797551 - IonMonkey: Use callWithABI() for Math.random()

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Sean Stangl [:sstangl]]

Attachment: patch

It's fairly common to see Math.random() in benchmarks intended to measure repeated performance of some other aspect of the engine. For example, Bug 797401, reported today.

V8 inlines Math.random(), and we have Bug 774364 and Bug 773859 to do the same in our engine, but we can very easily just emit a call using callWithABI() and shave some time off right now. So this patch does that.

If you take the benchmark in Bug 797401 and extend the loop to run for about 5 seconds, this patch has it run in 4 seconds.

Comment 1

[David Anderson [:dvander] - inactive, e-mail if emergency]

Comment on attachment 667651 [details] [diff] [review]
patch

Review of attachment 667651 [details] [diff] [review]:
-----------------------------------------------------------------

::: js/src/ion/CodeGenerator.cpp
@@ +1785,5 @@
> +    Register temp = ToRegister(ins->temp());
> +
> +    masm.setupUnalignedABICall(1, temp);
> +    masm.loadJSContext(temp);
> +    masm.passABIArg(temp);

if (temp == r0) will this break on ARM? I thought that the temporary couldn't conflict with one of the registers used for passABIArg. If so we'll need two temporaries.

Comment 2

[Sean Stangl [:sstangl]]

http://hg.mozilla.org/integration/mozilla-inbound/rev/64bf5f240ccb

It doesn't look like it would break on ARM, but temporaries are free at callsites anyway.

Comment 3

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/64bf5f240ccb