Hi,
> -----Original Message-----
> From: Richard Sandiford [mailto:richard.sandif...@arm.com]
> Sent: Sunday, May 31, 2020 12:01 AM
> To: Yangfei (Felix) <felix.y...@huawei.com>
> Cc: gcc-patches@gcc.gnu.org; Uros Bizjak <ubiz...@gmail.com>; Jakub
> Jelinek <ja...@redhat.com>; Hongtao Liu <crazy...@gmail.com>; H.J. Lu
> <hjl.to...@gmail.com>
> Subject: Re: [PATCH PR95254] aarch64: gcc generate inefficient code with
> fixed sve vector length
>
Snip...
> >
> > The v5 patch attached addressed this issue.
> >
> > There two added changes compared with the v4 patch:
> > 1. In candidate_mem_p, mov_optab for innermode should be available.
> > In this case, mov_optab for SDmode is not there and subreg are added
> back by emit_move_insn_1. So we won't get the benefit with the patch.
>
> I agree we should have this check. I think the rule applies to all of the
> transforms though, not just the mem one, so we should add the check to the
> register and constant cases too.
OK. I changed to make this an extra condition for calculating x_inner & y
_inner.
> > 2. Instead of using adjust_address, I changed to use adjust_address_nv to
> avoid the emit of invalid insn 13.
> > The latter call to validize_mem() in emit_move_insn will take care of
> > the
> address for us.
>
> The validation performed by validize_mem is the same as that performed by
> adjust_address, so the only case this should make a difference is for
> push_operands:
True.
> /* If X or Y are memory references, verify that their addresses are valid
> for the machine. */
> if (MEM_P (x)
> && (! memory_address_addr_space_p (GET_MODE (x), XEXP (x, 0),
> MEM_ADDR_SPACE (x))
> && ! push_operand (x, GET_MODE (x))))
> x = validize_mem (x);
>
> if (MEM_P (y)
> && ! memory_address_addr_space_p (GET_MODE (y), XEXP (y, 0),
> MEM_ADDR_SPACE (y)))
> y = validize_mem (y);
>
> So I think the fix is to punt on push_operands instead (and continue to use
> adjust_address rather than adjust_address_nv).
Not sure if I understand it correctly.
Do you mean excluding push_operand in candidate_mem_p? Like:
3830 auto candidate_mem_p = [&](machine_mode innermode, rtx mem) {
3831 return !targetm.can_change_mode_class (innermode, GET_MODE (mem),
ALL_REGS)
3832 && !push_operand (mem, GET_MODE (mem))
3833 /* Not a candiate if innermode requires too much alignment. */
3834 && (MEM_ALIGN (mem) >= GET_MODE_ALIGNMENT (innermode)
3835 || targetm.slow_unaligned_access (GET_MODE (mem),
3836 MEM_ALIGN (mem))
3837 || !targetm.slow_unaligned_access (innermode, MEM_ALIGN
(mem)));
3838 };
Thanks,
Felix
