Re: [PATCH] tree-vect.h: Compile check_vect with -O0

On Fri, Aug 7, 2026 at 2:19 PM Hongtao Liu <[email protected]> wrote:
>
> On Fri, Aug 7, 2026 at 10:59 AM H.J. Lu <[email protected]> wrote:
> >
> > On Fri, Aug 7, 2026 at 6:12 AM H.J. Lu <[email protected]> wrote:
> > >
> > > commit 44cc8e5718efd0cc1ef57c68052dbe33b047f158
> > > Author: Ewan <[email protected]>
> > > Date:   Tue Mar 17 16:12:15 2026 +0800
> > >
> > >     i386: Fix __get_cpuid() and __get_cpuid_count() for
> > > Centaur/Zhaoxin CPUID range
> > >
> > > caused many regressions, like
> > >
> > > FAIL: gcc.dg/vect/vect-100.c scan-tree-dump-not optimized "Invalid sum"
> > >
> > > on Linux/x86-64 with -m32.  The commit above changed __get_cpuid_count
> > > which is used by check_vect in tree-vect.h.  When GCC tried to vectorize
> > > check_vect, it outputted
> > >
> > > __attribute__((noinline))
> > > void check_vect ()
> > > {
> > > ...
> > > ;;   Invalid sum of incoming counts 966367640 (estimated locally, freq
> > > 0.9000), should be 719407024 (estimated locally, freq 0.6700)
> > >
> > > which failed
> > >
> > > /* { dg-final { scan-tree-dump-not "Invalid sum" "optimized" } } */
> > >
> > > Compile check_vect with -O0 to avoid it.
> > >
> > > * gcc.dg/vect/tree-vect.h (check_vect): Compile with -O0.
> > >
> > >
> > > --
> > > H.J.
> >
> > This fixes:
> >
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126697
>
> Can we use
>
> unsigned int __ext = __leaf & 0xC0000000;
>
> Assume it can also support zhaoxin's maximum secondary extended
> level(0xC0000000);?

Or we can fold it into __get_cpuid_max.

-- 
H.J.