[LLVMdev] 16-bit target problem

[Duncan Sands]

>   // 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!

Right, why aren't front-ends responsible for using a wide-enough type?

Ciao,

D.