llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp

   1 //===-- SystemZRegisterInfo.cpp - SystemZ register 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 #include "SystemZRegisterInfo.h"
  10 #include "SystemZInstrInfo.h"
  11 #include "SystemZSubtarget.h"
  12 #include "llvm/ADT/SmallSet.h"
  13 #include "llvm/CodeGen/LiveIntervals.h"
  14 #include "llvm/CodeGen/MachineInstrBuilder.h"
  15 #include "llvm/CodeGen/MachineRegisterInfo.h"
  16 #include "llvm/CodeGen/TargetFrameLowering.h"
  17 #include "llvm/CodeGen/VirtRegMap.h"
  18 #include "llvm/IR/DebugInfoMetadata.h"
  19
  20 using namespace llvm;
  21
  22 #define GET_REGINFO_TARGET_DESC
  23 #include "SystemZGenRegisterInfo.inc"
  24
  25 // Given that MO is a GRX32 operand, return either GR32 or GRH32 if MO
  26 // somehow belongs in it. Otherwise, return GRX32.
  27 static const TargetRegisterClass *getRC32(MachineOperand &MO,
  28                                           const VirtRegMap *VRM,
  29                                           const MachineRegisterInfo *MRI) {
  30   const TargetRegisterClass *RC = MRI->getRegClass(MO.getReg());
  31
  32   if (SystemZ::GR32BitRegClass.hasSubClassEq(RC) ||
  33       MO.getSubReg() == SystemZ::subreg_ll32 ||
  34       MO.getSubReg() == SystemZ::subreg_l32)
  35     return &SystemZ::GR32BitRegClass;
  36   if (SystemZ::GRH32BitRegClass.hasSubClassEq(RC) ||
  37       MO.getSubReg() == SystemZ::subreg_lh32 ||
  38       MO.getSubReg() == SystemZ::subreg_h32)
  39     return &SystemZ::GRH32BitRegClass;
  40
  41   if (VRM && VRM->hasPhys(MO.getReg())) {
  42     Register PhysReg = VRM->getPhys(MO.getReg());
  43     if (SystemZ::GR32BitRegClass.contains(PhysReg))
  44       return &SystemZ::GR32BitRegClass;
  45     assert (SystemZ::GRH32BitRegClass.contains(PhysReg) &&
  46             "Phys reg not in GR32 or GRH32?");
  47     return &SystemZ::GRH32BitRegClass;
  48   }
  49
  50   assert (RC == &SystemZ::GRX32BitRegClass);
  51   return RC;
  52 }
  53
  54 // Pass the registers of RC as hints while making sure that if any of these
  55 // registers are copy hints (and therefore already in Hints), hint them
  56 // first.
  57 static void addHints(ArrayRef<MCPhysReg> Order,
  58                      SmallVectorImpl<MCPhysReg> &Hints,
  59                      const TargetRegisterClass *RC,
  60                      const MachineRegisterInfo *MRI) {
  61   SmallSet<unsigned, 4> CopyHints;
  62   CopyHints.insert(Hints.begin(), Hints.end());
  63   Hints.clear();
  64   for (MCPhysReg Reg : Order)
  65     if (CopyHints.count(Reg) &&
  66         RC->contains(Reg) && !MRI->isReserved(Reg))
  67       Hints.push_back(Reg);
  68   for (MCPhysReg Reg : Order)
  69     if (!CopyHints.count(Reg) &&
  70         RC->contains(Reg) && !MRI->isReserved(Reg))
  71       Hints.push_back(Reg);
  72 }
  73
  74 bool SystemZRegisterInfo::getRegAllocationHints(
  75     Register VirtReg, ArrayRef<MCPhysReg> Order,
  76     SmallVectorImpl<MCPhysReg> &Hints, const MachineFunction &MF,
  77     const VirtRegMap *VRM, const LiveRegMatrix *Matrix) const {
  78   const MachineRegisterInfo *MRI = &MF.getRegInfo();
  79   const SystemZSubtarget &Subtarget = MF.getSubtarget<SystemZSubtarget>();
  80   const TargetRegisterInfo *TRI = Subtarget.getRegisterInfo();
  81
  82   bool BaseImplRetVal = TargetRegisterInfo::getRegAllocationHints(
  83       VirtReg, Order, Hints, MF, VRM, Matrix);
  84
  85   if (VRM != nullptr) {
  86     // Add any two address hints after any copy hints.
