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* [Bug build/28680] New: i686 builds broken with -ftree-vectorize
@ 2021-12-10 16:48 siddhesh at sourceware dot org
2021-12-10 16:49 ` [Bug build/28680] " siddhesh at sourceware dot org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: siddhesh at sourceware dot org @ 2021-12-10 16:48 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28680
Bug ID: 28680
Summary: i686 builds broken with -ftree-vectorize
Product: glibc
Version: 2.35
Status: NEW
Severity: normal
Priority: P2
Component: build
Assignee: unassigned at sourceware dot org
Reporter: siddhesh at sourceware dot org
CC: carlos at redhat dot com
Target Milestone: ---
See also:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103646
How to reproduce:
configure with vectorizer enabled:
$ ../configure --prefix=/usr CC="gcc -m32" CXX="g++ -m32" CFLAGS="-O2 -g
-Wp,-D_GLIBCXX_ASSERTIONS -m32 -march=i686 -mtune=generic -msse2 -mfpmath=sse
-mstackrealign -fasynchronous-unwind-tables -fstack-clash-protection
-ftree-vectorize" --build=i686-redhat-linux
Actual results:
../sysdeps/unix/sysv/linux/select.c: In function ‘__select64’:
../sysdeps/unix/sysv/linux/select.c:117:1: error: bp cannot be used in ‘asm’
here
117 | }
| ^
make[2]: *** [/home/siddhesh/src/upstream/glibc/build-32/sysd-rules:229:
/home/siddhesh/src/upstream/glibc/build-32/misc/select.os] Error 1
Expected results:
Successful build.
Additional Information:
The vectorizer may end up having to realign stack and hence use up ebp, making
it unavailable as a logal register variable. Adapting the configure test to
account for vectorization may prove to be flaky, so it probably makes sense to
simply disable the 6 argument syscall inlining if the vectorizer is enabled
since the vectorizer gains may potentially outstrip the benefit of the
inlining.
This will become a wider issue with gcc12, where the vectorizer is enabled at
-O2.
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* [Bug build/28680] i686 builds broken with -ftree-vectorize
2021-12-10 16:48 [Bug build/28680] New: i686 builds broken with -ftree-vectorize siddhesh at sourceware dot org
@ 2021-12-10 16:49 ` siddhesh at sourceware dot org
2021-12-10 17:01 ` fweimer at redhat dot com
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: siddhesh at sourceware dot org @ 2021-12-10 16:49 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28680
Siddhesh Poyarekar <siddhesh at sourceware dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target| |i686
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* [Bug build/28680] i686 builds broken with -ftree-vectorize
2021-12-10 16:48 [Bug build/28680] New: i686 builds broken with -ftree-vectorize siddhesh at sourceware dot org
2021-12-10 16:49 ` [Bug build/28680] " siddhesh at sourceware dot org
@ 2021-12-10 17:01 ` fweimer at redhat dot com
2021-12-10 17:48 ` siddhesh at sourceware dot org
2022-01-10 16:25 ` [Bug libc/28680] " fweimer at redhat dot com
3 siblings, 0 replies; 5+ messages in thread
From: fweimer at redhat dot com @ 2021-12-10 17:01 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28680
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |fweimer at redhat dot com
--- Comment #1 from Florian Weimer <fweimer at redhat dot com> ---
We will likely have to disable the vectorizer for i686 in Fedora, then.
I do not think this is a glibc issue.
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* [Bug build/28680] i686 builds broken with -ftree-vectorize
2021-12-10 16:48 [Bug build/28680] New: i686 builds broken with -ftree-vectorize siddhesh at sourceware dot org
2021-12-10 16:49 ` [Bug build/28680] " siddhesh at sourceware dot org
2021-12-10 17:01 ` fweimer at redhat dot com
@ 2021-12-10 17:48 ` siddhesh at sourceware dot org
2022-01-10 16:25 ` [Bug libc/28680] " fweimer at redhat dot com
3 siblings, 0 replies; 5+ messages in thread
From: siddhesh at sourceware dot org @ 2021-12-10 17:48 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28680
--- Comment #2 from Siddhesh Poyarekar <siddhesh at sourceware dot org> ---
I don't know, it seems quite like a glibc issue to me.
The configure check to see if ebp is usable with the current flags is
simplistic compared to actual usage and any enhancement of that check would be
flaky since it relies on knowledge of when the compiler needs ebp for the frame
pointer. The ebp based inlining is a hack and may not make sense in the long
term but I don't know if i686 will exist in that time frame :)
I can confirm that disabling the vectorizer with gcc12 works FWIW, but I think
dropping the asm("ebp") hack is a better idea.
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* [Bug libc/28680] i686 builds broken with -ftree-vectorize
2021-12-10 16:48 [Bug build/28680] New: i686 builds broken with -ftree-vectorize siddhesh at sourceware dot org
` (2 preceding siblings ...)
2021-12-10 17:48 ` siddhesh at sourceware dot org
@ 2022-01-10 16:25 ` fweimer at redhat dot com
3 siblings, 0 replies; 5+ messages in thread
From: fweimer at redhat dot com @ 2022-01-10 16:25 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28680
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|build |libc
Flags| |security-
Status|NEW |RESOLVED
Resolution|--- |DUPLICATE
CC| |drepper.fsp at gmail dot com
--- Comment #3 from Florian Weimer <fweimer at redhat dot com> ---
Let's track this under the earlier bug.
*** This bug has been marked as a duplicate of bug 27997 ***
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2021-12-10 16:48 [Bug build/28680] New: i686 builds broken with -ftree-vectorize siddhesh at sourceware dot org
2021-12-10 16:49 ` [Bug build/28680] " siddhesh at sourceware dot org
2021-12-10 17:01 ` fweimer at redhat dot com
2021-12-10 17:48 ` siddhesh at sourceware dot org
2022-01-10 16:25 ` [Bug libc/28680] " fweimer at redhat dot com
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