From: Segher Boessenkool <segher@kernel.crashing.org>
To: Joseph Myers <joseph@codesourcery.com>
Cc: Tejas Joshi <tejasjoshi9673@gmail.com>,
gcc@gcc.gnu.org, Martin Jambor <mjambor@suse.cz>,
hubicka@ucw.cz
Subject: Re: Expansion of narrowing math built-ins into power instructions
Date: Wed, 14 Aug 2019 20:21:00 -0000 [thread overview]
Message-ID: <20190814202102.GI31406@gate.crashing.org> (raw)
In-Reply-To: <alpine.DEB.2.21.1908141608430.14831@digraph.polyomino.org.uk>
On Wed, Aug 14, 2019 at 04:10:56PM +0000, Joseph Myers wrote:
> On Wed, 14 Aug 2019, Segher Boessenkool wrote:
>
> > I think you can do one RTL code that replaces float_truncate in
> >
> > > > > > (define_insn "add_truncdfsf3"
> > > > > > [(set (match_operand:SF 0 "gpc_reg_operand" "=f,wa")
> > > > > > (float_truncate:SF
> > > > > > (plus:DF (match_operand:DF 1 "gpc_reg_operand" "%d,wa")
> > > > > > (match_operand:DF 2 "gpc_reg_operand" "d,wa"))))]
> >
> > but that is only meant for such explicit contraction. This can then
> > happily be used to implement all such patterns. Is there some issue
> > with that I overlook?
>
> Yes, I think such a separate RTL code would work (as would an
> architecture-specific UNSPEC) - it just needs to avoid the pattern
> matching RTL that can arise other than from the built-in functions.
>
> (Everything to do with needing -fno-math-errno to expand into such
> instructions should be handled in the architecture-independent compiler.)
Does something like
float d; double a, b, x;
...
d = fadd (a + x, b - x);
work as wanted, with such a representation? It would simplify (does it?) to
d = fadd (a, b);
but is that allowed?
Segher
next prev parent reply other threads:[~2019-08-14 20:21 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-29 17:37 Martin Jambor
2019-07-29 18:40 ` Segher Boessenkool
2019-07-30 19:47 ` Joseph Myers
2019-07-30 9:20 ` Florian Weimer
2019-07-30 19:49 ` Joseph Myers
2019-07-31 6:47 ` Tejas Joshi
2019-07-31 14:47 ` Segher Boessenkool
2019-08-08 18:39 ` Tejas Joshi
2019-08-08 20:05 ` Segher Boessenkool
2019-08-08 23:09 ` Joseph Myers
2019-08-10 10:24 ` Tejas Joshi
2019-08-10 16:46 ` Segher Boessenkool
2019-08-11 4:58 ` Tejas Joshi
2019-08-11 7:20 ` Segher Boessenkool
2019-08-11 12:46 ` Tejas Joshi
2019-08-11 16:59 ` Segher Boessenkool
2019-08-12 17:25 ` Tejas Joshi
2019-08-12 17:55 ` Segher Boessenkool
2019-08-12 21:20 ` Joseph Myers
2019-08-12 21:52 ` Segher Boessenkool
2019-08-14 6:15 ` Tejas Joshi
2019-08-14 7:21 ` Segher Boessenkool
2019-08-14 16:11 ` Joseph Myers
2019-08-14 20:21 ` Segher Boessenkool [this message]
2019-08-14 20:23 ` Joseph Myers
2019-08-14 21:00 ` Segher Boessenkool
2019-08-15 9:52 ` Tejas Joshi
2019-08-15 12:47 ` Richard Sandiford
2019-08-15 13:55 ` Tejas Joshi
2019-08-15 18:45 ` Segher Boessenkool
2019-08-16 10:23 ` Richard Sandiford
2019-08-17 5:40 ` Tejas Joshi
2019-08-17 8:21 ` Richard Sandiford
2019-08-19 10:46 ` Tejas Joshi
2019-08-19 13:07 ` Segher Boessenkool
2019-08-20 7:41 ` Richard Sandiford
2019-08-20 12:11 ` Segher Boessenkool
2019-08-20 12:59 ` Richard Sandiford
2019-08-20 13:46 ` Segher Boessenkool
2019-08-20 14:43 ` Richard Sandiford
2019-08-20 15:12 ` Richard Sandiford
2019-08-20 19:42 ` Segher Boessenkool
2019-08-21 17:20 ` Tejas Joshi
2019-08-21 18:28 ` Segher Boessenkool
2019-08-21 19:17 ` Segher Boessenkool
2019-08-22 3:33 ` Tejas Joshi
2019-08-22 6:25 ` Segher Boessenkool
2019-08-22 7:57 ` Tejas Joshi
2019-08-22 9:56 ` Segher Boessenkool
2019-08-23 17:17 ` Martin Jambor
2019-08-23 19:13 ` Segher Boessenkool
2019-08-24 9:53 ` Richard Sandiford
2019-08-25 13:55 ` Tejas Joshi
2019-08-25 16:47 ` Segher Boessenkool
2019-08-26 7:07 ` Tejas Joshi
2019-08-26 7:42 ` Segher Boessenkool
2019-08-30 19:12 ` Tejas Joshi
2019-08-30 20:35 ` Segher Boessenkool
2019-09-02 3:19 ` Tejas Joshi
2019-09-02 11:30 ` Segher Boessenkool
2019-08-26 13:23 ` Martin Jambor
2019-08-20 16:04 ` Joseph Myers
2019-08-15 18:54 ` Segher Boessenkool
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=20190814202102.GI31406@gate.crashing.org \
--to=segher@kernel.crashing.org \
--cc=gcc@gcc.gnu.org \
--cc=hubicka@ucw.cz \
--cc=joseph@codesourcery.com \
--cc=mjambor@suse.cz \
--cc=tejasjoshi9673@gmail.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).