[gcc(refs/users/aoliva/heads/testme)] [PR105665] ivopts: check defs of names in base for undefs

[Alexandre Oliva <aoliva@gcc.gnu.org>]

https://gcc.gnu.org/g:8b85376e8c4279e620d7c9793776b42b9575b9ff

commit 8b85376e8c4279e620d7c9793776b42b9575b9ff
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Thu May 26 09:15:53 2022 -0300

    [PR105665] ivopts: check defs of names in base for undefs

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr105665.c |  2 +-
 gcc/tree-ssa-loop-ivopts.cc             | 22 ++++++++++++++++++----
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr105665.c b/gcc/testsuite/gcc.dg/torture/pr105665.c
index 12f0b78a4b4..34cfc658434 100644
--- a/gcc/testsuite/gcc.dg/torture/pr105665.c
+++ b/gcc/testsuite/gcc.dg/torture/pr105665.c
@@ -6,7 +6,7 @@ int main() {
   for (; b < 2; b++) {
     int g;
     if (f)
-      b = 40;
+      g++, b = 40;
     a = d[b * b];
     for (f = 0; f < 3; f++) {
       if (e)
diff --git a/gcc/tree-ssa-loop-ivopts.cc b/gcc/tree-ssa-loop-ivopts.cc
index 5b1c7340f77..654a0432ef4 100644
--- a/gcc/tree-ssa-loop-ivopts.cc
+++ b/gcc/tree-ssa-loop-ivopts.cc
@@ -3074,13 +3074,24 @@ get_loop_invariant_expr (struct ivopts_data *data, tree inv_expr)
 /* Find the first undefined SSA name in *TP.  */
 
 static tree
-find_ssa_undef (tree *tp, int *walk_subtrees, void *)
+find_ssa_undef (tree *tp, int *walk_subtrees, void *pset_)
 {
+  auto pset = static_cast<hash_set<tree> *> (pset_);
+
   if (TREE_CODE (*tp) == SSA_NAME)
     {
+      if (ssa_defined_default_def_p (*tp))
+	return NULL;
+
       if (ssa_undefined_value_p (*tp, false))
 	return *tp;
 
+      /* If we've already visited this SSA_NAME and got to it again,
+	 we know we didn't find it to be undefined, otherwise we'd
+	 have stopped the walk then.  */
+      if (pset && pset->add (*tp))
+	return NULL;
+
       gimple *def_stmt = SSA_NAME_DEF_STMT (*tp);
       /* ssa_undefined_value_p must have caught nop defs above.  */
       gcc_checking_assert (!gimple_nop_p (def_stmt));
@@ -3092,8 +3103,10 @@ find_ssa_undef (tree *tp, int *walk_subtrees, void *)
 	{
 	  tree use = USE_FROM_PTR (use_p);
 
-	  if (ssa_undefined_value_p (use, false))
-	    return use;
+	  int wsub = 1;
+	  tree result = find_ssa_undef (&use, &wsub, pset);
+	  if (result)
+	    return result;
 	}
     }
 
@@ -3132,7 +3145,8 @@ add_candidate_1 (struct ivopts_data *data, tree base, tree step, bool important,
   /* If BASE contains undefined SSA names make sure we only record
      the original IV.  */
   bool involves_undefs = false;
-  if (walk_tree (&base, find_ssa_undef, NULL, NULL))
+  hash_set<tree> pset;
+  if (walk_tree (&base, find_ssa_undef, &pset, NULL))
     {
       if (pos != IP_ORIGINAL)
 	return NULL;