lib/Target/ARM/Thumb2InstrInfo.cpp

//===- Thumb2InstrInfo.cpp - Thumb-2 Instruction Information --------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the Thumb-2 implementation of the TargetInstrInfo class.
//
//===----------------------------------------------------------------------===//

#include "ARMInstrInfo.h"
#include "ARM.h"
#include "ARMAddressingModes.h"
#include "ARMGenInstrInfo.inc"
#include "ARMMachineFunctionInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/ADT/SmallVector.h"
#include "Thumb2InstrInfo.h"

using namespace llvm;

Thumb2InstrInfo::Thumb2InstrInfo(const ARMSubtarget &STI)
  : ARMBaseInstrInfo(STI), RI(*this, STI) {
}

unsigned Thumb2InstrInfo::getUnindexedOpcode(unsigned Opc) const {
  // FIXME
  return 0;
}

bool
Thumb2InstrInfo::BlockHasNoFallThrough(const MachineBasicBlock &MBB) const {
  if (MBB.empty()) return false;

  switch (MBB.back().getOpcode()) {
  case ARM::t2LDM_RET:
  case ARM::t2B:        // Uncond branch.
  case ARM::t2BR_JT:    // Jumptable branch.
  case ARM::tBR_JTr:    // Jumptable branch (16-bit version).
  case ARM::tBX_RET:
  case ARM::tBX_RET_vararg:
  case ARM::tPOP_RET:
  case ARM::tB:
    return true;
  default:
    break;
  }

  return false;
}

bool
Thumb2InstrInfo::copyRegToReg(MachineBasicBlock &MBB,
                              MachineBasicBlock::iterator I,
                              unsigned DestReg, unsigned SrcReg,
                              const TargetRegisterClass *DestRC,
                              const TargetRegisterClass *SrcRC) const {
  DebugLoc DL = DebugLoc::getUnknownLoc();
  if (I != MBB.end()) DL = I->getDebugLoc();

  if (DestRC == ARM::GPRRegisterClass &&
      SrcRC == ARM::GPRRegisterClass) {
    AddDefaultCC(AddDefaultPred(BuildMI(MBB, I, DL, get(ARM::t2MOVr),
                                        DestReg).addReg(SrcReg)));
    return true;
  } else if (DestRC == ARM::GPRRegisterClass &&
      SrcRC == ARM::tGPRRegisterClass) {
    BuildMI(MBB, I, DL, get(ARM::tMOVtgpr2gpr), DestReg).addReg(SrcReg);
    return true;
  } else if (DestRC == ARM::tGPRRegisterClass &&
             SrcRC == ARM::GPRRegisterClass) {
    BuildMI(MBB, I, DL, get(ARM::tMOVgpr2tgpr), DestReg).addReg(SrcReg);
    return true;
  }

  // Handle SPR, DPR, and QPR copies.
  return ARMBaseInstrInfo::copyRegToReg(MBB, I, DestReg, SrcReg, DestRC, SrcRC);
}

void Thumb2InstrInfo::
storeRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
                    unsigned SrcReg, bool isKill, int FI,
                    const TargetRegisterClass *RC) const {
  DebugLoc DL = DebugLoc::getUnknownLoc();
  if (I != MBB.end()) DL = I->getDebugLoc();

  if (RC == ARM::GPRRegisterClass) {
    AddDefaultPred(BuildMI(MBB, I, DL, get(ARM::t2STRi12))
                   .addReg(SrcReg, getKillRegState(isKill))
                   .addFrameIndex(FI).addImm(0));
    return;
  }

  ARMBaseInstrInfo::storeRegToStackSlot(MBB, I, SrcReg, isKill, FI, RC);
}

void Thumb2InstrInfo::
loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
                     unsigned DestReg, int FI,
                     const TargetRegisterClass *RC) const {
  DebugLoc DL = DebugLoc::getUnknownLoc();
  if (I != MBB.end()) DL = I->getDebugLoc();

  if (RC == ARM::GPRRegisterClass) {
    AddDefaultPred(BuildMI(MBB, I, DL, get(ARM::t2LDRi12), DestReg)
                   .addFrameIndex(FI).addImm(0));
    return;
  }

