[Bug build/28680] New: i686 builds broken with -ftree-vectorize

["siddhesh at sourceware dot org" <sourceware-bugzilla@sourceware.org>]

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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