xref: /llvm-project-15.0.7/llvm/lib/Target/VE/VEISelLowering.cpp (revision bb33f925)

//===-- VEISelLowering.cpp - VE DAG Lowering Implementation ---------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements the interfaces that VE uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//

#include "VEISelLowering.h"
#include "MCTargetDesc/VEMCExpr.h"
#include "VEMachineFunctionInfo.h"
#include "VERegisterInfo.h"
#include "VETargetMachine.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
using namespace llvm;

#define DEBUG_TYPE "ve-lower"

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

#include "VEGenCallingConv.inc"

bool VETargetLowering::CanLowerReturn(
    CallingConv::ID CallConv, MachineFunction &MF, bool IsVarArg,
    const SmallVectorImpl<ISD::OutputArg> &Outs, LLVMContext &Context) const {
  CCAssignFn *RetCC = RetCC_VE;
  SmallVector<CCValAssign, 16> RVLocs;
  CCState CCInfo(CallConv, IsVarArg, MF, RVLocs, Context);
  return CCInfo.CheckReturn(Outs, RetCC);
}

SDValue
VETargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
                              bool IsVarArg,
                              const SmallVectorImpl<ISD::OutputArg> &Outs,
                              const SmallVectorImpl<SDValue> &OutVals,
                              const SDLoc &DL, SelectionDAG &DAG) const {
  // CCValAssign - represent the assignment of the return value to locations.
  SmallVector<CCValAssign, 16> RVLocs;

  // CCState - Info about the registers and stack slot.
  CCState CCInfo(CallConv, IsVarArg, DAG.getMachineFunction(), RVLocs,
                 *DAG.getContext());

  // Analyze return values.
  CCInfo.AnalyzeReturn(Outs, RetCC_VE);

  SDValue Flag;
  SmallVector<SDValue, 4> RetOps(1, Chain);

  // Copy the result values into the output registers.
  for (unsigned i = 0; i != RVLocs.size(); ++i) {
    CCValAssign &VA = RVLocs[i];
    assert(VA.isRegLoc() && "Can only return in registers!");
    SDValue OutVal = OutVals[i];

    // Integer return values must be sign or zero extended by the callee.
    switch (VA.getLocInfo()) {
    case CCValAssign::Full:
      break;
    case CCValAssign::SExt:
      OutVal = DAG.getNode(ISD::SIGN_EXTEND, DL, VA.getLocVT(), OutVal);
      break;
    case CCValAssign::ZExt:
      OutVal = DAG.getNode(ISD::ZERO_EXTEND, DL, VA.getLocVT(), OutVal);
      break;
    case CCValAssign::AExt:
      OutVal = DAG.getNode(ISD::ANY_EXTEND, DL, VA.getLocVT(), OutVal);
      break;
    case CCValAssign::BCvt: {
      // Convert a float return value to i64 with padding.
      //     63     31   0
      //    +------+------+
      //    | float|   0  |
      //    +------+------+
      assert(VA.getLocVT() == MVT::i64);
      assert(VA.getValVT() == MVT::f32);
      SDValue Undef = SDValue(
          DAG.getMachineNode(TargetOpcode::IMPLICIT_DEF, DL, MVT::i64), 0);
      SDValue Sub_f32 = DAG.getTargetConstant(VE::sub_f32, DL, MVT::i32);
      OutVal = SDValue(DAG.getMachineNode(TargetOpcode::INSERT_SUBREG, DL,
                                          MVT::i64, Undef, OutVal, Sub_f32),
                       0);
      break;
    }
    default:
      llvm_unreachable("Unknown loc info!");
    }

    assert(!VA.needsCustom() && "Unexpected custom lowering");

    Chain = DAG.getCopyToReg(Chain, DL, VA.getLocReg(), OutVal, Flag);

    // Guarantee that all emitted copies are stuck together with flags.
    Flag = Chain.getValue(1);
    RetOps.push_back(DAG.getRegister(VA.getLocReg(), VA.getLocVT()));
  }

  RetOps[0] = Chain; // Update chain.

  // Add the flag if we have it.
  if (Flag.getNode())
    RetOps.push_back(Flag);

  return DAG.getNode(VEISD::RET_FLAG, DL, MVT::Other, RetOps);
}

SDValue VETargetLowering::LowerFormalArguments(
    SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
    const SmallVectorImpl<ISD::InputArg> &Ins, const SDLoc &DL,
    SelectionDAG &DAG, SmallVectorImpl<SDValue> &InVals) const {
  MachineFunction &MF = DAG.getMachineFunction();

  // Get the base offset of the incoming arguments stack space.
  unsigned ArgsBaseOffset = 176;
  // Get the size of the preserved arguments area
  unsigned ArgsPreserved = 64;

  // Analyze arguments according to CC_VE.
  SmallVector<CCValAssign, 16> ArgLocs;
  CCState CCInfo(CallConv, IsVarArg, DAG.getMachineFunction(), ArgLocs,
                 *DAG.getContext());
  // Allocate the preserved area first.
  CCInfo.AllocateStack(ArgsPreserved, Align(8));
  // We already allocated the preserved area, so the stack offset computed
  // by CC_VE would be correct now.
  CCInfo.AnalyzeFormalArguments(Ins, CC_VE);

  for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
    CCValAssign &VA = ArgLocs[i];
    if (VA.isRegLoc()) {
      // This argument is passed in a register.
      // All integer register arguments are promoted by the caller to i64.

