Epilogue instructions don't set SourceLoc to return inst SourceLoc

[bjorn3]

• What are the steps to reproduce the issue?

  test compile
  target x86_64
  
  function u0:0() system_v {
  ebb0:
  nop
  @0001 return
  }
  

• What do you expect to happen? What does actually happen? Does it panic, and
  if so, with which assertion?

  test compile
  target x86_64
  function u0:0(i64 fp [%rbp]) -> i64 fp [%rbp] system_v {
      ss0 = incoming_arg 16, offset -16
  
                                  ebb0(v4: i64 [%rbp]):
  [RexOp1pushq#50]                    x86_push v4
  [RexOp1copysp#8089]                 copy_special %rsp -> %rbp
  [-]                                 nop
  [RexOp1popq#58,%rbp]                v5 = x86_pop.i64 ; <-- this should use @0001 as srcloc
  @0001 [Op1ret#c3]                   return v5
  }
  

  This causes debuggers to switch between function start and end as current position with cg_clif generated executables when returning from a function.

• Which Cranelift version / commit hash / branch are you using? 387593d

[bjorn3]

I get that this standard form can be useful when somebody barely posts any information otherwise, but it is a lot of work to fill in.

[bnjbvr]

I get that this standard form can be useful when somebody barely posts any information otherwise, but it is a lot of work to fill in.

With all the information that you've provided in the OP, this issue is actually perfect. Indeed it's more work to fill for the reporter, but if it makes it easier to understand what the problem is and how to fix it (which is the case here in my opinion), then it's a net win for everyone. Of course we're not married to the issue templates in their current forms, and we'll see how everyone feels about it. We can amend them, remove them, etc.

[bjorn3]

Fixed with new x64 backend.