[llvm-dev] LLD status update and performance chart

[Hal Finkel via llvm-dev]

----- Original Message -----
> From: "Rafael Avila de Espindola via llvm-dev" <llvm-dev at lists.llvm.org>
> To: "Andrew Kelley" <superjoe30 at gmail.com>, "Rui Ueyama" <ruiu at google.com>
> Cc: "llvm-dev" <llvm-dev at lists.llvm.org>
> Sent: Tuesday, December 13, 2016 2:30:41 PM
> Subject: Re: [llvm-dev] LLD status update and performance chart
> 
> Andrew Kelley via llvm-dev <llvm-dev at lists.llvm.org> writes:
> 
> > On Tue, Dec 13, 2016 at 1:06 PM, Rui Ueyama via llvm-dev <
> > llvm-dev at lists.llvm.org> wrote:
> >>
> >> That said, I think the current our "API" to allow users call our
> >> linker's
> >> main function hit the sweet spot. I know at least a few LLVM-based
> >> language
> >> developers who want to eliminate external dependencies and embed a
> >> linker
> >> to their compilers. That's a reasonable usage, and I think
> >> allowing them to
> >> pass a map from filename to MemoryBuffer objects makes sense, too.
> >> That
> >> would be done without affecting the overall linker architecture. I
> >> don't
> >> oppose to that idea, and if someone wrote a patch, I'm fine with
> >> that.
> >>
> >
> > As an LLVM-based language developer, this is exactly what I want to
> > do. In
> > short:
> >
> >  * Avoid depending on an external binary
> >  * Avoid a fork+exec
> >  * Avoid unnecessary use of the filesystem
> >
> > Does this feature compromise progress on the linker binary?
> >
> > Would it be reasonable for this feature to exist in the next minor
> > version
> > release of lld?
> 
> I would please ask for it to wait. It requires designing how the
> linker
> script parser and the thin archive system will fetch new files as
> they
> are found.

Instead of just waiting, I think we should discuss design requirements. Clang, for example, has a VFS layer too (in include/clang/Basic/VirtualFileSystem.h) which seems independent from Clang. Maybe we want to move it into LLVM and reuse it from both Clang and LLD. Would this VFS layer meet the requirements for an LLD VFS layer too?

 -Hal

> 
> Also, please consider what is so bad about writing a file. If your
> language has anything like translation unites than most of the
> program
> should already be in .o files.
> 
> Cheers,
> Rafael
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-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory