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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - Unite op_get_by_id_with_this with op_get_by_id"
href="https://bugs.webkit.org/show_bug.cgi?id=162124#c14">Comment # 14</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - Unite op_get_by_id_with_this with op_get_by_id"
href="https://bugs.webkit.org/show_bug.cgi?id=162124">bug 162124</a>
from <span class="vcard"><a class="email" href="mailto:ticaiolima@gmail.com" title="Caio Lima <ticaiolima@gmail.com>"> <span class="fn">Caio Lima</span></a>
</span></b>
<pre>(In reply to <a href="show_bug.cgi?id=162124#c13">comment #13</a>)
<span class="quote">> Comment on <span class=""><a href="attachment.cgi?id=289377&action=diff" name="attach_289377" title="Patch">attachment 289377</a> <a href="attachment.cgi?id=289377&action=edit" title="Patch">[details]</a></span>
> Patch
>
> View in context:
> <a href="https://bugs.webkit.org/attachment.cgi?id=289377&action=review">https://bugs.webkit.org/attachment.cgi?id=289377&action=review</a>
>
> > Source/JavaScriptCore/ChangeLog:11
> > + This patch is merging the op_get_by_id_with_this with op_get_by_id and
> > + this way we enable get_by_id optimizations such as Monomorphic/Polymorphic Inline
> > + Cache on JIT layers for super member access. These optimizations is improving access
> > + of super members in ~20%.
>
> Fully unoptimized property access is 10X slower than fully optimized
> property access. Therefore, it's surprising that this patch is not a bigger
> win on super-get-by-id-with-this-monomorphic. It looks like
> super-get-by-id-with-this-monomorphic is a getter/setter benchmark. Can you
> verify that the FTL successfully inlines the getter and setter for value()?
> Perhaps the win on this benchmark is not bigger because the benchmark
> includes an intermediate "calc" function, which is pretty expensive. Can you
> report the speedup on this benchmark if you remove the call to calc?</span >
Good to know that. I faced a problem while creating the patch to get GetById compiled in FTL layer. To get it working, I was using --accessInline=false. What I mean is that the reason can br related with that. I am going to investigate it.
<span class="quote">> > Source/JavaScriptCore/bytecode/PolymorphicAccess.cpp:1096
> > - GPRReg baseForCustomValue = m_type == CustomValueGetter || m_type == CustomValueSetter ? baseForAccessGPR : baseForGetGPR;
> > + GPRReg baseForCustomValue = m_type == CustomValueGetter || m_type == CustomValueSetter ? baseForAccessGPR : baseForCustomGetGPR;
>
> Isn't the answer always thisGPR? Under what conditions do I want to invoke a
> getter or setter without the specified this?</span >
If I am not wrong, no. This code is dominated by this manipulation over baseForGetGPR (<a href="https://github.com/caiolima/webkit/blob/merge_by_ids/Source/JavaScriptCore/bytecode/PolymorphicAccess.cpp#L879">https://github.com/caiolima/webkit/blob/merge_by_ids/Source/JavaScriptCore/bytecode/PolymorphicAccess.cpp#L879</a>). So, when thisGPR == baseGPR, it is safer get baseForGetGPR because of "Proxy observed" lookups. I am thinking that it is worth think in cases when thisOperand != baseOperand and it is "Proxy Observed". Does it make sense?</pre>
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