[Webkit-unassigned] [Bug 70706] Add boolean speculations to DFG JIT 32_64

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=70706


Filip Pizlo <fpizlo at apple.com> changed:

           What    |Removed                     |Added
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 Attachment #112166|review?, commit-queue?      |review+, commit-queue+
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--- Comment #4 from Filip Pizlo <fpizlo at apple.com>  2011-10-24 14:35:23 PST ---
(From update of attachment 112166)
View in context: https://bugs.webkit.org/attachment.cgi?id=112166&action=review

r=me.  The inline comments are suggestions only.

> Source/JavaScriptCore/assembler/MacroAssemblerX86Common.h:-952
> -            m_assembler.testb_i8r(mask.m_value, reg);

Could you have changed the if statement to test both the mask being 0x7f and the register being one of [ax, bx, cx, dx]?

> Source/JavaScriptCore/dfg/DFGGenerationInfo.h:132
>      switch (from) {

As a side-note, needDataFormatConversion is no longer called from anywhere.  Your call on whether you want to remove this method in this patch, or not commit any changes to it, or commit the changes you made.  Your changes to this method seem to be more-or-less in the spirit of what the method was initially doing, except that it's not doing anything, since it's not used.

> Source/JavaScriptCore/dfg/DFGJITCompiler32_64.cpp:237
> +                store32(TrustedImm32(JSValue::BooleanTag), reinterpret_cast<char*>(scratchBuffer + scratchIndex) + OBJECT_OFFSETOF(EncodedValueDescriptor, asBits.tag));

The code appears to be placing tags into the OSR scratch buffer, and then reading pairs of registers from the scratch buffer and placing them into the register file.  The scratch buffer is only used for temporary storage while this code is running.  Would it not be more profitable to dump unboxed values to the scratch buffer, and then box them when transfering from the scratch buffer back to the register file?  Seems like it would save you a load and a store, per unboxed virtual register.

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