      // Create a virtual register for the promoted live-in value.
      unsigned VReg =
          MF.addLiveIn(VA.getLocReg(), getRegClassFor(VA.getLocVT()));
      SDValue Arg = DAG.getCopyFromReg(Chain, DL, VReg, VA.getLocVT());

      // Get the high bits for i32 struct elements.
      if (VA.getValVT() == MVT::i32 && VA.needsCustom())
        Arg = DAG.getNode(ISD::SRL, DL, VA.getLocVT(), Arg,
                          DAG.getConstant(32, DL, MVT::i32));

      // The caller promoted the argument, so insert an Assert?ext SDNode so we
      // won't promote the value again in this function.
      switch (VA.getLocInfo()) {
      case CCValAssign::SExt:
        Arg = DAG.getNode(ISD::AssertSext, DL, VA.getLocVT(), Arg,
                          DAG.getValueType(VA.getValVT()));
        break;
      case CCValAssign::ZExt:
        Arg = DAG.getNode(ISD::AssertZext, DL, VA.getLocVT(), Arg,
                          DAG.getValueType(VA.getValVT()));
        break;
      case CCValAssign::BCvt: {
        // Extract a float argument from i64 with padding.
        //     63     31   0
        //    +------+------+
        //    | float|   0  |
        //    +------+------+
        assert(VA.getLocVT() == MVT::i64);
        assert(VA.getValVT() == MVT::f32);
        SDValue Sub_f32 = DAG.getTargetConstant(VE::sub_f32, DL, MVT::i32);
        Arg = SDValue(DAG.getMachineNode(TargetOpcode::EXTRACT_SUBREG, DL,
                                         MVT::f32, Arg, Sub_f32),
                      0);
        break;
      }
      default:
        break;
      }

      // Truncate the register down to the argument type.
      if (VA.isExtInLoc())
        Arg = DAG.getNode(ISD::TRUNCATE, DL, VA.getValVT(), Arg);

      InVals.push_back(Arg);
      continue;
    }

    // The registers are exhausted. This argument was passed on the stack.
    assert(VA.isMemLoc());
    // The CC_VE_Full/Half functions compute stack offsets relative to the
    // beginning of the arguments area at %fp+176.
    unsigned Offset = VA.getLocMemOffset() + ArgsBaseOffset;
    unsigned ValSize = VA.getValVT().getSizeInBits() / 8;

    // Adjust offset for a float argument by adding 4 since the argument is
    // stored in 8 bytes buffer with offset like below.  LLVM generates
    // 4 bytes load instruction, so need to adjust offset here.  This
    // adjustment is required in only LowerFormalArguments.  In LowerCall,
    // a float argument is converted to i64 first, and stored as 8 bytes
    // data, which is required by ABI, so no need for adjustment.
    //    0      4
    //    +------+------+
    //    | empty| float|
    //    +------+------+
    if (VA.getValVT() == MVT::f32)
      Offset += 4;

    int FI = MF.getFrameInfo().CreateFixedObject(ValSize, Offset, true);
    InVals.push_back(
        DAG.getLoad(VA.getValVT(), DL, Chain,
                    DAG.getFrameIndex(FI, getPointerTy(MF.getDataLayout())),
                    MachinePointerInfo::getFixedStack(MF, FI)));
  }

  if (!IsVarArg)
    return Chain;

  // This function takes variable arguments, some of which may have been passed
  // in registers %s0-%s8.
  //
  // The va_start intrinsic needs to know the offset to the first variable
  // argument.
  // TODO: need to calculate offset correctly once we support f128.
  unsigned ArgOffset = ArgLocs.size() * 8;
  VEMachineFunctionInfo *FuncInfo = MF.getInfo<VEMachineFunctionInfo>();
  // Skip the 176 bytes of register save area.
  FuncInfo->setVarArgsFrameOffset(ArgOffset + ArgsBaseOffset);

  return Chain;
}

// FIXME? Maybe this could be a TableGen attribute on some registers and
// this table could be generated automatically from RegInfo.
Register VETargetLowering::getRegisterByName(const char *RegName, LLT VT,
                                             const MachineFunction &MF) const {
  Register Reg = StringSwitch<Register>(RegName)
                     .Case("sp", VE::SX11)    // Stack pointer
                     .Case("fp", VE::SX9)     // Frame pointer
                     .Case("sl", VE::SX8)     // Stack limit
                     .Case("lr", VE::SX10)    // Link register
                     .Case("tp", VE::SX14)    // Thread pointer
                     .Case("outer", VE::SX12) // Outer regiser
                     .Case("info", VE::SX17)  // Info area register
                     .Case("got", VE::SX15)   // Global offset table register
                     .Case("plt", VE::SX16) // Procedure linkage table register
                     .Default(0);

  if (Reg)
    return Reg;

  report_fatal_error("Invalid register name global variable");
}

//===----------------------------------------------------------------------===//
// TargetLowering Implementation
//===----------------------------------------------------------------------===//

SDValue VETargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
                                    SmallVectorImpl<SDValue> &InVals) const {
  SelectionDAG &DAG = CLI.DAG;
  SDLoc DL = CLI.DL;
  SDValue Chain = CLI.Chain;
  auto PtrVT = getPointerTy(DAG.getDataLayout());

  // VE target does not yet support tail call optimization.
  CLI.IsTailCall = false;

  // Get the base offset of the outgoing arguments stack space.
  unsigned ArgsBaseOffset = 176;
  // Get the size of the preserved arguments area
  unsigned ArgsPreserved = 8 * 8u;

  // Analyze operands of the call, assigning locations to each operand.
  SmallVector<CCValAssign, 16> ArgLocs;
  CCState CCInfo(CLI.CallConv, CLI.IsVarArg, DAG.getMachineFunction(), ArgLocs,
                 *DAG.getContext());
  // Allocate the preserved area first.
  CCInfo.AllocateStack(ArgsPreserved, Align(8));
  // We already allocated the preserved area, so the stack offset computed
  // by CC_VE would be correct now.
  CCInfo.AnalyzeCallOperands(CLI.Outs, CC_VE);

