When CFG cleanup removes a backedge we have to be more careful with
loop update. In particular we need to clear niter info and estimates
and if we remove the last backedge of a loop we have to also mark
it for removal to prevent a following basic block merging to associate
loop info with an unrelated header.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/114787
* tree-cfg.cc (remove_edge_and_dominated_blocks): When
removing a loop backedge clear niter info and when removing
the last backedge of a loop mark that loop for removal.
* gcc.dg/torture/pr114787.c: New testcase.
---
gcc/testsuite/gcc.dg/torture/pr114787.c | 27 +++++++++++++++++++++++++
gcc/tree-cfg.cc | 26 +++++++++++++++++++++---
2 files changed, 50 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr114787.c
diff --git a/gcc/testsuite/gcc.dg/torture/pr114787.c
b/gcc/testsuite/gcc.dg/torture/pr114787.c
new file mode 100644
index 00000000000..1c7294bee7b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr114787.c
@@ -0,0 +1,27 @@
+/* { dg-do run } */
+
+int a, b, c, d, e = -1, f, g, h, j, k, n, o, p;
+int main() {
+ int i, l = 2, m;
+ for (b = 0; b < 1; b++)
+ l = 0;
+ for (; a >= 0; a--)
+ for (m = 3; m; m--) {
+ k = g;
+ i = 0;
+ for (; i < 1; i++)
+ for (; f < 1; f++)
+ h = g;
+ n = 2 & ((e ^ d) | 1) * j;
+ o = ~(e & n);
+ q:
+ if (c <= e)
+ return 0;
+ e = o;
+ }
+ p = l;
+ l = 0;
+ if (p)
+ goto q;
+ return 0;
+}
diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index bdffc3b4ed2..b936df9866b 100644
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -9004,10 +9004,30 @@ remove_edge_and_dominated_blocks (edge e)
/* If we are removing a path inside a non-root loop that may change
loop ownership of blocks or remove loops. Mark loops for fixup. */
+ class loop *src_loop = e->src->loop_father;
if (current_loops
- && loop_outer (e->src->loop_father) != NULL
- && e->src->loop_father == e->dest->loop_father)
- loops_state_set (LOOPS_NEED_FIXUP);
+ && loop_outer (src_loop) != NULL
+ && src_loop == e->dest->loop_father)
+ {
+ loops_state_set (LOOPS_NEED_FIXUP);
+ /* If we are removing a backedge clear the number of iterations
+ and estimates. */
+ class loop *dest_loop = e->dest->loop_father;
+ if (e->dest == src_loop->header
+ || (e->dest == dest_loop->header
+ && flow_loop_nested_p (dest_loop, src_loop)))
+ {
+ free_numbers_of_iterations_estimates (dest_loop);
+ /* If we removed the last backedge mark the loop for removal. */
+ FOR_EACH_EDGE (f, ei, dest_loop->header->preds)
+ if (f != e
+ && (f->src->loop_father == dest_loop
+ || flow_loop_nested_p (dest_loop, f->src->loop_father)))
+ break;
+ if (!f)
+ mark_loop_for_removal (dest_loop);
+ }
+ }
if (!dom_info_available_p (CDI_DOMINATORS))
{
--
2.25.1
