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Large System Extensions

The ARM64 extension that adds single atomic instructions such as ldadd, swp and cas, instead of retry loops.

The Armv8.1 Large System Extensions add single-instruction atomics (ldadd/ldclr/ldset/ldeor, swp, cas, casp with acquire/release variants) that scale better under contention than exclusive-pair loops; compilers use them with -march=armv8.1-a or later (Apple targets always), or choose at run time with -moutline-atomics.

See also

compare-and-swap atomic instruction contention fetch-and-add
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