[LLVMdev] Contributing the Apple ARM64 compiler backend

[Tim Northover]

Hi Hal,

> Is a different target triple the right thing to do here? I think that would introduce a ton of user confusion. How about we keep the target triples as they are, and add some other way to choose the desired backend?

In the short term, it's almost essential. Both of these targets are
going to be existing simultaneously for a while and all the LLVM tools
(for testing if nothing else) are setup to select the target based on
the triple.

Longer term we want a single backend (probably in the AArch64
directory since that's the official name). Theoretically, we could
drop "arm64" as a triple then (provided Clang still supported "-arch
arm64" for compatibility), but in reality it would be a little odd if
"-arch arm64" worked but "--target arm64" didn't. I suspect arm64 and
aarch64 will just become synonyms at that point.

Cheers.

Tim.