Re: 8-bit and 16-bit arithmetic

I think carter has it still right that it happens in the backends. If a new backend doesn't support these we could move this up into Cmm though without much issue I think. Am 28/10/2021 um 23:12 schrieb Carter Schonwald:

I think thats done on a per backend basis (though theres been a lot of changes since i last looked at some of the relevent pieces). (i'm actually based in Cambridge MA for the next 1-2 years if you wanna brain storm IRL sometime)

On Thu, Oct 28, 2021 at 4:59 PM Norman Ramsey wrote:

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.)

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