[PATCH] PR target/97312: Tweak gcc.target/aarch64/pr90838.c

[Wilco Dijkstra]

Hi Jakub, 

> Having it undefined allows optimizations, and has been that way for years.

Which optimizations does it enable that aren't possible if the value is defined?

> We just should make sure that we optimize code like x ? __builtin_c[lt]z (x) : 32;
> etc. properly (and I believe we do).

I think we do, but both the external and internal documentation are not clear
enough that most targets actually do define a value and will optimize for it.
Otherwise we wouldn't have this bug now...

Cheers,
Wilco