On Tue, Apr 18, 2023 at 10:51 PM Vineet Gupta <vine...@rivosinc.com> wrote:
>
> when debugging expmed.[ch] for PR/108987 saw that some of the cost arrays have
> less than ideal layout as follows:
>
> x_shift*cost[0..63][speed][modes]
>
> We would want speed to be first index since a typical compile will have
> that fixed, followed by mode and then the shift values.
>
> It should be non-functional from compiler semantics pov, except
> executing slightly faster due to better locality of shift values for
> given speed and mode. And also a bit more intutive when debugging.
OK, but please wait 24h in case somebody else wants to comment.
Thanks,
Richard.
> gcc/Changelog:
>
> * expmed.h (x_shift*_cost): convert to int [speed][mode][shift].
> (shift*_cost_ptr ()): Access x_shift*_cost array directly.
>
> Signed-off-by: Vineet Gupta <vine...@rivosinc.com>
> ---
> Changes since v1:
> - Post a non stale version of patch
> ---
> gcc/expmed.h | 27 +++++++++++++--------------
> 1 file changed, 13 insertions(+), 14 deletions(-)
>
> diff --git a/gcc/expmed.h b/gcc/expmed.h
> index c747a0da1637..22ae1d2d0743 100644
> --- a/gcc/expmed.h
> +++ b/gcc/expmed.h
> @@ -161,15 +161,14 @@ struct target_expmed {
> struct expmed_op_cheap x_sdiv_pow2_cheap;
> struct expmed_op_cheap x_smod_pow2_cheap;
>
> - /* Cost of various pieces of RTL. Note that some of these are indexed by
> - shift count and some by mode. */
> + /* Cost of various pieces of RTL. */
> int x_zero_cost[2];
> struct expmed_op_costs x_add_cost;
> struct expmed_op_costs x_neg_cost;
> - struct expmed_op_costs x_shift_cost[MAX_BITS_PER_WORD];
> - struct expmed_op_costs x_shiftadd_cost[MAX_BITS_PER_WORD];
> - struct expmed_op_costs x_shiftsub0_cost[MAX_BITS_PER_WORD];
> - struct expmed_op_costs x_shiftsub1_cost[MAX_BITS_PER_WORD];
> + int x_shift_cost[2][NUM_MODE_IPV_INT][MAX_BITS_PER_WORD];
> + int x_shiftadd_cost[2][NUM_MODE_IPV_INT][MAX_BITS_PER_WORD];
> + int x_shiftsub0_cost[2][NUM_MODE_IPV_INT][MAX_BITS_PER_WORD];
> + int x_shiftsub1_cost[2][NUM_MODE_IPV_INT][MAX_BITS_PER_WORD];
> struct expmed_op_costs x_mul_cost;
> struct expmed_op_costs x_sdiv_cost;
> struct expmed_op_costs x_udiv_cost;
> @@ -395,8 +394,8 @@ neg_cost (bool speed, machine_mode mode)
> inline int *
> shift_cost_ptr (bool speed, machine_mode mode, int bits)
> {
> - return expmed_op_cost_ptr (&this_target_expmed->x_shift_cost[bits],
> - speed, mode);
> + int midx = expmed_mode_index (mode);
> + return &this_target_expmed->x_shift_cost[speed][midx][bits];
> }
>
> /* Set the COST of doing a shift in MODE by BITS when optimizing for SPEED.
> */
> @@ -421,8 +420,8 @@ shift_cost (bool speed, machine_mode mode, int bits)
> inline int *
> shiftadd_cost_ptr (bool speed, machine_mode mode, int bits)
> {
> - return expmed_op_cost_ptr (&this_target_expmed->x_shiftadd_cost[bits],
> - speed, mode);
> + int midx = expmed_mode_index (mode);
> + return &this_target_expmed->x_shiftadd_cost[speed][midx][bits];
> }
>
> /* Set the COST of doing a shift in MODE by BITS followed by an add when
> @@ -448,8 +447,8 @@ shiftadd_cost (bool speed, machine_mode mode, int bits)
> inline int *
> shiftsub0_cost_ptr (bool speed, machine_mode mode, int bits)
> {
> - return expmed_op_cost_ptr (&this_target_expmed->x_shiftsub0_cost[bits],
> - speed, mode);
> + int midx = expmed_mode_index (mode);
> + return &this_target_expmed->x_shiftsub0_cost[speed][midx][bits];
> }
>
> /* Set the COST of doing a shift in MODE by BITS and then subtracting a
> @@ -475,8 +474,8 @@ shiftsub0_cost (bool speed, machine_mode mode, int bits)
> inline int *
> shiftsub1_cost_ptr (bool speed, machine_mode mode, int bits)
> {
> - return expmed_op_cost_ptr (&this_target_expmed->x_shiftsub1_cost[bits],
> - speed, mode);
> + int midx = expmed_mode_index (mode);
> + return &this_target_expmed->x_shiftsub1_cost[speed][midx][bits];
> }
>
> /* Set the COST of subtracting a shift in MODE by BITS from a value when
> --
> 2.34.1
>
