[Webkit-unassigned] [Bug 96286] Another SIGILL in JavaScriptCore on a Geode processor

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=96286





--- Comment #2 from Oliver Hunt <oliver at apple.com>  2012-09-27 16:13:15 PST ---
(In reply to comment #1)
> Oliver, you rescued us last time, can you help us here? :)
> 
> I have checked the basics from bug #82496: isSSE2Present() still returns false on this platform (cpuid feature bits does not suggest that SSE2 is supported), DFG canCompileOpcodes() still calls down to MacroAssembler::supportsFloatingPoint() which correctly says "no".
> 
> Searching through the source for e.g. mulsd, I see two potential places where mulsd instructions might be generated which aren't directly/obviously protected by the above checks. They are:
>  1. ./Source/JavaScriptCore/assembler/X86Assembler.h (mulsd_mr) ?
>  2. ./Source/JavaScriptCore/offlineasm/x86.rb
> 
> I guess offlineasm has a likelihood of being the culprit, given that this is a regression over webkitgtk-1.8 and offlineasm/LLint seems to be a new feature. CCing  Filip Pizlo who seems to be involved in this project. Filip, sorry to bother you, would you mind checking if llint/offlineasm checks that the x86 CPU supports SSE2 instructions before executing them? Or point us to a better candidate to ask?

Unfortunately the only solution for this is for the gtk port to disable the LLInt -- supporting non-SSE2 x86 chips in LLInt would simply be too expensive (in terms of both implementation and/or runtime).

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