CLZ when CLZ_DEFINED_VALUE_AT_ZERO is false

[Jakub Jelinek]

On Fri, Sep 01, 2023 at 10:13:40AM +0200, Richard Biener via Gcc wrote:
> The value of .CLZ (0) is undefined then.  I belive your analysis is correct in
> that both 63 - _35 might overflow and that dom3 (thus ranger) mis-computes
> the range for _35.  I wonder why we don't elide _36 ? _31 : 1 with that info
> (possibly no range-op for .CLZ?), of course it would be wrong to do so.
> 
> Can you open a bugreport please?

Seems similar to https://gcc.gnu.org/pipermail/gcc-patches/2023-February/thread.html#612214
except that case is at RTL level.
But arguably, I think at least at GIMPLE level we should just emit here
GIMPLE_COND + separate bb around it rather than COND_EXPR.

	Jakub