[PATCH PR95254] aarch64: gcc generate inefficient code with fixed sve vector length

[Tamar Christina]

Sending to list as well.. not sure why it was stripped from the reply all.

> -----Original Message-----
> From: Tamar Christina
> Sent: Monday, June 8, 2020 3:25 PM
> To: Jakub Jelinek <jakub@redhat.com>; Tobias Burnus
> <Tobias_Burnus@mentor.com>
> Cc: Uros Bizjak <ubizjak@gmail.com>; nd <nd@arm.com>
> Subject: RE: [PATCH PR95254] aarch64: gcc generate inefficient code with
> fixed sve vector length
> 
> This is a bug with where the C++11 feature test is located as discussed in
> https://gcc.gnu.org/pipermail/gcc-patches/2020-June/547395.html
> A patch was approved but not yet applied to trunk
> https://gcc.gnu.org/pipermail/gcc-patches/2020-June/547463.html
> 
> > -----Original Message-----
> > From: Gcc-patches <gcc-patches-bounces@gcc.gnu.org> On Behalf Of
> Jakub
> > Jelinek via Gcc-patches
> > Sent: Monday, June 8, 2020 2:57 PM
> > To: Tobias Burnus <Tobias_Burnus@mentor.com>
> > Cc: Uros Bizjak <ubizjak@gmail.com>; gcc-patches@gcc.gnu.org
> > Subject: Re: [PATCH PR95254] aarch64: gcc generate inefficient code
> > with fixed sve vector length
> >
> > On Mon, Jun 08, 2020 at 03:49:17PM +0200, Tobias Burnus wrote:
> > > Hi,
> > >
> > > I just observe that this patch causes our *nonbootstrap* builds to
> > > fail; I have not yet looked into this nor tried a bootstrap build.
> > >
> > > gcc-mainline/gcc/expr.c: In function 'rtx_insn* emit_move_insn(rtx, rtx)':
> > > gcc-mainline/gcc/expr.c:3830:3: warning: 'auto' changes meaning in
> > > C++11;
> > please remove it [-Wc++0x-compat]
> > >    auto candidate_subreg_p = [&](rtx subreg) {
> > >    ^
> >
> > That means you must be compiling with -std=gnu++98 rather than -
> > std=gnu++11.
> > Current trunk requires C++11.
> > Make sure this is done in a clean tree, or ./config.status -- recheck;
> > ./config.status has been done?
> >
> > 	Jakub