Home | History | Annotate | Download | only in Mips 
      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 "llvm/CodeGen/MachineFrameInfo.h"
     19 #include "llvm/CodeGen/MachineFunction.h"
     20 #include "llvm/CodeGen/MachineInstrBuilder.h"
     21 #include "llvm/CodeGen/MachineModuleInfo.h"
     22 #include "llvm/CodeGen/MachineRegisterInfo.h"
     23 #include "llvm/IR/DataLayout.h"
     24 #include "llvm/IR/Function.h"
     25 #include "llvm/Support/CommandLine.h"
     26 #include "llvm/Target/TargetOptions.h"
     27 
     28 using namespace llvm;
     29 
     30 void Mips16FrameLowering::emitPrologue(MachineFunction &MF) const {
     31   MachineBasicBlock &MBB = MF.front();
     32   MachineFrameInfo *MFI = MF.getFrameInfo();
     33   const Mips16InstrInfo &TII =
     34     *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
     35   MachineBasicBlock::iterator MBBI = MBB.begin();
     36   DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
     37   uint64_t StackSize = MFI->getStackSize();
     38 
     39   // No need to allocate space on the stack.
     40   if (StackSize == 0 && !MFI->adjustsStack()) return;
     41 
     42   MachineModuleInfo &MMI = MF.getMMI();
     43   const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
     44   MachineLocation DstML, SrcML;
     45 
     46   // Adjust stack.
     47   TII.makeFrame(Mips::SP, StackSize, MBB, MBBI);
     48 
     49   // emit ".cfi_def_cfa_offset StackSize"
     50   MCSymbol *AdjustSPLabel = MMI.getContext().CreateTempSymbol();
     51   BuildMI(MBB, MBBI, dl,
     52           TII.get(TargetOpcode::PROLOG_LABEL)).addSym(AdjustSPLabel);
     53   MMI.addFrameInst(
     54       MCCFIInstruction::createDefCfaOffset(AdjustSPLabel, -StackSize));
     55 
     56   MCSymbol *CSLabel = MMI.getContext().CreateTempSymbol();
     57   BuildMI(MBB, MBBI, dl,
     58           TII.get(TargetOpcode::PROLOG_LABEL)).addSym(CSLabel);
     59   unsigned S2 = MRI->getDwarfRegNum(Mips::S2, true);
     60   MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, S2, -8));
     61 
     62   unsigned S1 = MRI->getDwarfRegNum(Mips::S1, true);
     63   MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, S1, -12));
     64 
     65   unsigned S0 = MRI->getDwarfRegNum(Mips::S0, true);
     66   MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, S0, -16));
     67 
     68   unsigned RA = MRI->getDwarfRegNum(Mips::RA, true);
     69   MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, RA, -4));
     70 
     71   if (hasFP(MF))
     72     BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
     73       .addReg(Mips::SP);
     74 
     75 }
     76 
     77 void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
     78                                  MachineBasicBlock &MBB) const {
     79   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
     80   MachineFrameInfo *MFI = MF.getFrameInfo();
     81   const Mips16InstrInfo &TII =
     82     *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
     83   DebugLoc dl = MBBI->getDebugLoc();
     84   uint64_t StackSize = MFI->getStackSize();
     85 
     86   if (!StackSize)
     87     return;
     88 
     89   if (hasFP(MF))
     90     BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
     91       .addReg(Mips::S0);
     92 
     93   // Adjust stack.
     94   // assumes stacksize multiple of 8
     95   TII.restoreFrame(Mips::SP, StackSize, MBB, MBBI);
     96 }
     97 
     98 bool Mips16FrameLowering::
     99 spillCalleeSavedRegisters(MachineBasicBlock &MBB,
    100                           MachineBasicBlock::iterator MI,
    101                           const std::vector<CalleeSavedInfo> &CSI,
    102                           const TargetRegisterInfo *TRI) const {
    103   MachineFunction *MF = MBB.getParent();
    104   MachineBasicBlock *EntryBlock = MF->begin();
    105 
    106   //
    107   // Registers RA, S0,S1 are the callee saved registers and they
    108   // will be saved with the "save" instruction
    109   // during emitPrologue
    110   //
    111   for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
    112     // Add the callee-saved register as live-in. Do not add if the register is
    113     // RA and return address is taken, because it has already been added in
    114     // method MipsTargetLowering::LowerRETURNADDR.
    115     // It's killed at the spill, unless the register is RA and return address
    116     // is taken.
    117     unsigned Reg = CSI[i].getReg();
    118     bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
    119       && MF->getFrameInfo()->isReturnAddressTaken();
    120     if (!IsRAAndRetAddrIsTaken)
    121       EntryBlock->addLiveIn(Reg);
    122   }
    123 
    124   return true;
    125 }
    126 
    127 bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
    128                                           MachineBasicBlock::iterator MI,
    129                                        const std::vector<CalleeSavedInfo> &CSI,
    130                                        const TargetRegisterInfo *TRI) const {
    131   //
    132   // Registers RA,S0,S1 are the callee saved registers and they will be restored
    133   // with the restore instruction during emitEpilogue.
    134   // We need to override this virtual function, otherwise llvm will try and
    135   // restore the registers on it's on from the stack.
    136   //
    137 
    138   return true;
    139 }
    140 
    141 // Eliminate ADJCALLSTACKDOWN, ADJCALLSTACKUP pseudo instructions
    142 void Mips16FrameLowering::
    143 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
    144                               MachineBasicBlock::iterator I) const {
    145   if (!hasReservedCallFrame(MF)) {
    146     int64_t Amount = I->getOperand(0).getImm();
    147 
    148     if (I->getOpcode() == Mips::ADJCALLSTACKDOWN)
    149       Amount = -Amount;
    150 
    151     const Mips16InstrInfo &TII =
    152       *static_cast<const Mips16InstrInfo*>(MF.getTarget().getInstrInfo());
    153 
    154     TII.adjustStackPtr(Mips::SP, Amount, MBB, I);
    155   }
    156 
    157   MBB.erase(I);
    158 }
    159 
    160 bool
    161 Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
    162   const MachineFrameInfo *MFI = MF.getFrameInfo();
    163   // Reserve call frame if the size of the maximum call frame fits into 15-bit
    164   // immediate field and there are no variable sized objects on the stack.
    165   return isInt<15>(MFI->getMaxCallFrameSize()) && !MFI->hasVarSizedObjects();
    166 }
    167 
    168 void Mips16FrameLowering::
    169 processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
    170                                      RegScavenger *RS) const {
    171   MF.getRegInfo().setPhysRegUsed(Mips::RA);
    172   MF.getRegInfo().setPhysRegUsed(Mips::S0);
    173   MF.getRegInfo().setPhysRegUsed(Mips::S1);
    174   MF.getRegInfo().setPhysRegUsed(Mips::S2);
    175 }
    176 
    177 const MipsFrameLowering *
    178 llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
    179   return new Mips16FrameLowering(ST);
    180 }
    181