https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106590
Bug ID: 106590
Summary: x86-64 miscompilation starting with "i386: Improve
ix86_expand_int_movcc" w/ mtune=skylake
Product: gcc
Version: 12.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: andres at anarazel dot de
Target Milestone: ---
Hi,
The attached reproducer shows a miscompilation I found building postgres. I've
bisected postgres' failure to 1ceddd7497e, but it's of course possible it's
just surfacing a prior issue.
In my reproducer, and in postgres, the problem only occurs with -mtune=skylake
or higher, but I'm not sure how related that actually is.
$ /home/andres/build/gcc-master/install/bin/gcc --version
gcc (GCC) 12.0.1 20220423 (experimental)
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ gcc-11 --version
gcc-11 (Debian 11.3.0-5) 11.3.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ /home/andres/build/gcc-master/install/bin/gcc -Wall -Wextra -O1
-mtune=skylake /tmp/test.i -o /tmp/test
$ /tmp/test
wrong results: procform->prorettype: 23, restype: 20
$ /home/andres/build/gcc-master/install/bin/gcc -Wall -Wextra -O1
-mtune=broadwell /tmp/test.i -o /tmp/test
$ /tmp/test
everything ok: procform->prorettype: 23, restype: 23
$ gcc-11 -Wall -Wextra -O1 -mtune=skylake /tmp/test.i -o /tmp/test
$ /tmp/test
everything ok: procform->prorettype: 23, restype: 23
I think it's pretty obvious that the code should never be able to result in
restype == 20.
Regards,
Andres
