llvm/lib/Target/PowerPC/GISel/PPCCallLowering.cpp

//===-- PPCCallLowering.h - Call lowering for GlobalISel -------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file implements the lowering of LLVM calls to machine code calls for
/// GlobalISel.
///
//===----------------------------------------------------------------------===//

#include "PPCCallLowering.h"
#include "PPCISelLowering.h"
#include "PPCSubtarget.h"
#include "PPCTargetMachine.h"
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/GlobalISel/CallLowering.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/TargetCallingConv.h"
#include "llvm/Support/Debug.h"

#define DEBUG_TYPE "ppc-call-lowering"

using namespace llvm;

PPCCallLowering::PPCCallLowering(const PPCTargetLowering &TLI)
    : CallLowering(&TLI) {}

bool PPCCallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
                                  const Value *Val, ArrayRef<Register> VRegs,
                                  FunctionLoweringInfo &FLI,
                                  Register SwiftErrorVReg) const {
  assert(((Val && !VRegs.empty()) || (!Val && VRegs.empty())) &&
         "Return value without a vreg");
  if (VRegs.size() > 0)
    return false;

  MIRBuilder.buildInstr(PPC::BLR8);
  return true;
}

bool PPCCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
                                CallLoweringInfo &Info) const {
  return false;
}

bool PPCCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
                                           const Function &F,
                                           ArrayRef<ArrayRef<Register>> VRegs,
                                           FunctionLoweringInfo &FLI) const {
  MachineFunction &MF = MIRBuilder.getMF();
  MachineRegisterInfo &MRI = MF.getRegInfo();
  const auto &DL = F.getParent()->getDataLayout();
  auto &TLI = *getTLI<PPCTargetLowering>();

  // Loop over each arg, set flags and split to single value types
  SmallVector<ArgInfo, 8> SplitArgs;
  unsigned I = 0;
  for (const auto &Arg : F.args()) {
    if (DL.getTypeStoreSize(Arg.getType()).isZero())
      continue;

    ArgInfo OrigArg{VRegs[I], Arg, I};
    setArgFlags(OrigArg, I + AttributeList::FirstArgIndex, DL, F);
    splitToValueTypes(OrigArg, SplitArgs, DL, F.getCallingConv());
    ++I;
  }

  CCAssignFn *AssignFn =
      TLI.ccAssignFnForCall(F.getCallingConv(), false, F.isVarArg());
  IncomingValueAssigner ArgAssigner(AssignFn);
  FormalArgHandler ArgHandler(MIRBuilder, MRI);
  return determineAndHandleAssignments(ArgHandler, ArgAssigner, SplitArgs,
                                       MIRBuilder, F.getCallingConv(),
                                       F.isVarArg());
}

void PPCIncomingValueHandler::assignValueToReg(Register ValVReg,
                                               Register PhysReg,
                                               CCValAssign VA) {
  markPhysRegUsed(PhysReg);
  IncomingValueHandler::assignValueToReg(ValVReg, PhysReg, VA);
}

void PPCIncomingValueHandler::assignValueToAddress(Register ValVReg,
                                                   Register Addr, LLT MemTy,
                                                   MachinePointerInfo &MPO,
                                                   CCValAssign &VA) {
  // define a lambda expression to load value
  auto BuildLoad = [](MachineIRBuilder &MIRBuilder, MachinePointerInfo &MPO,
                      LLT MemTy, const DstOp &Res, Register Addr) {
    MachineFunction &MF = MIRBuilder.getMF();
    auto *MMO = MF.getMachineMemOperand(MPO, MachineMemOperand::MOLoad, MemTy,
                                        inferAlignFromPtrInfo(MF, MPO));
    return MIRBuilder.buildLoad(Res, Addr, *MMO);
  };

  BuildLoad(MIRBuilder, MPO, MemTy, ValVReg, Addr);
}

Register PPCIncomingValueHandler::getStackAddress(uint64_t Size, int64_t Offset,
                                                  MachinePointerInfo &MPO,
                                                  ISD::ArgFlagsTy Flags) {
  auto &MFI = MIRBuilder.getMF().getFrameInfo();
  const bool IsImmutable = !Flags.isByVal();
  int FI = MFI.CreateFixedObject(Size, Offset, IsImmutable);
  MPO = MachinePointerInfo::getFixedStack(MIRBuilder.getMF(), FI);

  // Build Frame Index based on whether the machine is 32-bit or 64-bit
  llvm::LLT FramePtr = LLT::pointer(
      0, MIRBuilder.getMF().getDataLayout().getPointerSizeInBits());
  MachineInstrBuilder AddrReg = MIRBuilder.buildFrameIndex(FramePtr, FI);
  StackUsed = std::max(StackUsed, Size + Offset);
  return AddrReg.getReg(0);
}

void FormalArgHandler::markPhysRegUsed(unsigned PhysReg) {
  MIRBuilder.getMRI()->addLiveIn(PhysReg);
  MIRBuilder.getMBB().addLiveIn(PhysReg);
}