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Bug 1940795: Don't tear aligned subwords in AtomicMemcpy. r=spidermonkey-reviewers,jandem
Reads/writes to integer typed arrays mustn't tear, so they can't be split into single byte operations. Replace single byte copy loops with `AtomicCopy{Down,Up}NoTearIfAlignedUnsynchronized`, which performs additional checks when aligned word or dword copying is needed. Test262 tests: <tc39/test262#4369> Differential Revision: https://phabricator.services.mozilla.com/D233710 UltraBlame original commit: 968d34f043635337c9ab03c4c3f975c39e52f057
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‎js/src/jit/GenerateAtomicOperations.py

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