[PATCH] LibDriver, llvm-lib: introduce.

[Peter Collingbourne]

On Sat, Jun 06, 2015 at 01:25:52PM -0400, Rafael Espíndola wrote:
> The lib format is really similar to the .a format.
> 
> I guess the only question I have about this direction is how would it
> compare with having lld fork+exec llvm-lib.exe and implementing
> llvm-lib.exe in the same binary as llvm-ar.exe (similar to how we do
> for llvm-ranlib.exe).

Either way seems reasonable to me, but I see a few minor advantages of the
approach I took:

1) The lld tool is more self-contained, so it could be shipped on its own
   if a target build system does not need lib.exe.
2) We save the cost of a fork+exec which could be expensive on Windows.
3) Setting up the fork+exec is more code than a function call.

One disadvantage is that there would be no way to swap out the llvm-lib.exe
tool with another tool that supports something that our tool currently
doesn't support (e.g. generating import libraries), but arguably the right
thing to do there would be to build that functionality into our own tool.

Thanks,
-- 
Peter