[LLVMdev] 16-bit target problem

[Bagel]

Has any one been successful with a 16-bit target?  I'm new to LLVM and am 
having problems.  One problem I found stems from code in
lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp: visitRet():

  // If this is an integer return value, we need to promote it ourselves to
  // the full width of a register, since getCopyToParts and Legalize will use
  // ANY_EXTEND rather than sign/zero.
  // FIXME: C calling convention requires the return type to be promoted to
  // at least 32-bit. But this is not necessary for non-C calling conventions.
  if (MVT::isInteger(RetOp.getValueType()) &&
      RetOp.getValueType() < MVT::i64) {
       MVT::ValueType TmpVT;
       if (TLI.getTypeAction(MVT::i32) == TargetLowering::Promote)
         TmpVT = TLI.getTypeToTransformTo(MVT::i32);
       else
         TmpVT = MVT::i32;

This is wrong in at least two ways:
1. First it encodes C semantics in the backend, making other language
    front-ends difficult.  The comment indicates that this is to be fixed.
2. But it even gets the C semantics wrong, the promotion is to "int", whatever
    an "int" is on the target machine, not always 32 bits.  How soon the PDP-11
    is forgotten!