The following fixes a dependence check where in the particular place
we cannot ignore self-dependences.
Bootstrapped / tested on x86_64-unknown-linux-gnu, pushed.
2020-09-21 Richard Biener <rguent...@suse.de>
PR tree-optimization/97135
* tree-ssa-loop-im.c (sm_seq_push_down): Do not ignore
self-dependences.
* gcc.dg/torture/pr97135.c: New testcase.
---
gcc/testsuite/gcc.dg/torture/pr97135.c | 21 +++++++++++++++++++++
gcc/tree-ssa-loop-im.c | 8 +++++---
2 files changed, 26 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr97135.c
diff --git a/gcc/testsuite/gcc.dg/torture/pr97135.c
b/gcc/testsuite/gcc.dg/torture/pr97135.c
new file mode 100644
index 00000000000..223f4d05b85
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr97135.c
@@ -0,0 +1,21 @@
+/* { dg-do run } */
+
+long long e, *d = &e;
+int a, b, c;
+
+int
+main ()
+{
+ for (; c <= 5; c++)
+ for (b = 0; b <= 5; b++)
+ {
+ for (a = 1; a <= 5; a++)
+ ;
+ *d = 0;
+ if (c)
+ break;
+ }
+ if (a != 6)
+ __builtin_abort ();
+ return 0;
+}
diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c
index f87c287d742..139c7e76e66 100644
--- a/gcc/tree-ssa-loop-im.c
+++ b/gcc/tree-ssa-loop-im.c
@@ -2232,9 +2232,11 @@ sm_seq_push_down (vec<seq_entry> &seq, unsigned ptr,
unsigned *at)
|| (against.second == sm_other && against.from != NULL_TREE))
/* Found the tail of the sequence. */
break;
- if (!refs_independent_p (memory_accesses.refs_list[new_cand.first],
- memory_accesses.refs_list[against.first],
- false))
+ /* We may not ignore self-dependences here. */
+ if (new_cand.first == against.first
+ || !refs_independent_p (memory_accesses.refs_list[new_cand.first],
+ memory_accesses.refs_list[against.first],
+ false))
/* ??? Prune new_cand from the list of refs to apply SM to. */
return false;
std::swap (new_cand, against);
--
2.26.2
