Bug 728623: disable jitcode address randomization on Win64, r=dvander

js/src/assembler/jit/ExecutableAllocatorWin.cpp

@@ -103,11 +103,15 @@ RandomizeIsBroken()
 ExecutablePool::Allocation ExecutableAllocator::systemAlloc(size_t n)
 {
     void *allocation = NULL;
+    // Randomization disabled to avoid a performance fault on x64 builds.
+    // See bug 728623.
+#ifndef JS_CPU_X64
     if (allocBehavior == AllocationCanRandomize && !RandomizeIsBroken()) {
         void *randomAddress = computeRandomAllocationAddress();
         allocation = VirtualAlloc(randomAddress, n, MEM_COMMIT | MEM_RESERVE,
                                   PAGE_EXECUTE_READWRITE);
     }
+#endif
     if (!allocation)
         allocation = VirtualAlloc(0, n, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);
     ExecutablePool::Allocation alloc = { reinterpret_cast<char*>(allocation), n };