When we fail to simplify an IV candidate step to zero SCEV might
still have simplified the before/after candidate to an IV with
zero step. Avoid crashing in such situation.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/126925
* tree-ssa-loop-ivopts.cc (create_new_iv): Avoid crashing
if the use IV is invariant.
* gcc.dg/torture/pr126925.c: New testcase.
---
gcc/testsuite/gcc.dg/torture/pr126925.c | 21 +++++++++++++++++++++
gcc/tree-ssa-loop-ivopts.cc | 11 ++++++++---
2 files changed, 29 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr126925.c
diff --git a/gcc/testsuite/gcc.dg/torture/pr126925.c
b/gcc/testsuite/gcc.dg/torture/pr126925.c
new file mode 100644
index 00000000000..06e601d6498
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr126925.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+
+int a;
+long b;
+int c(long d) {
+ for (;;)
+ if (d)
+ return b;
+}
+void e(int d) {
+ unsigned long f = 6;
+ int g;
+ while (c(f)) {
+ g = 0;
+ for (; g < 2; g++) {
+ a = 0;
+ short h = d;
+ f = d + f - (h + f + (a + 4 + f));
+ }
+ }
+}
diff --git a/gcc/tree-ssa-loop-ivopts.cc b/gcc/tree-ssa-loop-ivopts.cc
index 3c0ce1794c2..963e89e4b3c 100644
--- a/gcc/tree-ssa-loop-ivopts.cc
+++ b/gcc/tree-ssa-loop-ivopts.cc
@@ -7257,10 +7257,15 @@ create_new_iv (struct ivopts_data *data, struct iv_cand
*cand)
name_info (data, cand->var_before)->preserve_biv = true;
name_info (data, cand->var_after)->preserve_biv = true;
- /* Rewrite the increment so that it uses var_before directly. */
+ /* Rewrite the increment so that it uses var_before directly. Missed
+ optimization can result in a use IV with zero step, avoid
+ crashing in that case. */
use = find_interesting_uses_op (data, cand->var_after);
- group = data->vgroups[use->group_id];
- group->selected = cand;
+ if (use)
+ {
+ group = data->vgroups[use->group_id];
+ group->selected = cand;
+ }
return;
}
--
2.51.0
