Open Bug 897470 Opened 7 years ago Updated 3 years ago

Support asm.js using intel MPX instructions


(Core :: JavaScript Engine, defect)

Not set




(Reporter: jrmuizel, Unassigned)


(Blocks 1 open bug)


(Whiteboard: [platform-rel-Intel])

From my quick read of the specification (, these instructions seem reasonably well suited to the bounds checking needs of asm.js. They allow specifying a lower and upper bound such that all memory accesses outside of that bound will throw a bound range exception.

Emulation of these instructions is supported with the Intel Software Development Emulator.
This looks interesting.  On a quick first reading, I'm a little disappointed that MPX seems to require explicit bounds-check instructions instead of adding a prefix on load/store instructions (which is what I hoped).  Since we don't require any explicit bounds checking on x64, I expect this would only benefit x86.  By the time these instructions roll out in new processors, though, I wonder if we wouldn't be shipping FF 64-bit, though ;)
Assignee: general → nobody
Whiteboard: [platform-rel-Intel]
platform-rel: --- → ?
platform-rel: ? → ---
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