Hi,
When working on a cost tweaking patch, I found that a newly
added test case has different dumpings with stage-1 and
bootstrapped gcc. By looking into it, the apparent reason
is vect_analyze_loop_2 doesn't get slp_done_for_suggested_uf
set expectedly, the following retrying will use the garbage
slp_done_for_suggested_uf instead. In fact, the setting of
slp_done_for_suggested_uf only happens when the previous
analysis succeeds, for the mentioned test case, its previous
analysis does fail, it's unexpected to use the value of
slp_done_for_suggested_uf any more.
In function vect_analyze_loop_1, we only return success when
res is true, which is the result of 1st analysis. It means
we never try to vectorize with unroll_vinfo if the previous
analysis fails. So this patch shouldn't break anything, and
just stop some useless analysis early.
Bootstrapped and regtested on x86_64-redhat-linux,
aarch64-linux-gnu and powerpc64{,le}-linux-gnu.
Is it ok for trunk?
BR,
Kewen
-----
gcc/ChangeLog:
* tree-vect-loop.cc (vect_analyze_loop_1): Don't retry analysis with
suggested unroll factor once the previous analysis fails.
---
gcc/tree-vect-loop.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index ed0166fedab..905145ae97b 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -3044,7 +3044,7 @@ vect_analyze_loop_1 (class loop *loop, vec_info_shared
*shared,
res ? "succeeded" : " failed",
GET_MODE_NAME (loop_vinfo->vector_mode));
- if (!main_loop_vinfo && suggested_unroll_factor > 1)
+ if (res && !main_loop_vinfo && suggested_unroll_factor > 1)
{
if (dump_enabled_p ())
dump_printf_loc (MSG_NOTE, vect_location,
--
2.31.1