  87     SmallSet<unsigned, 4> TwoAddrHints;
  88     for (auto &Use : MRI->reg_nodbg_instructions(VirtReg))
  89       if (SystemZ::getTwoOperandOpcode(Use.getOpcode()) != -1) {
  90         const MachineOperand *VRRegMO = nullptr;
  91         const MachineOperand *OtherMO = nullptr;
  92         const MachineOperand *CommuMO = nullptr;
  93         if (VirtReg == Use.getOperand(0).getReg()) {
  94           VRRegMO = &Use.getOperand(0);
  95           OtherMO = &Use.getOperand(1);
  96           if (Use.isCommutable())
  97             CommuMO = &Use.getOperand(2);
  98         } else if (VirtReg == Use.getOperand(1).getReg()) {
  99           VRRegMO = &Use.getOperand(1);
 100           OtherMO = &Use.getOperand(0);
 101         } else if (VirtReg == Use.getOperand(2).getReg() &&
 102                    Use.isCommutable()) {
 103           VRRegMO = &Use.getOperand(2);
 104           OtherMO = &Use.getOperand(0);
 105         } else
 106           continue;
 107
 108         auto tryAddHint = [&](const MachineOperand *MO) -> void {
 109           Register Reg = MO->getReg();
 110           Register PhysReg =
 111               Reg.isPhysical() ? Reg : Register(VRM->getPhys(Reg));
 112           if (PhysReg) {
 113             if (MO->getSubReg())
 114               PhysReg = getSubReg(PhysReg, MO->getSubReg());
 115             if (VRRegMO->getSubReg())
 116               PhysReg = getMatchingSuperReg(PhysReg, VRRegMO->getSubReg(),
 117                                             MRI->getRegClass(VirtReg));
 118             if (!MRI->isReserved(PhysReg) && !is_contained(Hints, PhysReg))
 119               TwoAddrHints.insert(PhysReg);
 120           }
 121         };
 122         tryAddHint(OtherMO);
 123         if (CommuMO)
 124           tryAddHint(CommuMO);
 125       }
 126     for (MCPhysReg OrderReg : Order)
 127       if (TwoAddrHints.count(OrderReg))
 128         Hints.push_back(OrderReg);
 129   }
 130
 131   if (MRI->getRegClass(VirtReg) == &SystemZ::GRX32BitRegClass) {
 132     SmallVector<Register, 8> Worklist;
 133     SmallSet<Register, 4> DoneRegs;
 134     Worklist.push_back(VirtReg);
 135     while (Worklist.size()) {
 136       Register Reg = Worklist.pop_back_val();
 137       if (!DoneRegs.insert(Reg).second)
 138         continue;
 139
 140       for (auto &Use : MRI->reg_instructions(Reg)) {
 141         // For LOCRMux, see if the other operand is already a high or low
 142         // register, and in that case give the corresponding hints for
 143         // VirtReg. LOCR instructions need both operands in either high or
 144         // low parts. Same handling for SELRMux.
 145         if (Use.getOpcode() == SystemZ::LOCRMux ||
 146             Use.getOpcode() == SystemZ::SELRMux) {
 147           MachineOperand &TrueMO = Use.getOperand(1);
 148           MachineOperand &FalseMO = Use.getOperand(2);
 149           const TargetRegisterClass *RC =
 150             TRI->getCommonSubClass(getRC32(FalseMO, VRM, MRI),
 151                                    getRC32(TrueMO, VRM, MRI));
 152           if (Use.getOpcode() == SystemZ::SELRMux)
 153             RC = TRI->getCommonSubClass(RC,
 154                                         getRC32(Use.getOperand(0), VRM, MRI));
 155           if (RC && RC != &SystemZ::GRX32BitRegClass) {
 156             addHints(Order, Hints, RC, MRI);
 157             // Return true to make these hints the only regs available to
 158             // RA. This may mean extra spilling but since the alternative is
 159             // a jump sequence expansion of the LOCRMux, it is preferred.
 160             return true;
 161           }
 162
 163           // Add the other operand of the LOCRMux to the worklist.
