[committed] expansion: make layout of x_shift*cost[][][] more efficient

[Vineet Gupta <vineetg@rivosinc.com>]

On 4/19/23 00:05, Richard Biener wrote:
> On Tue, Apr 18, 2023 at 10:51 PM Vineet Gupta <vineetg@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.

Pushed.

Thx,
-Vineet


>
> 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 <vineetg@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
>>