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

Jakob Stoklund Olesen stoklund at 2pi.dk
Fri Aug 9 14:15:25 PDT 2013

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?


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