  ARMBaseInstrInfo::loadRegFromStackSlot(MBB, I, DestReg, FI, RC);
}


void llvm::emitT2RegPlusImmediate(MachineBasicBlock &MBB,
                               MachineBasicBlock::iterator &MBBI, DebugLoc dl,
                               unsigned DestReg, unsigned BaseReg, int NumBytes,
                               ARMCC::CondCodes Pred, unsigned PredReg,
                               const ARMBaseInstrInfo &TII) {
  bool isSub = NumBytes < 0;
  if (isSub) NumBytes = -NumBytes;

  // If profitable, use a movw or movt to materialize the offset.
  // FIXME: Use the scavenger to grab a scratch register.
  if (DestReg != ARM::SP && DestReg != BaseReg &&
      NumBytes >= 4096 &&
      ARM_AM::getT2SOImmVal(NumBytes) == -1) {
    bool Fits = false;
    if (NumBytes < 65536) {
      // Use a movw to materialize the 16-bit constant.
      BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi16), DestReg)
        .addImm(NumBytes)
        .addImm((unsigned)Pred).addReg(PredReg).addReg(0);
      Fits = true;
    } else if ((NumBytes & 0xffff) == 0) {
      // Use a movt to materialize the 32-bit constant.
      BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVTi16), DestReg)
        .addReg(DestReg)
        .addImm(NumBytes >> 16)
        .addImm((unsigned)Pred).addReg(PredReg).addReg(0);
      Fits = true;
    }

    if (Fits) {
      if (isSub) {
        BuildMI(MBB, MBBI, dl, TII.get(ARM::t2SUBrr), DestReg)
          .addReg(BaseReg, RegState::Kill)
          .addReg(DestReg, RegState::Kill)
          .addImm((unsigned)Pred).addReg(PredReg).addReg(0);
      } else {
        BuildMI(MBB, MBBI, dl, TII.get(ARM::t2ADDrr), DestReg)
          .addReg(DestReg, RegState::Kill)
          .addReg(BaseReg, RegState::Kill)
        .addImm((unsigned)Pred).addReg(PredReg).addReg(0);
      }
      return;
    }
  }

  while (NumBytes) {
    unsigned Opc = isSub ? ARM::t2SUBri : ARM::t2ADDri;
    unsigned ThisVal = NumBytes;
    if (ARM_AM::getT2SOImmVal(NumBytes) != -1) {
      NumBytes = 0;
    } else if (ThisVal < 4096) {
      Opc = isSub ? ARM::t2SUBri12 : ARM::t2ADDri12;
      NumBytes = 0;
    } else {
      // FIXME: Move this to ARMAddressingModes.h?
      unsigned RotAmt = CountLeadingZeros_32(ThisVal);
      ThisVal = ThisVal & ARM_AM::rotr32(0xff000000U, RotAmt);
      NumBytes &= ~ThisVal;
      assert(ARM_AM::getT2SOImmVal(ThisVal) != -1 &&
             "Bit extraction didn't work?");
    }

    // Build the new ADD / SUB.
    BuildMI(MBB, MBBI, dl, TII.get(Opc), DestReg)
      .addReg(BaseReg, RegState::Kill).addImm(ThisVal)
      .addImm((unsigned)Pred).addReg(PredReg).addReg(0);
    BaseReg = DestReg;
  }
}

static unsigned
negativeOffsetOpcode(unsigned opcode)
{
  switch (opcode) {
  case ARM::t2LDRi12:   return ARM::t2LDRi8;
  case ARM::t2LDRHi12:  return ARM::t2LDRHi8;
  case ARM::t2LDRBi12:  return ARM::t2LDRBi8;
  case ARM::t2LDRSHi12: return ARM::t2LDRSHi8;
  case ARM::t2LDRSBi12: return ARM::t2LDRSBi8;
  case ARM::t2STRi12:   return ARM::t2STRi8;
  case ARM::t2STRBi12:  return ARM::t2STRBi8;
  case ARM::t2STRHi12:  return ARM::t2STRHi8;

  case ARM::t2LDRi8:
  case ARM::t2LDRHi8:
  case ARM::t2LDRBi8:
  case ARM::t2LDRSHi8:
  case ARM::t2LDRSBi8:
  case ARM::t2STRi8:
  case ARM::t2STRBi8:
  case ARM::t2STRHi8:
    return opcode;

