x86 code generation question

Manuel Lauss manuel.lauss@gmail.com
Tue Dec 14 11:13:03 GMT 2021


On Mon, Dec 13, 2021 at 2:04 PM Florian Weimer <fweimer@redhat.com> wrote:
>
> * Manuel Lauss via Gcc-help:
>
> > Now the descriptions of "vmovdqa" I could find say that it generates a
> > #GP when the destination is not 16-byte aligned. Does this alignment
> > include the displacement, like above?  If yes, is this then a code
> > generation bug in gcc?
>
> If your build uses vector instructions, you need to build glibc with
> -mstackrealign for compatibility with legacy i386 applications.

I read that gcc-12 enables "-ftree-vectorize" with -O2 by default, and
indeed a glibc snapshot built with gcc-12 and "-O2 -march=haswell" suffers
now from the same problem.  Should "-mstackrealign" be added to 32bit x86 build
unconditionally?

Manuel


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