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      1 //===-- SparcFrameLowering.cpp - Sparc 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 Sparc implementation of TargetFrameLowering class.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "SparcFrameLowering.h"
     15 #include "SparcInstrInfo.h"
     16 #include "SparcMachineFunctionInfo.h"
     17 #include "SparcSubtarget.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 static cl::opt<bool>
     31 DisableLeafProc("disable-sparc-leaf-proc",
     32                 cl::init(false),
     33                 cl::desc("Disable Sparc leaf procedure optimization."),
     34                 cl::Hidden);
     35 
     36 SparcFrameLowering::SparcFrameLowering(const SparcSubtarget &ST)
     37     : TargetFrameLowering(TargetFrameLowering::StackGrowsDown,
     38                           ST.is64Bit() ? 16 : 8, 0, ST.is64Bit() ? 16 : 8) {}
     39 
     40 void SparcFrameLowering::emitSPAdjustment(MachineFunction &MF,
     41                                           MachineBasicBlock &MBB,
     42                                           MachineBasicBlock::iterator MBBI,
     43                                           int NumBytes,
     44                                           unsigned ADDrr,
     45                                           unsigned ADDri) const {
     46 
     47   DebugLoc dl = (MBBI != MBB.end()) ? MBBI->getDebugLoc() : DebugLoc();
     48   const SparcInstrInfo &TII =
     49       *static_cast<const SparcInstrInfo *>(MF.getSubtarget().getInstrInfo());
     50 
     51   if (NumBytes >= -4096 && NumBytes < 4096) {
     52     BuildMI(MBB, MBBI, dl, TII.get(ADDri), SP::O6)
     53       .addReg(SP::O6).addImm(NumBytes);
     54     return;
     55   }
     56 
     57   // Emit this the hard way.  This clobbers G1 which we always know is
     58   // available here.
     59   if (NumBytes >= 0) {
     60     // Emit nonnegative numbers with sethi + or.
     61     // sethi %hi(NumBytes), %g1
     62     // or %g1, %lo(NumBytes), %g1
     63     // add %sp, %g1, %sp
     64     BuildMI(MBB, MBBI, dl, TII.get(SP::SETHIi), SP::G1)
     65       .addImm(HI22(NumBytes));
     66     BuildMI(MBB, MBBI, dl, TII.get(SP::ORri), SP::G1)
     67       .addReg(SP::G1).addImm(LO10(NumBytes));
     68     BuildMI(MBB, MBBI, dl, TII.get(ADDrr), SP::O6)
     69       .addReg(SP::O6).addReg(SP::G1);
     70     return ;
     71   }
     72 
     73   // Emit negative numbers with sethi + xor.
     74   // sethi %hix(NumBytes), %g1
     75   // xor %g1, %lox(NumBytes), %g1
     76   // add %sp, %g1, %sp
     77   BuildMI(MBB, MBBI, dl, TII.get(SP::SETHIi), SP::G1)
     78     .addImm(HIX22(NumBytes));
     79   BuildMI(MBB, MBBI, dl, TII.get(SP::XORri), SP::G1)
     80     .addReg(SP::G1).addImm(LOX10(NumBytes));
     81   BuildMI(MBB, MBBI, dl, TII.get(ADDrr), SP::O6)
     82     .addReg(SP::O6).addReg(SP::G1);
     83 }
     84 
     85 void SparcFrameLowering::emitPrologue(MachineFunction &MF) const {
     86   SparcMachineFunctionInfo *FuncInfo = MF.getInfo<SparcMachineFunctionInfo>();
     87 
     88   MachineBasicBlock &MBB = MF.front();
     89   MachineFrameInfo *MFI = MF.getFrameInfo();
     90   const SparcInstrInfo &TII =
     91       *static_cast<const SparcInstrInfo *>(MF.getSubtarget().getInstrInfo());
     92   MachineBasicBlock::iterator MBBI = MBB.begin();
     93   DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
     94 
     95   // Get the number of bytes to allocate from the FrameInfo
     96   int NumBytes = (int) MFI->getStackSize();
     97 
     98   unsigned SAVEri = SP::SAVEri;
     99   unsigned SAVErr = SP::SAVErr;
    100   if (FuncInfo->isLeafProc()) {
    101     if (NumBytes == 0)
    102       return;
    103     SAVEri = SP::ADDri;
    104     SAVErr = SP::ADDrr;
    105   }
    106   NumBytes = -MF.getSubtarget<SparcSubtarget>().getAdjustedFrameSize(NumBytes);
    107   emitSPAdjustment(MF, MBB, MBBI, NumBytes, SAVErr, SAVEri);
    108 
    109   MachineModuleInfo &MMI = MF.getMMI();
    110   const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
    111   unsigned regFP = MRI->getDwarfRegNum(SP::I6, true);
    112 
    113   // Emit ".cfi_def_cfa_register 30".
    114   unsigned CFIIndex =
    115       MMI.addFrameInst(MCCFIInstruction::createDefCfaRegister(nullptr, regFP));
    116   BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
    117       .addCFIIndex(CFIIndex);
    118 
    119   // Emit ".cfi_window_save".
    120   CFIIndex = MMI.addFrameInst(MCCFIInstruction::createWindowSave(nullptr));
    121   BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
    122       .addCFIIndex(CFIIndex);
    123 
    124   unsigned regInRA = MRI->getDwarfRegNum(SP::I7, true);
    125   unsigned regOutRA = MRI->getDwarfRegNum(SP::O7, true);
    126   // Emit ".cfi_register 15, 31".
