[cfe-commits] [patch] Make ARM NEON polynomial types unsigned

[Tim Northover]

> So you're more willing to change the 32-bit ABI(s) than
> the 64-bit ABI?  That doesn't make sense to me.

The way I see it no 32-bit code should be relying on this behaviour
since it's not specified in any ABI document. The only portable 32-bit
choice (and the entire point of NEON intrinsics is portability) is to
take care of the sign yourself and not put scalar polynomials at a
public interface.

64-bit code can rely on unsigned since it's required there; and the
easiest way to write a compiler satisfying all documentation (as well
as behaving sanely) is to make polynomials unsigned everywhere.

In reality, I can't imagine this patch being a real issue for anything
except the complexity of our codebase. I'd be astonished if there was
a single library with a public interface exposing a poly8_t or
poly16_t. Or compiling half its code with GCC and half with Clang.

But that said, I will of course rewrite to make it AArch64 conditional
(typing through gritted teeth) if required. Just say the word.

Tim.