[LLVMdev] llvm-gfortran problems

[Ashay Rane]

Hmm.. I didn't explain the problem completely last time. I am creating a
drop-in replacement for gcc and gfortran that runs an additional pass on the
bitcode before generating the native binary. Here's whats happening: If the
source code compilation process builds a static library (.a archive file), I
need a means to link the `.a' file statically into the application. So if
the original statement was:

gfortran file.o -L somedir -lmylib -o file

then my modified compilation process would have to deal with file.o and
libmylib.a to generate the binary `file'. Now, all files essentially contain
bitcode (file.o and object files inside libmylib.a). So the pseudo-code
would look like:

-- QUOTE --

For all input files passed to compiler:
    If extension is .o:
        Use llc to generate .s file
        Add this filename to some collection
    Else if extension is .a:
        Extract contents of this archive
        Use llc on each file to generate .s file
        Add each filename to the collection
    End if
End for

Retrieve all `.s' filenames and pass them all to gcc or gfortran

-- UNQUOTE --

But the part that deals with `.a' files is a bit ugly. llvm-ld handles the
archive (.a) files without any manual extraction but I fear that because
llvm-ld is not a full-featured linker, I might run into a wall because of
incompatible options between gfortran/gcc and llvm-ld.

Ashay


On Mon, Sep 12, 2011 at 3:38 PM, Dmitry N. Mikushin <maemarcus at gmail.com>wrote:

> Sorry, at what step do you need archive? llc emits binary, it does not
> perform any linking, thus it does not need anything except the input
> bytecode file. Then during linking you can link whatever archives of
> binaries you want.
>
> 2011/9/13 Ashay Rane <ashay.rane at tacc.utexas.edu>:
> > Thats correct. But using llc becomes a problem when I have archives (.a
> > files). I could, in theory, extract its contents to a tempdir and then
> use
> > llc and link but just wondering if there is a more elegant solution.
> > Ashay
> >
> > On Mon, Sep 12, 2011 at 3:00 PM, Dmitry N. Mikushin <maemarcus at gmail.com
> >
> > wrote:
> >>
> >> Ashay,
> >>
> >> If I understand correctly, in hw.o you would have llvm bytecode, while
> >> linker expects regular object binary. Probably first you need to emit
> >> asm out of bytecode using llc?
> >>
> >> - D.
> >>
> >> 2011/9/12 Ashay Rane <ashay.rane at tacc.utexas.edu>:
> >> > Hello,
> >> > Sorry for the late reply. Using dragonegg worked well, thanks all!
> >> > Just as a note... I had to use llvm-ld during the link step because
> >> > gfortran
> >> > could not link bitcode. Here's an example of the error shown when
> using
> >> > gfortran instead of llvm-ld:
> >> > $ ${GCC_4_5_0}/bin/gfortran hw.f -c
> >> > -fplugin=${DRAGONEGG_PLUGIN}/dragonegg.so -o hw.o -flto -emit-llvm -S
> >> > $ ${LLVM_2_9}/bin/opt -mem2reg hw.o -o hw.o
> >> > $ ${GCC_4_5_0}/bin/gfortran
> >> >
> >> >
> -fplugin=${DRAGONEGG_PLUGIN}/dragonegg.so ${GCC_4_5_0}/lib64/libgfortran.a
> >> > hw.o -o hw
> >> > hw.o: file not recognized: File format not recognized
> >> > collect2: ld returned 1 exit status
> >> > $ file hw.o
> >> > hw.o: data
> >> > Instead, using llvm-ld:
> >> > $ ${LLVM_2_9}/bin/llvm-ld -native hw.o -o hw
> >> > ${GCC_4_5_0}/lib64/libgfortran.a -lm
> >> > llvm-gcc had the gold plugin. I wonder if there is any equivalent of
> >> > that
> >> > for dragonegg to be able to compile bitcode and native object code in
> a
> >> > transparent manner.
> >> > Thanks again!
> >> > Ashay
> >> >
> >> > On Wed, Aug 31, 2011 at 4:29 PM, Anton Korobeynikov
> >> > <anton at korobeynikov.info> wrote:
> >> >>
> >> >> Hello
> >> >>
> >> >> > I am not very familiar with Fortran programs. I saw a few programs
> >> >> > that
> >> >> > had
> >> >> > a "MAIN" subroutine defined, some others that did not. Am I missing
> >> >> > something while compiling the code? Is there a different way to
> >> >> > compile
> >> >> > bitcode (from Fortran programs) to a native binary?
> >> >> For Fortran MAIN is indeed something similar to C main, but not
> >> >> exactly the same.
> >> >> You have to link the runtime library (libgfortran.a) in order to get
> >> >> "proper" main, mak sure all stuff is initialized properly, etc.
> >> >>
> >> >> --
> >> >> With best regards, Anton Korobeynikov
> >> >> Faculty of Mathematics and Mechanics, Saint Petersburg State
> University
> >> >
> >> >
> >> > _______________________________________________
> >> > LLVM Developers mailing list
> >> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >> >
> >> >
> >
> >
>
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