[LLVMdev] Proposed Makefile Changes

[Reid Spencer]

Hi,

In buildling XPS using LLVM's makefile system, I'm finding that there's
a few things lacking in our support for LLVM-based projects. The items
below should help but may require changes to project makefiles. I
thought I'd check before just going and doing it.

     1. Various autoconf generated variables (e.g. abs_top_srcdir) are
        set in the makefiles but not used. They conflict with a user's
        project that might want to use them. I propose removing them or
        using names prefixed with llvm_ to ensure their use is only for
        llvm
     2. BUILD_SRC_DIR and BUILD_OBJ_DIR are poorly named. This has been
        a source of confusion for me personally and probably for others.
        They should really be PROJ_SRC_DIR and PROJ_OBJ_DIR to indicate
        they pertain to the project's src/obj dir not LLVM's
     3. The LLVM makefiles require a Makefile.config in the project. I'm
        going to try to make that optional because some projects can
        just use LLVM's Makefile.config.
     4. There should be no "default" directives because it prevents the
        use of a directive in the user's Makefile to document what will
        be built. Currently, the only such case is that we build a
        "relinked" object file by default for each library unless
        DONT_BUILD_RELINKED is specified. While this is common for LLVM,
        it isn't for projects which will want an archive or shared
        library. If a relinked library is needed, something link
        RELINKED_LIBRARY=1 should be specified so that it documents in
        the makefile what is getting built.
     5. Some of the names of the directives are a little confusing. We
        have BUILD_ARCHIVE to specify building an archive. But, we have
        SHARED_LIBRARY to specify building a shared library. I think
        these should all be named BUILD_<thing_to_build> so we'd have
        BUILD_ARCHIVE_LIBRARY and BUILD_SHARED_LIBRARY and
        BUILD_RELINKD_LIBRARY and BUILD_TOOL
     6. The directive names are concatenated in some cases. I'd like to
        see TOOL_NAME instead of TOOLNAME and LIBRARY_NAME instead of
        LIBRARYNAME. Its easier for *me* to read, but I'd like some
        feedback on this one as its as "gratuitous" change.
     7. The documentation in MakefileGuide.html is lacking a tutorial on
        how to use the LLVM Makefile system for projects (as opposed to
        LLVM itself).  I think its time to add one. There are things in
        the configure.ac file that are needed to support the makefile
        system. Those need to be documented as well.

The end result should be that using the LLVM Makefile for things other
than LLVM itself gets a easier/clearer and better documented. 

I'm signing up to do the necessary changes in llvm and llvm-test. I'll
also help anyone with the necessary changes in their project.

Please let me know if these changes will be a significant burden or they
are inadvisable for your project.

Thanks,

Reid.
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