lib/Target/PTX/PTXISelLowering.cpp

//===-- PTXISelLowering.cpp - PTX DAG Lowering Implementation -------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the PTXTargetLowering class.
//
//===----------------------------------------------------------------------===//

#include "PTX.h"
#include "PTXISelLowering.h"
#include "PTXRegisterInfo.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"

using namespace llvm;

PTXTargetLowering::PTXTargetLowering(TargetMachine &TM)
  : TargetLowering(TM, new TargetLoweringObjectFileELF()) {
  // Set up the register classes.
  addRegisterClass(MVT::i1,  PTX::PredsRegisterClass);
  addRegisterClass(MVT::i32, PTX::RRegs32RegisterClass);

  // Compute derived properties from the register classes
  computeRegisterProperties();
}

const char *PTXTargetLowering::getTargetNodeName(unsigned Opcode) const {
  switch (Opcode) {
    default:           llvm_unreachable("Unknown opcode");
    case PTXISD::EXIT: return "PTXISD::EXIT";
    case PTXISD::RET:  return "PTXISD::RET";
  }
}

//===----------------------------------------------------------------------===//
//                      Calling Convention Implementation
//===----------------------------------------------------------------------===//

namespace {
struct argmap_entry {
  MVT::SimpleValueType VT;
  TargetRegisterClass *RC;
  TargetRegisterClass::iterator loc;

  argmap_entry(MVT::SimpleValueType _VT, TargetRegisterClass *_RC)
    : VT(_VT), RC(_RC), loc(_RC->begin()) {}

  void reset() { loc = RC->begin(); }
  bool operator==(MVT::SimpleValueType _VT) const { return VT == _VT; }
} argmap[] = {
  argmap_entry(MVT::i1,  PTX::PredsRegisterClass),
  argmap_entry(MVT::i32, PTX::RRegs32RegisterClass)
};
} // end anonymous namespace

static SDValue lower_kernel_argument(int i,
                                     SDValue Chain,
                                     DebugLoc dl,
                                     MVT::SimpleValueType VT,
                                     argmap_entry *entry,
                                     SelectionDAG &DAG,
                                     unsigned *argreg) {
  // TODO
  llvm_unreachable("Not implemented yet");
}

static SDValue lower_device_argument(int i,
                                     SDValue Chain,
                                     DebugLoc dl,
                                     MVT::SimpleValueType VT,
                                     argmap_entry *entry,
                                     SelectionDAG &DAG,
                                     unsigned *argreg) {
  MachineRegisterInfo &RegInfo = DAG.getMachineFunction().getRegInfo();

  unsigned preg = *++(entry->loc); // allocate start from register 1
  unsigned vreg = RegInfo.createVirtualRegister(entry->RC);
  RegInfo.addLiveIn(preg, vreg);

  *argreg = preg;
  return DAG.getCopyFromReg(Chain, dl, vreg, VT);
}

typedef SDValue (*lower_argument_func)(int i,
                                       SDValue Chain,
                                       DebugLoc dl,
                                       MVT::SimpleValueType VT,
                                       argmap_entry *entry,
                                       SelectionDAG &DAG,
                                       unsigned *argreg);

SDValue PTXTargetLowering::
  LowerFormalArguments(SDValue Chain,
                       CallingConv::ID CallConv,
                       bool isVarArg,
                       const SmallVectorImpl<ISD::InputArg> &Ins,
                       DebugLoc dl,
                       SelectionDAG &DAG,
                       SmallVectorImpl<SDValue> &InVals) const {
  if (isVarArg) llvm_unreachable("PTX does not support varargs");

  lower_argument_func lower_argument;

  switch (CallConv) {
    default:
      llvm_unreachable("Unsupported calling convention");
      break;
    case CallingConv::PTX_Kernel:
      lower_argument = lower_kernel_argument;
      break;
    case CallingConv::PTX_Device:
      lower_argument = lower_device_argument;
      break;
  }

  // Reset argmap before allocation
  for (struct argmap_entry *i = argmap, *e = argmap + array_lengthof(argmap);
       i != e; ++ i)
    i->reset();

  for (int i = 0, e = Ins.size(); i != e; ++ i) {
    MVT::SimpleValueType VT = Ins[i].VT.SimpleTy;

    struct argmap_entry *entry = std::find(argmap,
                                           argmap + array_lengthof(argmap), VT);
    if (entry == argmap + array_lengthof(argmap))
      llvm_unreachable("Type of argument is not supported");

    unsigned reg;
    SDValue arg = lower_argument(i, Chain, dl, VT, entry, DAG, &reg);
    InVals.push_back(arg);
  }

  return Chain;
}

SDValue PTXTargetLowering::
  LowerReturn(SDValue Chain,
              CallingConv::ID CallConv,
              bool isVarArg,
              const SmallVectorImpl<ISD::OutputArg> &Outs,
              const SmallVectorImpl<SDValue> &OutVals,
              DebugLoc dl,
              SelectionDAG &DAG) const {
  if (isVarArg) llvm_unreachable("PTX does not support varargs");

  switch (CallConv) {
    default:
      llvm_unreachable("Unsupported calling convention.");
    case CallingConv::PTX_Kernel:
      assert(Outs.size() == 0 && "Kernel must return void.");
      return DAG.getNode(PTXISD::EXIT, dl, MVT::Other, Chain);
    case CallingConv::PTX_Device:
      assert(Outs.size() <= 1 && "Can at most return one value.");
      break;
  }

  // PTX_Device

  // return void
  if (Outs.size() == 0)
    return DAG.getNode(PTXISD::RET, dl, MVT::Other, Chain);

  assert(Outs[0].VT == MVT::i32 && "Can return only basic types");

  SDValue Flag;
  unsigned reg = PTX::R0;

  // If this is the first return lowered for this function, add the regs to the
  // liveout set for the function
  if (DAG.getMachineFunction().getRegInfo().liveout_empty())
    DAG.getMachineFunction().getRegInfo().addLiveOut(reg);

  // Copy the result values into the output registers
  Chain = DAG.getCopyToReg(Chain, dl, reg, OutVals[0], Flag);

  // Guarantee that all emitted copies are stuck together,
  // avoiding something bad
  Flag = Chain.getValue(1);

  return DAG.getNode(PTXISD::RET, dl, MVT::Other, Chain, Flag);
}