[Bug rtl-optimization/92180] Missed optimization on casting __builtin_ia32_rdtsc result to int32

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92180

--- Comment #2 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Combine *does* combine setters of hard registers.

nonzero_bits is not reliable, it depends on the order things are tried in.