  // VE requires to use both register and stack for varargs or no-prototyped
  // functions.
  bool UseBoth = CLI.IsVarArg;

  // Analyze operands again if it is required to store BOTH.
  SmallVector<CCValAssign, 16> ArgLocs2;
  CCState CCInfo2(CLI.CallConv, CLI.IsVarArg, DAG.getMachineFunction(),
                  ArgLocs2, *DAG.getContext());
  if (UseBoth)
    CCInfo2.AnalyzeCallOperands(CLI.Outs, CC_VE2);

  // Get the size of the outgoing arguments stack space requirement.
  unsigned ArgsSize = CCInfo.getNextStackOffset();

  // Keep stack frames 16-byte aligned.
  ArgsSize = alignTo(ArgsSize, 16);

  // Adjust the stack pointer to make room for the arguments.
  // FIXME: Use hasReservedCallFrame to avoid %sp adjustments around all calls
  // with more than 6 arguments.
  Chain = DAG.getCALLSEQ_START(Chain, ArgsSize, 0, DL);

  // Collect the set of registers to pass to the function and their values.
  // This will be emitted as a sequence of CopyToReg nodes glued to the call
  // instruction.
  SmallVector<std::pair<unsigned, SDValue>, 8> RegsToPass;

  // Collect chains from all the memory opeations that copy arguments to the
  // stack. They must follow the stack pointer adjustment above and precede the
  // call instruction itself.
  SmallVector<SDValue, 8> MemOpChains;

  // VE needs to get address of callee function in a register
  // So, prepare to copy it to SX12 here.

  // If the callee is a GlobalAddress node (quite common, every direct call is)
  // turn it into a TargetGlobalAddress node so that legalize doesn't hack it.
  // Likewise ExternalSymbol -> TargetExternalSymbol.
  SDValue Callee = CLI.Callee;

  bool IsPICCall = isPositionIndependent();

  // PC-relative references to external symbols should go through $stub.
  // If so, we need to prepare GlobalBaseReg first.
  const TargetMachine &TM = DAG.getTarget();
  const Module *Mod = DAG.getMachineFunction().getFunction().getParent();
  const GlobalValue *GV = nullptr;
  auto *CalleeG = dyn_cast<GlobalAddressSDNode>(Callee);
  if (CalleeG)
    GV = CalleeG->getGlobal();
  bool Local = TM.shouldAssumeDSOLocal(*Mod, GV);
  bool UsePlt = !Local;
  MachineFunction &MF = DAG.getMachineFunction();

  // Turn GlobalAddress/ExternalSymbol node into a value node
  // containing the address of them here.
  if (CalleeG) {
    if (IsPICCall) {
      if (UsePlt)
        Subtarget->getInstrInfo()->getGlobalBaseReg(&MF);
      Callee = DAG.getTargetGlobalAddress(GV, DL, PtrVT, 0, 0);
      Callee = DAG.getNode(VEISD::GETFUNPLT, DL, PtrVT, Callee);
    } else {
      Callee =
          makeHiLoPair(Callee, VEMCExpr::VK_VE_HI32, VEMCExpr::VK_VE_LO32, DAG);
    }
  } else if (ExternalSymbolSDNode *E = dyn_cast<ExternalSymbolSDNode>(Callee)) {
    if (IsPICCall) {
      if (UsePlt)
        Subtarget->getInstrInfo()->getGlobalBaseReg(&MF);
      Callee = DAG.getTargetExternalSymbol(E->getSymbol(), PtrVT, 0);
      Callee = DAG.getNode(VEISD::GETFUNPLT, DL, PtrVT, Callee);
    } else {
      Callee =
          makeHiLoPair(Callee, VEMCExpr::VK_VE_HI32, VEMCExpr::VK_VE_LO32, DAG);
    }
  }

  RegsToPass.push_back(std::make_pair(VE::SX12, Callee));

  for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
    CCValAssign &VA = ArgLocs[i];
    SDValue Arg = CLI.OutVals[i];

    // Promote the value if needed.
    switch (VA.getLocInfo()) {
    default:
      llvm_unreachable("Unknown location info!");
    case CCValAssign::Full:
      break;
    case CCValAssign::SExt:
      Arg = DAG.getNode(ISD::SIGN_EXTEND, DL, VA.getLocVT(), Arg);
      break;
    case CCValAssign::ZExt:
      Arg = DAG.getNode(ISD::ZERO_EXTEND, DL, VA.getLocVT(), Arg);
      break;
    case CCValAssign::AExt:
      Arg = DAG.getNode(ISD::ANY_EXTEND, DL, VA.getLocVT(), Arg);
      break;
    case CCValAssign::BCvt: {
      // Convert a float argument to i64 with padding.
      //     63     31   0
      //    +------+------+
      //    | float|   0  |
      //    +------+------+
      assert(VA.getLocVT() == MVT::i64);
      assert(VA.getValVT() == MVT::f32);
      SDValue Undef = SDValue(
          DAG.getMachineNode(TargetOpcode::IMPLICIT_DEF, DL, MVT::i64), 0);
      SDValue Sub_f32 = DAG.getTargetConstant(VE::sub_f32, DL, MVT::i32);
      Arg = SDValue(DAG.getMachineNode(TargetOpcode::INSERT_SUBREG, DL,
                                       MVT::i64, Undef, Arg, Sub_f32),
                    0);
      break;
    }
    }

    if (VA.isRegLoc()) {
      RegsToPass.push_back(std::make_pair(VA.getLocReg(), Arg));
      if (!UseBoth)
        continue;
      VA = ArgLocs2[i];
    }

    assert(VA.isMemLoc());

