[LLVMdev] [global-isel] Random comments on Proposal for a global instruction selector

Jakob Stoklund Olesen
Fri, 09 Aug 2013 21:15:25 -0000

On Aug 9, 2013, at 2:16 AM, David Chisnall <David.Chisnall at
cl.cam.ac.uk> wrote:

> For our back end, we absolutely do not want a type system without pointers
- not only do we have separate registers for pointers, we also have separate
instructions for manipulating them and representing this in SelectionDAG
requires some very ugly hacks. This is also the case for several DSPs, which
have separate address and data registers, and for upcoming Intel chips with MPX
that have 4 hardware bounds registers that need keeping in sync with pointers.

I am a bit skeptical about the need for pointer types; I don’t think it is the
right level of abstraction for an instruction selector. The processors I know
about with separate address and data registers (Blackfin, m86k, TriCore) would
be modeled perfectly by the register bank labels in the proposal.

Won’t that work for your case?

Thanks,
/jakob