[Bug target/101384] [9/10 Regression] wrong code at -Og and above with vector shift/multiply
cvs-commit at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Wed May 11 06:21:40 GMT 2022
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101384
--- Comment #13 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:883690ff6bd8e4f16c871b307cebb13d6c14edcb
commit r9-10092-g883690ff6bd8e4f16c871b307cebb13d6c14edcb
Author: Jakub Jelinek <jakub@redhat.com>
Date: Tue Jul 20 16:41:29 2021 +0200
rs6000: Fix up easy_vector_constant_msb handling [PR101384]
The following gcc.dg/pr101384.c testcase is miscompiled on
powerpc64le-linux.
easy_altivec_constant has code to try construct vector constants with
different element sizes, perhaps different from CONST_VECTOR's mode. But
as
written, that works fine for vspltis[bhw] cases, but not for the vspltisw
x,-1; vsl[bhw] x,x,x case, because that creates always a V16QImode,
V8HImode
or V4SImode constant containing broadcasted constant with just the MSB set.
The vspltis_constant function etc. expects the vspltis[bhw] instructions
where the small [-16..15] or even [-32..30] constant is sign-extended to
the
remaining step bytes, but that is not the case for the 0x80...00 constants,
with step 1 we can't handle e.g.
{ 0x80, 0xff, 0xff, 0xff, 0x80, 0xff, 0xff, 0xff, 0x80, 0xff, 0xff, 0xff,
0x80, 0xff, 0xff, 0xff }
vectors but do want to handle e.g.
{ 0, 0, 0, 0x80, 0, 0, 0, 0x80, 0, 0, 0, 0x80, 0, 0, 0, 0x80 }
and similarly with copies 1 we do want to handle e.g.
{ 0x80808080, 0x80808080, 0x80808080, 0x80808080 }.
This is a simpler version of the fix for backports, which limits the
EASY_VECTOR_MSB case
matching to step == 1 && copies == 1, because that is the only case the
splitter handles correctly.
2021-07-20 Jakub Jelinek <jakub@redhat.com>
PR target/101384
* config/rs6000/rs6000.c (vspltis_constant): Accept EASY_VECTOR_MSB
only if step and copies are equal to 1.
* gcc.dg/pr101384.c: New test.
(cherry picked from commit dc386b020869ad0095cf58f8c76a40ea457e7a2c)
More information about the Gcc-bugs
mailing list