RE: [PATCH] Makefile.in: clean up match.pd-related dependencies

[Alexander Monakov <amonakov@ispras.ru>]

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On Fri, 5 May 2023, Tamar Christina wrote:

> > -----Original Message-----
> > From: Alexander Monakov <amonakov@ispras.ru>
> > Sent: Friday, May 5, 2023 6:59 PM
> > To: Tamar Christina <Tamar.Christina@arm.com>
> > Cc: Richard Biener <richard.guenther@gmail.com>; gcc-patches@gcc.gnu.org
> > Subject: RE: [PATCH] Makefile.in: clean up match.pd-related dependencies
> > 
> > 
> > On Fri, 5 May 2023, Tamar Christina wrote:
> > 
> > > > > Am 05.05.2023 um 19:03 schrieb Alexander Monakov via Gcc-patches
> > > > > <gcc-
> > > > patches@gcc.gnu.org>:
> > > > >
> > > > > Clean up confusing changes from the recent refactoring for
> > > > > parallel match.pd build.
> > > > >
> > > > > gimple-match-head.o is not built. Remove related flags adjustment.
> > > > >
> > > > > Autogenerated gimple-match-N.o files do not depend on
> > > > > gimple-match-exports.cc.
> > > > >
> > > > > {gimple,generic)-match-auto.h only depend on the prerequisites of
> > > > > the corresponding s-{gimple,generic}-match stamp file, not any .cc file.
> > > >
> > > > LGTM
> > > >
> > > > > gcc/ChangeLog:
> > > > >
> > > > >    * Makefile.in: (gimple-match-head.o-warn): Remove.
> > > > >    (GIMPLE_MATCH_PD_SEQ_SRC): Do not depend on
> > > > >    gimple-match-exports.cc.
> > > > >    (gimple-match-auto.h): Only depend on s-gimple-match.
> > > > >    (generic-match-auto.h): Likewise.
> > > > > ---
> > > > >
> > > > > Tamar, do I understand correctly that you do not have more plans
> > > > > for match.pd and I won't collide with you if I attempt more
> > > > > cleanups in this
> > > > area? Thanks!
> > >
> > > No, but I'm also not sure why this change.
> > > The idea here was that if gimple-head-export.cc changes you must have
> > > changed genmatch.cc and so you need to regenerate the gimple-match-*
> > which could change the header.
> > 
> > gimple-head-export.cc does not exist.
> > 
> > gimple-match-exports.cc is not a generated file. It's under source control and
> > edited independently from genmatch.cc. It is compiled separately, producing
> > gimple-match-exports.o.
> > 
> > gimple-match-head.cc is also not a generated file, also under source control.
> > It is transitively included into gimple-match-N.o files. If it changes, they will be
> > rebuilt. This is not changed by my patch.
> > 
> > gimple-match-auto.h is a generated file. It depends on s-gimple-match stamp
> > file, which in turn depends on genmatch and match.pd. If either changes, the
> > rule for the stamp file triggers. gimple-match-N.o files also depend on the
> > stamp file, so they will be rebuilt as well.
> 
> s-gimple-match does not depend on gimple-match-head.cc. if it changes the stamp
> is not invalidated. 

Right, this is correct: there's no need to rerun the recipe for the stamp,
because contents of gimple-match-head.cc do not affect it.

> This happens to work because gimple-match-N.cc does depend on gimple-match-head.cc,
> but if the gimple-match-N.cc already exists then nothing changes.

No, if gimple-match-N.cc already exist, make notices they are out-of-date via

$(GIMPLE_MATCH_PD_SEQ_SRC): s-gimple-match gimple-match-head.cc; @true

and this triggers rebuilding gimple-match-N.o.

I tested this. After 'touch gimple-match-head.cc' all ten gimple-match-N.o files
are rebuilt.

> So I don't think this changes anything. If anything I would say the stamp file needs to
> depend on gimple-match-head.cc. 

Is my explanation above satisfactory?

Thanks.
Alexander

> 
> Thanks,
> Tamar
> 
> > 
> > Is there some problem I'm not seeing?
> > 
> > Thanks.
> > Alexander
> > 
> > > So not sure I agree with this.
> > >
> > > Thanks,
> > > Tamar
> > >
> > > > >
> > > > > gcc/Makefile.in | 9 +++------
> > > > > 1 file changed, 3 insertions(+), 6 deletions(-)
> > > > >
> > > > > diff --git a/gcc/Makefile.in b/gcc/Makefile.in index
> > > > > 7e7ac078c5..0cc13c37d0 100644
> > > > > --- a/gcc/Makefile.in
> > > > > +++ b/gcc/Makefile.in
> > > > > @@ -230,7 +230,6 @@ gengtype-lex.o-warn = -Wno-error
> > > > > libgcov-util.o-warn = -Wno-error libgcov-driver-tool.o-warn =
> > > > > -Wno-error libgcov-merge-tool.o-warn = -Wno-error
> > > > > -gimple-match-head.o-warn = -Wno-unused
> > > > > gimple-match-exports.o-warn
> > > > =
> > > > > -Wno-unused dfp.o-warn = -Wno-strict-aliasing
> > > > >
> > > > > @@ -2674,12 +2673,10 @@ s-tm-texi: build/genhooks$(build_exeext)
> > > > $(srcdir)/doc/tm.texi.in
> > > > >      false; \
> > > > >    fi
> > > > >
> > > > > -$(GIMPLE_MATCH_PD_SEQ_SRC): s-gimple-match gimple-match-
> > head.cc \
> > > > > -            gimple-match-exports.cc; @true
> > > > > -gimple-match-auto.h: s-gimple-match gimple-match-head.cc \
> > > > > -            gimple-match-exports.cc; @true
> > > > > +$(GIMPLE_MATCH_PD_SEQ_SRC): s-gimple-match gimple-match-
> > head.cc;
> > > > > +@true
> > > > > +gimple-match-auto.h: s-gimple-match; @true
> > > > > $(GENERIC_MATCH_PD_SEQ_SRC): s-generic-match
> > > > > generic-match-head.cc; @true
> > > > > -generic-match-auto.h: s-generic-match generic-match-head.cc;
> > > > > @true
> > > > > +generic-match-auto.h: s-generic-match; @true
> > > > >
> > > > > s-gimple-match: build/genmatch$(build_exeext) \
> > > > >        $(srcdir)/match.pd cfn-operators.pd
> > > > > --
> > > > > 2.39.2
> > > > >
> > >
>