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Re: creating specialized linking rules?

From: John Wohlbier
Subject: Re: creating specialized linking rules?
Date: Tue, 11 Aug 2009 05:50:47 -0600

On Wed, Aug 5, 2009 at 8:04 PM, John Wohlbier <address@hidden> wrote:
I'm using libtool in a project where I'm compiling code for the cell processor. The cell requires different compilers to be used on sources compiled for the PowerPC core (PPU) and the "synergistic processing unit" (SPU). I'm building (trying to build) a libtool library for the ppu which embeds the spu executable into the library.

Something that works for embedding "by hand" is to have a rule such as:

lib%.o: /pathto/spu/lib/%
    cp /pathto/spu/lib/$* .
    ${PEMB} ${PEMBFLAGS} $* $* $*-emb.o
    ${PAR} -qcs $@ $*-emb.o
    rm $*

where % refers to a "spucode" compiled executable with a main, and have the library link in libspucode.o.
What this translates to on the compile line (evaluating the variables) is

ppu-embedspu -m64 spucode spucode spucode-emb.o
ppu-ar -qcs libspucode.o spucode-emb.o

However, this doesn't work when making libtool libraries. I'd like to do something like

mylibtoollib_la_LIBADD += libspucode.o

but libtool (understandably) complains that libspucode.o is not a libtool object. What I'm wondering about is how to write the embedding and archiving rule using libtool, perhaps to make libspucode.lo.

Thanks much.


A coworker figured this out for me, and I thought I'd post it to the list for future reference (also posting to automake as it seems relevant to that list as well).

For embedding an spe program into a ppe program, something like this works:

## ppe test executables that need to link in an spe executable
test_Program_LDADD += lib-root_segment.o

lib-%.o : @SPE_BUILDDIR@/lib/%
        cp @SPE_BUILDDIR@/lib/$* .
        ${PEMB} ${PEMBFLAGS} $* $* $*-emb.o
        ${PAR} -qcs $@ $*-emb.o
        rm $*

where @SPE_BUILDDIR@ is the build path to the spe program.

The real issue, though, was getting the spe program to link into a libtool library, for which this works:

## special rules for the ppe library to link in the spe executable
libtest_lib_la_LIBADD += \

# make the emb-%.lo files depend on the emb-%.o files
# this triggers the emb-%.o rule which tricks libtool into
# thinking that the object created from embedding is a
# libtool object.
emb-%.lo : emb-%.o
        @echo "Ha! Tricked libtool"

emb-%.o: @SPE_BUILDDIR@/lib/%
        echo "void lotrickdummy() {}" > dummy.c
        $(LTCOMPILE) -MT $@ -MD -MP -MF "$(DEPDIR)/$*.Tpo" -c -o $@ dummy.c
        rm $@
        rm dummy.c
        cp @SPE_BUILDDIR@/lib/$* .
        ${PEMB} ${PEMBFLAGS} $* $* emb-$*.o
        rm $*

where again, in my case, the following evaluate as
${PEMB} ${PEMBFLAGS} = ppu-embedspu -m64
${PAR} = ppu-ar

Hope this may help someone out there.


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