[SystemZ] [NFC] Add SystemZELFFrameLowering and SystemZXPLINKFrameLowering classes.

[Everybody0523]

Summary

This patch adds class SystemZFrameLowering which is a SystemZ-specific class detailing special registers used by calling conventions on the target. SystemZELFFrameLowering and SystemZXPLINKFrameLowering implement this class for ELF and XPLINK64 respectively. Previous functionality in SystemZFrameLowering is moved to SystemZELFFrameLowering. SystemZXPLINKFrameLowering can then be implemented in future patches.

[uweigand]

LGTM

[Everybody0523]

Fix some formatting issues + use make_unique in create method instead of having it return a raw ptr.

[Everybody0523]

More formatting issues.

[Kai]

LGTM.
Please have a look of the formatting of the line I commented. Thanks.

llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp

768–770

This line seems to be too long. Please, can you check again?

[Everybody0523]

Update length of line in accordance with feedback

[Everybody0523]

No change, hopefully applying patch won't result in a bug again.

[Kai]

Sorry, after seeing the pre-check builds, I checked the formatting again.
The code looks ok, but almost all function heads with argument lists running over several lines needs reformatting.

llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp

64

Formatting looks wrong.

79

Formatting looks wrong.

80

Trailing space at end of line.

208

Formatting seems to be wrong.

[Everybody0523]

Formatting changes as per clang-format.

[uweigand]

Formatting looks good to me now as well. Still LGTM.

[Kai]

LGTM.

llvm/lib/Target/SystemZ/SystemZFrameLowering.h

 #include "llvm/CodeGen/TargetFrameLowering.h"
 #include "llvm/Support/TypeSize.h"
 
 namespace llvm {
 class SystemZTargetMachine;
 class SystemZSubtarget;
 
 class SystemZFrameLowering : public TargetFrameLowering {
+
+public:
+  SystemZFrameLowering(StackDirection D, Align StackAl, int LAO, Align TransAl,
+                       bool StackReal);
+
+  static std::unique_ptr<SystemZFrameLowering> create(const SystemZSubtarget &STI);
+
+  // Override TargetFrameLowering.
+  bool isFPCloseToIncomingSP() const override { return false; }
+  bool hasReservedCallFrame(const MachineFunction &MF) const override;
+  MachineBasicBlock::iterator
+  eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
+                                MachineBasicBlock::iterator MI) const override;
+};
+
+class SystemZELFFrameLowering : public SystemZFrameLowering {
   IndexedMap<unsigned> RegSpillOffsets;
 
 public:
-  SystemZFrameLowering();
+  SystemZELFFrameLowering();
 
   // Override TargetFrameLowering.
   bool isFPCloseToIncomingSP() const override { return false; }
   bool
   assignCalleeSavedSpillSlots(MachineFunction &MF,
                               const TargetRegisterInfo *TRI,
                               std::vector<CalleeSavedInfo> &CSI) const override;
   void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,
restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
                               const TargetRegisterInfo *TRI) const override;
   void processFunctionBeforeFrameFinalized(MachineFunction &MF,
                                            RegScavenger *RS) const override;
   void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
   void inlineStackProbe(MachineFunction &MF,
                         MachineBasicBlock &PrologMBB) const override;
   bool hasFP(const MachineFunction &MF) const override;
-  bool hasReservedCallFrame(const MachineFunction &MF) const override;
   StackOffset getFrameIndexReference(const MachineFunction &MF, int FI,
                                      Register &FrameReg) const override;
-  MachineBasicBlock::iterator
-  eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
-                                MachineBasicBlock::iterator MI) const override;
 
   // Return the byte offset from the incoming stack pointer of Reg's
   // ABI-defined save slot.  Return 0 if no slot is defined for Reg.  Adjust
   // the offset in case MF has packed-stack.
   unsigned getRegSpillOffset(MachineFunction &MF, Register Reg) const;
 
-  // Get or create the frame index of where the old frame pointer is stored.
-  int getOrCreateFramePointerSaveIndex(MachineFunction &MF) const;
-
   bool usePackedStack(MachineFunction &MF) const;
 
