Bug 86552

Summary:

DFG should optimize aliased uses of the Arguments object of the current call frame

Product:

WebKit

Reporter:

Filip Pizlo <fpizlo>

Component:

JavaScriptCore

Assignee:

Nobody <webkit-unassigned>

Status:

RESOLVED FIXED

Severity:

Normal

Priority:

Version:

528+ (Nightly build)

Hardware:

All

OS:

All

Bug Depends on:

87378

Bug Blocks:

Attachments:

Description	Flags
work in progress	none
more	none
fixed some issues	none
it's starting to do things	none
the patch	ggaren: review+
almost ready	none

Filip Pizlo

Reported 2012-05-15 17:31:21 PDT

We currently optimize the heck out of: arguments[i] arguments.length But we fail to do the same optimizations if we have: var x = arguments; x[i] x.length In particular, we will presently allocate (and tear off) an arguments object, and then optimize x[i] and x.length to be array-like accesses to that arguments object. While that is faster than what the baseline JIT and LLInt would do, it's still rather redundant, since the DFG has most of the machinery in place to realize that this aliased form of arguments access is equivalent to the non-aliased form.

Attachments
work in progress (39.78 KB, patch) 2012-05-15 17:35 PDT, Filip Pizlo	no flags	Details Formatted Diff Diff
more (52.43 KB, patch) 2012-05-15 18:21 PDT, Filip Pizlo	no flags	Details Formatted Diff Diff
fixed some issues (53.21 KB, patch) 2012-05-15 18:29 PDT, Filip Pizlo	no flags	Details Formatted Diff Diff
it's starting to do things (65.84 KB, patch) 2012-05-15 23:04 PDT, Filip Pizlo	no flags	Details Formatted Diff Diff
the patch (66.71 KB, patch) 2012-05-17 15:06 PDT, Filip Pizlo	ggaren: review+	Details Formatted Diff Diff
almost ready (81.52 KB, patch) 2012-05-17 18:45 PDT, Filip Pizlo	no flags	Details Formatted Diff Diff
Show Obsolete (5) View All Add attachment proposed patch, testcase, etc.

Filip Pizlo

Comment 1 2012-05-15 17:35:14 PDT

Created attachment 142107 [details] work in progress Still need to implement the OSR side of this optimization. And check that the code even compiles. ;-)

Filip Pizlo

Comment 2 2012-05-15 18:21:54 PDT

Created attachment 142114 [details] more Wrote the 64-bit side of the OSR part of this optimization. Still haven't even tried compiling this.

Filip Pizlo

Comment 3 2012-05-15 18:29:32 PDT

Created attachment 142115 [details] fixed some issues Fixed some issues that I found through code inspection.

Filip Pizlo

Comment 4 2012-05-15 23:04:06 PDT

Created attachment 142158 [details] it's starting to do things Still more work to be done though.

Filip Pizlo

Comment 5 2012-05-17 15:06:08 PDT

Created attachment 142563 [details] the patch

Geoffrey Garen

Comment 6 2012-05-17 15:53:10 PDT

Comment on attachment 142563 [details] the patch View in context: https://bugs.webkit.org/attachment.cgi?id=142563&action=review Test cases and 32bit, please. > Source/JavaScriptCore/dfg/DFGArgumentsSimplificationPhase.cpp:442 > + // we should remote the phantom reference, since: s/remote/remove/

Filip Pizlo

Comment 7 2012-05-17 18:45:55 PDT

Created attachment 142606 [details] almost ready I just need to turn some of my ad-hoc tests into LayoutTests.

Filip Pizlo

Comment 8 2012-05-17 22:30:16 PDT

Landed with a bunch of LayoutTests in http://trac.webkit.org/changeset/117542

Filip Pizlo

Comment 9 2012-05-17 22:32:52 PDT

> s/remote/remove/ Forgot to fix in the main commit. Fix landed in http://trac.webkit.org/changeset/117543

Filip Pizlo

Comment 10 2012-05-23 22:32:42 PDT

Merged in http://trac.webkit.org/changeset/118323

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