[gcc r14-149] expansion: make layout of x_shift*cost[][][] more efficient

[gcc r14-149] expansion: make layout of x_shift*cost[][][] more efficient

[Vineet Gupta]

https://gcc.gnu.org/g:1fe9bef9f5536e46b901139631863b3b86b97898

commit r14-149-g1fe9bef9f5536e46b901139631863b3b86b97898
Author: Vineet Gupta <vineetg@rivosinc.com>
Date:   Tue Feb 28 19:27:26 2023 -0800

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

Diff:
---
 gcc/expmed.h | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/gcc/expmed.h b/gcc/expmed.h
index c747a0da163..22ae1d2d074 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