[llvm] [M68k] always use movem for register spills (PR #106715)

[Janis Heims via llvm-commits]

TechnoElf wrote:

To be honest, I have no idea how to test for the correct spill size. I guess it may be possible to force a spill of a specific size by assigning more variables of that size than there are registers, but I'm not sure if that would guarantee this behavior. Only checking the generated instructions also wouldn't ensure that enough space for the variable actually gets allocated on the stack.

I didn't add any tests specifically for this issue thus far, as it probably affects a lot of generated code. I only made sure that all of the existing tests pass with the new spill instructions. Adding the test case from #106206 might make sense, although that code also only accounts for one very specific occurrence of a spill. What do you think?

https://github.com/llvm/llvm-project/pull/106715