[Webkit-unassigned] [Bug 63173] DFG non-speculative JIT lacks basic optimizations for GetById and GetByVal

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=63173


Gavin Barraclough <barraclough at apple.com> changed:

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--- Comment #6 from Gavin Barraclough <barraclough at apple.com>  2011-06-22 15:02:24 PST ---
(From update of attachment 98231)
View in context: https://bugs.webkit.org/attachment.cgi?id=98231&action=review

Please fix comments above, as discussed!

> Source/JavaScriptCore/dfg/DFGNonSpeculativeJIT.cpp:502
> +        NodeIndex alias = node.child3;

The alias optimization is unsafe on the non-speculative path.
This assumes that between subsequent GetByVals to the same location, the value / array has not changed.  We ensure this is true on the speculative path by restricting generation of operations that would trigger side-effects, but do not do so on the non-speculative path.

> Source/JavaScriptCore/dfg/DFGNonSpeculativeJIT.cpp:586
> +        cachedGetById(baseGPR, resultGPR, node.identifierNumber());

The code generation for this method is going to generate two calls, please refactor to make one call.

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