[llvm-dev] [RFC] Strategies for Bootstrapping Compiler-RT builtins

[Chris Bieneman via llvm-dev]

> On Nov 2, 2015, at 2:44 PM, Steve King <steve at metrokings.com> wrote:
> 
> On Mon, Nov 2, 2015 at 1:02 PM, Chris Bieneman <beanz at apple.com> wrote:
>> Sadly, I believe there are licensing reasons why the builtins can’t be in the LLVM repo.
> 
> Repos and licenses are orthogonal, but I get the concern.
> 
> Switching gears to other questions:
> Should the bootstrap build automatically produce a built-ins library
> for each target in "llvm-config --targets-built" or is the developer
> expected to provide an explicit list?  Hopefully the former.

Today there isn’t really a simple answer. For Linux I think the bootstrap only builds for the host architecture by default. For Darwin, it builds all supported Darwin architectures, which can be complicated to determine.

> 
> Is it reasonable that bootstrap build not depend on GNU binutils?

Not necessarily. To my understanding LLVM doesn’t fully replace bin utils on any platform yet, and I think we’re a long way from saying the LLVM toolchain is the default builtin toolchain.

> This might be mission creep, but it's a drag that the unspoken first
> step in developing an LLVM based toolchain is "port binutils".  I
> haven't kept watch on LLD progress, but perhaps it's far enough along
> that bootstrap process can depend on it.

On Darwin ar and lld are the biggest pieces that aren’t fully featured yet. On other platforms I think there are still places that lld isn’t fully fleshed.

-Chris

> 
> Regards,
> -steve