From: "H.J. Lu" <hjl.tools@gmail.com>
To: Andrew Stubbs <ams@codesourcery.com>
Cc: Senthil Kumar Selvaraj <senthil.thecoder@gmail.com>,
Hans-Peter Nilsson <hp@bitrange.com>,
GCC Development <gcc@gcc.gnu.org>,
Eric Botcazou <ebotcazou@adacore.com>
Subject: Re: Clobber REG_CC only for some constraint alternatives?
Date: Thu, 20 Aug 2020 03:59:41 -0700 [thread overview]
Message-ID: <CAMe9rOoOq5qMYsPnM35KqeSROk0eJwW-U0FtqkhCZobbRnosLA@mail.gmail.com> (raw)
In-Reply-To: <3a9a87f4-6c6a-fa1b-128f-2b656840d9bd@codesourcery.com>
On Thu, Aug 20, 2020 at 1:53 AM Andrew Stubbs <ams@codesourcery.com> wrote:
>
> On 20/08/2020 06:40, Senthil Kumar Selvaraj via Gcc wrote:
> > What I didn't understand was the (set-attr "cc<cccc><ccnz><ccnzvc>")
> > part - as far I can tell, this results in (set_attr "cc_enabled" ...) in
> > all of the three substituted patterns, so I wondered why not just have
> > (set_attr "cc_enabled" ...) in the original define_insn instead.
> >
> > I now realize that with (set-attr "cc<cccc><ccnz><ccnzvc>"), the original
> > unsubstituted pattern will have only a (set_attr "cc" ...) and would
> > therefore not match the attr check for "enabled" - correctly so, as the
> > original insn pattern clobbers CRIS_CC0_REGNUM. Did I get that right?
>
> The best (only?) way to understand define_subst is to read the expanded
> machine description. This is not written anywhere, by default, but
> there's a way to get it.
>
> cd <build>/gcc
> make mddump
> less tmp-mddump.md
>
> Not only are all the define_subst expanded, but so are all the other
> iterators.
Shouldn't it be documented?
--
H.J.
next prev parent reply other threads:[~2020-08-20 11:00 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-14 11:16 Senthil Kumar Selvaraj
2020-08-14 15:32 ` Matt Wette
2020-08-14 17:42 ` Pip Cet
2020-08-14 16:23 ` Segher Boessenkool
2020-08-14 17:47 ` Pip Cet
2020-08-15 0:29 ` Segher Boessenkool
2020-08-15 10:18 ` Pip Cet
2020-08-16 0:50 ` Segher Boessenkool
2020-08-16 18:28 ` Pip Cet
2020-08-17 7:31 ` Senthil Kumar Selvaraj
2020-08-17 9:18 ` Pip Cet
2020-08-18 6:52 ` Senthil Kumar Selvaraj
2020-08-20 11:51 ` Pip Cet
2020-08-20 16:06 ` Senthil Kumar Selvaraj
2020-08-24 18:18 ` Jeff Law
2020-08-26 3:58 ` Hans-Peter Nilsson
2020-08-26 16:20 ` Jeff Law
2020-08-26 18:26 ` Hans-Peter Nilsson
2020-08-26 11:18 ` Pip Cet
2020-08-26 16:21 ` Jeff Law
[not found] ` <87h7so2w0c.fsf@gcc.gnu.org>
2020-08-27 14:48 ` Jeff Law
2020-09-01 19:38 ` Hans-Peter Nilsson
2020-08-17 17:21 ` Segher Boessenkool
2020-08-18 15:17 ` Hans-Peter Nilsson
2020-08-16 3:25 ` Hans-Peter Nilsson
2020-08-19 5:57 ` Senthil Kumar Selvaraj
2020-08-19 22:31 ` Hans-Peter Nilsson
2020-08-20 5:40 ` Senthil Kumar Selvaraj
2020-08-20 8:51 ` Andrew Stubbs
2020-08-20 10:59 ` H.J. Lu [this message]
2020-08-20 16:53 ` Hans-Peter Nilsson
2020-08-17 16:45 ` Jeff Law
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