[flang] [llvm] [flang-rt] Runtime implementation of extended intrinsic function SECNDS() (PR #152021)

[Peter Klausler via llvm-commits]

https://github.com/klausler commented:

I think that you can replace that loop with just a single compare & swap if zero.  Only the first thread to ever execute it would succeed, and all later ones would fail and return the first thread's value.

https://github.com/llvm/llvm-project/pull/152021