mmx silently ignored in function argument

[eponier]

This program exhibits the problem.

fn f (#mmx reg u64 y) -> reg u64 {
  reg u64 x;
  x = 0;
  return x;
}

export fn main () -> reg u64 {
  reg u64 x;
  x=0;
  x = f(x);
  return x;
}

y is compiled as RAX. This works because y is not used.

[MrDaiki]

A little question here : what is the compilation pass where register used for variables are computed (I think it is reg-alloc but I would prefer to be sure) ?

[vbgl]

Yes: the compiler step mapping variables to registers is called register allocation. However, this is unrelated to this issue: here there is a “kind” mismatch between the parameter and the argument that is silently ignored: this could be detected early by a simple check.