MipsRegisterInfo.cpp

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//===- MipsRegisterInfo.cpp - MIPS Register Information -------------------===//
//
// 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 contains the MIPS implementation of the TargetRegisterInfo class.
//
//===----------------------------------------------------------------------===//
 
#include "MipsRegisterInfo.h"
#include "MCTargetDesc/MipsABIInfo.h"
#include "Mips.h"
#include "MipsMachineFunction.h"
#include "MipsSubtarget.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <cstdint>
 
using namespace llvm;
 
#define DEBUG_TYPE "mips-reg-info"
 
#define GET_REGINFO_TARGET_DESC
#include "MipsGenRegisterInfo.inc"
 
MipsRegisterInfo::MipsRegisterInfo(const MipsSubtarget &STI)
    : MipsGenRegisterInfo(Mips::RA), ArePtrs64bit(STI.getABI().ArePtrs64bit()) {
  MIPS_MC::initLLVMToCVRegMapping(this);
}
 
unsigned MipsRegisterInfo::getPICCallReg() { return Mips::T9; }
 
unsigned
MipsRegisterInfo::getRegPressureLimit(const TargetRegisterClass *RC,
                                      MachineFunction &MF) const {
  switch (RC->getID()) {
  default:
    return 0;
  case Mips::GPR32RegClassID:
  case Mips::GPR64RegClassID:
  case Mips::DSPRRegClassID: {
    const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
    return 28 - TFI->hasFP(MF);
  }
  case Mips::FGR32RegClassID:
    return 32;
  case Mips::AFGR64RegClassID:
    return 16;
  case Mips::FGR64RegClassID:
    return 32;
  }
}
 
//===----------------------------------------------------------------------===//
// Callee Saved Registers methods
//===----------------------------------------------------------------------===//
 
/// Check if the user has declared $gp/$28 as a global regiater.
bool isGPUsedAsGlobalRegister(const MachineFunction &MF) {
  const Module *Module = MF.getFunction().getParent();
 
  return Module->getNamedMetadata("llvm.named.register.$28");
}
 
/// Mips Callee Saved Registers
const MCPhysReg *
MipsRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
  const MipsSubtarget &Subtarget = MF->getSubtarget<MipsSubtarget>();
  const Function &F = MF->getFunction();
  if (F.hasFnAttribute("interrupt")) {
    if (Subtarget.hasMips64())
      return Subtarget.hasMips64r6() ? CSR_Interrupt_64R6_SaveList
                                     : CSR_Interrupt_64_SaveList;
    else
      return Subtarget.hasMips32r6() ? CSR_Interrupt_32R6_SaveList
                                     : CSR_Interrupt_32_SaveList;
  }
 
  bool GPIsGlobal = isGPUsedAsGlobalRegister(*MF);
  // N64 ABI
  if (Subtarget.isABI_N64()) {
    if (Subtarget.isSingleFloat())
      return GPIsGlobal ? CSR_N64_SingleFloat_NoGP_SaveList
                        : CSR_N64_SingleFloat_SaveList;
 
    return GPIsGlobal ? CSR_N64_NoGP_SaveList : CSR_N64_SaveList;
  }
 
  // N32 ABI
  if (Subtarget.isABI_N32()) {
    if (Subtarget.isSingleFloat())
      return GPIsGlobal ? CSR_N32_SingleFloat_NoGP_SaveList
                        : CSR_N32_SingleFloat_SaveList;
 
    return GPIsGlobal ? CSR_N32_NoGP_SaveList : CSR_N32_SaveList;
  }
 
  // O32 ABI
  if (Subtarget.isSingleFloat())
    return CSR_O32_SingleFloat_SaveList;
 
  if (Subtarget.isFP64bit())
    return CSR_O32_FP64_SaveList;
 
  if (Subtarget.isFPXX())
    return CSR_O32_FPXX_SaveList;
 
