1987005 - Consider enabling jitspew for nightly shell builds for better IONPERF support

Status: NEW

(Core :: JavaScript Engine, task, P3)

Description

[Ryan Hunt [:rhunt]]

Bug 1918139 enabled jit-dump support in nightly so that we wouldn't need to rebuild anything to use it. I'm curious if we can get away with enabling jitspew too, as that will allow us to use IONPERF=ir-graph on Nightly without rebuilding.

I think the biggest risk here is binary size, but I'm not entirely sure. There has been execution overhead before (e.g. 1817483).

Comment 1

[Ben Visness [:bvisness]]

If the execution overhead is too large to have on by default, perhaps we could toggle it on via a pref in the Firefox profiler? It seems reasonable to let people opt into recording that data when they're actively taking a profile.

Comment 2

[Ryan Hunt [:rhunt]]

This would really only benefit the SpiderMonkey shell unless we added support to the Gecko Profiler for JIT debugging through JitDump. So we could possibly just enable it in the shell.

We also discussed that we could split this into just the 'static' part of strings included in the binary, but exclude the runtime checking for if 'jitspew' logging is enabled that happens in some hot parts of the compilers.