   // Return the offset of the backchain.
   unsigned getBackchainOffset(MachineFunction &MF) const {
     // The back chain is stored topmost with packed-stack.
     return usePackedStack(MF) ? SystemZMC::ELFCallFrameSize - 8 : 0;
   }
+
+  // Get or create the frame index of where the old frame pointer is stored.
+  int getOrCreateFramePointerSaveIndex(MachineFunction &MF) const;
+};
+
+class SystemZXPLINKFrameLowering : public SystemZFrameLowering {
+public:
+  SystemZXPLINKFrameLowering();
+
+  void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
+
+  void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
+
+  bool hasFP(const MachineFunction &MF) const override;
 };
 } // end namespace llvm
 
 #endif

llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp

static const TargetFrameLowering::SpillSlot SpillOffsetTable[] = {
   { SystemZ::R15D, 0x78 },
   { SystemZ::F0D,  0x80 },
   { SystemZ::F2D,  0x88 },
   { SystemZ::F4D,  0x90 },
   { SystemZ::F6D,  0x98 }
 };
 } // end anonymous namespace
 
-SystemZFrameLowering::SystemZFrameLowering()
-    : TargetFrameLowering(TargetFrameLowering::StackGrowsDown, Align(8),
-                          0, Align(8), false /* StackRealignable */),
-      RegSpillOffsets(0) {
-  // Due to the SystemZ ABI, the DWARF CFA (Canonical Frame Address) is not
-  // equal to the incoming stack pointer, but to incoming stack pointer plus
-  // 160.  Instead of using a Local Area Offset, the Register save area will
-  // be occupied by fixed frame objects, and all offsets are actually
-  // relative to CFA.
+SystemZFrameLowering::SystemZFrameLowering(StackDirection D, Align StackAl,
+                                           int LAO, Align TransAl,
+                                           bool StackReal)
+    : TargetFrameLowering(D, StackAl, LAO, TransAl, StackReal) {}
+
+std::unique_ptr<SystemZFrameLowering>
+SystemZFrameLowering::create(const SystemZSubtarget &STI) {
+  if (STI.isTargetXPLINK64())
+    return std::make_unique<SystemZXPLINKFrameLowering>();
+  return std::make_unique<SystemZELFFrameLowering>();
+}
 
-  // Create a mapping from register number to save slot offset.
-  // These offsets are relative to the start of the register save area.
-  RegSpillOffsets.grow(SystemZ::NUM_TARGET_REGS);
-  for (unsigned I = 0, E = array_lengthof(SpillOffsetTable); I != E; ++I)
-    RegSpillOffsets[SpillOffsetTable[I].Reg] = SpillOffsetTable[I].Offset;
+MachineBasicBlock::iterator SystemZFrameLowering::
+eliminateCallFramePseudoInstr(MachineFunction &MF,
+                              MachineBasicBlock &MBB,
+                              MachineBasicBlock::iterator MI) const {
+  switch (MI->getOpcode()) {
+  case SystemZ::ADJCALLSTACKDOWN:
+  case SystemZ::ADJCALLSTACKUP:
+    assert(hasReservedCallFrame(MF) &&
+           "ADJSTACKDOWN and ADJSTACKUP should be no-ops");
+    return MBB.erase(MI);
+    break;
+
+  default:
+    llvm_unreachable("Unexpected call frame instruction");
+  }
 }
 
-bool SystemZFrameLowering::
+bool
+SystemZFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
+  // The ELF ABI requires us to allocate 160 bytes of stack space for the 
+  // callee, with any outgoing stack arguments being placed above that. It
+  // seems better to make that area a permanent feature of the frame even if
+  // we're using a frame pointer. Similarly, 64-bit XPLINK requires 96 bytes
+  // of stack space for the register save area.
+  return true;
+}
+
+bool SystemZELFFrameLowering::
 assignCalleeSavedSpillSlots(MachineFunction &MF,
                             const TargetRegisterInfo *TRI,
                             std::vector<CalleeSavedInfo> &CSI) const {
   SystemZMachineFunctionInfo *ZFI = MF.getInfo<SystemZMachineFunctionInfo>();
   MachineFrameInfo &MFFrame = MF.getFrameInfo();
   bool IsVarArg = MF.getFunction().isVarArg();
   if (CSI.empty())
     return true; // Early exit if no callee saved registers are modified!
assert(CurrOffset % 8 == 0 &&
            "8-byte alignment required for for all register save slots");
     int FrameIdx = MFFrame.CreateFixedSpillStackObject(Size, CurrOffset);
     CS.setFrameIdx(FrameIdx);
   }
 
