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

[Vineet Gupta]

On 4/19/23 00:05, Richard Biener wrote:

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.

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 <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