https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93565
--- Comment #31 from Wilco <wilco at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #29)
> Looking back at this one, I (In reply to Wilco from comment #8)
> > Here is a much simpler example:
> >
> > void f (int *p, int y)
> > {
> > int a = y & 14;
> > *p = a | p[a];
> > }
> After r14-9692-g839bc42772ba7af66af3bd16efed4a69511312ae, we now get:
> f:
> .LFB0:
> .cfi_startproc
> and w2, w1, 14
> mov x1, x2
> ldr w2, [x0, x2, lsl 2]
> orr w1, w2, w1
> str w1, [x0]
> ret
> .cfi_endproc
>
> There is an extra move still but the duplicated and is gone. (with
> -frename-registers added, the move is gone as REE is able to remove the zero
> extend but then there is a life range conflict so can't remove the move too).
Even with the mov it is better since that can be done with zero latency in
rename in most CPUs.
> So maybe this should be closed as fixed for GCC 14 and the cost changes for
> clz reverted.
The ctz costs are correct since it is a 2-instruction sequence - it only needs
adjusting for CSSC.