    // Create a store off the stack pointer for this argument.
    SDValue StackPtr = DAG.getRegister(VE::SX11, PtrVT);
    // The argument area starts at %fp+176 in the callee frame,
    // %sp+176 in ours.
    SDValue PtrOff =
        DAG.getIntPtrConstant(VA.getLocMemOffset() + ArgsBaseOffset, DL);
    PtrOff = DAG.getNode(ISD::ADD, DL, PtrVT, StackPtr, PtrOff);
    MemOpChains.push_back(
        DAG.getStore(Chain, DL, Arg, PtrOff, MachinePointerInfo()));
  }

  // Emit all stores, make sure they occur before the call.
  if (!MemOpChains.empty())
    Chain = DAG.getNode(ISD::TokenFactor, DL, MVT::Other, MemOpChains);

  // Build a sequence of CopyToReg nodes glued together with token chain and
  // glue operands which copy the outgoing args into registers. The InGlue is
  // necessary since all emitted instructions must be stuck together in order
  // to pass the live physical registers.
  SDValue InGlue;
  for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i) {
    Chain = DAG.getCopyToReg(Chain, DL, RegsToPass[i].first,
                             RegsToPass[i].second, InGlue);
    InGlue = Chain.getValue(1);
  }

  // Build the operands for the call instruction itself.
  SmallVector<SDValue, 8> Ops;
  Ops.push_back(Chain);
  for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i)
    Ops.push_back(DAG.getRegister(RegsToPass[i].first,
                                  RegsToPass[i].second.getValueType()));

  // Add a register mask operand representing the call-preserved registers.
  const VERegisterInfo *TRI = Subtarget->getRegisterInfo();
  const uint32_t *Mask =
      TRI->getCallPreservedMask(DAG.getMachineFunction(), CLI.CallConv);
  assert(Mask && "Missing call preserved mask for calling convention");
  Ops.push_back(DAG.getRegisterMask(Mask));

  // Make sure the CopyToReg nodes are glued to the call instruction which
  // consumes the registers.
  if (InGlue.getNode())
    Ops.push_back(InGlue);

  // Now the call itself.
  SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
  Chain = DAG.getNode(VEISD::CALL, DL, NodeTys, Ops);
  InGlue = Chain.getValue(1);

  // Revert the stack pointer immediately after the call.
  Chain = DAG.getCALLSEQ_END(Chain, DAG.getIntPtrConstant(ArgsSize, DL, true),
                             DAG.getIntPtrConstant(0, DL, true), InGlue, DL);
  InGlue = Chain.getValue(1);

  // Now extract the return values. This is more or less the same as
  // LowerFormalArguments.

  // Assign locations to each value returned by this call.
  SmallVector<CCValAssign, 16> RVLocs;
  CCState RVInfo(CLI.CallConv, CLI.IsVarArg, DAG.getMachineFunction(), RVLocs,
                 *DAG.getContext());

  // Set inreg flag manually for codegen generated library calls that
  // return float.
  if (CLI.Ins.size() == 1 && CLI.Ins[0].VT == MVT::f32 && !CLI.CB)
    CLI.Ins[0].Flags.setInReg();

  RVInfo.AnalyzeCallResult(CLI.Ins, RetCC_VE);

  // Copy all of the result registers out of their specified physreg.
  for (unsigned i = 0; i != RVLocs.size(); ++i) {
    CCValAssign &VA = RVLocs[i];
    unsigned Reg = VA.getLocReg();

    // When returning 'inreg {i32, i32 }', two consecutive i32 arguments can
    // reside in the same register in the high and low bits. Reuse the
    // CopyFromReg previous node to avoid duplicate copies.
    SDValue RV;
    if (RegisterSDNode *SrcReg = dyn_cast<RegisterSDNode>(Chain.getOperand(1)))
      if (SrcReg->getReg() == Reg && Chain->getOpcode() == ISD::CopyFromReg)
        RV = Chain.getValue(0);

    // But usually we'll create a new CopyFromReg for a different register.
    if (!RV.getNode()) {
      RV = DAG.getCopyFromReg(Chain, DL, Reg, RVLocs[i].getLocVT(), InGlue);
      Chain = RV.getValue(1);
      InGlue = Chain.getValue(2);
    }

    // Get the high bits for i32 struct elements.
    if (VA.getValVT() == MVT::i32 && VA.needsCustom())
      RV = DAG.getNode(ISD::SRL, DL, VA.getLocVT(), RV,
                       DAG.getConstant(32, DL, MVT::i32));

    // The callee promoted the return value, so insert an Assert?ext SDNode so
    // we won't promote the value again in this function.
    switch (VA.getLocInfo()) {
    case CCValAssign::SExt:
      RV = DAG.getNode(ISD::AssertSext, DL, VA.getLocVT(), RV,
                       DAG.getValueType(VA.getValVT()));
      break;
    case CCValAssign::ZExt:
      RV = DAG.getNode(ISD::AssertZext, DL, VA.getLocVT(), RV,
                       DAG.getValueType(VA.getValVT()));
      break;
    case CCValAssign::BCvt: {
      // Extract a float return value from i64 with padding.
      //     63     31   0
      //    +------+------+
      //    | float|   0  |
      //    +------+------+
      assert(VA.getLocVT() == MVT::i64);
      assert(VA.getValVT() == MVT::f32);
      SDValue Sub_f32 = DAG.getTargetConstant(VE::sub_f32, DL, MVT::i32);
      RV = SDValue(DAG.getMachineNode(TargetOpcode::EXTRACT_SUBREG, DL,
                                      MVT::f32, RV, Sub_f32),
                   0);
      break;
    }
    default:
      break;
    }