 164           Register OtherReg =
 165               (TrueMO.getReg() == Reg ? FalseMO.getReg() : TrueMO.getReg());
 166           if (MRI->getRegClass(OtherReg) == &SystemZ::GRX32BitRegClass)
 167             Worklist.push_back(OtherReg);
 168         } // end LOCRMux
 169         else if (Use.getOpcode() == SystemZ::CHIMux ||
 170                  Use.getOpcode() == SystemZ::CFIMux) {
 171           if (Use.getOperand(1).getImm() == 0) {
 172             bool OnlyLMuxes = true;
 173             for (MachineInstr &DefMI : MRI->def_instructions(VirtReg))
 174               if (DefMI.getOpcode() != SystemZ::LMux)
 175                 OnlyLMuxes = false;
 176             if (OnlyLMuxes) {
 177               addHints(Order, Hints, &SystemZ::GR32BitRegClass, MRI);
 178               // Return false to make these hints preferred but not obligatory.
 179               return false;
 180             }
 181           }
 182         } // end CHIMux / CFIMux
 183       }
 184     }
 185   }
 186
 187   return BaseImplRetVal;
 188 }
 189
 190 const MCPhysReg *
 191 SystemZXPLINK64Registers::getCalleeSavedRegs(const MachineFunction *MF) const {
 192   const SystemZSubtarget &Subtarget = MF->getSubtarget<SystemZSubtarget>();
 193   return Subtarget.hasVector() ? CSR_SystemZ_XPLINK64_Vector_SaveList
 194                                : CSR_SystemZ_XPLINK64_SaveList;
 195 }
 196
 197 const MCPhysReg *
 198 SystemZELFRegisters::getCalleeSavedRegs(const MachineFunction *MF) const {
 199   const SystemZSubtarget &Subtarget = MF->getSubtarget<SystemZSubtarget>();
 200   if (MF->getFunction().getCallingConv() == CallingConv::GHC)
 201     return CSR_SystemZ_NoRegs_SaveList;
 202   if (MF->getFunction().getCallingConv() == CallingConv::AnyReg)
 203     return Subtarget.hasVector()? CSR_SystemZ_AllRegs_Vector_SaveList
 204                                 : CSR_SystemZ_AllRegs_SaveList;
 205   if (MF->getSubtarget().getTargetLowering()->supportSwiftError() &&
 206       MF->getFunction().getAttributes().hasAttrSomewhere(
 207           Attribute::SwiftError))
 208     return CSR_SystemZ_SwiftError_SaveList;
 209   return CSR_SystemZ_ELF_SaveList;
 210 }
 211
 212 const uint32_t *
 213 SystemZXPLINK64Registers::getCallPreservedMask(const MachineFunction &MF,
 214                                                CallingConv::ID CC) const {
 215   const SystemZSubtarget &Subtarget = MF.getSubtarget<SystemZSubtarget>();
 216   return Subtarget.hasVector() ? CSR_SystemZ_XPLINK64_Vector_RegMask
 217                                : CSR_SystemZ_XPLINK64_RegMask;
 218 }
 219
 220 const uint32_t *
 221 SystemZELFRegisters::getCallPreservedMask(const MachineFunction &MF,
 222                                           CallingConv::ID CC) const {
 223   const SystemZSubtarget &Subtarget = MF.getSubtarget<SystemZSubtarget>();
 224   if (CC == CallingConv::GHC)
 225     return CSR_SystemZ_NoRegs_RegMask;
 226   if (CC == CallingConv::AnyReg)
 227     return Subtarget.hasVector()? CSR_SystemZ_AllRegs_Vector_RegMask
 228                                 : CSR_SystemZ_AllRegs_RegMask;
 229   if (MF.getSubtarget().getTargetLowering()->supportSwiftError() &&
 230       MF.getFunction().getAttributes().hasAttrSomewhere(
 231           Attribute::SwiftError))
 232     return CSR_SystemZ_SwiftError_RegMask;
 233   return CSR_SystemZ_ELF_RegMask;
 234 }
 235
 236 SystemZRegisterInfo::SystemZRegisterInfo(unsigned int RA)
 237     : SystemZGenRegisterInfo(RA) {}
 238
 239 const MCPhysReg *
 240 SystemZRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
 241
 242   const SystemZSubtarget *Subtarget = &MF->getSubtarget<SystemZSubtarget>();
 243   SystemZCallingConventionRegisters *Regs = Subtarget->getSpecialRegisters();
 244
 245   return Regs->getCalleeSavedRegs(MF);
 246 }
 247
 248 const uint32_t *
 249 SystemZRegisterInfo::getCallPreservedMask(const MachineFunction &MF,
 250                                           CallingConv::ID CC) const {
 251
 252   const SystemZSubtarget *Subtarget = &MF.getSubtarget<SystemZSubtarget>();
 253   SystemZCallingConventionRegisters *Regs = Subtarget->getSpecialRegisters();
 254   return Regs->getCallPreservedMask(MF, CC);
 255 }
 256
 257 const uint32_t *SystemZRegisterInfo::getNoPreservedMask() const {
 258   return CSR_SystemZ_NoRegs_RegMask;
 259 }
 260
 261 BitVector
 262 SystemZRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
 263   BitVector Reserved(getNumRegs());
 264   const SystemZFrameLowering *TFI = getFrameLowering(MF);
 265   const SystemZSubtarget *Subtarget = &MF.getSubtarget<SystemZSubtarget>();
 266   SystemZCallingConventionRegisters *Regs = Subtarget->getSpecialRegisters();
 267   if (TFI->hasFP(MF))
 268     // The frame pointer. Reserve all aliases.
