1524178 - feeling-lucky atomics fallbacks should consider simulators specially so as to handle wasm

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, enhancement, P2)

Description

[Lars T Hansen [:lth]]

Our ARM and ARM64 simulators do not get native jitted atomics, but instead use the fallback feeling-lucky quasi-UB C++ code. (Buy me beer and I'll tell you why, but basically this comes down to the difficulty of defining JS_CODEGEN_X86 and JS_CODEGEN_ARM in the same build.)

But this means the simulators do not properly support wasm. Wasm requires lockfree8 but the feeling-lucky path only has that if opted into. However, the feeling-lucky code opts into that for neither simulator. For the ARM64 simulator it's easy; for the ARM32 simulator a little more annoying because we may require -latomic for the 64-bit primitives on x86.

Comment 1

[Lars T Hansen [:lth]]

Attachment: bug1524178-lockfree8-for-simulators.patch

Julian, see how this works out for you.

Comment 2

[Julian Seward [:jseward]]

Comment on attachment 9040335 [details] [diff] [review]
bug1524178-lockfree8-for-simulators.patch

Review of attachment 9040335 [details] [diff] [review]:
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This looks OK with local testing and also on try.  Thanks for the quick fix.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/c474d2c881f5
Enable lock-free 8-byte atomics for ARM+ARM64 simulators. r=jseward

Comment 4

[Razvan Maries]

https://hg.mozilla.org/mozilla-central/rev/c474d2c881f5