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Re: [PATCH] i386: Use TImode for BLKmode values in 2 integer registers


On Sat, Oct 6, 2018 at 12:48 AM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> On Fri, Oct 5, 2018 at 1:43 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Sat, Sep 29, 2018 at 11:02 AM Uros Bizjak <ubizjak@gmail.com> wrote:
> > >
> > > On Sat, Sep 29, 2018 at 6:36 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > >
> > > > When passing and returning BLKmode values in 2 integer registers, use
> > > > 1 TImode register instead of 2 DImode registers. Otherwise, V1TImode
> > > > may be used to move and store such BLKmode values, which prevent RTL
> > > > optimizations.
> > > >
> > > > Tested on x86-64.  OK for trunk?
> > > >
> > > > Thanks.
> > > >
> > > > H.J.
> > > > ---
> > > > gcc/
> > > >
> > > >         PR target/87370
> > > >         * config/i386/i386.c (construct_container): Use TImode for
> > > >         BLKmode values in 2 integer registers.
> > > >
> > > > gcc/testsuite/
> > > >
> > > >         PR target/87370
> > > >         * gcc.target/i386/pr87370.c: New test.
> > >
> > > OK.
> >
> > I'd like to backport it to release branches.  Is that OK?
>
> This is a minor optimization bug, not a wrong-code bug, so unless the
> patch is super-safe, I think we should leave release branches
> unpatched.
>

This is a regression against GCC 6.  I think we should fix it for
GCC 7 and 8.

-- 
H.J.


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