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

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


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
(650) 331-3385 x713

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