RFC: Patch to allow spill slot alignment greater than the stack alignment

[Mike Stump]

On Oct 5, 2015, at 9:46 AM, Steve Ellcey <sellcey@imgtec.com> wrote:
> One example of an issue I have run into is with the DWARF unwind
> generation and 'Rule 16' in dwarf2cfi.c.  It assumes the AND instruction
> has an integer constant argument but MIPS can't do an AND with a
> constant like -16 so it has to put it in a register first and do the AND
> with the register.

If you are using any detail about the architecture to imagine limitations with dwarf generation, then I think you’re missing that fact that the validity of the dwarf can be uncoupled from target considerations.  See dwarf_pattern on frv for example, or more generally REG_FRAME_RELATED_EXPR on all the ports.  When _must_ one use this?  Whenever the generated dwarf is other than trivial.  If trivial, it will usually just work.

You didn’t include a lot of detail in your email, so I’m just extrapolating that I think you did and what you saw.