[Webkit-unassigned] [Bug 75342] Adjust spill order in DFG

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=75342





--- Comment #9 from Yuqiang Xian <yuqiang.xian at intel.com>  2013-10-31 18:00:27 PST ---
Thanks for taking a look at this "nearly two years old" patch. :)

(In reply to comment #8)
> (From update of attachment 121216 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=121216&action=review
> 
> Does changing any of this have any effect on performance?

The performance data was presented in comment #2. The second patch doesn't change the order for JSVALUE64 and as I can remember there's no performance impact on 64bit platforms.

> 
> > Source/JavaScriptCore/dfg/DFGSpeculativeJIT.h:-674
> > -            // We need to box int32 and cell values ...
> > -            // but on JSVALUE64 boxing a cell is a no-op!
> > -            if (spillFormat == DataFormatInteger)
> > -                m_jit.orPtr(GPRInfo::tagTypeNumberRegister, reg);
> > -            
> 
> Why is this removed?  Seems wrong.

This can be removed. Actually we already captured the DataFormatInteger (now DataFormatInt32) case in a previous "case", and when we reached here we actually only have the following cases:

RELEASE_ASSERT(spillFormat == DataFormatCell || spillFormat & DataFormatJS);

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