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tree-optimization/114787 - more careful loop update with CFG cleanup

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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.

	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.
This commit is contained in:
Richard Biener 2024-04-24 08:42:40 +02:00
parent e28e8ab1a9
commit cc48418cfc
2 changed files with 50 additions and 3 deletions
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27
gcc/testsuite/gcc.dg/torture/pr114787.c Normal file
View file

@ -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;
}

26
gcc/tree-cfg.cc
View file

@ -9013,10 +9013,30 @@ 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))
{