[PATCH] Implement Named Register Global Variables in LLVM

[Rafael Ávila de Espíndola]

> to and will abort in case the register is not supported or not existent

We always reject at compile time.

> Pointer types are used to make sure it has the same bit width as the
register itself.

Having i32 and i64 versions seems better.

> Warning: There is no register reservation at the moment, so it only
works reliably on non-allocatable registers.

We just just error for now if the register is allocatable.

What was the use case for writing to registers? Maybe split that to
another patch?

Do we need the "stack" pseudo register? If it is only to implement
__builting_stack_pointer, it seems better to do it there. In fact, it
could be implemented as regular function once this is in, no?

http://reviews.llvm.org/D3261