llvm/lib/Target/Mips/Mips16FrameLowering.cpp

   1 //===- Mips16FrameLowering.cpp - Mips16 Frame Information -----------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file contains the Mips16 implementation of TargetFrameLowering class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "Mips16FrameLowering.h"
  14 #include "MCTargetDesc/MipsBaseInfo.h"
  15 #include "Mips16InstrInfo.h"
  16 #include "MipsInstrInfo.h"
  17 #include "MipsRegisterInfo.h"
  18 #include "MipsSubtarget.h"
  19 #include "llvm/ADT/BitVector.h"
  20 #include "llvm/CodeGen/MachineBasicBlock.h"
  21 #include "llvm/CodeGen/MachineFrameInfo.h"
  22 #include "llvm/CodeGen/MachineFunction.h"
  23 #include "llvm/CodeGen/MachineInstr.h"
  24 #include "llvm/CodeGen/MachineInstrBuilder.h"
  25 #include "llvm/CodeGen/MachineModuleInfo.h"
  26 #include "llvm/IR/DebugLoc.h"
  27 #include "llvm/MC/MCContext.h"
  28 #include "llvm/MC/MCDwarf.h"
  29 #include "llvm/MC/MCRegisterInfo.h"
  30 #include "llvm/MC/MachineLocation.h"
  31 #include "llvm/Support/MathExtras.h"
  32 #include "llvm/CodeGen/TargetFrameLowering.h"
  33 #include <cassert>
  34 #include <cstdint>
  35 #include <vector>
  36
  37 using namespace llvm;
  38
  39 Mips16FrameLowering::Mips16FrameLowering(const MipsSubtarget &STI)
  40     : MipsFrameLowering(STI, STI.getStackAlignment()) {}
  41
  42 void Mips16FrameLowering::emitPrologue(MachineFunction &MF,
  43                                        MachineBasicBlock &MBB) const {
  44   MachineFrameInfo &MFI = MF.getFrameInfo();
  45   const Mips16InstrInfo &TII =
  46       *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
  47   MachineBasicBlock::iterator MBBI = MBB.begin();
  48
  49   // Debug location must be unknown since the first debug location is used
  50   // to determine the end of the prologue.
  51   DebugLoc dl;
  52
  53   uint64_t StackSize = MFI.getStackSize();
  54
  55   // No need to allocate space on the stack.
  56   if (StackSize == 0 && !MFI.adjustsStack()) return;
  57
  58   MachineModuleInfo &MMI = MF.getMMI();
  59   const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
  60
  61   // Adjust stack.
  62   TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
  63
  64   // emit ".cfi_def_cfa_offset StackSize"
  65   unsigned CFIIndex =
  66       MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, StackSize));
  67   BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
  68       .addCFIIndex(CFIIndex);
  69
  70   const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
  71
  72   if (!CSI.empty()) {
  73     const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
  74
  75     for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
  76          E = CSI.end(); I != E; ++I) {
  77       int64_t Offset = MFI.getObjectOffset(I->getFrameIdx());
  78       unsigned Reg = I->getReg();
  79       unsigned DReg = MRI->getDwarfRegNum(Reg, true);
  80       unsigned CFIIndex = MF.addFrameInst(
  81           MCCFIInstruction::createOffset(nullptr, DReg, Offset));
  82       BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
  83           .addCFIIndex(CFIIndex);
  84     }
  85   }
  86   if (hasFP(MF))
  87     BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
  88       .addReg(Mips::SP).setMIFlag(MachineInstr::FrameSetup);
  89 }
  90
  91 void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
  92                                  MachineBasicBlock &MBB) const {
  93   MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
  94   MachineFrameInfo &MFI = MF.getFrameInfo();
  95   const Mips16InstrInfo &TII =
  96       *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
  97   DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
  98   uint64_t StackSize = MFI.getStackSize();
  99
 100   if (!StackSize)
 101     return;
 102
 103   if (hasFP(MF))
 104     BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
 105       .addReg(Mips::S0);
 106
 107   // Adjust stack.
 108   // assumes stacksize multiple of 8
 109   TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
 110 }
 111
 112 bool Mips16FrameLowering::spillCalleeSavedRegisters(
 113     MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
 114     ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
 115   MachineFunction *MF = MBB.getParent();
 116
 117   //
 118   // Registers RA, S0,S1 are the callee saved registers and they
 119   // will be saved with the "save" instruction
 120   // during emitPrologue
 121   //
 122   for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
 123     // Add the callee-saved register as live-in. Do not add if the register is
 124     // RA and return address is taken, because it has already been added in
 125     // method MipsTargetLowering::lowerRETURNADDR.
 126     // It's killed at the spill, unless the register is RA and return address
 127     // is taken.
 128     unsigned Reg = CSI[i].getReg();
 129     bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
 130       && MF->getFrameInfo().isReturnAddressTaken();
 131     if (!IsRAAndRetAddrIsTaken)
 132       MBB.addLiveIn(Reg);
 133   }
 134
 135   return true;
 136 }
 137
 138 bool Mips16FrameLowering::restoreCalleeSavedRegisters(
 139     MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
 140     MutableArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
 141   //
 142   // Registers RA,S0,S1 are the callee saved registers and they will be restored
 143   // with the restore instruction during emitEpilogue.
 144   // We need to override this virtual function, otherwise llvm will try and
 145   // restore the registers on it's on from the stack.
 146   //
 147
 148   return true;
 149 }
 150
 151 bool
 152 Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
 153   const MachineFrameInfo &MFI = MF.getFrameInfo();
 154   // Reserve call frame if the size of the maximum call frame fits into 15-bit
 155   // immediate field and there are no variable sized objects on the stack.
 156   return isInt<15>(MFI.getMaxCallFrameSize()) && !MFI.hasVarSizedObjects();
 157 }
 158
 159 void Mips16FrameLowering::determineCalleeSaves(MachineFunction &MF,
 160                                                BitVector &SavedRegs,
 161                                                RegScavenger *RS) const {
 162   TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
 163   const Mips16InstrInfo &TII =
 164       *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
 165   const MipsRegisterInfo &RI = TII.getRegisterInfo();
 166   const BitVector Reserved = RI.getReservedRegs(MF);
 167   bool SaveS2 = Reserved[Mips::S2];
 168   if (SaveS2)
 169     SavedRegs.set(Mips::S2);
 170   if (hasFP(MF))
 171     SavedRegs.set(Mips::S0);
 172 }
 173
 174 const MipsFrameLowering *
 175 llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
 176   return new Mips16FrameLowering(ST);
 177 }