 269     for (MCRegAliasIterator AI(Regs->getFramePointerRegister(), this, true);
 270          AI.isValid(); ++AI)
 271       Reserved.set(*AI);
 272
 273   // Reserve all aliases for the stack pointer.
 274   for (MCRegAliasIterator AI(Regs->getStackPointerRegister(), this, true);
 275        AI.isValid(); ++AI)
 276     Reserved.set(*AI);
 277
 278   // A0 and A1 hold the thread pointer.
 279   Reserved.set(SystemZ::A0);
 280   Reserved.set(SystemZ::A1);
 281
 282   // FPC is the floating-point control register.
 283   Reserved.set(SystemZ::FPC);
 284
 285   return Reserved;
 286 }
 287
 288 bool
 289 SystemZRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator MI,
 290                                          int SPAdj, unsigned FIOperandNum,
 291                                          RegScavenger *RS) const {
 292   assert(SPAdj == 0 && "Outgoing arguments should be part of the frame");
 293
 294   MachineBasicBlock &MBB = *MI->getParent();
 295   MachineFunction &MF = *MBB.getParent();
 296   auto *TII = MF.getSubtarget<SystemZSubtarget>().getInstrInfo();
 297   const SystemZFrameLowering *TFI = getFrameLowering(MF);
 298   DebugLoc DL = MI->getDebugLoc();
 299
 300   // Decompose the frame index into a base and offset.
 301   int FrameIndex = MI->getOperand(FIOperandNum).getIndex();
 302   Register BasePtr;
 303   int64_t Offset =
 304       (TFI->getFrameIndexReference(MF, FrameIndex, BasePtr).getFixed() +
 305        MI->getOperand(FIOperandNum + 1).getImm());
 306
 307   // Special handling of dbg_value instructions.
 308   if (MI->isDebugValue()) {
 309     MI->getOperand(FIOperandNum).ChangeToRegister(BasePtr, /*isDef*/ false);
 310     if (MI->isNonListDebugValue()) {
 311       MI->getDebugOffset().ChangeToImmediate(Offset);
 312     } else {
 313       unsigned OpIdx = MI->getDebugOperandIndex(&MI->getOperand(FIOperandNum));
 314       SmallVector<uint64_t, 3> Ops;
 315       DIExpression::appendOffset(
 316           Ops, TFI->getFrameIndexReference(MF, FrameIndex, BasePtr).getFixed());
 317       MI->getDebugExpressionOp().setMetadata(
 318           DIExpression::appendOpsToArg(MI->getDebugExpression(), Ops, OpIdx));
 319     }
 320     return false;
 321   }
 322
 323   // See if the offset is in range, or if an equivalent instruction that
 324   // accepts the offset exists.
 325   unsigned Opcode = MI->getOpcode();
 326   unsigned OpcodeForOffset = TII->getOpcodeForOffset(Opcode, Offset, &*MI);
 327   if (OpcodeForOffset) {
 328     if (OpcodeForOffset == SystemZ::LE &&
 329         MF.getSubtarget<SystemZSubtarget>().hasVector()) {
 330       // If LE is ok for offset, use LDE instead on z13.
 331       OpcodeForOffset = SystemZ::LDE32;
 332     }
 333     MI->getOperand(FIOperandNum).ChangeToRegister(BasePtr, false);
 334   }
 335   else {
 336     // Create an anchor point that is in range.  Start at 0xffff so that
 337     // can use LLILH to load the immediate.
