ARMSelectionDAGInfo.cpp

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//===-- ARMSelectionDAGInfo.cpp - ARM SelectionDAG Info -------------------===//
//
//                     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 ARMSelectionDAGInfo class.
//
//===----------------------------------------------------------------------===//

#include "ARMTargetMachine.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/IR/DerivedTypes.h"
using namespace llvm;

#define DEBUG_TYPE "arm-selectiondag-info"

ARMSelectionDAGInfo::ARMSelectionDAGInfo(const DataLayout &DL)
    : TargetSelectionDAGInfo(&DL) {}

ARMSelectionDAGInfo::~ARMSelectionDAGInfo() {
}

SDValue
ARMSelectionDAGInfo::EmitTargetCodeForMemcpy(SelectionDAG &DAG, SDLoc dl,
                                             SDValue Chain,
                                             SDValue Dst, SDValue Src,
                                             SDValue Size, unsigned Align,
                                             bool isVolatile, bool AlwaysInline,
                                             MachinePointerInfo DstPtrInfo,
                                          MachinePointerInfo SrcPtrInfo) const {
  const ARMSubtarget &Subtarget = DAG.getTarget().getSubtarget<ARMSubtarget>();
  // Do repeated 4-byte loads and stores. To be improved.
  // This requires 4-byte alignment.
  if ((Align & 3) != 0)
    return SDValue();
  // This requires the copy size to be a constant, preferably
  // within a subtarget-specific limit.
  ConstantSDNode *ConstantSize = dyn_cast<ConstantSDNode>(Size);
  if (!ConstantSize)
    return SDValue();
  uint64_t SizeVal = ConstantSize->getZExtValue();
  if (!AlwaysInline && SizeVal > Subtarget.getMaxInlineSizeThreshold())
    return SDValue();

  unsigned BytesLeft = SizeVal & 3;
  unsigned NumMemOps = SizeVal >> 2;
  unsigned EmittedNumMemOps = 0;
  EVT VT = MVT::i32;
  unsigned VTSize = 4;
  unsigned i = 0;
  // Emit a maximum of 4 loads in Thumb1 since we have fewer registers
  const unsigned MAX_LOADS_IN_LDM = Subtarget.isThumb1Only() ? 4 : 6;
  SDValue TFOps[6];
  SDValue Loads[6];
  uint64_t SrcOff = 0, DstOff = 0;

  // Emit up to MAX_LOADS_IN_LDM loads, then a TokenFactor barrier, then the
  // same number of stores.  The loads and stores will get combined into
  // ldm/stm later on.
  while (EmittedNumMemOps < NumMemOps) {
    for (i = 0;
         i < MAX_LOADS_IN_LDM && EmittedNumMemOps + i < NumMemOps; ++i) {
      Loads[i] = DAG.getLoad(VT, dl, Chain,
                             DAG.getNode(ISD::ADD, dl, MVT::i32, Src,
                                         DAG.getConstant(SrcOff, MVT::i32)),
                             SrcPtrInfo.getWithOffset(SrcOff), isVolatile,
                             false, false, 0);
      TFOps[i] = Loads[i].getValue(1);
      SrcOff += VTSize;
    }
    Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
                        makeArrayRef(TFOps, i));

    for (i = 0;
         i < MAX_LOADS_IN_LDM && EmittedNumMemOps + i < NumMemOps; ++i) {
      TFOps[i] = DAG.getStore(Chain, dl, Loads[i],
                              DAG.getNode(ISD::ADD, dl, MVT::i32, Dst,
                                          DAG.getConstant(DstOff, MVT::i32)),
                              DstPtrInfo.getWithOffset(DstOff),
                              isVolatile, false, 0);
      DstOff += VTSize;
    }
    Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
                        makeArrayRef(TFOps, i));

    EmittedNumMemOps += i;
  }

  if (BytesLeft == 0)
    return Chain;