   return true;
 }
 
-void SystemZFrameLowering::determineCalleeSaves(MachineFunction &MF,
+void SystemZELFFrameLowering::determineCalleeSaves(MachineFunction &MF,
                                                    BitVector &SavedRegs,
                                                    RegScavenger *RS) const {
   TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
 
   MachineFrameInfo &MFFrame = MF.getFrameInfo();
   const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
   bool HasFP = hasFP(MF);
   SystemZMachineFunctionInfo *MFI = MF.getInfo<SystemZMachineFunctionInfo>();
   bool IsVarArg = MF.getFunction().isVarArg();
 
for (unsigned I = 0; CSRegs[I]; ++I) {
     unsigned Reg = CSRegs[I];
     if (SystemZ::GR64BitRegClass.contains(Reg) && SavedRegs.test(Reg)) {
       SavedRegs.set(SystemZ::R15D);
       break;
     }
   }
 }
 
+SystemZELFFrameLowering::SystemZELFFrameLowering()
+    : SystemZFrameLowering(TargetFrameLowering::StackGrowsDown, Align(8),
+                           0, Align(8), false /* StackRealignable */),
+                           RegSpillOffsets(0) {
+  // Due to the SystemZ ABI, the DWARF CFA (Canonical Frame Address) is not
+  // equal to the incoming stack pointer, but to incoming stack pointer plus
+  // 160.  Instead of using a Local Area Offset, the Register save area will
+  // be occupied by fixed frame objects, and all offsets are actually
+  // relative to CFA.
+
+  // Create a mapping from register number to save slot offset.
+  // These offsets are relative to the start of the register save area.
+  RegSpillOffsets.grow(SystemZ::NUM_TARGET_REGS);
+  for (unsigned I = 0, E = array_lengthof(SpillOffsetTable); I != E; ++I)
+    RegSpillOffsets[SpillOffsetTable[I].Reg] = SpillOffsetTable[I].Offset;
+}
+
 // Add GPR64 to the save instruction being built by MIB, which is in basic
 // block MBB.  IsImplicit says whether this is an explicit operand to the
 // instruction, or an implicit one that comes between the explicit start
 // and end registers.
 static void addSavedGPR(MachineBasicBlock &MBB, MachineInstrBuilder &MIB,
                         unsigned GPR64, bool IsImplicit) {
   const TargetRegisterInfo *RI =
       MBB.getParent()->getSubtarget().getRegisterInfo();
   Register GPR32 = RI->getSubReg(GPR64, SystemZ::subreg_l32);
   bool IsLive = MBB.isLiveIn(GPR64) || MBB.isLiveIn(GPR32);
   if (!IsLive || !IsImplicit) {
     MIB.addReg(GPR64, getImplRegState(IsImplicit) | getKillRegState(!IsLive));
     if (!IsLive)
       MBB.addLiveIn(GPR64);
   }
 }
 
-bool SystemZFrameLowering::spillCalleeSavedRegisters(
+bool SystemZELFFrameLowering::spillCalleeSavedRegisters(
     MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
     ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
   if (CSI.empty())
     return false;
 
   MachineFunction &MF = *MBB.getParent();
   const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
   SystemZMachineFunctionInfo *ZFI = MF.getInfo<SystemZMachineFunctionInfo>();
if (SystemZ::VR128BitRegClass.contains(Reg)) {
       TII->storeRegToStackSlot(MBB, MBBI, Reg, true, CSI[I].getFrameIdx(),
                                &SystemZ::VR128BitRegClass, TRI);
     }
   }
 
   return true;
 }
 
-bool SystemZFrameLowering::restoreCalleeSavedRegisters(
+bool SystemZELFFrameLowering::restoreCalleeSavedRegisters(
     MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
     MutableArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
   if (CSI.empty())
     return false;
 