    127   CFIIndex = MMI.addFrameInst(
    128       MCCFIInstruction::createRegister(nullptr, regOutRA, regInRA));
    129   BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
    130       .addCFIIndex(CFIIndex);
    131 }
    132 
    133 void SparcFrameLowering::
    134 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
    135                               MachineBasicBlock::iterator I) const {
    136   if (!hasReservedCallFrame(MF)) {
    137     MachineInstr &MI = *I;
    138     int Size = MI.getOperand(0).getImm();
    139     if (MI.getOpcode() == SP::ADJCALLSTACKDOWN)
    140       Size = -Size;
    141 
    142     if (Size)
    143       emitSPAdjustment(MF, MBB, I, Size, SP::ADDrr, SP::ADDri);
    144   }
    145   MBB.erase(I);
    146 }
    147 
    148 
    149 void SparcFrameLowering::emitEpilogue(MachineFunction &MF,
    150                                   MachineBasicBlock &MBB) const {
    151   SparcMachineFunctionInfo *FuncInfo = MF.getInfo<SparcMachineFunctionInfo>();
    152   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
    153   const SparcInstrInfo &TII =
    154       *static_cast<const SparcInstrInfo *>(MF.getSubtarget().getInstrInfo());
    155   DebugLoc dl = MBBI->getDebugLoc();
    156   assert(MBBI->getOpcode() == SP::RETL &&
    157          "Can only put epilog before 'retl' instruction!");
    158   if (!FuncInfo->isLeafProc()) {
    159     BuildMI(MBB, MBBI, dl, TII.get(SP::RESTORErr), SP::G0).addReg(SP::G0)
    160       .addReg(SP::G0);
    161     return;
    162   }
    163   MachineFrameInfo *MFI = MF.getFrameInfo();
    164 
    165   int NumBytes = (int) MFI->getStackSize();
    166   if (NumBytes == 0)
    167     return;
    168 
    169   NumBytes = MF.getSubtarget<SparcSubtarget>().getAdjustedFrameSize(NumBytes);
    170   emitSPAdjustment(MF, MBB, MBBI, NumBytes, SP::ADDrr, SP::ADDri);
    171 }
    172 
    173 bool SparcFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
    174   // Reserve call frame if there are no variable sized objects on the stack.
    175   return !MF.getFrameInfo()->hasVarSizedObjects();
    176 }
    177 
    178 // hasFP - Return true if the specified function should have a dedicated frame
    179 // pointer register.  This is true if the function has variable sized allocas or
    180 // if frame pointer elimination is disabled.
    181 bool SparcFrameLowering::hasFP(const MachineFunction &MF) const {
    182   const MachineFrameInfo *MFI = MF.getFrameInfo();
    183   return MF.getTarget().Options.DisableFramePointerElim(MF) ||
    184     MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken();
    185 }
    186 
    187 
    188 static bool LLVM_ATTRIBUTE_UNUSED verifyLeafProcRegUse(MachineRegisterInfo *MRI)
    189 {
    190 
    191   for (unsigned reg = SP::I0; reg <= SP::I7; ++reg)
    192     if (MRI->isPhysRegUsed(reg))
    193       return false;
    194 
    195   for (unsigned reg = SP::L0; reg <= SP::L7; ++reg)
    196     if (MRI->isPhysRegUsed(reg))
    197       return false;
    198 
    199   return true;
    200 }
    201 
    202 bool SparcFrameLowering::isLeafProc(MachineFunction &MF) const
    203 {
    204 
    205   MachineRegisterInfo &MRI = MF.getRegInfo();
    206   MachineFrameInfo    *MFI = MF.getFrameInfo();
    207 
    208   return !(MFI->hasCalls()              // has calls
    209            || MRI.isPhysRegUsed(SP::L0) // Too many registers needed
    210            || MRI.isPhysRegUsed(SP::O6) // %SP is used
    211            || hasFP(MF));               // need %FP
    212 }
    213 
    214 void SparcFrameLowering::remapRegsForLeafProc(MachineFunction &MF) const {
    215 
    216   MachineRegisterInfo &MRI = MF.getRegInfo();
    217 
    218   // Remap %i[0-7] to %o[0-7].
    219   for (unsigned reg = SP::I0; reg <= SP::I7; ++reg) {
    220     if (!MRI.isPhysRegUsed(reg))
    221       continue;
    222     unsigned mapped_reg = (reg - SP::I0 + SP::O0);
    223     assert(!MRI.isPhysRegUsed(mapped_reg));
    224 
    225     // Replace I register with O register.
    226     MRI.replaceRegWith(reg, mapped_reg);
    227 
    228     // Mark the reg unused.
    229     MRI.setPhysRegUnused(reg);
    230   }
    231 
    232   // Rewrite MBB's Live-ins.
    233   for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
    234        MBB != E; ++MBB) {
    235     for (unsigned reg = SP::I0; reg <= SP::I7; ++reg) {
    236       if (!MBB->isLiveIn(reg))
    237         continue;
    238       MBB->removeLiveIn(reg);
    239       MBB->addLiveIn(reg - SP::I0 + SP::O0);
    240     }
    241   }
    242 
    243   assert(verifyLeafProcRegUse(&MRI));
    244 #ifdef XDEBUG
    245   MF.verify(0, "After LeafProc Remapping");
    246 #endif
    247 }
    248 
    249 void SparcFrameLowering::processFunctionBeforeCalleeSavedScan
    250                   (MachineFunction &MF, RegScavenger *RS) const {
    251 
    252   if (!DisableLeafProc && isLeafProc(MF)) {
    253     SparcMachineFunctionInfo *MFI = MF.getInfo<SparcMachineFunctionInfo>();
    254     MFI->setLeafProc(true);
    255 
    256     remapRegsForLeafProc(MF);
    257   }
    258 
    259 }
    260