  return CSR_O32_SaveList;
}
 
const uint32_t *
MipsRegisterInfo::getCallPreservedMask(const MachineFunction &MF,
                                       CallingConv::ID) const {
  const MipsSubtarget &Subtarget = MF.getSubtarget<MipsSubtarget>();
  // N64 ABI
  if (Subtarget.isABI_N64()) {
    if (Subtarget.isSingleFloat())
      return CSR_N64_SingleFloat_RegMask;
 
    return CSR_N64_RegMask;
  }
 
  // N32 ABI
  if (Subtarget.isABI_N32()) {
    if (Subtarget.isSingleFloat())
      return CSR_N32_SingleFloat_RegMask;
 
    return CSR_N32_RegMask;
  }
 
  // O32 ABI
  if (Subtarget.isSingleFloat())
    return CSR_O32_SingleFloat_RegMask;
 
  if (Subtarget.isFP64bit())
    return CSR_O32_FP64_RegMask;
 
  if (Subtarget.isFPXX())
    return CSR_O32_FPXX_RegMask;
 
  return CSR_O32_RegMask;
}
 
const uint32_t *MipsRegisterInfo::getMips16RetHelperMask() {
  return CSR_Mips16RetHelper_RegMask;
}
 
BitVector MipsRegisterInfo::
getReservedRegs(const MachineFunction &MF) const {
  static const MCPhysReg ReservedGPR32[] = {
    Mips::ZERO, Mips::K0, Mips::K1, Mips::SP
  };
 
  static const MCPhysReg ReservedGPR64[] = {
    Mips::ZERO_64, Mips::K0_64, Mips::K1_64, Mips::SP_64
  };
 
  BitVector Reserved(getNumRegs());
  const MipsSubtarget &Subtarget = MF.getSubtarget<MipsSubtarget>();
 
  for (MCPhysReg R : ReservedGPR32)
    Reserved.set(R);
 
  for (MCPhysReg R : ReservedGPR64)
    Reserved.set(R);
 
  // Mark user-reserved GPRs and their 64-bit super-registers.
  for (unsigned I = 1; I < 32; ++I)
    if (Subtarget.isGPRReservedByUser(I))
      markSuperRegs(Reserved, Mips::GPR32RegClass.getRegister(I));
 
  // For mno-abicalls, GP is a program invariant!
  bool GPIsGlobal = isGPUsedAsGlobalRegister(MF);
  if (!Subtarget.isABICalls() || GPIsGlobal) {
    Reserved.set(Mips::GP);
    Reserved.set(Mips::GP_64);
  }
 
  if (Subtarget.isFP64bit()) {
    // Reserve all registers in AFGR64.
    for (MCPhysReg Reg : Mips::AFGR64RegClass)
      Reserved.set(Reg);
  } else {
    // Reserve all registers in FGR64.
    for (MCPhysReg Reg : Mips::FGR64RegClass)
      Reserved.set(Reg);
  }
  // Reserve FP if this function should have a dedicated frame pointer register.
  if (Subtarget.getFrameLowering()->hasFP(MF)) {
    if (Subtarget.inMips16Mode())
      Reserved.set(Mips::S0);
    else {
      Reserved.set(Mips::FP);
      Reserved.set(Mips::FP_64);
 
      // Reserve the base register if we need to both realign the stack and
      // allocate variable-sized objects at runtime. This should test the
      // same conditions as MipsFrameLowering::hasBP().
      if (hasStackRealignment(MF) && MF.getFrameInfo().hasVarSizedObjects()) {
        Reserved.set(Mips::S7);
        Reserved.set(Mips::S7_64);
      }
    }
  }
  // Reserve fp control and status register
  Reserved.set(Mips::FCR31);
 
  // Reserve hardware registers.
  Reserved.set(Mips::HWR29);
  Reserved.set(Mips::HWR2);
 
  // Reserve DSP control register.
  Reserved.set(Mips::DSPPos);
  Reserved.set(Mips::DSPSCount);
  Reserved.set(Mips::DSPCarry);
  Reserved.set(Mips::DSPEFI);
  Reserved.set(Mips::DSPOutFlag);
 
  // Reserve MSA control registers.
  for (MCPhysReg Reg : Mips::MSACtrlRegClass)
    Reserved.set(Reg);
 
