sabre at nondot.org
Thu Aug 31 12:17:54 CDT 2006
On Wed, 30 Aug 2006, Michael McCracken wrote:
> Hi, in a thread this afternoon about compiling the Fortran SPEC2000 to
> LLVM bytecode, Chris mentioned that it should be possible to compile
> to LLVM with the gfortran front end, although no one has necessarily
> tried it.
> I was surprised (and happy) to hear this, as under the impression that
> it would require a "complete rewrite of the gfortran backend" . Now,
> I probably misinterpreted that exchange, but it was the only public
> record I could find of discussion about using LLVM and gfortran. What's
> the difference between how it works now and what Steven Bosscher was
> saying would be a huge job?
This comment meant that a "complete rewrite" was needed to go from
GFortran AST's directly to LLVM, without going through GENERIC/GIMPLE. If
you use GENERIC/GIMPLE (as we currently do) it should be straight-forward.
> Also, is there any rough idea of how far from working it might be - I
> note that there's considerable room for interpretation in the phrasing
> of "See what works and what doesn't, debug, fix, submit patch, repeat."
I don't know that anyone has tried it. I'd suggest configuring llvm-gcc4
with gfortran enabled, then try some simple fortran programs. I expect
that there are only minor corner cases missing, e.g. some forms of
ARRAY_REF we don't implement or something.
> The reason I'm asking is that if it sounds like something I'll be able
> to make a dent in, I'm going to start on it first thing tomorrow
> morning. Like it's my job.
Very cool, that would certainly be welcome.
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