From: "Paul Edwards" <mutazilah@gmail.com>
To: "Ulrich Weigand" <Ulrich.Weigand@de.ibm.com>
Cc: <gcc@gcc.gnu.org>, "Ulrich Weigand" <uweigand@de.ibm.com>
Subject: Re: s390 port
Date: Fri, 3 Sep 2021 21:35:10 +1000 [thread overview]
Message-ID: <FBD4FD41ECA047C0885101B7D265C4E5@DESKTOP0OKG1VA> (raw)
In-Reply-To: <OF84EAA015.F8030BB9-ONC1258745.003C61D5-C1258745.003E26D4@ibm.com>
> - AMODE64 means the native address size is 64 bits. This
> implies that Pmode has to be DImode, since Pmode tells
> the compiler what the native address size is.
> Specifically, if you try to run AMODE64 with Pmode equals
> SImode, the compiler will not be aware that the hardware
> uses the high 32 bits of base and index registers, and
> will not necessarily keep them zero.
The compiler naturally keeps them zero. The
instructions that are used to load registers
do not pollute the high-order 32 bits.
> Also, the compiler
> will assume the base + index (+ displacement) arithmetic
> will operate in 32 bits -- I'm pretty sure this is
> actually the root cause of your "negative index" problem.
Where is this logic please? Can I do a #if 0 or similar
to disable it?
> Note that even if Pmode == DImode, you can still use 32-bit
> *pointer* sizes. This is exactly what e.g. the Intel x32
> mode does (as was mentioned by Andreas).
I’m happy to try the approach from BOTH directions
and see which one hits “-m32” first.
>> I’d like to approach the problem from the other
>> direction – what modifications are required to
>> be made to “-m31” so that it does “-m32” instead?
>> I’m happy to simply retire “-m31”, but I don’t care
>> if both exist.
> If you want to go for an "x32" like mode, I think this
> is wrong approach. The right approach would be to
> start from "-m64", and simply modify the pointer size
> to be 32 bits.
> This would work by setting POINTER_SIZE to 32, while
> leaving everything else like for -m64.
That will generate 64-bit z/Arch instructions.
I wish to generate ESA/390 instructions.
> I'm sure there
> will be a few other places that need adaptation, but
> it should be pretty straightforward.
No, modifying GCC is beyond my ability. I
need 20 lines of code from someone who is
familiar with the system.
> You can also
> check the Intel back-end where they're using the
> TARGET_X32 macro.
See above about beyond my ability.
> We've thought about implementing this mode for Linux,
> but decided not to do it, since it would only provide
> marginal performance improvements, and has the drawback
> of being another new ABI that would be incompatible to
> the whole existing software ecosystem.
Shouldn’t the end user be able to decide this
for themselves? No-one at all is interested in
32-bit mainframes?
> (The latter point may not be an issue for you if you're
> looking into a completely new OS anyway.)
Correct.
Thanks. Paul.
next prev parent reply other threads:[~2021-09-03 11:35 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-05 12:45 i370 port Paul Edwards
2009-06-05 14:33 ` Joseph S. Myers
2009-06-05 14:57 ` Paul Edwards
2009-06-05 15:03 ` Joseph S. Myers
2009-06-05 15:24 ` Paul Edwards
2009-06-05 15:47 ` Joseph S. Myers
2009-09-11 17:35 ` i370 port - in search of hooks Paul Edwards
2017-03-31 10:34 ` i370 port Paul Edwards
2009-09-12 12:41 ` Paul Edwards
2009-06-05 15:21 ` Ulrich Weigand
2009-06-05 15:39 ` Paul Edwards
2009-06-05 15:49 ` Daniel Jacobowitz
2009-06-05 15:57 ` Paul Edwards
2009-06-05 20:20 ` Joseph S. Myers
2009-06-05 20:45 ` Paul Edwards
2009-06-06 15:00 ` Paul Edwards
2009-06-15 17:46 ` Ulrich Weigand
2009-06-19 0:06 ` Paul Edwards
2009-06-19 12:28 ` Ulrich Weigand
2009-07-18 11:28 ` Paul Edwards
2009-07-20 14:27 ` Ulrich Weigand
2009-08-08 12:04 ` Paul Edwards
2009-08-10 21:25 ` Ulrich Weigand
2009-08-11 0:34 ` Paul Edwards
2009-08-11 15:21 ` Ulrich Weigand
2009-08-12 11:52 ` Paul Edwards
2009-08-12 15:27 ` Paolo Bonzini
2009-08-12 16:35 ` Ulrich Weigand
2009-08-12 17:27 ` Paul Edwards
2009-08-12 17:56 ` Paolo Bonzini
2009-08-12 19:46 ` Ulrich Weigand
2009-08-12 20:31 ` Paul Edwards
2009-08-19 12:07 ` Paul Edwards
2009-08-19 12:27 ` Paolo Bonzini
2009-08-20 12:49 ` Paul Edwards
2009-08-20 22:48 ` Ulrich Weigand
2009-08-21 2:37 ` Paul Edwards
2009-08-21 16:46 ` Ulrich Weigand
2009-06-05 15:44 ` Joseph S. Myers
2009-06-05 15:52 ` Paul Edwards
2009-09-08 15:55 ` Paul Edwards
2009-09-14 15:32 ` Ulrich Weigand
2021-09-02 8:15 ` s390 port Paul Edwards
2021-09-02 14:34 ` Ulrich Weigand
2021-09-02 14:50 ` Paul Edwards
2021-09-02 14:53 ` Ulrich Weigand
2021-09-02 15:01 ` Paul Edwards
2021-09-02 15:13 ` Ulrich Weigand
2021-09-02 15:26 ` Paul Edwards
2021-09-02 19:46 ` Ulrich Weigand
2021-09-02 20:05 ` Paul Edwards
2021-09-02 20:16 ` Andreas Schwab
2021-09-03 11:18 ` Ulrich Weigand
2021-09-03 11:35 ` Paul Edwards [this message]
2021-09-03 12:12 ` Ulrich Weigand
2021-09-03 12:38 ` Paul Edwards
2021-09-03 12:53 ` Jakub Jelinek
2021-09-03 13:12 ` Paul Edwards
2022-12-20 4:27 ` Paul Edwards
2021-09-02 10:56 Paul Edwards
2021-09-06 22:44 Build gcc question Gary Oblock
2021-09-07 7:21 ` s390 port Joe Monk
2021-09-08 3:46 ` Paul Edwards
2021-09-30 0:08 Paul Edwards
2021-09-30 0:59 ` Joe Monk
2021-09-30 21:39 Paul Edwards
2023-01-28 18:51 Paul Edwards
2023-01-29 13:08 ` Joe Monk
2023-01-29 14:30 ` Paul Edwards
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=FBD4FD41ECA047C0885101B7D265C4E5@DESKTOP0OKG1VA \
--to=mutazilah@gmail.com \
--cc=Ulrich.Weigand@de.ibm.com \
--cc=gcc@gcc.gnu.org \
--cc=uweigand@de.ibm.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).