1361383 - Enable asm spew only in JS_JITSPEW builds

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, enhancement)

Description

[Jan de Mooij [:jandem]]

Attachment: Patch

For each instruction we emit on x86/x64 we check this:

    if (MOZ_UNLIKELY(printer || JitSpewEnabled(JitSpew_Codegen))) {
        va_list va;
        va_start(va, fmt);
        spew(fmt, va);
        va_end(va);
    }

JitSpewEnabled is a no-op in opt builds but we still have to null-check |printer| and the spew() call is likely messing with inlining heuristics.

Considering only a handful of people use this, let's only enable it in DEBUG/--enable-jitspew builds.

Comment 1

[Jan de Mooij [:jandem]]

I wouldn't be surprised if this is actually a measurable speedup with Wasm Baseline.

Comment 2

[Lars T Hansen [:lth]]

Seems plausible.  It hasn't shown up in profiles, but if it's inline it wouldn't, and anyway I haven't profiled in a while...

Comment 3

[Nicolas B. Pierron [:nbp]]

Comment on attachment 8863757 [details] [diff] [review]
Patch

Review of attachment 8863757 [details] [diff] [review]:
-----------------------------------------------------------------

This will might cause issues with the Ion counter, used by -D, and one addon, but this patch sounds fine to me.
Note: The ARM backend also has a printer_ field used by the disassembler/simulator.

Comment 4

[Jan de Mooij [:jandem]]

(In reply to Nicolas B. Pierron [:nbp] from comment #3)
> This will might cause issues with the Ion counter, used by -D, and one
> addon, but this patch sounds fine to me.

Yup, I think we can ask the few people using these to use an --enable-jitspew build.

> Note: The ARM backend also has a printer_ field used by the
> disassembler/simulator.

Yeah that one is already guarded by JS_DISASM_ARM (disabled by default in opt builds as far as I can see).

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/270e22be3545
Enable x86/x64 asm spew only in JS_JITSPEW builds. r=nbp

Comment 6

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/270e22be3545