  default:
    break;
  }

  return 0;
}

static unsigned
positiveOffsetOpcode(unsigned opcode)
{
  switch (opcode) {
  case ARM::t2LDRi8:   return ARM::t2LDRi12;
  case ARM::t2LDRHi8:  return ARM::t2LDRHi12;
  case ARM::t2LDRBi8:  return ARM::t2LDRBi12;
  case ARM::t2LDRSHi8: return ARM::t2LDRSHi12;
  case ARM::t2LDRSBi8: return ARM::t2LDRSBi12;
  case ARM::t2STRi8:   return ARM::t2STRi12;
  case ARM::t2STRBi8:  return ARM::t2STRBi12;
  case ARM::t2STRHi8:  return ARM::t2STRHi12;

  case ARM::t2LDRi12:
  case ARM::t2LDRHi12:
  case ARM::t2LDRBi12:
  case ARM::t2LDRSHi12:
  case ARM::t2LDRSBi12:
  case ARM::t2STRi12:
  case ARM::t2STRBi12:
  case ARM::t2STRHi12:
    return opcode;

  default:
    break;
  }

  return 0;
}

static unsigned
immediateOffsetOpcode(unsigned opcode)
{
  switch (opcode) {
  case ARM::t2LDRs:   return ARM::t2LDRi12;
  case ARM::t2LDRHs:  return ARM::t2LDRHi12;
  case ARM::t2LDRBs:  return ARM::t2LDRBi12;
  case ARM::t2LDRSHs: return ARM::t2LDRSHi12;
  case ARM::t2LDRSBs: return ARM::t2LDRSBi12;
  case ARM::t2STRs:   return ARM::t2STRi12;
  case ARM::t2STRBs:  return ARM::t2STRBi12;
  case ARM::t2STRHs:  return ARM::t2STRHi12;

  case ARM::t2LDRi12:
  case ARM::t2LDRHi12:
  case ARM::t2LDRBi12:
  case ARM::t2LDRSHi12:
  case ARM::t2LDRSBi12:
  case ARM::t2STRi12:
  case ARM::t2STRBi12:
  case ARM::t2STRHi12:
  case ARM::t2LDRi8:
  case ARM::t2LDRHi8:
  case ARM::t2LDRBi8:
  case ARM::t2LDRSHi8:
  case ARM::t2LDRSBi8:
  case ARM::t2STRi8:
  case ARM::t2STRBi8:
  case ARM::t2STRHi8:
    return opcode;

  default:
    break;
  }

  return 0;
}

int llvm::rewriteT2FrameIndex(MachineInstr &MI, unsigned FrameRegIdx,
                              unsigned FrameReg, int Offset,
                              const ARMBaseInstrInfo &TII) {
  unsigned Opcode = MI.getOpcode();
  unsigned NewOpc = Opcode;
  const TargetInstrDesc &Desc = MI.getDesc();
  unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
  bool isSub = false;

  // Memory operands in inline assembly always use AddrModeT2_i12.
  if (Opcode == ARM::INLINEASM)
    AddrMode = ARMII::AddrModeT2_i12; // FIXME. mode for thumb2?
  
  if (Opcode == ARM::t2ADDri || Opcode == ARM::t2ADDri12) {
    Offset += MI.getOperand(FrameRegIdx+1).getImm();
    if (Offset == 0) {
      // Turn it into a move.
      MI.setDesc(TII.get(ARM::t2MOVr));
      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
      MI.RemoveOperand(FrameRegIdx+1);
      return 0;
    }

    if (Offset < 0) {
      Offset = -Offset;
      isSub = true;
      MI.setDesc(TII.get(ARM::t2SUBri));
    }

    // Common case: small offset, fits into instruction.
    if (ARM_AM::getT2SOImmVal(Offset) != -1) {
      NewOpc = isSub ? ARM::t2SUBri : ARM::t2ADDri;
      if (NewOpc != Opcode)
        MI.setDesc(TII.get(NewOpc));
      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
      MI.getOperand(FrameRegIdx+1).ChangeToImmediate(Offset);
      return 0;
    }
    // Another common case: imm12.
    if (Offset < 4096) {
      NewOpc = isSub ? ARM::t2SUBri12 : ARM::t2ADDri12;
      if (NewOpc != Opcode)
        MI.setDesc(TII.get(NewOpc));
      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
      MI.getOperand(FrameRegIdx+1).ChangeToImmediate(Offset);
      return 0;
    }