    // Truncate the register down to the return value type.
    if (VA.isExtInLoc())
      RV = DAG.getNode(ISD::TRUNCATE, DL, VA.getValVT(), RV);

    InVals.push_back(RV);
  }

  return Chain;
}

/// isFPImmLegal - Returns true if the target can instruction select the
/// specified FP immediate natively. If false, the legalizer will
/// materialize the FP immediate as a load from a constant pool.
bool VETargetLowering::isFPImmLegal(const APFloat &Imm, EVT VT,
                                    bool ForCodeSize) const {
  return VT == MVT::f32 || VT == MVT::f64;
}

/// Determine if the target supports unaligned memory accesses.
///
/// This function returns true if the target allows unaligned memory accesses
/// of the specified type in the given address space. If true, it also returns
/// whether the unaligned memory access is "fast" in the last argument by
/// reference. This is used, for example, in situations where an array
/// copy/move/set is converted to a sequence of store operations. Its use
/// helps to ensure that such replacements don't generate code that causes an
/// alignment error (trap) on the target machine.
bool VETargetLowering::allowsMisalignedMemoryAccesses(EVT VT,
                                                      unsigned AddrSpace,
                                                      unsigned Align,
                                                      MachineMemOperand::Flags,
                                                      bool *Fast) const {
  if (Fast) {
    // It's fast anytime on VE
    *Fast = true;
  }
  return true;
}

bool VETargetLowering::hasAndNot(SDValue Y) const {
  EVT VT = Y.getValueType();

  // VE doesn't have vector and not instruction.
  if (VT.isVector())
    return false;

  // VE allows different immediate values for X and Y where ~X & Y.
  // Only simm7 works for X, and only mimm works for Y on VE.  However, this
  // function is used to check whether an immediate value is OK for and-not
  // instruction as both X and Y.  Generating additional instruction to
  // retrieve an immediate value is no good since the purpose of this
  // function is to convert a series of 3 instructions to another series of
  // 3 instructions with better parallelism.  Therefore, we return false
  // for all immediate values now.
  // FIXME: Change hasAndNot function to have two operands to make it work
  //        correctly with Aurora VE.
  if (isa<ConstantSDNode>(Y))
    return false;

  // It's ok for generic registers.
  return true;
}

VETargetLowering::VETargetLowering(const TargetMachine &TM,
                                   const VESubtarget &STI)
    : TargetLowering(TM), Subtarget(&STI) {
  // Instructions which use registers as conditionals examine all the
  // bits (as does the pseudo SELECT_CC expansion). I don't think it
  // matters much whether it's ZeroOrOneBooleanContent, or
  // ZeroOrNegativeOneBooleanContent, so, arbitrarily choose the
  // former.
  setBooleanContents(ZeroOrOneBooleanContent);
  setBooleanVectorContents(ZeroOrOneBooleanContent);

  // Set up the register classes.
  addRegisterClass(MVT::i32, &VE::I32RegClass);
  addRegisterClass(MVT::i64, &VE::I64RegClass);
  addRegisterClass(MVT::f32, &VE::F32RegClass);
  addRegisterClass(MVT::f64, &VE::I64RegClass);

  /// Load & Store {
  for (MVT FPVT : MVT::fp_valuetypes()) {
    for (MVT OtherFPVT : MVT::fp_valuetypes()) {
      // Turn FP extload into load/fpextend
      setLoadExtAction(ISD::EXTLOAD, FPVT, OtherFPVT, Expand);

      // Turn FP truncstore into trunc + store.
      setTruncStoreAction(FPVT, OtherFPVT, Expand);
    }
  }

  // VE doesn't have i1 sign extending load
  for (MVT VT : MVT::integer_valuetypes()) {
    setLoadExtAction(ISD::SEXTLOAD, VT, MVT::i1, Promote);
    setLoadExtAction(ISD::ZEXTLOAD, VT, MVT::i1, Promote);
    setLoadExtAction(ISD::EXTLOAD, VT, MVT::i1, Promote);
    setTruncStoreAction(VT, MVT::i1, Expand);
  }
  /// } Load & Store

  // Custom legalize address nodes into LO/HI parts.
  MVT PtrVT = MVT::getIntegerVT(TM.getPointerSizeInBits(0));
  setOperationAction(ISD::BlockAddress, PtrVT, Custom);
  setOperationAction(ISD::GlobalAddress, PtrVT, Custom);
  setOperationAction(ISD::GlobalTLSAddress, PtrVT, Custom);

  /// VAARG handling {
  setOperationAction(ISD::VASTART, MVT::Other, Custom);
  // VAARG needs to be lowered to access with 8 bytes alignment.
  setOperationAction(ISD::VAARG, MVT::Other, Custom);
  // Use the default implementation.
  setOperationAction(ISD::VACOPY, MVT::Other, Expand);
  setOperationAction(ISD::VAEND, MVT::Other, Expand);
  /// } VAARG handling

  /// Stack {
  setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i32, Custom);
  setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i64, Custom);
  /// } Stack

  /// Int Ops {
  for (MVT IntVT : {MVT::i32, MVT::i64}) {
    // VE has no REM or DIVREM operations.
    setOperationAction(ISD::UREM, IntVT, Expand);
    setOperationAction(ISD::SREM, IntVT, Expand);
    setOperationAction(ISD::SDIVREM, IntVT, Expand);
    setOperationAction(ISD::UDIVREM, IntVT, Expand);

    setOperationAction(ISD::CTTZ, IntVT, Expand);
    setOperationAction(ISD::ROTL, IntVT, Expand);
    setOperationAction(ISD::ROTR, IntVT, Expand);

    // Use isel patterns for i32 and i64
    setOperationAction(ISD::BSWAP, IntVT, Legal);
    setOperationAction(ISD::CTLZ, IntVT, Legal);
    setOperationAction(ISD::CTPOP, IntVT, Legal);

    // Use isel patterns for i64, Promote i32
    LegalizeAction Act = (IntVT == MVT::i32) ? Promote : Legal;
    setOperationAction(ISD::BITREVERSE, IntVT, Act);
  }
  /// } Int Ops

  /// Conversion {
  // VE doesn't have instructions for fp<->uint, so expand them by llvm
  setOperationAction(ISD::FP_TO_UINT, MVT::i32, Promote); // use i64
  setOperationAction(ISD::UINT_TO_FP, MVT::i32, Promote); // use i64
  setOperationAction(ISD::FP_TO_UINT, MVT::i64, Expand);
  setOperationAction(ISD::UINT_TO_FP, MVT::i64, Expand);

  // fp16 not supported
  for (MVT FPVT : MVT::fp_valuetypes()) {
    setOperationAction(ISD::FP16_TO_FP, FPVT, Expand);
    setOperationAction(ISD::FP_TO_FP16, FPVT, Expand);
  }
  /// } Conversion

  setStackPointerRegisterToSaveRestore(VE::SX11);

  // Set function alignment to 16 bytes
  setMinFunctionAlignment(Align(16));

  // VE stores all argument by 8 bytes alignment
  setMinStackArgumentAlignment(Align(8));

  computeRegisterProperties(Subtarget->getRegisterInfo());
}

const char *VETargetLowering::getTargetNodeName(unsigned Opcode) const {
#define TARGET_NODE_CASE(NAME)                                                 \
  case VEISD::NAME:                                                            \
    return "VEISD::" #NAME;
  switch ((VEISD::NodeType)Opcode) {
  case VEISD::FIRST_NUMBER:
    break;
    TARGET_NODE_CASE(Lo)
    TARGET_NODE_CASE(Hi)
    TARGET_NODE_CASE(GETFUNPLT)
    TARGET_NODE_CASE(GETSTACKTOP)
    TARGET_NODE_CASE(GETTLSADDR)
    TARGET_NODE_CASE(CALL)
    TARGET_NODE_CASE(RET_FLAG)
    TARGET_NODE_CASE(GLOBAL_BASE_REG)
  }
#undef TARGET_NODE_CASE
  return nullptr;
}

EVT VETargetLowering::getSetCCResultType(const DataLayout &, LLVMContext &,
                                         EVT VT) const {
  return MVT::i32;
}

// Convert to a target node and set target flags.
SDValue VETargetLowering::withTargetFlags(SDValue Op, unsigned TF,
                                          SelectionDAG &DAG) const {
  if (const GlobalAddressSDNode *GA = dyn_cast<GlobalAddressSDNode>(Op))
    return DAG.getTargetGlobalAddress(GA->getGlobal(), SDLoc(GA),
                                      GA->getValueType(0), GA->getOffset(), TF);

  if (const BlockAddressSDNode *BA = dyn_cast<BlockAddressSDNode>(Op))
    return DAG.getTargetBlockAddress(BA->getBlockAddress(), Op.getValueType(),
                                     0, TF);

  if (const ExternalSymbolSDNode *ES = dyn_cast<ExternalSymbolSDNode>(Op))
    return DAG.getTargetExternalSymbol(ES->getSymbol(), ES->getValueType(0),
                                       TF);

  llvm_unreachable("Unhandled address SDNode");
}

// Split Op into high and low parts according to HiTF and LoTF.
// Return an ADD node combining the parts.
SDValue VETargetLowering::makeHiLoPair(SDValue Op, unsigned HiTF, unsigned LoTF,
                                       SelectionDAG &DAG) const {
  SDLoc DL(Op);
  EVT VT = Op.getValueType();
  SDValue Hi = DAG.getNode(VEISD::Hi, DL, VT, withTargetFlags(Op, HiTF, DAG));
  SDValue Lo = DAG.getNode(VEISD::Lo, DL, VT, withTargetFlags(Op, LoTF, DAG));
  return DAG.getNode(ISD::ADD, DL, VT, Hi, Lo);
}

// Build SDNodes for producing an address from a GlobalAddress, ConstantPool,
// or ExternalSymbol SDNode.
SDValue VETargetLowering::makeAddress(SDValue Op, SelectionDAG &DAG) const {
  SDLoc DL(Op);
  EVT PtrVT = Op.getValueType();

  // Handle PIC mode first. VE needs a got load for every variable!
  if (isPositionIndependent()) {
    // GLOBAL_BASE_REG codegen'ed with call. Inform MFI that this
    // function has calls.
    MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
    MFI.setHasCalls(true);
    auto GlobalN = dyn_cast<GlobalAddressSDNode>(Op);

    if (isa<ConstantPoolSDNode>(Op) ||
        (GlobalN && GlobalN->getGlobal()->hasLocalLinkage())) {
      // Create following instructions for local linkage PIC code.
      //     lea %s35, %gotoff_lo(.LCPI0_0)
      //     and %s35, %s35, (32)0
      //     lea.sl %s35, %gotoff_hi(.LCPI0_0)(%s35)
      //     adds.l %s35, %s15, %s35                  ; %s15 is GOT
      // FIXME: use lea.sl %s35, %gotoff_hi(.LCPI0_0)(%s35, %s15)
      SDValue HiLo = makeHiLoPair(Op, VEMCExpr::VK_VE_GOTOFF_HI32,
                                  VEMCExpr::VK_VE_GOTOFF_LO32, DAG);
      SDValue GlobalBase = DAG.getNode(VEISD::GLOBAL_BASE_REG, DL, PtrVT);
      return DAG.getNode(ISD::ADD, DL, PtrVT, GlobalBase, HiLo);
    }
    // Create following instructions for not local linkage PIC code.
    //     lea %s35, %got_lo(.LCPI0_0)
    //     and %s35, %s35, (32)0
    //     lea.sl %s35, %got_hi(.LCPI0_0)(%s35)
    //     adds.l %s35, %s15, %s35                  ; %s15 is GOT
    //     ld     %s35, (,%s35)
    // FIXME: use lea.sl %s35, %gotoff_hi(.LCPI0_0)(%s35, %s15)
    SDValue HiLo = makeHiLoPair(Op, VEMCExpr::VK_VE_GOT_HI32,
                                VEMCExpr::VK_VE_GOT_LO32, DAG);
    SDValue GlobalBase = DAG.getNode(VEISD::GLOBAL_BASE_REG, DL, PtrVT);
    SDValue AbsAddr = DAG.getNode(ISD::ADD, DL, PtrVT, GlobalBase, HiLo);
    return DAG.getLoad(PtrVT, DL, DAG.getEntryNode(), AbsAddr,
                       MachinePointerInfo::getGOT(DAG.getMachineFunction()));
  }

  // This is one of the absolute code models.
  switch (getTargetMachine().getCodeModel()) {
  default:
    llvm_unreachable("Unsupported absolute code model");
  case CodeModel::Small:
  case CodeModel::Medium:
  case CodeModel::Large:
    // abs64.
    return makeHiLoPair(Op, VEMCExpr::VK_VE_HI32, VEMCExpr::VK_VE_LO32, DAG);
  }
}

/// Custom Lower {

SDValue VETargetLowering::LowerGlobalAddress(SDValue Op,
                                             SelectionDAG &DAG) const {
  return makeAddress(Op, DAG);
}

SDValue VETargetLowering::LowerBlockAddress(SDValue Op,
                                            SelectionDAG &DAG) const {
  return makeAddress(Op, DAG);
}

SDValue
VETargetLowering::LowerToTLSGeneralDynamicModel(SDValue Op,
                                                SelectionDAG &DAG) const {
  SDLoc dl(Op);

  // Generate the following code:
  //   t1: ch,glue = callseq_start t0, 0, 0
  //   t2: i64,ch,glue = VEISD::GETTLSADDR t1, label, t1:1
  //   t3: ch,glue = callseq_end t2, 0, 0, t2:2
  //   t4: i64,ch,glue = CopyFromReg t3, Register:i64 $sx0, t3:1
  SDValue Label = withTargetFlags(Op, 0, DAG);
  EVT PtrVT = Op.getValueType();

  // Lowering the machine isd will make sure everything is in the right
  // location.
  SDValue Chain = DAG.getEntryNode();
  SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
  const uint32_t *Mask = Subtarget->getRegisterInfo()->getCallPreservedMask(
      DAG.getMachineFunction(), CallingConv::C);
  Chain = DAG.getCALLSEQ_START(Chain, 64, 0, dl);
  SDValue Args[] = {Chain, Label, DAG.getRegisterMask(Mask), Chain.getValue(1)};
  Chain = DAG.getNode(VEISD::GETTLSADDR, dl, NodeTys, Args);
  Chain = DAG.getCALLSEQ_END(Chain, DAG.getIntPtrConstant(64, dl, true),
                             DAG.getIntPtrConstant(0, dl, true),
                             Chain.getValue(1), dl);
  Chain = DAG.getCopyFromReg(Chain, dl, VE::SX0, PtrVT, Chain.getValue(1));

  // GETTLSADDR will be codegen'ed as call. Inform MFI that function has calls.
  MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
  MFI.setHasCalls(true);

  // Also generate code to prepare a GOT register if it is PIC.
  if (isPositionIndependent()) {
    MachineFunction &MF = DAG.getMachineFunction();
    Subtarget->getInstrInfo()->getGlobalBaseReg(&MF);
  }

  return Chain;
}

SDValue VETargetLowering::LowerGlobalTLSAddress(SDValue Op,
                                                SelectionDAG &DAG) const {
  // The current implementation of nld (2.26) doesn't allow local exec model
  // code described in VE-tls_v1.1.pdf (*1) as its input. Instead, we always
  // generate the general dynamic model code sequence.
  //
  // *1: https://www.nec.com/en/global/prod/hpc/aurora/document/VE-tls_v1.1.pdf
  return LowerToTLSGeneralDynamicModel(Op, DAG);
}

SDValue VETargetLowering::LowerVASTART(SDValue Op, SelectionDAG &DAG) const {
  MachineFunction &MF = DAG.getMachineFunction();
  VEMachineFunctionInfo *FuncInfo = MF.getInfo<VEMachineFunctionInfo>();
  auto PtrVT = getPointerTy(DAG.getDataLayout());

  // Need frame address to find the address of VarArgsFrameIndex.
  MF.getFrameInfo().setFrameAddressIsTaken(true);

  // vastart just stores the address of the VarArgsFrameIndex slot into the
  // memory location argument.
  SDLoc DL(Op);
  SDValue Offset =
      DAG.getNode(ISD::ADD, DL, PtrVT, DAG.getRegister(VE::SX9, PtrVT),
                  DAG.getIntPtrConstant(FuncInfo->getVarArgsFrameOffset(), DL));
  const Value *SV = cast<SrcValueSDNode>(Op.getOperand(2))->getValue();
  return DAG.getStore(Op.getOperand(0), DL, Offset, Op.getOperand(1),
                      MachinePointerInfo(SV));
}

SDValue VETargetLowering::LowerVAARG(SDValue Op, SelectionDAG &DAG) const {
  SDNode *Node = Op.getNode();
  EVT VT = Node->getValueType(0);
  SDValue InChain = Node->getOperand(0);
  SDValue VAListPtr = Node->getOperand(1);
  EVT PtrVT = VAListPtr.getValueType();
  const Value *SV = cast<SrcValueSDNode>(Node->getOperand(2))->getValue();
  SDLoc DL(Node);
  SDValue VAList =
      DAG.getLoad(PtrVT, DL, InChain, VAListPtr, MachinePointerInfo(SV));
  SDValue Chain = VAList.getValue(1);
  SDValue NextPtr;

  if (VT == MVT::f32) {
    // float --> need special handling like below.
    //    0      4
    //    +------+------+
    //    | empty| float|
    //    +------+------+
    // Increment the pointer, VAList, by 8 to the next vaarg.
    NextPtr =
        DAG.getNode(ISD::ADD, DL, PtrVT, VAList, DAG.getIntPtrConstant(8, DL));
    // Then, adjust VAList.
    unsigned InternalOffset = 4;
    VAList = DAG.getNode(ISD::ADD, DL, PtrVT, VAList,
                         DAG.getConstant(InternalOffset, DL, PtrVT));
  } else {
    // Increment the pointer, VAList, by 8 to the next vaarg.
    NextPtr =
        DAG.getNode(ISD::ADD, DL, PtrVT, VAList, DAG.getIntPtrConstant(8, DL));
  }

  // Store the incremented VAList to the legalized pointer.
  InChain = DAG.getStore(Chain, DL, NextPtr, VAListPtr, MachinePointerInfo(SV));

  // Load the actual argument out of the pointer VAList.
  // We can't count on greater alignment than the word size.
  return DAG.getLoad(VT, DL, InChain, VAList, MachinePointerInfo(),
                     std::min(PtrVT.getSizeInBits(), VT.getSizeInBits()) / 8);
}

SDValue VETargetLowering::lowerDYNAMIC_STACKALLOC(SDValue Op,
                                                  SelectionDAG &DAG) const {
  // Generate following code.
  //   (void)__llvm_grow_stack(size);
  //   ret = GETSTACKTOP;        // pseudo instruction
  SDLoc DL(Op);

  // Get the inputs.
  SDNode *Node = Op.getNode();
  SDValue Chain = Op.getOperand(0);
  SDValue Size = Op.getOperand(1);
  MaybeAlign Alignment(Op.getConstantOperandVal(2));
  EVT VT = Node->getValueType(0);

  // Chain the dynamic stack allocation so that it doesn't modify the stack
  // pointer when other instructions are using the stack.
  Chain = DAG.getCALLSEQ_START(Chain, 0, 0, DL);

  const TargetFrameLowering &TFI = *Subtarget->getFrameLowering();
  Align StackAlign = TFI.getStackAlign();
  bool NeedsAlign = Alignment.valueOrOne() > StackAlign;

  // Prepare arguments
  TargetLowering::ArgListTy Args;
  TargetLowering::ArgListEntry Entry;
  Entry.Node = Size;
  Entry.Ty = Entry.Node.getValueType().getTypeForEVT(*DAG.getContext());
  Args.push_back(Entry);
  if (NeedsAlign) {
    Entry.Node = DAG.getConstant(~(Alignment->value() - 1ULL), DL, VT);
    Entry.Ty = Entry.Node.getValueType().getTypeForEVT(*DAG.getContext());
    Args.push_back(Entry);
  }
  Type *RetTy = Type::getVoidTy(*DAG.getContext());

  EVT PtrVT = Op.getValueType();
  SDValue Callee;
  if (NeedsAlign) {
    Callee = DAG.getTargetExternalSymbol("__ve_grow_stack_align", PtrVT, 0);
  } else {
    Callee = DAG.getTargetExternalSymbol("__ve_grow_stack", PtrVT, 0);
  }

  TargetLowering::CallLoweringInfo CLI(DAG);
  CLI.setDebugLoc(DL)
      .setChain(Chain)
      .setCallee(CallingConv::PreserveAll, RetTy, Callee, std::move(Args))
      .setDiscardResult(true);
  std::pair<SDValue, SDValue> pair = LowerCallTo(CLI);
  Chain = pair.second;
  SDValue Result = DAG.getNode(VEISD::GETSTACKTOP, DL, VT, Chain);
  if (NeedsAlign) {
    Result = DAG.getNode(ISD::ADD, DL, VT, Result,
                         DAG.getConstant((Alignment->value() - 1ULL), DL, VT));
    Result = DAG.getNode(ISD::AND, DL, VT, Result,
                         DAG.getConstant(~(Alignment->value() - 1ULL), DL, VT));
  }
  //  Chain = Result.getValue(1);
  Chain = DAG.getCALLSEQ_END(Chain, DAG.getIntPtrConstant(0, DL, true),
                             DAG.getIntPtrConstant(0, DL, true), SDValue(), DL);

  SDValue Ops[2] = {Result, Chain};
  return DAG.getMergeValues(Ops, DL);
}

SDValue VETargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
  switch (Op.getOpcode()) {
  default:
    llvm_unreachable("Should not custom lower this!");
  case ISD::BlockAddress:
    return LowerBlockAddress(Op, DAG);
  case ISD::DYNAMIC_STACKALLOC:
    return lowerDYNAMIC_STACKALLOC(Op, DAG);
  case ISD::GlobalAddress:
    return LowerGlobalAddress(Op, DAG);
  case ISD::GlobalTLSAddress:
    return LowerGlobalTLSAddress(Op, DAG);
  case ISD::VASTART:
    return LowerVASTART(Op, DAG);
  case ISD::VAARG:
    return LowerVAARG(Op, DAG);
  }
}
/// } Custom Lower