expmed.c (shiftsub_cost): Rename to shiftsub0_cost.

	* expmed.c (shiftsub_cost): Rename to shiftsub0_cost.
	(shiftsub1_cost): New.
	(init_expmed): Compute shiftsub1_cost.
	(synth_mult): Optimize multiplications by constants of the form
	-(2^^m-1) for some constant positive integer m.

From-SVN: r147086

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5ac28ebde3aaff543d1d41f5368d3fe3cc95296d..b67be5b78e0dfa8f97d9a511027c18a8ac0ba26c 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2009-05-04  Kazu Hirata  <kazu@codesourcery.com>
+
+       * expmed.c (shiftsub_cost): Rename to shiftsub0_cost.
+       (shiftsub1_cost): New.
+       (init_expmed): Compute shiftsub1_cost.
+       (synth_mult): Optimize multiplications by constants of the form
+       -(2^^m-1) for some constant positive integer m.
+
 2009-05-03  Richard Guenther  <rguenther@suse.de>
 
        PR c/39983

diff --git a/gcc/expmed.c b/gcc/expmed.c
index acbc09b1b87e93667af04abc6ee4b9bbc6c5562d..7ffb693dcdd4db18fca0d01733251b9beca79e4b 100644 (file)
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -103,7 +103,8 @@ static int add_cost[2][NUM_MACHINE_MODES];
 static int neg_cost[2][NUM_MACHINE_MODES];
 static int shift_cost[2][NUM_MACHINE_MODES][MAX_BITS_PER_WORD];
 static int shiftadd_cost[2][NUM_MACHINE_MODES][MAX_BITS_PER_WORD];
-static int shiftsub_cost[2][NUM_MACHINE_MODES][MAX_BITS_PER_WORD];
+static int shiftsub0_cost[2][NUM_MACHINE_MODES][MAX_BITS_PER_WORD];
+static int shiftsub1_cost[2][NUM_MACHINE_MODES][MAX_BITS_PER_WORD];
 static int mul_cost[2][NUM_MACHINE_MODES];
 static int sdiv_cost[2][NUM_MACHINE_MODES];
 static int udiv_cost[2][NUM_MACHINE_MODES];
@@ -130,7 +131,8 @@ init_expmed (void)
     struct rtx_def shift;      rtunion shift_fld1;
     struct rtx_def shift_mult; rtunion shift_mult_fld1;
     struct rtx_def shift_add;  rtunion shift_add_fld1;
-    struct rtx_def shift_sub;  rtunion shift_sub_fld1;
+    struct rtx_def shift_sub0; rtunion shift_sub0_fld1;
+    struct rtx_def shift_sub1; rtunion shift_sub1_fld1;
   } all;
 
   rtx pow2[MAX_BITS_PER_WORD];
@@ -201,9 +203,13 @@ init_expmed (void)
   XEXP (&all.shift_add, 0) = &all.shift_mult;
   XEXP (&all.shift_add, 1) = &all.reg;
 
-  PUT_CODE (&all.shift_sub, MINUS);
-  XEXP (&all.shift_sub, 0) = &all.shift_mult;
-  XEXP (&all.shift_sub, 1) = &all.reg;
+  PUT_CODE (&all.shift_sub0, MINUS);
+  XEXP (&all.shift_sub0, 0) = &all.shift_mult;
+  XEXP (&all.shift_sub0, 1) = &all.reg;
+
+  PUT_CODE (&all.shift_sub1, MINUS);
+  XEXP (&all.shift_sub1, 0) = &all.reg;
+  XEXP (&all.shift_sub1, 1) = &all.shift_mult;
 
   for (speed = 0; speed < 2; speed++)
     {
@@ -226,7 +232,8 @@ init_expmed (void)
          PUT_MODE (&all.shift, mode);
          PUT_MODE (&all.shift_mult, mode);
          PUT_MODE (&all.shift_add, mode);
-         PUT_MODE (&all.shift_sub, mode);
+         PUT_MODE (&all.shift_sub0, mode);
+         PUT_MODE (&all.shift_sub1, mode);
 
