make swap argument of vect_get_and_check_slp_defs readonly

Since some time we're only using this argument to communicate from
vect_build_slp_tree_1 to vect_get_and_check_slp_defs.  This makes
the direction of information flow clear.

2020-09-15  Richard Biener  <rguenther@suse.de>

	* tree-vect-slp.c (vect_get_and_check_slp_defs): Make swap
	argument by-value and do not change it.
	(vect_build_slp_tree_2): Adjust, set swap to NULL after last
	use.

diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index d844fe4d6bb6e1ecc8ec9ab3948bc728f76241a9..f9f4d706f0abd3a82dbf6e345c090ac829a79ae3 100644 (file)
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -391,7 +391,7 @@ can_duplicate_and_interleave_p (vec_info *vinfo, unsigned int count,
    swapping operands of father node of this one, return 1; if everything is
    ok return 0.  */
 static int
-vect_get_and_check_slp_defs (vec_info *vinfo, unsigned char *swap,
+vect_get_and_check_slp_defs (vec_info *vinfo, unsigned char swap,
                             vec<stmt_vec_info> stmts, unsigned stmt_num,
                             vec<slp_oprnd_info> *oprnds_info)
 {
@@ -441,7 +441,7 @@ vect_get_and_check_slp_defs (vec_info *vinfo, unsigned char *swap,
   else
     return -1;
 
-  bool swapped = (*swap != 0);
+  bool swapped = (swap != 0);
   gcc_assert (!swapped || first_op_cond);
   for (i = 0; i < number_of_oprnds; i++)
     {
@@ -450,7 +450,7 @@ again:
        {
          /* Map indicating how operands of cond_expr should be swapped.  */
          int maps[3][4] = {{0, 1, 2, 3}, {1, 0, 2, 3}, {0, 1, 3, 2}};
-         int *map = maps[*swap];
+         int *map = maps[swap];
 
          if (i < 2)
            oprnd = TREE_OPERAND (gimple_op (stmt_info->stmt,
@@ -607,7 +607,6 @@ again:
                         stmt_info->stmt);
     }
 
-  *swap = swapped;
   return 0;
 }
 
@@ -1391,7 +1390,7 @@ vect_build_slp_tree_2 (vec_info *vinfo,
   slp_oprnd_info oprnd_info;
   FOR_EACH_VEC_ELT (stmts, i, stmt_info)
     {
-      int res = vect_get_and_check_slp_defs (vinfo, &swap[i],
+      int res = vect_get_and_check_slp_defs (vinfo, swap[i],
                                             stmts, i, &oprnds_info);
       if (res != 0)
        matches[(res == -1) ? 0 : i] = false;
@@ -1404,6 +1403,7 @@ vect_build_slp_tree_2 (vec_info *vinfo,
        vect_free_oprnd_info (oprnds_info);
        return NULL;
       }
+  swap = NULL;
 
   auto_vec<slp_tree, 4> children;