Move RegisterFile growth check to callee

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Cameron Zwarich (cpst)]

We currently do the RegisterFile growth check in the caller, when it should really be in the callee, except in the case where there are too few arguments and you need to fill the unpassed ones with jsUndefined().

If we do this, then we can conceivably inline the "correct number of arguments" case of op_call in the generated machine code. The only thing preventing this is the check for the existence of the CodeBlock on the JSFunction, but this could possibly be done in assembly with a jump to a slow case.

I have a patch to only move the check to the callee that is a wash on V8's benchmark suite and a slight speedup on SunSpider, but I might be able to speed it up a bit more. I will post it.

[Cameron Zwarich (cpst)]

Created attachment 24287 [details]
Patch in progress

[Cameron Zwarich (cpst)]

Created attachment 24288 [details]
Patch in progress

This is a 1.1% progression on SunSpider and a wash on V8. However, it is a significant speedup on DeltaBlue and Earley-Boyer, and only a wash because of a massive (hopefully random) slowdown on Richards.

I still need to implement the exception-handling correctly, and there might be a better way to do the branch to the slow case at the start of a function.

[Cameron Zwarich (cpst)]

Here are the results on the V8 harness. Before:

Richards: 1530
DeltaBlue: 1165
Crypto: 2140
RayTrace: 1439
EarleyBoyer: 2894
----
Score (version 2): 1739

After:

Richards: 1640
DeltaBlue: 1216
Crypto: 2109
RayTrace: 1454
EarleyBoyer: 2939
----
Score (version 2): 1782

[Cameron Zwarich (cpst)]

Created attachment 24289 [details]
SunSpider harness results

[Cameron Zwarich (cpst)]

Created attachment 24324 [details]
Proposed patch

[Cameron Zwarich (cpst)]

Created attachment 24326 [details]
Proposed patch

Oops. I accidentally removed a comment that is useful in cti_op_construct_JSConstruct.

[Geoffrey Garen]

Comment on attachment 24326 [details]
Proposed patch

r=me

[Cameron Zwarich (cpst)]

Landed in r37570.