   MachineFunction &MF = *MBB.getParent();
   const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
   SystemZMachineFunctionInfo *ZFI = MF.getInfo<SystemZMachineFunctionInfo>();
for (unsigned I = 0, E = CSI.size(); I != E; ++I) {
           SystemZ::GR64BitRegClass.contains(Reg))
         MIB.addReg(Reg, RegState::ImplicitDefine);
     }
   }
 
   return true;
 }
 
-void SystemZFrameLowering::
+void SystemZELFFrameLowering::
 processFunctionBeforeFrameFinalized(MachineFunction &MF,
                                     RegScavenger *RS) const {
   MachineFrameInfo &MFFrame = MF.getFrameInfo();
   SystemZMachineFunctionInfo *ZFI = MF.getInfo<SystemZMachineFunctionInfo>();
   MachineRegisterInfo *MRI = &MF.getRegInfo();
   bool BackChain = MF.getFunction().hasFnAttribute("backchain");
 
   if (!usePackedStack(MF) || BackChain)
static void buildDefCFAReg(MachineBasicBlock &MBB,
   const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
   unsigned RegNum = MRI->getDwarfRegNum(Reg, true);
   unsigned CFIIndex = MF.addFrameInst(
                         MCCFIInstruction::createDefCfaRegister(nullptr, RegNum));
   BuildMI(MBB, MBBI, DL, ZII->get(TargetOpcode::CFI_INSTRUCTION))
     .addCFIIndex(CFIIndex);
 }
 
-void SystemZFrameLowering::emitPrologue(MachineFunction &MF,
+void SystemZELFFrameLowering::emitPrologue(MachineFunction &MF,
                                            MachineBasicBlock &MBB) const {
   assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
   const SystemZSubtarget &STI = MF.getSubtarget<SystemZSubtarget>();
   const SystemZTargetLowering &TLI = *STI.getTargetLowering();
   MachineFrameInfo &MFFrame = MF.getFrameInfo();
   auto *ZII = static_cast<const SystemZInstrInfo *>(STI.getInstrInfo());
   SystemZMachineFunctionInfo *ZFI = MF.getInfo<SystemZMachineFunctionInfo>();
   MachineBasicBlock::iterator MBBI = MBB.begin();
   MachineModuleInfo &MMI = MF.getMMI();
void SystemZELFFrameLowering::emitPrologue(MachineFunction &MF,
   // Complete the CFI for the FPR/VR saves, modelling them as taking effect
   // after the last save.
   for (auto CFIIndex : CFIIndexes) {
     BuildMI(MBB, MBBI, DL, ZII->get(TargetOpcode::CFI_INSTRUCTION))
         .addCFIIndex(CFIIndex);
   }
 }
 
-void SystemZFrameLowering::emitEpilogue(MachineFunction &MF,
+void SystemZELFFrameLowering::emitEpilogue(MachineFunction &MF,
                                            MachineBasicBlock &MBB) const {
   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
   auto *ZII =
       static_cast<const SystemZInstrInfo *>(MF.getSubtarget().getInstrInfo());
   SystemZMachineFunctionInfo *ZFI = MF.getInfo<SystemZMachineFunctionInfo>();
   MachineFrameInfo &MFFrame = MF.getFrameInfo();
 
-  // See SystemZFrameLowering::emitPrologue
+  // See SystemZELFFrameLowering::emitPrologue
   if (MF.getFunction().getCallingConv() == CallingConv::GHC)
     return;
 
   // Skip the return instruction.
   assert(MBBI->isReturn() && "Can only insert epilogue into returning blocks");
 
   uint64_t StackSize = MFFrame.getStackSize();
   if (ZFI->getRestoreGPRRegs().LowGPR) {
if (ZFI->getRestoreGPRRegs().LowGPR) {
     MBBI->setDesc(ZII->get(NewOpcode));
     MBBI->getOperand(AddrOpNo + 1).ChangeToImmediate(Offset);
   } else if (StackSize) {
     DebugLoc DL = MBBI->getDebugLoc();
     emitIncrement(MBB, MBBI, DL, SystemZ::R15D, StackSize, ZII);
   }
 }
 
