From: Richard Biener <richard.guenther@gmail.com>
To: John Darrington <john@darrington.wattle.id.au>
Cc: Segher Boessenkool <segher@kernel.crashing.org>,
Vladimir Makarov <vmakarov@redhat.com>,
GCC Development <gcc@gcc.gnu.org>
Subject: Re: Special Memory Constraint [was Re: Indirect memory addresses vs. lra]
Date: Tue, 20 Aug 2019 06:56:00 -0000 [thread overview]
Message-ID: <CAFiYyc2ER5kvra+T+fmf6tn2cYgKqy2zWrAxCDXP7owdCThdag@mail.gmail.com> (raw)
In-Reply-To: <20190819180644.wn7s2dxdgjlwvdw7@jocasta.intra>
On Mon, Aug 19, 2019 at 8:06 PM John Darrington
<john@darrington.wattle.id.au> wrote:
>
> On Mon, Aug 19, 2019 at 10:07:11AM -0500, Segher Boessenkool wrote:
>
> > ? As I remember there were a few other ideas from Richard Biener and
> > Segher Boessenkool.? I also proposed to add a new address register which
> > will be always a fixed stack memory slot at the end. Unfortunately I am
> > not familiar with the target and the port to say in details how to do
> > it.? But I think it is worth to try.
>
> The m68hc11 port used the fake Z register approach, and I believe it had
> some special machine pass to get rid of it right before assembler output.
>
> (r171302 is when it was removed -- last version was
> https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/m68hc11/m68hc11.c;h=1e414102c3f1fed985e4fb8db7954342e965190b;hb=bae8bb65d842d7ffefe990c1f0ac004491f3c105#l4061
> for the machine reorg stuff).
>
> No idea how well it works... But it's only needed if you are forced to
> have a frame pointer IIUC?
>
>
> Segher
>
>
> Most of these suggestions involve adding some sort of virtual registers
> So I hacked the machine description to add two new registers Z1 and Z2
> with the same mode as X and Y.
>
> Obviously the assembler balks at this. However the compiler still
> ICEs at the same place as before.
>
> So this suggests that our original diagnosis, viz: there are not enough
> address registers was not accurate, and in fact there is some other
> problem?
That sounds likely. Given you have indirect addressing you could
simulate N virtual regs by placing them in a virtual reg table in memory
and accessed via a fixed address register (assuming all instructions
that would need an address reg also can take that indirect from memory).
Richard.
> J'
>
> --
> Avoid eavesdropping. Send strong encrypted email.
> PGP Public key ID: 1024D/2DE827B3
> fingerprint = 8797 A26D 0854 2EAB 0285 A290 8A67 719C 2DE8 27B3
> See http://sks-keyservers.net or any PGP keyserver for public key.
>
next prev parent reply other threads:[~2019-08-20 6:56 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-04 19:18 Indirect memory addresses vs. lra John Darrington
2019-08-08 16:25 ` Vladimir Makarov
2019-08-08 16:44 ` Paul Koning
2019-08-08 17:21 ` Segher Boessenkool
2019-08-08 17:25 ` Paul Koning
2019-08-08 19:09 ` Segher Boessenkool
2019-08-08 17:30 ` Paul Koning
2019-08-08 19:19 ` Segher Boessenkool
2019-08-08 19:57 ` Jeff Law
2019-08-09 8:14 ` John Darrington
2019-08-09 14:17 ` Segher Boessenkool
2019-08-09 14:23 ` Paul Koning
2019-08-10 6:10 ` John Darrington
2019-08-10 16:15 ` Segher Boessenkool
2019-08-09 16:07 ` Jeff Law
2019-08-09 17:34 ` Vladimir Makarov
2019-08-10 6:06 ` John Darrington
2019-08-10 16:12 ` Segher Boessenkool
2019-08-12 6:47 ` John Darrington
2019-08-12 8:40 ` Segher Boessenkool
2019-08-12 13:35 ` Vladimir Makarov
2019-08-15 16:29 ` Vladimir Makarov
2019-08-15 16:38 ` Richard Biener
2019-08-15 17:41 ` John Darrington
2019-08-15 18:30 ` Vladimir Makarov
2019-08-15 21:22 ` Segher Boessenkool
2019-08-15 17:36 ` John Darrington
2019-08-15 18:23 ` Vladimir Makarov
2019-08-16 11:24 ` Special Memory Constraint [was Re: Indirect memory addresses vs. lra] John Darrington
2019-08-16 14:50 ` Vladimir Makarov
2019-08-19 7:36 ` John Darrington
2019-08-19 13:14 ` Vladimir Makarov
2019-08-19 15:07 ` Segher Boessenkool
2019-08-19 18:06 ` John Darrington
2019-08-20 6:56 ` Richard Biener [this message]
2019-08-20 7:07 ` John Darrington
2019-08-20 7:30 ` Richard Biener
2019-08-08 18:46 ` Indirect memory addresses vs. lra Vladimir Makarov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAFiYyc2ER5kvra+T+fmf6tn2cYgKqy2zWrAxCDXP7owdCThdag@mail.gmail.com \
--to=richard.guenther@gmail.com \
--cc=gcc@gcc.gnu.org \
--cc=john@darrington.wattle.id.au \
--cc=segher@kernel.crashing.org \
--cc=vmakarov@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).