1724716 - jsshell fails to start if Wasm SIMD is disabled

Status: RESOLVED FIXED

(Core :: JavaScript: WebAssembly, defect, P3)

Description

[Yury Delendik (:yury)]

There is

Assertion failure: framePushed() - framePushedInitial == PushRegsInMaskSizeInBytes(set), at ./mozilla-unified/js/src/jit/x86-shared/MacroAssembler-x86-shared.cpp:445

when ac_add_options --disable-wasm-simd is used

Comment 1

[Yury Delendik (:yury)]

Attachment: Bug 1724716 - Reduce set in PushRegsInMaskSizeInBytes. r?jseward

Comment 2

[Lars T Hansen [:lth]]

Well, "defect". I guess so :-)

Comment 3

[Julian Seward [:jseward]]

The invariants around stack-dump layout are fragile and are documented
at jit/MacroAssembler.h:393 and after. Can you give some background here
about why the failure occurs and why the fix is correct? And does the fix
observe those documented invariants?

Comment 4

[Yury Delendik (:yury)]

The problem is that in the PushRegsInMask the push size is calculated based on the reduced FPU set of registers. Though the assert is using PushRegsInMaskSizeInBytes, which calculates size based on non-reduced FPU set. The patch changes logic of PushRegsInMaskSizeInBytes to make asserts in PushRegsInMask and friends happy, and that is what required by invariant documented in MacroAssembler.h.

Comment 5

[Julian Seward [:jseward]]

Thanks for the clarifications.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/417d86db010f
Reduce set in PushRegsInMaskSizeInBytes. r=jseward

Comment 7

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/417d86db010f