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fetch-and-add

An atomic operation that adds to a memory value and hands back what it was before: lock xadd on x86-64, ldadd on ARM64.

Fetch-and-add atomically replaces *p with *p + v and returns the old value (x86-64 lock xadd; ARM64 LSE ldadd; RISC-V amoadd; C++ std::atomic::fetch_add).

Examples

  • lock xadd [rdi], eax adds eax to memory and leaves the old memory value in eax.

See also

std::atomic atomic read-modify-write Large System Extensions
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