Re: 2nd Ping: Re: [PATCH v3] doc: Document order of define_peephole2 scanning

[Richard Biener <richard.guenther@gmail.com>]

On Thu, May 4, 2023 at 2:10 AM Hans-Peter Nilsson via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Ping again.

OK.

> > From: Hans-Peter Nilsson <hp@axis.com>
> > Date: Thu, 27 Apr 2023 01:55:24 +0200
> >
> > > From: Hans-Peter Nilsson <hp@axis.com>
> > > Date: Wed, 19 Apr 2023 18:59:14 +0200
> > [...]
> >
> > > So again: Approvers: pdf output reviewed.  Ok to commit?
> > > -- >8 --
> > > I was a bit surprised when my newly-added define_peephole2 didn't
> > > match, but it was because it was expected to partially match the
> > > generated output of a previous define_peephole2, which matched and
> > > modified the last insn of a sequence to be matched.  I had assumed
> > > that the algorithm backed-up the size of the match-buffer, thereby
> > > exposing newly created opportunities *with sufficient context* to all
> > > define_peephole2's.  While things can change in that direction, let's
> > > start with documenting the current state.
> > >
> > >     * doc/md.texi (define_peephole2): Document order of scanning.
> > > ---
> > >  gcc/doc/md.texi | 9 +++++++++
> > >  1 file changed, 9 insertions(+)
> > >
> > > diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
> > > index 07bf8bdebffb..300d104d58ab 100644
> > > --- a/gcc/doc/md.texi
> > > +++ b/gcc/doc/md.texi
> > > @@ -9362,6 +9362,15 @@ If the preparation falls through (invokes neither @code{DONE} nor
> > >  @code{FAIL}), then the @code{define_peephole2} uses the replacement
> > >  template.
> > >
> > > +Insns are scanned in forward order from beginning to end for each basic
> > > +block.  Matches are attempted in order of @code{define_peephole2}
> > > +appearance in the @file{md} file.  After a successful replacement,
> > > +scanning for further opportunities for @code{define_peephole2}, resumes
> > > +with the first generated replacement insn as the first insn to be
> > > +matched against all @code{define_peephole2}.  For the example above,
> > > +after its successful replacement, the first insn that can be matched by
> > > +a @code{define_peephole2} is @code{(set (match_dup 4) (match_dup 1))}.
> > > +
> > >  @end ifset
> > >  @ifset INTERNALS
> > >  @node Insn Attributes
> > > --
> > > 2.30.2
> > >
> >