Mozilla Firefox JS engine Januari 2012

There are again a lot of improvements in the JavaScript engine in Mozilla Firefox. Here I will list the speed improvements and regressions happened in the month Januari. This time with three benchmarks. They are know as sunspider (a popular benchmark released by WebKit), V8 (released by google) and jslinux (a pc emulator running linux). The improvements will eventually come into Firefox 12 together with the improvements of the last week of December.

Current JS engine (Jaegermonkey + Type Interference)

Benchmark   December 31st   Januari 26th
jslinux      5306.0 ms         4596.0 ms   improvement of 15%
V8           7196.6            6953.4      regression in score of 3.5%
sunspider    165.87 ms        167.445 ms   regression of 0.1%

The biggest difference is the huge improvement on the jslinux benchmark. This is like Bhackett promised due to  landing of bug 706914. This compiles scripts in smaller chunks. This way the compilation time gets decreased.

Detailed overview
Note this list just gives an indication what revisions/bugs potentially increased/decreased performance. It could be that I’ve listed bugs that actually don’t give the listed speed-up and there could be revisions that have a huge influence on the speed, but that I failed to list here.

be81e5f7850f – Bug 714218 – Specialize some get* implementations to do property-type-specific handling, with their getGeneric forwarding to the appropriate specific implementation.
sunspider: regression of 0.8%

db8ea6327311 – Bug 607692 – Inline parseInt(, <0|10>) in JM.
sunspider: improvement of 0.5%

23f3b97f655a – Bug 710163: (part 2) fix EXT_context_loss semantics.
sunspider: regression of 0.4%

faf5f8842fec – Bug 703157 – Don’t modify dictionary shapes in place.
sunspider: improvement of 0.5%

78d17e22a223 – Bug 712714 – Remove JOF_CALLOP.
sunspider: regression of 0.6%

e12b877ae637 – Convert a couple always-true appends to infallibleAppend, since that’s what they should have been using
sunspider: improvement of 1%

d0c192e5bd41 – Bug 706914 – Compile large scripts in chunks.
jslinux: improvement of 17.4%
Huge improvement and indeed fixes the regression introduced last month by compiling switch and try blocks.

96a9dffede07 – Bug 717494 – Pass scope chain explicitly to FindProperty
jslinux: improvement of 0.7%

a85cf7f0d235 – Bug 716512 – make sure that gcparam in shell cannot set MAX_GC_BYTES to a value les than the current GC_BYTES.
V8: improvement of 0.8%

7ab4f1ebc7cc – Backout 54cd89b0f1fa (Bug 712714 backout). Talos will probably report fake regressions for this patch, do not back out for this reason.
V8: regression of 2.5%
Note: Like the commit message already states, this could be a fake regression. But I’m not sure. Every timing I do, shows this is a regression …

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