1115531 - 8% regression in onctane navier-stokes 32bit Mac

Status: RESOLVED INVALID

(Core :: JavaScript Engine: JIT, defect)

Description

[Tom S. (please needinfo tschuster)]

Apparently somehow caused by bug 1113677, not obvious why.

Comment 1

[Jan de Mooij [:jandem]]

navier-stokes doesn't use instanceof at all and it only affected the Mac 32-bit shell with LSRA. Fortunately it's back to normal now, thanks to Waldo. The fix range has:

http://hg.mozilla.org/integration/mozilla-inbound/rev/4fd307cbb9d9

This doesn't make sense either. Maybe a (JIT-)code alignment or build thing? Sucks because it means some other random change could easily trigger this again..

We've had this before, especially with (micro-)benchmarks that spend a lot of time in JIT code. Maybe aligning loop headers (bug 867001) will make us more reliable, but I've really no idea what we can do about this.

Anyway, the "regression" is gone now so I'm closing this.