Re: 8-bit and 16-bit arithmetic

yeah, like, currently the XOR for setting registers to zero trick / code optimization (first implemented in ghc backend by reid barton) is done as part of the pretty printer on X86/AMD_64 targets this and a lot of other easy win peephole optimizations that are platform /target dependent happen in the pretty printer atm I thnk On Thu, Oct 28, 2021 at 5:38 PM Ben Gamari wrote:

Norman Ramsey writes:

...

On x86, GHC can translate 8-bit and 16-bit operations directly into the 8-bit and 16-bit machine instructions that the hardware supports. But there are other platforms on which the smallest unit of arithmetic may be 32 or even 64 bits. Is there a central module in GHC that can take care of rewriting 8-bit and 16-bit operations into 32-bit or 64-bit operations? Or is each back end on its own for this?

(One of my students did some nice work on implementing this transformation with a minimal set of sign-extension and zero-extension operations: https://www.cs.tufts.edu/~nr/pubs/widen.pdf.)

As Carter indicated, this is currently done on a per-backend basis. This could indeed probably be consolidated, although we would want to make sure that in so doing we do not leave easy money on the table: It seems plausible to me that the backend may be able to generate better code than a naive lowering to wide arithmetic might otherwise generate.

Cheers,

- Ben _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs