Bug 16186

Summary:	Reduce number of c-stack-based MatchFrames
Product:	WebKit	Reporter:	Eric Seidel (no email) <eric>
Component:	JavaScriptCore	Assignee:	Nobody <webkit-unassigned>
Status:	RESOLVED INVALID
Severity:	Normal	CC:	barraclough, darin, ggaren, mjs
Priority:	P2
Version:	523.x (Safari 3)
Hardware:	Mac
OS:	OS X 10.4
Bug Depends on:	16185, 16187
Bug Blocks:

Description Eric Seidel (no email) 2007-11-29 04:12:23 PST

Reduce number of c-stack-based MatchFrames

I believe the credit for this idea goes to Darin, I heard about it through Maciej.  Currently we allocate space for 16 match frames every time we call into match().  That's excessive, since very very very few regexps ever go beyond a few frames.

Supposedly darin tried this and found that reducing to 4 frames was a big speedup.  I expect we could probably reduce to 8 frames w/o worrying too much about affecting real-world performance.  Until bug 16185 is fixed, we always use 2 frames for every regexp. :(

Comment 1 Eric Seidel (no email) 2007-11-29 05:06:11 PST

I just tested reducing FRAMES_ON_STACK to 8 and 4, and saw no change in SunSpider.  Unless I missed something, we might just want to close this bug.

Comment 2 Gavin Barraclough 2011-09-06 22:31:16 PDT

This is a proposed optimization for PCRE; we no longer use PCRE.