[PATCH] ARM: Homogeneous aggregates must be allocated to contiguous registers

[Renato Golin]

  Hi Oliver,

  I'm in favour of having a PCS helper in the IRBuilder in any form or shape, but that's orthogonal to any front-end's inability to produce correct ABI code. I wouldn't want a new, generic PCS helper to be moulded based on a single ARM HA issue, but to be developed from scratch, with most PCSs in mind, including x86, Mips, PPC, AArch64, etc.

  In that sense, I agree with Anton that this *very* specific problem sould be fixed in the front-end, as it has historically being done by ARM-compatible front-ends (llvm-gcc, clang, our own EDG bridge, and others), and a more generic approach should be taken to a wider audience, mixing Clang and LLVM developers in a "grand design".

  In the end, other front-ends will have to adapt to your own implementation's specific details anyway, and it doesn't matter what kind of specific behaviour for the front-end engineer, as long as it works. The only better scenario is when there is *NO* PCS specific knowledge in a function declaration, and all of it is done by the PCS helper. Anything in between will be just another shoddy contract.

  I do want to see that happening, but not starting from a corner case.

  cheers,
  --renato

http://llvm-reviews.chandlerc.com/D3082