-void SystemZFrameLowering::inlineStackProbe(MachineFunction &MF,
+void SystemZELFFrameLowering::inlineStackProbe(MachineFunction &MF,
                                                MachineBasicBlock &PrologMBB) const {
   auto *ZII =
     static_cast<const SystemZInstrInfo *>(MF.getSubtarget().getInstrInfo());
   const SystemZSubtarget &STI = MF.getSubtarget<SystemZSubtarget>();
   const SystemZTargetLowering &TLI = *STI.getTargetLowering();
 
   MachineInstr *StackAllocMI = nullptr;
   for (MachineInstr &MI : PrologMBB)
     if (MI.getOpcode() == SystemZ::PROBED_STACKALLOC) {
void SystemZELFFrameLowering::inlineStackProbe(MachineFunction &MF,
   StackAllocMI->eraseFromParent();
   if (DoneMBB != nullptr) {
     // Compute the live-in lists for the new blocks.
     recomputeLiveIns(*DoneMBB);
     recomputeLiveIns(*LoopMBB);
   }
 }
 
-bool SystemZFrameLowering::hasFP(const MachineFunction &MF) const {
+bool SystemZELFFrameLowering::hasFP(const MachineFunction &MF) const {
   return (MF.getTarget().Options.DisableFramePointerElim(MF) ||
           MF.getFrameInfo().hasVarSizedObjects() ||
           MF.getInfo<SystemZMachineFunctionInfo>()->getManipulatesSP());
 }
 
-bool
-SystemZFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
-  // The ABI requires us to allocate 160 bytes of stack space for the callee,
-  // with any outgoing stack arguments being placed above that.  It seems
-  // better to make that area a permanent feature of the frame even if
-  // we're using a frame pointer.
-  return true;
-}
-
 StackOffset
-SystemZFrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
+SystemZELFFrameLowering::getFrameIndexReference(const MachineFunction &MF,
+                                                int FI,
                                                 Register &FrameReg) const {
   // Our incoming SP is actually SystemZMC::ELFCallFrameSize below the CFA, so
   // add that difference here.
   StackOffset Offset =
       TargetFrameLowering::getFrameIndexReference(MF, FI, FrameReg);
   return Offset + StackOffset::getFixed(SystemZMC::ELFCallFrameSize);
 }
 
-MachineBasicBlock::iterator SystemZFrameLowering::
-eliminateCallFramePseudoInstr(MachineFunction &MF,
-                              MachineBasicBlock &MBB,
-                              MachineBasicBlock::iterator MI) const {
-  switch (MI->getOpcode()) {
-  case SystemZ::ADJCALLSTACKDOWN:
-  case SystemZ::ADJCALLSTACKUP:
-    assert(hasReservedCallFrame(MF) &&
-           "ADJSTACKDOWN and ADJSTACKUP should be no-ops");
-    return MBB.erase(MI);
-    break;
-
-  default:
-    llvm_unreachable("Unexpected call frame instruction");
-  }
-}
-
-unsigned SystemZFrameLowering::getRegSpillOffset(MachineFunction &MF,
+unsigned SystemZELFFrameLowering::getRegSpillOffset(MachineFunction &MF,
                                                     Register Reg) const {
   bool IsVarArg = MF.getFunction().isVarArg();
   bool BackChain = MF.getFunction().hasFnAttribute("backchain");
   bool SoftFloat = MF.getSubtarget<SystemZSubtarget>().hasSoftFloat();
   unsigned Offset = RegSpillOffsets[Reg];
   if (usePackedStack(MF) && !(IsVarArg && !SoftFloat)) {
     if (SystemZ::GR64BitRegClass.contains(Reg))
       // Put all GPRs at the top of the Register save area with packed
       // stack. Make room for the backchain if needed.
       Offset += BackChain ? 24 : 32;
     else
       Offset = 0;
   }
   return Offset;
 }
 
