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