1798246 - [loong64] Some jit-tests failed due to scratch register usage conflict: Assertion failure: !this->has(reg), at js/src/jit/RegisterSets.h:820

Status: RESOLVED FIXED

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

Description

[Zhao Jiazhong]

Some jit-tests failed on loongarch64 platform after Bug 1794439 - Inline HasNativeDataPropertyPure cache lookup in Ion r?jandem is landed:

basic/dictionary-delete-compact.js
cacheir/has.js
ion/hasOwn-megamorphic.js
ion/has-definite-folding.js
ion/testStringMatch.js
--enable-watchtower watchtower/megamorphic-long-proto-chain.js

js::jit::SpecializedRegSet<js::jit::AllocatableSetAccessors<js::jit::RegisterSet>, js::jit::RegisterSet>::add (this=<optimized out>, reg=...)
at /mnt/zjz/workspace/mozilla/mozilla-central/js/src/jit/RegisterSets.h:820
820 MOZ_ASSERT(!this->has(reg));

And it's because the patch introduced a new function MacroAssembler::loadAtomOrSymbolAndHash, which requires SecondScratchRegister twice on loongarch64 by ScratchTagScope and branchTest32.

Comment 1

[Zhao Jiazhong]

1. Change the scratch registers management strategy of loong64 port may fix it, but it's kind of big change, and needs time to implement.
2. We can also work around this issue by adjust the MacroAssembler::loadAtomOrSymbolAndHash function, and reduce the scope of ScratchTagScope tag, so it could release SecondScratchRegister before function branchTest32 is called.

Currently, I prefer the second way.

Comment 2

[Zhao Jiazhong]

Attachment: Bug 1798246 - Reduce ScratchTagScope in function loadAtomOrSymbolAndHash. r=dthayer

This is a workaround for scratch register usage conflict issue on loongarch64.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1794439

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5dc6a7bca27e
Reduce ScratchTagScope in function loadAtomOrSymbolAndHash. r=dthayer,jandem

Comment 5

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/5dc6a7bca27e