Re: [PATCH] Generate gimple-match.c and generic-match.c earlier

[Michael Matz <matz@suse.de>]

Hello,

On Fri, 28 May 2021, Bernd Edlinger wrote:

> >> I was wondering, why gimple-match.c and generic-match.c
> >> are not built early but always last, which slows down parallel
> >> makes significantly.
> >>
> >> The reason seems to be that generated_files does not
> >> mention gimple-match.c and generic-match.c.
> >>
> >> This comment in Makefile.in says it all:
> >>
> >> $(ALL_HOST_OBJS) : | $(generated_files)
> >>
> >> So this patch adds gimple-match.c generic-match.c to generated_files.
> >>
> >>
> >> Tested on x86_64-pc-linux-gnu.
> >> Is it OK for trunk?
> > 
> > This should help for what I was complaining about in
> > https://gcc.gnu.org/pipermail/gcc/2021-May/235963.html . I build with
> > -j24 and it was stalling on compiling gimple-match.c for me.
> > Looks like insn-attrtab.c is missed too; I saw genattrtab was running last too.
> > 
> 
> Yeah, probably insn-automata.c as well, sometimes it is picked up early 
> sometimes not. maybe $(simple_generated_c) should be added to 
> generated_files, but insn-attrtab.c is yet another exception.

You can't put files in there that are sometimes slow to generate (which 
insn-{attrtab,automata}.c are on some targets), as _everything_ then waits 
for them to be created first.

Ideally there would be a way for gnumake to mark some targets as 
"ugh-slow" and back-propagate this to all dependencies so that those are 
put in front of the work queue in a parallel make.  Alas, something like 
that never came into existence :-/  (When order-only deps were introduced 
I got excited, but then came to realize that that wasn't what was really 
needed for this case, a "weak" version of it would be required at least, 
or better yet a specific facility to impose a cost with a target)


Ciao,
Michael.

> 
> 
> Bernd.
> 
> > Thanks,
> > Andrew
> > 
> >>
> >>
> >> Thanks
> >> Bernd.
> >>
> >>
> >> 2021-05-28  Bernd Edlinger  <bernd.edlinger@hotmail.de>
> >>
> >>         * Makefile.in (generated_files): Add gimple-match.c and
> >>         generic-match.c
>