1914979 - Definition of non-volatile SIMD registers for ARM64 is wrong

Status: RESOLVED FIXED

(Core :: JavaScript: WebAssembly, task, P2)

Description

[Jan de Mooij [:jandem]]

See bug 1897792 comment 50. We currently mark the v8-v15 registers as non-volatile (preserved by calls) on ARM64, but this only applies to the bottom 64 bits so this is wrong for SIMD registers.

This might affect CodeGenerator::visitOutOfLineWasmCallPostWriteBarrierImmediate where we call saveLiveVolatile to only save the volatile registers.

This isn't security sensitive but this should stay hidden until bug 1897792 is fixed.

Comment 2

[Jan de Mooij [:jandem]]

anba wrote a test for this bug. It's in the patch in bug 1919803.

Comment 3

[Jan de Mooij [:jandem]]

André confirmed that the obvious fix for NonVolatileSingleMask fixes his test case so NI myself to post that patch next week...

Comment 4

[Jan de Mooij [:jandem]]

Attachment: Bug 1914979 - Don't mark v8-v15 arm64 SIMD registers as non-volatile. r?yury!

Only the bottom 64 bits will be preserved by C++ code so we shouldn't treat the SIMD registers
as non-volatile.

The patch in bug 1919803 has a Wasm test for this.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/db06e8ac3482
Don't mark v8-v15 arm64 SIMD registers as non-volatile. r=yury

Comment 6

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/db06e8ac3482