lib/Target/Mips/Mips16FrameLowering.cpp

   1 //===- Mips16FrameLowering.cpp - Mips16 Frame Information -----------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file contains the Mips16 implementation of TargetFrameLowering class.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "Mips16FrameLowering.h"
  15 #include "MCTargetDesc/MipsBaseInfo.h"
  16 #include "Mips16InstrInfo.h"
  17 #include "MipsInstrInfo.h"
  18 #include "MipsRegisterInfo.h"
  19 #include "MipsSubtarget.h"
  20 #include "llvm/ADT/BitVector.h"
  21 #include "llvm/CodeGen/MachineBasicBlock.h"
  22 #include "llvm/CodeGen/MachineFrameInfo.h"
  23 #include "llvm/CodeGen/MachineFunction.h"
  24 #include "llvm/CodeGen/MachineInstr.h"
  25 #include "llvm/CodeGen/MachineInstrBuilder.h"
  26 #include "llvm/CodeGen/MachineModuleInfo.h"
  27 #include "llvm/IR/DebugLoc.h"
  28 #include "llvm/MC/MCContext.h"
  29 #include "llvm/MC/MCDwarf.h"
  30 #include "llvm/MC/MCRegisterInfo.h"
  31 #include "llvm/MC/MachineLocation.h"
  32 #include "llvm/Support/MathExtras.h"
  33 #include "llvm/CodeGen/TargetFrameLowering.h"
  34 #include <cassert>
  35 #include <cstdint>
  36 #include <vector>
  37
  38 using namespace llvm;
  39
  40 Mips16FrameLowering::Mips16FrameLowering(const MipsSubtarget &STI)
  41     : MipsFrameLowering(STI, STI.getStackAlignment()) {}
  42
  43 void Mips16FrameLowering::emitPrologue(MachineFunction &MF,
  44                                        MachineBasicBlock &MBB) const {
  45   MachineFrameInfo &MFI = MF.getFrameInfo();
  46   const Mips16InstrInfo &TII =
  47       *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
  48   MachineBasicBlock::iterator MBBI = MBB.begin();
  49
  50   // Debug location must be unknown since the first debug location is used
  51   // to determine the end of the prologue.
  52   DebugLoc dl;
  53
  54   uint64_t StackSize = MFI.getStackSize();
  55
  56   // No need to allocate space on the stack.
  57   if (StackSize == 0 && !MFI.adjustsStack()) return;
  58
  59   MachineModuleInfo &MMI = MF.getMMI();
  60   const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
  61
  62   // Adjust stack.
  63   TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
  64
  65   // emit ".cfi_def_cfa_offset StackSize"
  66   unsigned CFIIndex = MF.addFrameInst(
  67       MCCFIInstruction::createDefCfaOffset(nullptr, -StackSize));
  68   BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
  69       .addCFIIndex(CFIIndex);
  70
  71   const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
  72
  73   if (!CSI.empty()) {
  74     const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
  75
  76     for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
  77          E = CSI.end(); I != E; ++I) {
  78       int64_t Offset = MFI.getObjectOffset(I->getFrameIdx());
  79       unsigned Reg = I->getReg();
  80       unsigned DReg = MRI->getDwarfRegNum(Reg, true);
  81       unsigned CFIIndex = MF.addFrameInst(
  82           MCCFIInstruction::createOffset(nullptr, DReg, Offset));
  83       BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
  84           .addCFIIndex(CFIIndex);
  85     }
  86   }
  87   if (hasFP(MF))
  88     BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
  89       .addReg(Mips::SP).setMIFlag(MachineInstr::FrameSetup);
  90 }
  91
  92 void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
  93                                  MachineBasicBlock &MBB) const {
  94   MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
  95   MachineFrameInfo &MFI = MF.getFrameInfo();
  96   const Mips16InstrInfo &TII =
  97       *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
  98   DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
  99   uint64_t StackSize = MFI.getStackSize();
 100
 101   if (!StackSize)
 102     return;
 103
 104   if (hasFP(MF))
 105     BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
 106       .addReg(Mips::S0);
 107
 108   // Adjust stack.
 109   // assumes stacksize multiple of 8
 110   TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
 111 }
 112
 113 bool Mips16FrameLowering::
 114 spillCalleeSavedRegisters(MachineBasicBlock &MBB,
 115                           MachineBasicBlock::iterator MI,
 116                           const std::vector<CalleeSavedInfo> &CSI,
 117                           const TargetRegisterInfo *TRI) const {
 118   MachineFunction *MF = MBB.getParent();
 119
 120   //
 121   // Registers RA, S0,S1 are the callee saved registers and they
 122   // will be saved with the "save" instruction
 123   // during emitPrologue
 124   //
 125   for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
 126     // Add the callee-saved register as live-in. Do not add if the register is
 127     // RA and return address is taken, because it has already been added in
 128     // method MipsTargetLowering::lowerRETURNADDR.
 129     // It's killed at the spill, unless the register is RA and return address
 130     // is taken.
 131     unsigned Reg = CSI[i].getReg();
 132     bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
 133       && MF->getFrameInfo().isReturnAddressTaken();
 134     if (!IsRAAndRetAddrIsTaken)
 135       MBB.addLiveIn(Reg);
 136   }
 137
 138   return true;
 139 }
 140
 141 bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
 142                                           MachineBasicBlock::iterator MI,
 143                                        std::vector<CalleeSavedInfo> &CSI,
 144                                        const TargetRegisterInfo *TRI) const {
 145   //
 146   // Registers RA,S0,S1 are the callee saved registers and they will be restored
 147   // with the restore instruction during emitEpilogue.
 148   // We need to override this virtual function, otherwise llvm will try and
 149   // restore the registers on it's on from the stack.
 150   //
 151
 152   return true;
 153 }
 154
 155 bool
 156 Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
 157   const MachineFrameInfo &MFI = MF.getFrameInfo();
 158   // Reserve call frame if the size of the maximum call frame fits into 15-bit
 159   // immediate field and there are no variable sized objects on the stack.
 160   return isInt<15>(MFI.getMaxCallFrameSize()) && !MFI.hasVarSizedObjects();
 161 }
 162
 163 void Mips16FrameLowering::determineCalleeSaves(MachineFunction &MF,
 164                                                BitVector &SavedRegs,
 165                                                RegScavenger *RS) const {
 166   TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
 167   const Mips16InstrInfo &TII =
 168       *static_cast<const Mips16InstrInfo *>(STI.getInstrInfo());
 169   const MipsRegisterInfo &RI = TII.getRegisterInfo();
 170   const BitVector Reserved = RI.getReservedRegs(MF);
 171   bool SaveS2 = Reserved[Mips::S2];
 172   if (SaveS2)
 173     SavedRegs.set(Mips::S2);
 174   if (hasFP(MF))
 175     SavedRegs.set(Mips::S0);
 176 }
 177
 178 const MipsFrameLowering *
 179 llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
 180   return new Mips16FrameLowering(ST);
 181 }