r206963 - [ARM64] Change inline assembly constraints to be more lax, to match the behaviour of Clang/AArch64 and GCC.

[Tim Northover]

On 24 April 2014 00:35, Jim Grosbach <grosbach at apple.com> wrote:
> I share Eric’s concern here. As I recall, the spec from ARM was very clear on this point, requiring a modifier to specify anything other than a 64-bit GPR. Matching the behavior of GCC is not a sufficient reason to change that unless the specification changed as well.

Unfortunately, that spec doesn't seem to have made it to GCC, either
in code or in documentation form.

Personally, I don't think GPR64 has any more claim to being general
purpose than GPR32. The options I'd favour are to *require* an operand
modifier in all cases (I'm always in favour of explicit assembly), or
what GCC actually does by inferring the size. The first is clearly not
viable though.

Cheers.

Tim.