-int SystemZFrameLowering::
+int SystemZELFFrameLowering::
 getOrCreateFramePointerSaveIndex(MachineFunction &MF) const {
   SystemZMachineFunctionInfo *ZFI = MF.getInfo<SystemZMachineFunctionInfo>();
   int FI = ZFI->getFramePointerSaveIndex();
   if (!FI) {
     MachineFrameInfo &MFFrame = MF.getFrameInfo();
     int Offset = getBackchainOffset(MF) - SystemZMC::ELFCallFrameSize;
     FI = MFFrame.CreateFixedObject(8, Offset, false);
     ZFI->setFramePointerSaveIndex(FI);
   }
   return FI;
 }
 
-bool SystemZFrameLowering::usePackedStack(MachineFunction &MF) const {
+bool SystemZELFFrameLowering::usePackedStack(MachineFunction &MF) const {
   bool HasPackedStackAttr = MF.getFunction().hasFnAttribute("packed-stack");
   bool BackChain = MF.getFunction().hasFnAttribute("backchain");
   bool SoftFloat = MF.getSubtarget<SystemZSubtarget>().hasSoftFloat();
   if (HasPackedStackAttr && BackChain && !SoftFloat)
     report_fatal_error("packed-stack + backchain + hard-float is unsupported.");
   bool CallConv = MF.getFunction().getCallingConv() != CallingConv::GHC;
   return HasPackedStackAttr && CallConv;
 }
+
+SystemZXPLINKFrameLowering::SystemZXPLINKFrameLowering()
+    : SystemZFrameLowering(TargetFrameLowering::StackGrowsUp, Align(32),
+                           128, Align(32), false /* StackRealignable */) {}
+
+void SystemZXPLINKFrameLowering::emitPrologue(MachineFunction &MF,
+                                              MachineBasicBlock &MBB) const {}
+
+void SystemZXPLINKFrameLowering::emitEpilogue(MachineFunction &MF,
+                                              MachineBasicBlock &MBB) const {}
+
+bool SystemZXPLINKFrameLowering::hasFP(const MachineFunction &MF) const {
+  return false;
+}

llvm/lib/Target/SystemZ/SystemZISelLowering.cpp

SDValue SystemZTargetLowering::LowerFormalArguments(
     SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
     const SmallVectorImpl<ISD::InputArg> &Ins, const SDLoc &DL,
     SelectionDAG &DAG, SmallVectorImpl<SDValue> &InVals) const {
   MachineFunction &MF = DAG.getMachineFunction();
   MachineFrameInfo &MFI = MF.getFrameInfo();
   MachineRegisterInfo &MRI = MF.getRegInfo();
   SystemZMachineFunctionInfo *FuncInfo =
       MF.getInfo<SystemZMachineFunctionInfo>();
-  auto *TFL =
-      static_cast<const SystemZFrameLowering *>(Subtarget.getFrameLowering());
+  auto *TFL = Subtarget.getFrameLowering<SystemZELFFrameLowering>();
   EVT PtrVT = getPointerTy(DAG.getDataLayout());
 
   // Detect unsupported vector argument types.
   if (Subtarget.hasVector())
     VerifyVectorTypes(Ins);
 
   // Assign locations to all of the incoming arguments.
   SmallVector<CCValAssign, 16> ArgLocs;
Result = DAG.getTargetConstantPool(CP->getConstVal(), PtrVT, CP->getAlign(),
                                        CP->getOffset());
 
   // Use LARL to load the address of the constant pool entry.
   return DAG.getNode(SystemZISD::PCREL_WRAPPER, DL, PtrVT, Result);
 }
 
 SDValue SystemZTargetLowering::lowerFRAMEADDR(SDValue Op,
                                               SelectionDAG &DAG) const {
-  auto *TFL =
-      static_cast<const SystemZFrameLowering *>(Subtarget.getFrameLowering());
+  auto *TFL = Subtarget.getFrameLowering<SystemZELFFrameLowering>();
   MachineFunction &MF = DAG.getMachineFunction();
   MachineFrameInfo &MFI = MF.getFrameInfo();
   MFI.setFrameAddressIsTaken(true);
 
