[o11c]

For 32-bit x86 it's certainly not. The C standard permits intermediates to preserve excess precision, and the only way to avoid that is by flushing to memory, which is slow. On Windows you usually get 64-bit intermediates and on other OSes usually 80-bit.

64-bit x86 and modern non-x86 architectures are usually deterministic for primitive operations at least, but libm differences abound.