 0x7ff) << 52)
 #define JSDOUBLE_MANTMASK ((((uint64) 1) << 52) - 1)
+#define JSDOUBLE_HI32_SIGNBIT   0x80000000
 
 static JS_ALWAYS_INLINE JSBool
 JSDOUBLE_IS_NEGZERO(jsdouble d)
 {
+    if (d != 0)
+        return false;
     union {
+        struct {
+#if defined(IS_LITTLE_ENDIAN) && !defined(FPU_IS_ARM_FPA)
+            uint32 lo, hi;
+#else
+            uint32 hi, lo;
+#endif
+        } s;
         jsdouble d;
-        uint64 bits;
     } x;
     x.d = d;
-    return x.bits == JSDOUBLE_SIGNBIT;
+    return (x.s.hi & JSDOUBLE_HI32_SIGNBIT) != 0;
 }
 
 static inline bool