   SDLoc DL(Op);
   unsigned Depth = cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue();
   EVT PtrVT = getPointerTy(DAG.getDataLayout());
 
MachineBasicBlock *SystemZTargetLowering::emitProbedAlloca(
 
   MI.eraseFromParent();
   return DoneMBB;
 }
 
 SDValue SystemZTargetLowering::
 getBackchainAddress(SDValue SP, SelectionDAG &DAG) const {
   MachineFunction &MF = DAG.getMachineFunction();
-  auto *TFL =
-      static_cast<const SystemZFrameLowering *>(Subtarget.getFrameLowering());
+  auto *TFL = Subtarget.getFrameLowering<SystemZELFFrameLowering>();
   SDLoc DL(SP);
   return DAG.getNode(ISD::ADD, DL, MVT::i64, SP,
                      DAG.getIntPtrConstant(TFL->getBackchainOffset(MF), DL));
 }
 
 MachineBasicBlock *SystemZTargetLowering::EmitInstrWithCustomInserter(
     MachineInstr &MI, MachineBasicBlock *MBB) const {
   switch (MI.getOpcode()) {

llvm/lib/Target/SystemZ/SystemZSubtarget.h

protected:
   bool HasSoftFloat;
 
 private:
   Triple TargetTriple;
   std::unique_ptr<SystemZCallingConventionRegisters> SpecialRegisters;
   SystemZInstrInfo InstrInfo;
   SystemZTargetLowering TLInfo;
   SystemZSelectionDAGInfo TSInfo;
-  SystemZFrameLowering FrameLowering;
+  std::unique_ptr<const SystemZFrameLowering> FrameLowering;
 
   SystemZSubtarget &initializeSubtargetDependencies(StringRef CPU,
                                                     StringRef FS);
   SystemZCallingConventionRegisters *initializeSpecialRegisters(void);
 
 public:
   SystemZSubtarget(const Triple &TT, const std::string &CPU,
                    const std::string &FS, const TargetMachine &TM);
 
   SystemZCallingConventionRegisters *getSpecialRegisters() const {
     assert(SpecialRegisters && "Unsupported SystemZ calling convention");
     return SpecialRegisters.get();
   }
 
   const TargetFrameLowering *getFrameLowering() const override {
-    return &FrameLowering;
+    return FrameLowering.get();
   }
+
+  template <class TFL> const TFL *getFrameLowering() const {
+    return static_cast<const TFL *>(getFrameLowering());
+  }
+
   const SystemZInstrInfo *getInstrInfo() const override { return &InstrInfo; }
   const SystemZRegisterInfo *getRegisterInfo() const override {
     return &InstrInfo.getRegisterInfo();
   }
   const SystemZTargetLowering *getTargetLowering() const override {
     return &TLInfo;
   }
   const SelectionDAGTargetInfo *getSelectionDAGInfo() const override {

llvm/lib/Target/SystemZ/SystemZSubtarget.cpp

: SystemZGenSubtargetInfo(TT, CPU, /*TuneCPU*/ CPU, FS),
       HasMessageSecurityAssist9(false), HasVectorEnhancements2(false),
       HasVectorPackedDecimalEnhancement(false), HasEnhancedSort(false),
       HasDeflateConversion(false), HasVectorPackedDecimalEnhancement2(false),
       HasNNPAssist(false), HasBEAREnhancement(false),
       HasResetDATProtection(false), HasProcessorActivityInstrumentation(false),
       HasSoftFloat(false), TargetTriple(TT),
       SpecialRegisters(initializeSpecialRegisters()),
       InstrInfo(initializeSubtargetDependencies(CPU, FS)), TLInfo(TM, *this),
-      TSInfo(), FrameLowering() {}
+      TSInfo(), FrameLowering(SystemZFrameLowering::create(*this)) {}
 
 bool SystemZSubtarget::enableSubRegLiveness() const {
   return UseSubRegLiveness;
 }
 
 bool SystemZSubtarget::isPC32DBLSymbol(const GlobalValue *GV,
                                        CodeModel::Model CM) const {
   // PC32DBL accesses require the low bit to be clear.