1564117 - Use std::sqrt in fdlibm

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement, P1)

Description

[André Bargull [:anba]]

std::sqrt is required to have an error less than 0.5 ulp, so there's no need to use the slower sqrt implementation from fdlibm.

This improves all fdlibm functions calling sqrt, for example see the results below for hypot and acosh.

// Improves from ~150ms to ~27ms.
function test_hypot() {
    var xs = [1023, 10230];
    var ys = [Math.PI, 2*Math.PI];

    var q = 0;
    var t = dateNow();
    for (var i = 0; i < 1000000; ++i) {
        q += Math.hypot(xs[i & 1], ys[i & 1]);
    }
    return [dateNow() - t, q];
}

// Improves from ~200ms to ~44ms.
function test_acosh() {
    var xs = [1023, 10230];
    var q = 0;
    var t = dateNow();
    for (var i = 0; i < 1000000; ++i) {
        q += Math.acosh(xs[i & 1]);
    }
    return [dateNow() - t, q];
}

Comment 1

[André Bargull [:anba]]

Attachment: Bug 1564117 - Part 1: Use std::sqrt in fdlibm. r=arai!

std::sqrt is guaranteed to have an error less than 0.5 ulp, so there's no need
to use fdlibm's slower implementation.

Comment 2

[André Bargull [:anba]]

Attachment: Bug 1564117 - Part 2: Allow to reimport a specific fdlibm commit. r=arai!

This makes it easier to test if modified patch files still apply.

Additionally "--no-backup-if-mismatch" was added to the patch command to
avoid generating ".orig" files.

Depends on D37256

Comment 3

[André Bargull [:anba]]

Try: https://treeherder.mozilla.org/#/jobs?repo=try&revision=ce0e1893b9c0de1b79ac2935d96e04830b486f1e

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/67c757b08c76
Part 1: Use std::sqrt in fdlibm. r=arai
https://hg.mozilla.org/integration/autoland/rev/478e22e44bdf
Part 2: Allow to reimport a specific fdlibm commit. r=arai

Comment 5

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/67c757b08c76
https://hg.mozilla.org/mozilla-central/rev/478e22e44bdf