Bug 451743 - On x86 processors, only use SSE2 if the processor supports it, otherwise default back to x87 FPU (r=gal, sr=mrbkap)

js/src/jstracer.cpp

@@ -117,6 +117,7 @@ static avmplus::AvmCore* core = &s_core;
 /* We really need a better way to configure the JIT. Shaver, where is my fancy JIT object? */
 static bool nesting_enabled = true;
 static bool oracle_enabled = true;
+static bool did_we_check_sse2 = false;
 
 #ifdef DEBUG
 static bool verbose_debug = getenv("TRACEMONKEY") && strstr(getenv("TRACEMONKEY"), "verbose");
@@ -2167,9 +2168,44 @@ js_AbortRecording(JSContext* cx, jsbytecode* abortpc, const char* reason)
     }
 }
 
+#if defined NANOJIT_IA32
+static bool
+js_CheckForSSE2()
+{
+    int features = 0;
+#if defined _MSC_VER
+    __asm
+    {
+        pushad
+        mov eax, 1
+        cpuid
+        mov features, edx
+        popad
+    }
+#elif defined __GNUC__
+    asm("pusha\n"
+        "mov $0x01, %%eax\n"
+        "cpuid\n"
+        "mov %%edx, %0\n"
+        "popa\n"
+        : "=m" (features)
+        : /* We have no inputs */
+        : /* We don't clobber anything */
+       );
+#endif
+    return (features & (1<<26)) != 0;
+}
+#endif
+
 extern void
 js_InitJIT(JSTraceMonitor *tm)
 {
+#if defined NANOJIT_IA32
+    if (!did_we_check_sse2) {
+        avmplus::AvmCore::sse2_available = js_CheckForSSE2();
+        did_we_check_sse2 = true;
+    }
+#endif
     if (!tm->fragmento) {
         JS_ASSERT(!tm->globalSlots && !tm->globalTypeMap);
         Fragmento* fragmento = new (&gc) Fragmento(core, 24);

js/src/nanojit/avmplus.cpp

@@ -39,3 +39,5 @@ static GC _gc;
 GC* AvmCore::gc = &_gc;
 GCHeap GC::heap;
 String* AvmCore::k_str[] = { (String*)"" };
+bool AvmCore::sse2_available = false;
+

js/src/nanojit/avmplus.h

@@ -394,11 +394,12 @@ namespace avmplus
         static AvmConfiguration config;
         static GC* gc;
         static String* k_str[];
+        static bool sse2_available;
 
         static inline bool
         use_sse2()
         {
-            return true;
+            return sse2_available;
         }
 
         static inline bool