[LLVMdev] Linking tools

[Reid Kleckner]

On Mon, Jul 27, 2015 at 10:39 AM, Steve King <steve at metrokings.com> wrote:

> On Mon, Jul 27, 2015 at 9:52 AM, Reid Kleckner <rnk at google.com> wrote:
>
> > From the perspective of LTO, we just want users to be able
> > to add -flto to their compile and link lines, and make that produce a
> faster
> > executable, without the user ever being aware of the bitcode.
>
> For targets without GNU binutils and gcc driver support, has this goal
> been achieved?  The few times I've tried, Clang's hard-coded
> dependencies on host GNU tools block LTO and linked binaries in
> general.  For my target, manually running llvm-link and llc is the
> only way to get LTO-like output, but otherwise works pretty well.
>
> For this same reason, I get worried when I hear maintainers state that
> llvm-link, llc, llvm-mc, etc are developer only tools.  GNUless
> targets use these tools for production code for lack of working
> alternatives.
>
> If there's been recent progress on removing GNU dependencies, I'm all ears.
>

Basically, LTO for projects that have pre-compiled objects requires
integration with a real static linker. Currently we use plugins to
integrate with binutils linkers, Mac ld64, and some other closed-source
linkers. To cut this dependency, we need a new linker, which is what LLD is
intended to become.
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