This issue was observed in rs6000 specific PR102658 as well.
I've looked into it a bit, it's caused by the "conditional store replacement" which
is originally disabled without vectorization as below code.
/* If either vectorization or if-conversion is disabled then do
not sink any stores. */
if (param_max_stores_to_sink == 0
|| (!flag_tree_loop_vectorize && !flag_tree_slp_vectorize)
|| !flag_tree_loop_if_convert)
return false;
The new change makes the innermost loop look like
for (int c1 = 0; c1 <= 1499; c1 += 1) {
if (c1 <= 500) {
S_10(c0, c1);
} else {
S_9(c0, c1);
}
S_11(c0, c1);
}
and can not be splitted as:
for (int c1 = 0; c1 <= 500; c1 += 1)
S_10(c0, c1);
for (int c1 = 501; c1 <= 1499; c1 += 1)
S_9(c0, c1);
So instead of disabling vectorization, could we just disable this cs replacement
with parameter "--param max-stores-to-sink=0"?
I tested this proposal on ppc64le, it should work as well.
2021-10-11 Kewen Lin <linkw@linux.ibm.com>
libgomp/ChangeLog:
* testsuite/libgomp.graphite/force-parallel-8.c: Add --param max-stores-to-sink=0.
d61ce6ab04