793905 - IonMonkey: JM is recompiling when generating calls for newly Ion-compiled functions.

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Nicolas B. Pierron [:nbp]]

The bug show up in sunspider 3d-raytrace, but is likely to appear in many other benchmarks.  The following spew is produced by executing a debug build with JMFLAGS=scripts,recompile IONFLAGS=scripts,inlining environment variables.

[jaeger] Recompile  recompiling script (file "./tests/sunspider-1.0/3d-raytrace.js") (line "160") (length "312") (usecount="10240")
[jaeger] Recompile  interpreter rejoin (file "./tests/sunspider-1.0/3d-raytrace.js") (line "160") (op js_this_str) (opline "161")
[Scripts] Analyzing script ./tests/sunspider-1.0/3d-raytrace.js:160 (0x7f211530ddd8) (usecount=10240) (maxloopcount=0)
[jaeger] Recompile  recompiling script (file "./tests/sunspider-1.0/3d-raytrace.js") (line "244") (length "181") (usecount="4458")
[jaeger] Recompile  interpreter rejoin (file "./tests/sunspider-1.0/3d-raytrace.js") (line "244") (op "call") (opline "249")
[jaeger] Recompile  recompiling script (file "./tests/sunspider-1.0/3d-raytrace.js") (line "189") (length "871") (usecount="7694")
[jaeger] Recompile  interpreter rejoin (file "./tests/sunspider-1.0/3d-raytrace.js") (line "189") (op "call") (opline "193")

The goal is to prevent such recompilation each time a sub-function got Ion-compiled.

The reason why functions at line 244 and 189 are getting recompiled is loop invariant & bounds check which /somehow/ ensure that its arguments are not indirectly modified by checking if the current function is inlineable(*).  When we generate a IonStub, we check that the current JM function is uninlineable.

PS: (*) This might also have some weird interaction with the Native stubs too.

Comment 1

[Nicolas B. Pierron [:nbp]]

Attachment: Prevent JM recompilation when generating Ion stubs.

This patch should hopefully not have big side effects except removing a few JM compilations.

I do not expect any noticeable kraken or v8 improvement, and I noticed a 1ms on sunspider over 196.7ms — 0.5ms from 3d-raytrace and 0.5ms from 3d-cube.

Comment 2

[Nicolas B. Pierron [:nbp]]

Comment on attachment 664600 [details] [diff] [review]
Prevent JM recompilation when generating Ion stubs.

https://hg.mozilla.org/integration/mozilla-inbound/rev/ec211607e914

Comment 3

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/ec211607e914