On Wed, Feb 24, 2021 at 6:39 PM Segher Boessenkool
<seg...@kernel.crashing.org> wrote:
>
> Hi!
>
> On Tue, Feb 23, 2021 at 09:48:28AM +0100, Richard Biener wrote:
> > On Tue, Feb 23, 2021 at 4:48 AM acsawdey--- via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > From: Aaron Sawdey <acsaw...@linux.ibm.com>
> > >
> > > This patch implements a RTL pass that looks for pc-relative loads of the
> > > address of an external variable using the PCREL_GOT relocation and a
> > > single load or store that uses that external address.
> > >
> > > Produced by a cast of thousands:
> > >  * Michael Meissner
> > >  * Peter Bergner
> > >  * Bill Schmidt
> > >  * Alan Modra
> > >  * Segher Boessenkool
> > >  * Aaron Sawdey
> > >
> > > This incorporates the changes requested in Segher's review. A few things I
> > > did not change were the insn-at-a-time scan that could be done with DF, 
> > > and
> > > I did not change to using statistics.[ch] for the counters struct. I did 
> > > try
> > > to improve the naming, and rewrote a number of comments to make them 
> > > consistent
> > > with the code, and generally tried to make things more readable.
> > >
> > > OK for trunk if bootstrap/regtest passes?
> >
> > stage1 please?
>
> Versions of this patch were first submitted in August.  Of 2019.
>
> We have quite a lot of experience with it so far.  There are no known
> wrong-code (or ICE) problems with it.
>
> All of this is only when targetting power10 (which isn't shipping
> hardware yet), and is behind a flag anyway, so you can easily disable
> the optimisation.
>
> So, there is virtually no risk.

So it's enabled by default when targeting power10?  But power10
won't ship before the GCC 11 release?

> On the other hand, we do want to get this into the hands of everyone
> who should test it, and trunk works so much better for that than private
> builds or patch sets.
>
> If it misses 11.1, we'll have to backport it to 11.2 .

I see.

> So, I'd really like it to get in now.  Do any of these arguments change
> your position on that?

Well, in the end target maintainers have the say on target specific
changes.  I guess hitting problems with the patch in testing GCC 11
is unlikely to happen, and if it does we won't block shipping 11.1.

I do note that GCC 10 seems to know -mpower10 so technically
such "regression" would block a release.

Richard.

>
> Segher

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