  // Reserve RA if in mips16 mode.
  if (Subtarget.inMips16Mode()) {
    const MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
    Reserved.set(Mips::RA);
    Reserved.set(Mips::RA_64);
    Reserved.set(Mips::T0);
    Reserved.set(Mips::T1);
    if (MF.getFunction().hasFnAttribute("saveS2") || MipsFI->hasSaveS2())
      Reserved.set(Mips::S2);
  }
 
  // Reserve GP if small section is used.
  if (Subtarget.useSmallSection()) {
    Reserved.set(Mips::GP);
    Reserved.set(Mips::GP_64);
  }
 
  return Reserved;
}
 
// FrameIndex represent objects inside a abstract stack.
// We must replace FrameIndex with an stack/frame pointer
// direct reference.
bool MipsRegisterInfo::
eliminateFrameIndex(MachineBasicBlock::iterator II, int SPAdj,
                    unsigned FIOperandNum, RegScavenger *RS) const {
  MachineInstr &MI = *II;
  MachineFunction &MF = *MI.getParent()->getParent();
 
  LLVM_DEBUG(errs() << "\nFunction : " << MF.getName() << "\n";
             errs() << "<--------->\n"
                    << MI);
 
  int FrameIndex = MI.getOperand(FIOperandNum).getIndex();
  uint64_t stackSize = MF.getFrameInfo().getStackSize();
  int64_t spOffset = MF.getFrameInfo().getObjectOffset(FrameIndex);
 
  LLVM_DEBUG(errs() << "FrameIndex : " << FrameIndex << "\n"
                    << "spOffset   : " << spOffset << "\n"
                    << "stackSize  : " << stackSize << "\n"
                    << "alignment  : "
                    << DebugStr(MF.getFrameInfo().getObjectAlign(FrameIndex))
                    << "\n");
 
  eliminateFI(MI, FIOperandNum, FrameIndex, stackSize, spOffset);
  return false;
}
 
Register MipsRegisterInfo::
getFrameRegister(const MachineFunction &MF) const {
  const MipsSubtarget &Subtarget = MF.getSubtarget<MipsSubtarget>();
  const TargetFrameLowering *TFI = Subtarget.getFrameLowering();
  bool IsN64 = Subtarget.getABI().IsN64();
 
  if (Subtarget.inMips16Mode())
    return TFI->hasFP(MF) ? Mips::S0 : Mips::SP;
  else
    return TFI->hasFP(MF) ? (IsN64 ? Mips::FP_64 : Mips::FP) :
                            (IsN64 ? Mips::SP_64 : Mips::SP);
}
 
bool MipsRegisterInfo::canRealignStack(const MachineFunction &MF) const {
  // Avoid realigning functions that explicitly do not want to be realigned.
  // Normally, we should report an error when a function should be dynamically
  // realigned but also has the attribute no-realign-stack. Unfortunately,
  // with this attribute, MachineFrameInfo clamps each new object's alignment
  // to that of the stack's alignment as specified by the ABI. As a result,
  // the information of whether we have objects with larger alignment
  // requirement than the stack's alignment is already lost at this point.
  if (!TargetRegisterInfo::canRealignStack(MF))
    return false;
 
  const MipsSubtarget &Subtarget = MF.getSubtarget<MipsSubtarget>();
  unsigned FP = Subtarget.isGP32bit() ? Mips::FP : Mips::FP_64;
  unsigned BP = Subtarget.getABI().getSavedReg(7, Subtarget.isGP64bit());
 
  // Support dynamic stack realignment for all targets except Mips16.
  if (Subtarget.inMips16Mode())
    return false;
 
  // We can't perform dynamic stack realignment if we can't reserve the
  // frame pointer register.
  if (!MF.getRegInfo().canReserveReg(FP))
    return false;
 
  // We can realign the stack if we know the maximum call frame size and we
  // don't have variable sized objects.
  if (Subtarget.getFrameLowering()->hasReservedCallFrame(MF))
    return true;
 
  // We have to reserve the base pointer register in the presence of variable
  // sized objects.
  return MF.getRegInfo().canReserveReg(BP);
}