чт, 5 дек. 2024 г. в 14:23, Georg-Johann Lay <a...@gjlay.de>:
>
> This is an addendum to the -msplit-ldst patch.
>
> When -msplit-ldst is on, it may be possible to propagate __zero_reg__
> to the sources of the new stores. For example, without this patch,
>
> unsigned long lx;
>
> void store_lsr17 (void)
> {
> lx >>= 17;
> }
>
> compiles to:
>
> store_lsr17:
> lds r26,lx+2 ; movqi_insn
> lds r27,lx+3 ; movqi_insn
> movw r24,r26 ; *movhi
> lsr r25 ; *lshrhi3_const
> ror r24
> ldi r26,0 ; movqi_insn
> ldi r27,0 ; movqi_insn
> sts lx,r24 ; movqi_insn
> sts lx+1,r25 ; movqi_insn
> sts lx+2,r26 ; movqi_insn
> sts lx+3,r27 ; movqi_insn
> ret
>
> but with this patch it becomes:
>
> store_lsr17:
> lds r26,lx+2 ; movqi_insn
> lds r27,lx+3 ; movqi_insn
> movw r24,r26 ; *movhi
> lsr r25 ; *lshrhi3_const
> ror r24
> sts lx,r24 ; movqi_insn
> sts lx+1,r25 ; movqi_insn
> sts lx+2,__zero_reg__ ; movqi_insn
> sts lx+3,__zero_reg__ ; movqi_insn
> ret
>
> Ok for trunk?
>
Ok.
Denis
