tree-optimization/111387 - BB SLP and irreducible regions

When we split an irreducible region for BB vectorization analysis
the defensive handling of external backedge defs in
vect_get_and_check_slp_defs doesn't work since that relies on
dominance info to identify a backedge.  The testcase also shows
we are iterating over the function in a sub-optimal way which is
why we split the irreducible region in the first place.  The fix
is to mark backedges and use EDGE_DFS_BACK to identify them and
to use the region RPO compute which can produce a RPO order keeping
cycles in a better order (and as side effect marks backedges).

	PR tree-optimization/111387
	* tree-vect-slp.cc (vect_get_and_check_slp_defs): Check
	EDGE_DFS_BACK when doing BB vectorization.
	(vect_slp_function): Use rev_post_order_and_mark_dfs_back_seme
	to compute RPO and mark backedges.

	* gcc.dg/torture/pr111387.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/torture/pr111387.c b/gcc/testsuite/gcc.dg/torture/pr111387.c
new file mode 100644 (file)
index 0000000..e14eeef
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr111387.c
@@ -0,0 +1,34 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-ftree-vectorize -fno-vect-cost-model" } */
+
+struct {
+  unsigned a;
+  unsigned b;
+} c;
+int d, e, f, g, h;
+int main()
+{
+  if (c.b && g && g > 7)
+    goto i;
+ j:
+  if (c.a) {
+    int k = 0;
+    unsigned l = c.b;
+    if (0) {
+    m:
+      k = l = c.b;
+    }
+    c.a = k;
+    c.b = l;
+  }
+  if (0) {
+  i:
+    goto m;
+  }
+  if (d)
+    goto j;
+  for (f = 5; f; f--)
+    if (h)
+      e = 0;
+  return 0;
+}

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index 0cf6e02285e90f73d20ac8188edc453e10929e08..a3e54ebf62a29d2ff1c35546a742763c84f2d8b5 100644 (file)
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -628,9 +628,13 @@ vect_get_and_check_slp_defs (vec_info *vinfo, unsigned char swap,
        {
          oprnd = gimple_arg (stmt_info->stmt, opno);
          if (gphi *stmt = dyn_cast <gphi *> (stmt_info->stmt))
-           backedge = dominated_by_p (CDI_DOMINATORS,
-                                      gimple_phi_arg_edge (stmt, opno)->src,
-                                      gimple_bb (stmt_info->stmt));
+           {
+             edge e = gimple_phi_arg_edge (stmt, opno);
+             backedge = (is_a <bb_vec_info> (vinfo)
+                         ? e->flags & EDGE_DFS_BACK
+                         : dominated_by_p (CDI_DOMINATORS, e->src,
+                                           gimple_bb (stmt_info->stmt)));
+           }
        }
       if (TREE_CODE (oprnd) == VIEW_CONVERT_EXPR)
        oprnd = TREE_OPERAND (oprnd, 0);
@@ -7771,7 +7775,11 @@ vect_slp_function (function *fun)
 {
   bool r = false;
   int *rpo = XNEWVEC (int, n_basic_blocks_for_fn (fun));
-  unsigned n = pre_and_rev_post_order_compute_fn (fun, NULL, rpo, false);
+  auto_bitmap exit_bbs;
+  bitmap_set_bit (exit_bbs, EXIT_BLOCK);
+  edge entry = single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (fun));
+  unsigned n = rev_post_order_and_mark_dfs_back_seme (fun, entry, exit_bbs,
+                                                     true, rpo, NULL);
 
   /* For the moment split the function into pieces to avoid making
      the iteration on the vector mode moot.  Split at points we know