          add_cost[speed][mode] = rtx_cost (&all.plus, SET, speed);
          neg_cost[speed][mode] = rtx_cost (&all.neg, SET, speed);
@@ -254,8 +261,8 @@ init_expmed (void)
            }
 
          shift_cost[speed][mode][0] = 0;
-         shiftadd_cost[speed][mode][0] = shiftsub_cost[speed][mode][0]
-           = add_cost[speed][mode];
+         shiftadd_cost[speed][mode][0] = shiftsub0_cost[speed][mode][0]
+           = shiftsub1_cost[speed][mode][0] = add_cost[speed][mode];
 
          n = MIN (MAX_BITS_PER_WORD, GET_MODE_BITSIZE (mode));
          for (m = 1; m < n; m++)
@@ -265,7 +272,8 @@ init_expmed (void)
 
              shift_cost[speed][mode][m] = rtx_cost (&all.shift, SET, speed);
              shiftadd_cost[speed][mode][m] = rtx_cost (&all.shift_add, SET, speed);
-             shiftsub_cost[speed][mode][m] = rtx_cost (&all.shift_sub, SET, speed);
+             shiftsub0_cost[speed][mode][m] = rtx_cost (&all.shift_sub0, SET, speed);
+             shiftsub1_cost[speed][mode][m] = rtx_cost (&all.shift_sub1, SET, speed);
            }
        }
     }
@@ -2397,6 +2405,7 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
   struct mult_cost best_cost;
   struct mult_cost new_limit;
   int op_cost, op_latency;
+  unsigned HOST_WIDE_INT orig_t = t;
   unsigned HOST_WIDE_INT q;
   int maxm = MIN (BITS_PER_WORD, GET_MODE_BITSIZE (mode));
   int hash_index;
@@ -2604,6 +2613,29 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
              best_alg->op[best_alg->ops] = alg_add_t_m2;
            }
        }
+
+      /* We may be able to calculate a * -7, a * -15, a * -31, etc
+        quickly with a - a * n for some appropriate constant n.  */
+      m = exact_log2 (-orig_t + 1);
+      if (m >= 0 && m < maxm)
+       {
+         op_cost = shiftsub1_cost[speed][mode][m];
+         new_limit.cost = best_cost.cost - op_cost;
+         new_limit.latency = best_cost.latency - op_cost;
+         synth_mult (alg_in, (unsigned HOST_WIDE_INT) (-orig_t + 1) >> m, &new_limit, mode);
+
+         alg_in->cost.cost += op_cost;
+         alg_in->cost.latency += op_cost;
+         if (CHEAPER_MULT_COST (&alg_in->cost, &best_cost))
+           {
+             struct algorithm *x;
+             best_cost = alg_in->cost;
+             x = alg_in, alg_in = best_alg, best_alg = x;
+             best_alg->log[best_alg->ops] = m;
+             best_alg->op[best_alg->ops] = alg_sub_t_m2;
+           }
+       }
+
       if (cache_hit)
        goto done;
     }
@@ -2673,9 +2705,9 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
             hardware the shift may be executed concurrently with the
             earlier steps in the algorithm.  */
          op_cost = add_cost[speed][mode] + shift_cost[speed][mode][m];
-         if (shiftsub_cost[speed][mode][m] < op_cost)
+         if (shiftsub0_cost[speed][mode][m] < op_cost)
            {
-             op_cost = shiftsub_cost[speed][mode][m];
+             op_cost = shiftsub0_cost[speed][mode][m];
              op_latency = op_cost;
            }
          else
@@ -2738,7 +2770,7 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
       m = exact_log2 (q);
       if (m >= 0 && m < maxm)
        {
-         op_cost = shiftsub_cost[speed][mode][m];
+         op_cost = shiftsub0_cost[speed][mode][m];
          new_limit.cost = best_cost.cost - op_cost;
          new_limit.latency = best_cost.latency - op_cost;
          synth_mult (alg_in, (t + 1) >> m, &new_limit, mode);