1986348 - Prefer std functions in fdlibm when precise results are guaranteed

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P3)

Description

[André Bargull [:anba]]

Use std version for sqrtf, fabs(f), scalb(f), copysign(f), ceil(f), floor(f), trunc(f), nearbyint(f), and rint(f), because they're guaranteed to be precise per https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf, Annex F.

Comment 1

[André Bargull [:anba]]

Attachment: Bug 1986348 - Part 1: Use standard rounding functions for JS. r=jandem!

Comment 2

[André Bargull [:anba]]

Attachment: Bug 1986348 - Part 2: Use standard rounding functions for Wasm. r=jandem!

Comment 3

[André Bargull [:anba]]

Attachment: Bug 1986348 - Part 3: Use standard math functions in fdlibm. r=jandem!

And remove no longer used imports.

Comment 4

[André Bargull [:anba]]

There are some unfortunate complications on Windows:

1. Rounding functions on Windows x64 can return the wrong NaN value for some Wasm tests. Probably fixable by adding a wrapper function which handles NaN.
2. Try-runs on Windows x86 are broken all over the place (tests abort with Windows error code 0xC0000409). There seems to be an issue when the JIT calls into the runtime and the runtime performs a call to std rounding functions. Probably some calling convention or stack alignment issue involving x87 instructions. I don't have a Windows setup right now, so diagnosing and fixing this issue is difficult for me.

Try-run: https://treeherder.mozilla.org/jobs?repo=try&revision=fd508dc771f2f6b1b4e11747a2eb1678c7d5e2fe

Comment 5

[André Bargull [:anba]]

Attachment: Bug 1986348 - Part 4: Force stack alignment and handle NaN values. r=jandem!

Add force_align_arg_pointer to ensure the stack is aligned to 16 bytes on
Windows x86. Without the extra stack alignment, calls from the JITs abort with
error code 0xC0000409.

And for Wasm additionally ensure NaN values are handled consistently across
different platforms. Tests in "jit-test/tests/wasm/spec/spec/f{32,64}.wast.js"
fail without this change. See also [1].

[1] https://webassembly.github.io/spec/core/exec/numerics.html#nan-propagation

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/fb30038c8ca7
https://hg.mozilla.org/integration/autoland/rev/0a301cd9de0b
Part 1: Use standard rounding functions for JS. r=jandem
https://github.com/mozilla-firefox/firefox/commit/7c4b022297ba
https://hg.mozilla.org/integration/autoland/rev/5a965aa46724
Part 2: Use standard rounding functions for Wasm. r=jandem
https://github.com/mozilla-firefox/firefox/commit/80501e827f1f
https://hg.mozilla.org/integration/autoland/rev/4938f06c075e
Part 3: Use standard math functions in fdlibm. r=jandem
https://github.com/mozilla-firefox/firefox/commit/7bba1019cea0
https://hg.mozilla.org/integration/autoland/rev/d2459d918cdf
Part 4: Force stack alignment and handle NaN values. r=jandem

Comment 7

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/0a301cd9de0b
https://hg.mozilla.org/mozilla-central/rev/5a965aa46724
https://hg.mozilla.org/mozilla-central/rev/4938f06c075e
https://hg.mozilla.org/mozilla-central/rev/d2459d918cdf