[clang] [compiler-rt] [llvm] [clang] builtins for atomicrmw fminmax/_num (PR #187139)

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gonzalobg wrote:

> I think the versions returning the new value exist because code using the new value can lower to something simpler in some cases on some targets. Not sure how much that matters in practice for an optimizing compiler.

@efriedma-quic do you know which sw needs the new value? (e.g. c++ does not provide these apis so libc++ at least doesn't need them)

https://github.com/llvm/llvm-project/pull/187139