725254 - IonMonkey: Need optimistic GVN for gaussian-blur

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Jan de Mooij [:jandem]]

Kraken gaussian-blur has many duplicate expressions, so it's a good CSE/GVN testcase:
--
r += squidImageData[4 * ((y + j) * width + (x + i)) + 0] * kernel[Math.abs(j)][Math.abs(i)];
g += squidImageData[4 * ((y + j) * width + (x + i)) + 1] * kernel[Math.abs(j)][Math.abs(i)];
b += squidImageData[4 * ((y + j) * width + (x + i)) + 2] * kernel[Math.abs(j)][Math.abs(i)];
a += squidImageData[4 * ((y + j) * width + (x + i)) + 3] * kernel[Math.abs(j)][Math.abs(i)];
--
For bug 723536, the default GVN mode was switched from optimistic to pessimistic. Turns out that we probably need optimistic GVN here:

IM+TI optimistic GVN : 325 ms
JM+TI                : 498 ms
IM+TI no GVN         : 507 ms
IM+TI pessimistic GVN: 522 ms

Comment 1

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

Interesting that no GVN is faster than pessimistic GVN?

Comment 2

[Ryan Pearl [:rpearl]]

(In reply to David Anderson [:dvander] from comment #1)
> Interesting that no GVN is faster than pessimistic GVN?

I would assume due to register pressure increasing.

Comment 3

[Marty Rosenberg [:mjrosenb]]

GVN was recently turned on with the following commits:
http://hg.mozilla.org/projects/ionmonkey/rev/488290bd2644
http://hg.mozilla.org/projects/ionmonkey/rev/60def326b4d0
http://hg.mozilla.org/projects/ionmonkey/rev/1d0f999708ca

Comment 4

[Jan de Mooij [:jandem]]

Yeah, we're doing pretty well on gaussian-blur nowadays.