1637946 - Fold MUnbox with Int32 MBox input

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, task, P3)

Description

[Jan de Mooij [:jandem]]

The micro-benchmark below ends up boxing i and then immediately unboxes it as double. We can easily fix that in MUnbox::foldsTo and then I get the same JIT code and perf as Ion.

function f() {
    var x = 1.1;
    for (var i = 0; i < 10000000; i++) {
        x = 1.1 + i;
    }
    return x;
}
var t = dateNow();
f();
print(dateNow() - t);

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1637946 - Fold MUnbox(MBox(x), Double) to MToDouble if possible. r?evilpie!

This pattern is very common in MIR transpiled from CacheIR.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/564493b2e3c6
Fold MUnbox(MBox(x), Double) to MToDouble if possible. r=evilpie

Comment 3

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/564493b2e3c6