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

Philip Reames via llvm-dev llvm-dev at lists.llvm.org
Mon May 6 15:56:49 PDT 2019

On 5/6/19 2:43 AM, Tim Northover via llvm-dev 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.
+1 Please don't try; insisting on a distinction will confuse many new
>> 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.

Strongly agreed.

My personal take is this is an invasive enough change with enough likely
ongoing maintenance fall out to require substantial justification before
the work was undertaken upstream.  A open source backend proposed for
inclusion upstream would be one part of that.  Active contribution from
the sponsors in other areas would also be a key factor.

> Cheers.
> Tim.
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