  // Issue loads / stores for the trailing (1 - 3) bytes.
  unsigned BytesLeftSave = BytesLeft;
  i = 0;
  while (BytesLeft) {
    if (BytesLeft >= 2) {
      VT = MVT::i16;
      VTSize = 2;
    } else {
      VT = MVT::i8;
      VTSize = 1;
    }

    Loads[i] = DAG.getLoad(VT, dl, Chain,
                           DAG.getNode(ISD::ADD, dl, MVT::i32, Src,
                                       DAG.getConstant(SrcOff, MVT::i32)),
                           SrcPtrInfo.getWithOffset(SrcOff),
                           false, false, false, 0);
    TFOps[i] = Loads[i].getValue(1);
    ++i;
    SrcOff += VTSize;
    BytesLeft -= VTSize;
  }
  Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
                      makeArrayRef(TFOps, i));

  i = 0;
  BytesLeft = BytesLeftSave;
  while (BytesLeft) {
    if (BytesLeft >= 2) {
      VT = MVT::i16;
      VTSize = 2;
    } else {
      VT = MVT::i8;
      VTSize = 1;
    }

    TFOps[i] = DAG.getStore(Chain, dl, Loads[i],
                            DAG.getNode(ISD::ADD, dl, MVT::i32, Dst,
                                        DAG.getConstant(DstOff, MVT::i32)),
                            DstPtrInfo.getWithOffset(DstOff), false, false, 0);
    ++i;
    DstOff += VTSize;
    BytesLeft -= VTSize;
  }
  return DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
                     makeArrayRef(TFOps, i));
}

// Adjust parameters for memset, EABI uses format (ptr, size, value),
// GNU library uses (ptr, value, size)
// See RTABI section 4.3.4
SDValue ARMSelectionDAGInfo::
EmitTargetCodeForMemset(SelectionDAG &DAG, SDLoc dl,
                        SDValue Chain, SDValue Dst,
                        SDValue Src, SDValue Size,
                        unsigned Align, bool isVolatile,
                        MachinePointerInfo DstPtrInfo) const {
  const ARMSubtarget &Subtarget = DAG.getTarget().getSubtarget<ARMSubtarget>();
  // Use default for non-AAPCS (or MachO) subtargets
  if (!Subtarget.isAAPCS_ABI() || Subtarget.isTargetMachO() ||
      Subtarget.isTargetWindows())
    return SDValue();

  const ARMTargetLowering &TLI =
      *DAG.getTarget().getSubtarget<ARMSubtarget>().getTargetLowering();
  TargetLowering::ArgListTy Args;
  TargetLowering::ArgListEntry Entry;

  // First argument: data pointer
  Type *IntPtrTy = TLI.getDataLayout()->getIntPtrType(*DAG.getContext());
  Entry.Node = Dst;
  Entry.Ty = IntPtrTy;
  Args.push_back(Entry);

  // Second argument: buffer size
  Entry.Node = Size;
  Entry.Ty = IntPtrTy;
  Entry.isSExt = false;
  Args.push_back(Entry);

  // Extend or truncate the argument to be an i32 value for the call.
  if (Src.getValueType().bitsGT(MVT::i32))
    Src = DAG.getNode(ISD::TRUNCATE, dl, MVT::i32, Src);
  else
    Src = DAG.getNode(ISD::ZERO_EXTEND, dl, MVT::i32, Src);

  // Third argument: value to fill
  Entry.Node = Src;
  Entry.Ty = Type::getInt32Ty(*DAG.getContext());
  Entry.isSExt = true;
  Args.push_back(Entry);

  // Emit __eabi_memset call
  TargetLowering::CallLoweringInfo CLI(DAG);
  CLI.setDebugLoc(dl).setChain(Chain)
    .setCallee(TLI.getLibcallCallingConv(RTLIB::MEMSET),
               Type::getVoidTy(*DAG.getContext()),
               DAG.getExternalSymbol(TLI.getLibcallName(RTLIB::MEMSET),
                                     TLI.getPointerTy()), std::move(Args), 0)
    .setDiscardResult();

  std::pair<SDValue,SDValue> CallResult = TLI.LowerCallTo(CLI);
  return CallResult.second;
}