Currently, to make SIMD.int32x4 / SIMD.float32x4 callable, we create these objects with the Function as a proto [1]. Due to this trick, we flag the typeSet as having unknownProperties [2], which cause addType to flag the type set of int32x4 / float32x4 objects to be AnyObject [3]. This makes IonMonkey unable to predict what is the function which should be used for the function call (Bug 1112154), and force us to "guard; load; typebarrier" before every SIMD function call (Bug 1112155). [1] http://dxr.mozilla.org/mozilla-central/source/js/src/builtin/SIMD.cpp#250,257 [2] http://dxr.mozilla.org/mozilla-central/source/js/src/jsinfer.cpp#4470-4478 [3] http://dxr.mozilla.org/mozilla-central/source/js/src/jsinfer.cpp#552-556,566-567

Comment on attachment 8538571 [details] [diff] [review] SIMD types are now created as Singleton objects. Review of attachment 8538571 [details] [diff] [review]: ----------------------------------------------------------------- Good catch!