[llvm-dev] RFC: On removing magic numbers assuming 8-bit bytes

Jesper Antonsson via llvm-dev llvm-dev at lists.llvm.org
Wed May 8 01:04:07 PDT 2019

On Mon, 2019-05-06 at 10:43 +0100, Tim Northover wrote:
> On Mon, 6 May 2019 at 10:13, James Courtier-Dutton via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > Although the above is mentioning bytes, looking at the "/ 8"   and
> > "& 0x7" makes it look like the author meant octets and not bytes.
> > Bytes can be any size of bits.
> I don't think you'll have much luck trying to make that stick for a
> general audience, or even a general compiler-writer audience. Byte is
> far too strongly associated with 8 bits these days.
> > Octets are only ever 8 bits.
> You might be able to convert all uses of byte to octet and abandon
> byte entirely, but at that point why bother? It feels like a change
> just for the sake of pedantry.
> I like the "addressable unit" name, though it's a bit long (AddrUnit
> seems OK). It at least signals to a reader that there might be
> something weird going on. Getting someone writing new code to think
> in
> those terms is a different matter, of course, but I don't think any
> of
> the changes under discussion really help there.
> BTW, is there an open source backend (in a fork, I assume) that does
> this? So that we can get some kind of idea of the real scope of the
> changes needed.

Unfortunately, there is not AFAIK. If you like, we can try to expand on
the showcase patch to show more, but the changes are numerous enough to
make it difficult to assemble something that will show it all.


> Cheers.
> Tim.

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