tree-optimization/117874 - optimize SLP discovery budget use

The following tries to avoid eating into the SLP discovery limit
when we can do cheaper checks first.  Together with the previous
patch this allows to use two-lane SLP discovery for mult_su3_an
in 433.milc.

	PR tree-optimization/117874
	* tree-vect-slp.cc (vect_build_slp_tree_2): Perform early
	reassoc checks before eating into discovery limit.

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index 1799d5a619b1d20e0393021b22f5a8b9cd51841e..425135a9ee0afd409c6c371fe4faab9c9723beba 100644 (file)
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -2292,6 +2292,9 @@ vect_build_slp_tree_2 (vec_info *vinfo, slp_tree node,
                }
            }
          /* 2. try to build children nodes, associating as necessary.  */
+         /* 2a. prepare and perform early checks to avoid eating into
+            discovery limit unnecessarily.  */
+         vect_def_type *dts = XALLOCAVEC (vect_def_type, chain_len);
          for (unsigned n = 0; n < chain_len; ++n)
            {
              vect_def_type dt = chains[0][n].dt;
@@ -2319,6 +2322,7 @@ vect_build_slp_tree_2 (vec_info *vinfo, slp_tree node,
                    matches[0] = false;
                  goto out;
                }
+             dts[n] = dt;
              if (dt == vect_constant_def
                  || dt == vect_external_def)
                {
@@ -2333,16 +2337,6 @@ vect_build_slp_tree_2 (vec_info *vinfo, slp_tree node,
                      matches[0] = false;
                      goto out;
                    }
-                 vec<tree> ops;
-                 ops.create (group_size);
-                 for (lane = 0; lane < group_size; ++lane)
-                   if (stmts[lane])
-                     ops.quick_push (chains[lane][n].op);
-                   else
-                     ops.quick_push (NULL_TREE);
-                 slp_tree child = vect_create_new_slp_node (ops);
-                 SLP_TREE_DEF_TYPE (child) = dt;
-                 children.safe_push (child);
                }
              else if (dt != vect_internal_def)
                {
@@ -2354,6 +2348,26 @@ vect_build_slp_tree_2 (vec_info *vinfo, slp_tree node,
                  hard_fail = false;
                  goto out;
                }
+           }
+         /* 2b. do the actual build.  */
+         for (unsigned n = 0; n < chain_len; ++n)
+           {
+             vect_def_type dt = dts[n];
+             unsigned lane;
+             if (dt == vect_constant_def
+                 || dt == vect_external_def)
+               {
+                 vec<tree> ops;
+                 ops.create (group_size);
+                 for (lane = 0; lane < group_size; ++lane)
+                   if (stmts[lane])
+                     ops.quick_push (chains[lane][n].op);
+                   else
+                     ops.quick_push (NULL_TREE);
+                 slp_tree child = vect_create_new_slp_node (ops);
+                 SLP_TREE_DEF_TYPE (child) = dt;
+                 children.safe_push (child);
+               }
              else
                {
                  vec<stmt_vec_info> op_stmts;
@@ -2396,6 +2410,11 @@ vect_build_slp_tree_2 (vec_info *vinfo, slp_tree node,
                                term = true;
                                break;
                              }
+                           if (dump_enabled_p ())
+                             dump_printf_loc (MSG_NOTE, vect_location,
+                                              "swapping operand %d and %d "
+                                              "of lane %d\n",
+                                              n, n + perms[lane] + 1, lane);
                            std::swap (chains[lane][n],
                                       chains[lane][n + perms[lane] + 1]);
                            perms[lane]++;