> determinism vs non-determinism
Here are the reported miscompilation bugs in GCC so far in 2026. The ones labeled "wrong-code".
https://gcc.gnu.org/bugzilla/buglist.cgi?chfield=%5BBug%20cr...
I count 121 of them. It appears that code-generation is not as deterministic as you seem to think it is.
Deterministic doesn't mean correct. Compilers can have bugs. What deterministic means, given the same input you get the same output every time. So long as given the same code it generates the same wrong thing every time, its still deterministic.
99.9% vs about 20%. Pretty weak argument.