tree-optimization/98855 - fix some vectorizer cost issues

This fixes us not costing vectorized bswap for SLP as well as
avoiding biasing to the vectorized side when costing single-argument
PHIs.  Instead we assume coalescing here and cost them with zero cost
for both the scalar and vectorized code.

This doesn't fix the PR on its own.

2021-02-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/98855
	* tree-vect-loop.c (vectorizable_phi): Do not cost
	single-argument PHIs.
	* tree-vect-slp.c (vect_bb_slp_scalar_cost): Likewise.
	* tree-vect-stmts.c (vectorizable_bswap): Also perform
	costing for SLP operation.

diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index 200ed27..f1f16e3 100644 (file)
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -7777,8 +7777,12 @@ vectorizable_phi (vec_info *,
                               "incompatible vector types for invariants\n");
            return false;
          }
-      record_stmt_cost (cost_vec, SLP_TREE_NUMBER_OF_VEC_STMTS (slp_node),
-                       vector_stmt, stmt_info, vectype, 0, vect_body);
+      /* For single-argument PHIs assume coalescing which means zero cost
+        for the scalar and the vector PHIs.  This avoids artificially
+        favoring the vector path (but may pessimize it in some cases).  */
+      if (gimple_phi_num_args (as_a <gphi *> (stmt_info->stmt)) > 1)
+       record_stmt_cost (cost_vec, SLP_TREE_NUMBER_OF_VEC_STMTS (slp_node),
+                         vector_stmt, stmt_info, vectype, 0, vect_body);
       STMT_VINFO_TYPE (stmt_info) = phi_info_type;
       return true;
     }

diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index 10b876f..2305bbd 100644 (file)
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -4297,6 +4297,13 @@ vect_bb_slp_scalar_cost (vec_info *vinfo,
        }
       else if (vect_nop_conversion_p (orig_stmt_info))
        continue;
+      /* For single-argument PHIs assume coalescing which means zero cost
+        for the scalar and the vector PHIs.  This avoids artificially
+        favoring the vector path (but may pessimize it in some cases).  */
+      else if (is_a <gphi *> (orig_stmt_info->stmt)
+              && gimple_phi_num_args
+                   (as_a <gphi *> (orig_stmt_info->stmt)) == 1)
+       continue;
       else
        kind = scalar_stmt;
       record_stmt_cost (cost_vec, 1, kind, orig_stmt_info,

diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
index 5eb7b2d..0bc1cb1 100644 (file)
--- a/gcc/tree-vect-stmts.c
+++ b/gcc/tree-vect-stmts.c
@@ -3002,13 +3002,12 @@ vectorizable_bswap (vec_info *vinfo,
 
       STMT_VINFO_TYPE (stmt_info) = call_vec_info_type;
       DUMP_VECT_SCOPE ("vectorizable_bswap");
-      if (! slp_node)
-       {
-         record_stmt_cost (cost_vec,
-                           1, vector_stmt, stmt_info, 0, vect_prologue);
-         record_stmt_cost (cost_vec,
-                           ncopies, vec_perm, stmt_info, 0, vect_body);
-       }
+      record_stmt_cost (cost_vec,
+                       1, vector_stmt, stmt_info, 0, vect_prologue);
+      record_stmt_cost (cost_vec,
+                       slp_node
+                       ? SLP_TREE_NUMBER_OF_VEC_STMTS (slp_node) : ncopies,
+                       vec_perm, stmt_info, 0, vect_body);
       return true;
     }