Re: [lto] PATCH: fill in code to merge declarations

[Mark Mitchell <mark at codesourcery dot com>]

Kenneth Zadeck wrote:
> Mark Mitchell wrote:
> > Sandra Loosemore wrote:
> >
> > > I haven't figured out how to test this yet -- when I try to run more
> > > than one file through the driver with -x lto -c, it seems to want to
> > > compile them separately instead of merging them.  Do I need some
> > > other switch, or has this not been implemented yet?
> > I will review the patch later today.  However, I think that "-combine"
> > should work, e.g.:
> >
> >   gcc -x lto -c -combine a.o b.o
> >
> > Thanks,
> i do not see how -combine can work since it will try to gimplify text
> that has already been gimplified.

That's an orthogonal issue.  All -combine does is tell the driver to 
pass all of the input "source files" (which, in the case of LTO, are 
what we usually call object files) to the front end at once, rather than 
in separate invocations.  The re-gimplification issue applies just as 
much for a single object file as for multiple object files.

But, I'm not sure why re-gimplification is a problem, per se.  GIMPLE is 
presumably already valid GIMPLE, so the gimplifier should presumably 
leave it intact.  Are you just concerned about the wasted time, or do is 
there a correctness problem with re-gimplifying?

--
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713