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* [Bug c++/98949] New: gcc-9.3 aarch64 -ftree-vectorize generates wrong code
@ 2021-02-03 4:23 cyb70289 at gmail dot com
2021-02-03 7:53 ` [Bug c++/98949] " rguenth at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: cyb70289 at gmail dot com @ 2021-02-03 4:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98949
Bug ID: 98949
Summary: gcc-9.3 aarch64 -ftree-vectorize generates wrong code
Product: gcc
Version: 9.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: cyb70289 at gmail dot com
Target Milestone: ---
Assertion fired in below test code when compiled with g++-9.3 aarch64 -O3.
Disable tree-vectorize fixes the issue.
g++-7, g++-10 don't have this problem.
$ uname -m
aarch64
$ g++-9 --version
g++-9 (Ubuntu 9.3.0-11ubuntu0~18.04.1) 9.3.0
$ g++-9 -O3 -march=armv8-a test.cc && ./a.out
a.out: test.cc:27: int main(): Assertion `bitmap[7] != 0' failed.
Aborted (core dumped)
$ g++-9 -O3 -fno-tree-vectorize -march=armv8-a test.cc && ./a.out
[assertion not fired]
test.cc
=======
#include <cassert>
#include <cstdint>
int main(void) {
uint64_t a[64], b[64];
for (int i = 0; i < 64; ++i) {
a[i] = 1;
b[i] = 2;
}
a[63] = b[63]; // only last element is the same
uint8_t bitmap[8]; // holds 64 bits, bit_i = 1 if (a[i] == b[i]) else 0, i =
0 ~ 63
int index = 0; // index to a[], b[]
for (int byte = 0; byte < 8; ++byte) {
uint8_t out_results[8]; // holds 8 comparison results temporarily
for (int bit = 0; bit < 8; ++bit) {
out_results[bit] = a[index] == b[index];
++index;
}
bitmap[byte] = (out_results[0] | out_results[1] << 1 | out_results[2] << 2
|
out_results[3] << 3 | out_results[4] << 4 | out_results[5]
<< 5 |
out_results[6] << 6 | out_results[7] << 7);
}
// last bitmap should be non-zero, fired on gcc-9.3 aarch64 -O3
assert(bitmap[7] != 0);
return 0;
}
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/98949] gcc-9.3 aarch64 -ftree-vectorize generates wrong code
2021-02-03 4:23 [Bug c++/98949] New: gcc-9.3 aarch64 -ftree-vectorize generates wrong code cyb70289 at gmail dot com
@ 2021-02-03 7:53 ` rguenth at gcc dot gnu.org
2021-02-03 9:46 ` [Bug tree-optimization/98949] " cyb70289 at gmail dot com
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2021-02-03 7:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98949
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |needs-bisection
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
There are several open vectorizer regressions on older branches, some harder to
fix and thus fixes not backported.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/98949] gcc-9.3 aarch64 -ftree-vectorize generates wrong code
2021-02-03 4:23 [Bug c++/98949] New: gcc-9.3 aarch64 -ftree-vectorize generates wrong code cyb70289 at gmail dot com
2021-02-03 7:53 ` [Bug c++/98949] " rguenth at gcc dot gnu.org
@ 2021-02-03 9:46 ` cyb70289 at gmail dot com
2021-02-03 10:12 ` marxin at gcc dot gnu.org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: cyb70289 at gmail dot com @ 2021-02-03 9:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98949
--- Comment #2 from Yibo Cai <cyb70289 at gmail dot com> ---
Thanks for quick response.
Ubuntu 20.04 installs gcc-9.3. It suffers from this bug. Looks no good.
$ g++ --version
g++ (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/98949] gcc-9.3 aarch64 -ftree-vectorize generates wrong code
2021-02-03 4:23 [Bug c++/98949] New: gcc-9.3 aarch64 -ftree-vectorize generates wrong code cyb70289 at gmail dot com
2021-02-03 7:53 ` [Bug c++/98949] " rguenth at gcc dot gnu.org
2021-02-03 9:46 ` [Bug tree-optimization/98949] " cyb70289 at gmail dot com
@ 2021-02-03 10:12 ` marxin at gcc dot gnu.org
2021-02-05 10:25 ` ktkachov at gcc dot gnu.org
2021-02-05 15:44 ` ktkachov at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: marxin at gcc dot gnu.org @ 2021-02-03 10:12 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98949
--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Fixed on master with g:74166aabeb7f22990476b1169bba031b8323ee92, so likely a
dup of PR97236.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/98949] gcc-9.3 aarch64 -ftree-vectorize generates wrong code
2021-02-03 4:23 [Bug c++/98949] New: gcc-9.3 aarch64 -ftree-vectorize generates wrong code cyb70289 at gmail dot com
` (2 preceding siblings ...)
2021-02-03 10:12 ` marxin at gcc dot gnu.org
@ 2021-02-05 10:25 ` ktkachov at gcc dot gnu.org
2021-02-05 15:44 ` ktkachov at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: ktkachov at gcc dot gnu.org @ 2021-02-05 10:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98949
ktkachov at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ktkachov at gcc dot gnu.org
--- Comment #4 from ktkachov at gcc dot gnu.org ---
I can confirm that the commit
https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=1ab88985631dd2c5a5e3b5c0dce47cf8b6ed2f82
from PR97236 fixes the abort here.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/98949] gcc-9.3 aarch64 -ftree-vectorize generates wrong code
2021-02-03 4:23 [Bug c++/98949] New: gcc-9.3 aarch64 -ftree-vectorize generates wrong code cyb70289 at gmail dot com
` (3 preceding siblings ...)
2021-02-05 10:25 ` ktkachov at gcc dot gnu.org
@ 2021-02-05 15:44 ` ktkachov at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: ktkachov at gcc dot gnu.org @ 2021-02-05 15:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98949
ktkachov at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #5 from ktkachov at gcc dot gnu.org ---
Dup. The patch fixing PR 97236 has been backported to the GCC 9 branch for GCC
9.4
*** This bug has been marked as a duplicate of bug 97236 ***
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-02-05 15:44 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2021-02-03 4:23 [Bug c++/98949] New: gcc-9.3 aarch64 -ftree-vectorize generates wrong code cyb70289 at gmail dot com
2021-02-03 7:53 ` [Bug c++/98949] " rguenth at gcc dot gnu.org
2021-02-03 9:46 ` [Bug tree-optimization/98949] " cyb70289 at gmail dot com
2021-02-03 10:12 ` marxin at gcc dot gnu.org
2021-02-05 10:25 ` ktkachov at gcc dot gnu.org
2021-02-05 15:44 ` ktkachov at gcc dot gnu.org
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