Andrew Pinski <[email protected]> writes:
> While looking into PR 112454, I found the cost for
> `(if_then_else (cmp) (const_int 1) (reg))` was being recorded as 8
> (or `COSTS_N_INSNS (2)`) but it should have been 4 (or `COSTS_N_INSNS (1)`).
> This improves the cost by not adding the cost of `(const_int 1)` to
> the total cost.
>
> It does not does not fix PR 112454 as that requires other changes to forwprop
> the `(const_int 1)` earlier than combine.
>
> Bootstrapped and tested on aarch64-linux-gnu with no regressions.
>
> gcc/ChangeLog:
>
> * config/aarch64/aarch64.cc (aarch64_if_then_else_costs):
> Don't add the cost of `1` or `-1`.
>
> Signed-off-by: Andrew Pinski <[email protected]>
> ---
> gcc/config/aarch64/aarch64.cc | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
> index f6f6f94bf43..63241c5aaa5 100644
> --- a/gcc/config/aarch64/aarch64.cc
> +++ b/gcc/config/aarch64/aarch64.cc
> @@ -11642,9 +11642,16 @@ aarch64_if_then_else_costs (rtx op0, rtx op1, rtx
> op2, int *cost, bool speed)
> /* CSINV/NEG with zero extend + const 0 (*csinv3_uxtw_insn3). */
> op1 = XEXP (inner, 0);
> }
> -
> - *cost += rtx_cost (op1, VOIDmode, IF_THEN_ELSE, 1, speed);
> - *cost += rtx_cost (op2, VOIDmode, IF_THEN_ELSE, 2, speed);
> + if (op2 == constm1_rtx || op2 == const1_rtx)
> + *cost += rtx_cost (op1, VOIDmode, IF_THEN_ELSE, 1, speed);
> + else if (op1 == constm1_rtx || op1 == const1_rtx)
> + *cost += rtx_cost (op2, VOIDmode, IF_THEN_ELSE, 2, speed);
It looks like this is really an extra option on top of the previous
if-else chain, since it only applies when OP1 and OP2 are still the
operands of the if_then_else. So how about:
else if (op1 == constm1_rtx || op1 == const1_rtx)
{
/* Use CSINV. */
*cost += rtx_cost (op2, VOIDmode, IF_THEN_ELSE, 2, speed);
return true;
}
else if (op2 == constm1_rtx || op2 == const1_rtx)
{
/* Use CSINV. */
*cost += rtx_cost (op1, VOIDmode, IF_THEN_ELSE, 1, speed);
return true;
}
leaving the code to fall through to:
*cost += rtx_cost (op1, VOIDmode, IF_THEN_ELSE, 1, speed);
*cost += rtx_cost (op2, VOIDmode, IF_THEN_ELSE, 2, speed);
return true;
as it does currently. OK in that form if you agree.
Let me know if you don't. But in that case:
> + else
> + {
> + *cost += rtx_cost (op1, VOIDmode, IF_THEN_ELSE, 1, speed);
> + *cost += rtx_cost (op2, VOIDmode, IF_THEN_ELSE, 1, speed);
should be 2, speed
> + }
> +
Thanks,
Richard
