[llvm-commits] [llvm] r48459 - in /llvm/trunk/lib/Target/PowerPC: PPCCallingConv.td PPCISelLowering.cpp

[Dale Johannesen]

On Mar 17, 2008, at 11:27 AM, Evan Cheng wrote:
> The part of call can really use some refactoring. Look at the case of
> MVT::i32, it can be significantly simplified into something like:
> unsigned NumValues = Op.Val->getNumValues();
> if (Op.Val->getValueType(NumValues-1) == MVT::i32)
> for (unsigned i = 0; i != NumValues; ++i) {
>   Chain = DAG.getCopyFromReg(Chain, CallRegs[i], MVT::i32,
> InFlag).getValue(1);
>   InFlag = Chain.getValue(2);
>   ResultVals.push_back(Chain.getValue(0));
>   NodeTys.push_back(MVT::i32);
> }

I had it like that and decided I prefer this.  Generally I'd rather  
list the cases
that are supposed to work explicitly rather than have something more  
general
and trust we won't get handed cases that aren't supposed to happen.
Shorter is not always better.

> BTW, why is it we are using tablegen generated CC code to handle
> arguments, but not return types (same issue on x86)? I've forgotten
> the history behind the tablegen CC development.

That is the way I found it.  According to Chris, the PPC BE preceded  
tablegen.  Return values, at least for ppc32, can be handled easily by  
the existing tablegen stuff.  Parameters would need some extensions,  
e.g. same value in both regs and memory, structs passed part in regs  
and part in memory.