Re: Patch ping Re: [PATCH] i386: Fix up ix86_gimplify_va_arg [PR105331]

[Uros Bizjak <ubizjak@gmail.com>]

On Thu, Apr 28, 2022 at 10:31 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> Hi!
>
> I'd like to ping this patch.  I know it isn't a full week yet, but we are
> almost out of P1s and GCC 12 branching is any time now.
>
> Thanks:
> On Fri, Apr 22, 2022 at 09:25:04AM +0200, Jakub Jelinek via Gcc-patches wrote:
> > On the following testcase we emit a bogus
> > 'va_arg_tmp.5' may be used uninitialized
> > warning.  The reason is that when gimplifying the addr = &temp;
> > statement, the va_arg_tmp temporary var for which we emit ADDR_EXPR
> > is not TREE_ADDRESSABLE, prepare_gimple_addressable emits some extra
> > code to initialize the newly addressable var from its previous value,
> > but it is a new variable which hasn't been initialized yet and will
> > be later, so we end up initializing it with uninitialized SSA_NAME:
> >   va_arg_tmp.6 = va_arg_tmp.5_14(D);
> >   addr.2_16 = &va_arg_tmp.6;
> >   _17 = MEM[(double *)sse_addr.4_13];
> >   MEM[(double * {ref-all})addr.2_16] = _17;
> > and with -O1 we actually don't DSE it before the warning is emitted.
> > If we make the temp TREE_ADDRESSABLE before the gimplification, then
> > this prepare_gimple_addressable path isn't taken and we effectively
> > omit the first statement above and so the bogus warning is gone.
> >
> > I went through other backends and didn't find another instance of this
> > problem.
> >
> > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
> >
> > 2022-04-22  Jakub Jelinek  <jakub@redhat.com>
> >
> >       PR target/105331
> >       * config/i386/i386.cc (ix86_gimplify_va_arg): Mark va_arg_tmp
> >       temporary TREE_ADDRESSABLE before trying to gimplify ADDR_EXPR
> >       of it.
> >
> >       * gcc.dg/pr105331.c: New test.

Sorry, I have no idea if this patch is correct or not.

Uros.