    // Otherwise, extract 8 adjacent bits from the immediate into this
    // t2ADDri/t2SUBri.
    unsigned RotAmt = CountLeadingZeros_32(Offset);
    unsigned ThisImmVal = Offset & ARM_AM::rotr32(0xff000000U, RotAmt);

    // We will handle these bits from offset, clear them.
    Offset &= ~ThisImmVal;

    assert(ARM_AM::getT2SOImmVal(ThisImmVal) != -1 &&
           "Bit extraction didn't work?");
    MI.getOperand(FrameRegIdx+1).ChangeToImmediate(ThisImmVal);
  } else {
    // AddrModeT2_so cannot handle any offset. If there is no offset
    // register then we change to an immediate version.
    NewOpc = Opcode;
    if (AddrMode == ARMII::AddrModeT2_so) {
      unsigned OffsetReg = MI.getOperand(FrameRegIdx+1).getReg();
      if (OffsetReg != 0) {
        MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
        return Offset;
      }
      
      MI.RemoveOperand(FrameRegIdx+1);
      MI.getOperand(FrameRegIdx+1).ChangeToImmediate(0);
      NewOpc = immediateOffsetOpcode(Opcode);
      AddrMode = ARMII::AddrModeT2_i12;
    }

    unsigned NumBits = 0;
    unsigned Scale = 1;
    if (AddrMode == ARMII::AddrModeT2_i8 || AddrMode == ARMII::AddrModeT2_i12) {
      // i8 supports only negative, and i12 supports only positive, so
      // based on Offset sign convert Opcode to the appropriate
      // instruction
      Offset += MI.getOperand(FrameRegIdx+1).getImm();
      if (Offset < 0) {
        NewOpc = negativeOffsetOpcode(Opcode);
        NumBits = 8;
        isSub = true;
        Offset = -Offset;
      } else {
        NewOpc = positiveOffsetOpcode(Opcode);
        NumBits = 12;
      }
    } else {
      // VFP address modes.
      assert(AddrMode == ARMII::AddrMode5);
      int InstrOffs=ARM_AM::getAM5Offset(MI.getOperand(FrameRegIdx+1).getImm());
      if (ARM_AM::getAM5Op(MI.getOperand(FrameRegIdx+1).getImm()) ==ARM_AM::sub)
        InstrOffs *= -1;
      NumBits = 8;
      Scale = 4;
      Offset += InstrOffs * 4;
      assert((Offset & (Scale-1)) == 0 && "Can't encode this offset!");
      if (Offset < 0) {
        Offset = -Offset;
        isSub = true;
      }
    }

    if (NewOpc != Opcode)
      MI.setDesc(TII.get(NewOpc));

    MachineOperand &ImmOp = MI.getOperand(FrameRegIdx+1);

    // Attempt to fold address computation
    // Common case: small offset, fits into instruction.
    int ImmedOffset = Offset / Scale;
    unsigned Mask = (1 << NumBits) - 1;
    if ((unsigned)Offset <= Mask * Scale) {
      // Replace the FrameIndex with fp/sp
      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
      if (isSub) {
        if (AddrMode == ARMII::AddrMode5)
          // FIXME: Not consistent.
          ImmedOffset |= 1 << NumBits;
        else 
          ImmedOffset = -ImmedOffset;
      }
      ImmOp.ChangeToImmediate(ImmedOffset);
      return 0;
    }
      
    // Otherwise, offset doesn't fit. Pull in what we can to simplify
    ImmedOffset = Offset & Mask;
    if (isSub) {
      if (AddrMode == ARMII::AddrMode5)
        // FIXME: Not consistent.
        ImmedOffset |= 1 << NumBits;
      else
        ImmedOffset = -ImmedOffset;
    }
    ImmOp.ChangeToImmediate(ImmedOffset);
    Offset &= ~(Mask*Scale);
  }

  return (isSub) ? -Offset : Offset;
}