[Webkit-unassigned] [Bug 133156] make css jit work on arm64

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=133156


Benjamin Poulain <benjamin at webkit.org> changed:

           What    |Removed                     |Added
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 Attachment #231836|review?                     |review-
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--- Comment #4 from Benjamin Poulain <benjamin at webkit.org>  2014-05-21 13:35:26 PST ---
(From update of attachment 231836)
View in context: https://bugs.webkit.org/attachment.cgi?id=231836&action=review

> Source/WebCore/cssjit/SelectorCompiler.cpp:874
> +#if CPU(ARM64)
> +    m_assembler.pushPair(JSC::ARM64Registers::lr, JSC::ARM64Registers::fp);
> +#endif
> +}
> +
> +void SelectorCodeGenerator::generateEpilogue()
> +{
> +#if CPU(ARM64)
> +    m_assembler.popPair(JSC::ARM64Registers::lr, JSC::ARM64Registers::fp);
> +#endif

I would prefer this to be done through the stack allocator.

Here, if we have a mismatch of pushPair/popPair, we could run into security problems.

> Source/WebCore/cssjit/SelectorCompiler.cpp:935
> +            generateEpilogue();
>              m_assembler.ret();
>  
>              // Failure.
>              if (!failureCases.empty()) {
>                  failureCases.link(&m_assembler);
>                  m_assembler.move(Assembler::TrustedImm32(0), returnRegister);
> +                generateEpilogue();
>                  m_assembler.ret();

The duplicated epilogue may be slower than an unconditional jump. You may want to generalize reservedCalleeSavedRegisters.

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