The patch for PR 100810 tested for undefined SSA_NAMEs appearing
directly in the base expression of the potential IV candidate, but
that's not enough. The testcase for PR105665 shows an undefined
SSA_NAME has the same ill effect if it's referenced as an PHI_NODE arg
in the referenced SSA_NAME. The variant of that test shows it can be
further removed from the referenced SSA_NAME.
To avoid deep recursion, precompute SSA_NAMEs deemed unsuitable
candidates, so that we can skip them with a flag test.
Regstrapped on x86_64-linux-gnu. Ok to install?
for gcc/ChangeLog
PR tree-optimization/105665
PR tree-optimization/100810
* tree-ssa-loop-ivopts.cc (mark_ssa_undefs): Precompute
unsuitability of SSA_NAMEs in TREE_VISITED.
(find_ssa_undef): Check the precomputed flag.
(tree_ssa_iv_optimize): Call mark_ssa_undefs.
for gcc/testsuite/ChangeLog
PR tree-optimization/105665
PR tree-optimization/100810
* gcc.dg/torture/pr105665.c: New.
---
gcc/testsuite/gcc.dg/torture/pr105665.c | 20 ++++++++++
gcc/tree-ssa-loop-ivopts.cc | 62 ++++++++++++++++++++++++++++++-
2 files changed, 80 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr105665.c
diff --git a/gcc/testsuite/gcc.dg/torture/pr105665.c
b/gcc/testsuite/gcc.dg/torture/pr105665.c
new file mode 100644
index 0000000000000..34cfc65843495
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr105665.c
@@ -0,0 +1,20 @@
+/* { dg-do run } */
+
+int a, b, c[1], d[2], *e = c;
+int main() {
+ int f = 0;
+ for (; b < 2; b++) {
+ int g;
+ if (f)
+ g++, b = 40;
+ a = d[b * b];
+ for (f = 0; f < 3; f++) {
+ if (e)
+ break;
+ g--;
+ if (a)
+ a = g;
+ }
+ }
+ return 0;
+}
diff --git a/gcc/tree-ssa-loop-ivopts.cc b/gcc/tree-ssa-loop-ivopts.cc
index 81b536f930415..d8200f2a53b21 100644
--- a/gcc/tree-ssa-loop-ivopts.cc
+++ b/gcc/tree-ssa-loop-ivopts.cc
@@ -3071,13 +3071,70 @@ get_loop_invariant_expr (struct ivopts_data *data, tree
inv_expr)
return *slot;
}
-/* Find the first undefined SSA name in *TP. */
+/* Mark as TREe_VISITED any SSA_NAMEs that are unsuitable as ivopts
+ candidates for potentially involving undefined behavior. */
+
+static void
+mark_ssa_undefs (void)
+{
+ auto_vec<tree> queue;
+
+ unsigned int i;
+ tree var;
+ FOR_EACH_SSA_NAME (i, var, cfun)
+ {
+ if (SSA_NAME_IS_VIRTUAL_OPERAND (var)
+ || ssa_defined_default_def_p (var)
+ || !ssa_undefined_value_p (var, false))
+ TREE_VISITED (var) = false;
+ else
+ {
+ TREE_VISITED (var) = true;
+ queue.safe_push (var);
+ if (dump_file)
+ fprintf (dump_file, "marking _%i as undef\n",
+ SSA_NAME_VERSION (var));
+ }
+ }
+
+ while (!queue.is_empty ())
+ {
+ var = queue.pop ();
+ gimple *stmt;
+ imm_use_iterator iter;
+ FOR_EACH_IMM_USE_STMT (stmt, iter, var)
+ {
+ if (is_gimple_call (stmt) || is_a <gasm *> (stmt))
+ continue;
+
+ def_operand_p defvar;
+ ssa_op_iter diter;
+ FOR_EACH_PHI_OR_STMT_DEF (defvar, stmt, diter, SSA_OP_DEF)
+ {
+ gcc_checking_assert (is_gimple_assign (stmt)
+ || is_a <gphi *> (stmt));
+ tree def = DEF_FROM_PTR (defvar);
+ if (TREE_VISITED (def))
+ continue;
+ TREE_VISITED (def) = true;
+ queue.safe_push (def);
+ if (dump_file)
+ fprintf (dump_file, "Marking _%i as undef because of _%i\n",
+ SSA_NAME_VERSION (def), SSA_NAME_VERSION (var));
+ }
+ }
+ }
+}
+
+/* Return *TP if it is an SSA_NAME marked with TREE_VISITED, i.e., as
+ unsuitable as ivopts candidates for potentially involving undefined
+ behavior. */
static tree
find_ssa_undef (tree *tp, int *walk_subtrees, void *)
{
if (TREE_CODE (*tp) == SSA_NAME
- && ssa_undefined_value_p (*tp, false))
+ && TREE_VISITED (*tp))
return *tp;
if (!EXPR_P (*tp))
*walk_subtrees = 0;
@@ -8192,6 +8249,7 @@ tree_ssa_iv_optimize (void)
auto_bitmap toremove;
tree_ssa_iv_optimize_init (&data);
+ mark_ssa_undefs ();
/* Optimize the loops starting with the innermost ones. */
for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts. Ask me about <https://stallmansupport.org>