 338     int64_t OldOffset = Offset;
 339     int64_t Mask = 0xffff;
 340     do {
 341       Offset = OldOffset & Mask;
 342       OpcodeForOffset = TII->getOpcodeForOffset(Opcode, Offset);
 343       Mask >>= 1;
 344       assert(Mask && "One offset must be OK");
 345     } while (!OpcodeForOffset);
 346
 347     Register ScratchReg =
 348         MF.getRegInfo().createVirtualRegister(&SystemZ::ADDR64BitRegClass);
 349     int64_t HighOffset = OldOffset - Offset;
 350
 351     if (MI->getDesc().TSFlags & SystemZII::HasIndex
 352         && MI->getOperand(FIOperandNum + 2).getReg() == 0) {
 353       // Load the offset into the scratch register and use it as an index.
 354       // The scratch register then dies here.
 355       TII->loadImmediate(MBB, MI, ScratchReg, HighOffset);
 356       MI->getOperand(FIOperandNum).ChangeToRegister(BasePtr, false);
 357       MI->getOperand(FIOperandNum + 2).ChangeToRegister(ScratchReg,
 358                                                         false, false, true);
 359     } else {
 360       // Load the anchor address into a scratch register.
 361       unsigned LAOpcode = TII->getOpcodeForOffset(SystemZ::LA, HighOffset);
 362       if (LAOpcode)
 363         BuildMI(MBB, MI, DL, TII->get(LAOpcode),ScratchReg)
 364           .addReg(BasePtr).addImm(HighOffset).addReg(0);
 365       else {
 366         // Load the high offset into the scratch register and use it as
 367         // an index.
 368         TII->loadImmediate(MBB, MI, ScratchReg, HighOffset);
 369         BuildMI(MBB, MI, DL, TII->get(SystemZ::LA), ScratchReg)
 370           .addReg(BasePtr, RegState::Kill).addImm(0).addReg(ScratchReg);
 371       }
 372
 373       // Use the scratch register as the base.  It then dies here.
 374       MI->getOperand(FIOperandNum).ChangeToRegister(ScratchReg,
 375                                                     false, false, true);
 376     }
 377   }
 378   MI->setDesc(TII->get(OpcodeForOffset));
 379   MI->getOperand(FIOperandNum + 1).ChangeToImmediate(Offset);
 380   return false;
 381 }
 382
 383 bool SystemZRegisterInfo::shouldCoalesce(MachineInstr *MI,
 384                                          const TargetRegisterClass *SrcRC,
 385                                          unsigned SubReg,
 386                                          const TargetRegisterClass *DstRC,
 387                                          unsigned DstSubReg,
 388                                          const TargetRegisterClass *NewRC,
 389                                          LiveIntervals &LIS) const {
 390   assert (MI->isCopy() && "Only expecting COPY instructions");
 391
 392   // Coalesce anything which is not a COPY involving a subreg to/from GR128.
 393   if (!(NewRC->hasSuperClassEq(&SystemZ::GR128BitRegClass) &&
 394         (getRegSizeInBits(*SrcRC) <= 64 || getRegSizeInBits(*DstRC) <= 64) &&
 395         !MI->getOperand(1).isUndef()))
 396     return true;
 397
 398   // Allow coalescing of a GR128 subreg COPY only if the subreg liverange is
 399   // local to one MBB with not too many interferring physreg clobbers. Otherwise
 400   // regalloc may run out of registers.
 401   unsigned SubregOpIdx = getRegSizeInBits(*SrcRC) == 128 ? 0 : 1;
 402   LiveInterval &LI = LIS.getInterval(MI->getOperand(SubregOpIdx).getReg());
 403
 404   // Check that the subreg is local to MBB.
 405   MachineBasicBlock *MBB = MI->getParent();
 406   MachineInstr *FirstMI = LIS.getInstructionFromIndex(LI.beginIndex());
 407   MachineInstr *LastMI = LIS.getInstructionFromIndex(LI.endIndex());
 408   if (!FirstMI || FirstMI->getParent() != MBB ||
 409       !LastMI || LastMI->getParent() != MBB)
 410     return false;
 411
 412   // Check if coalescing seems safe by finding the set of clobbered physreg
 413   // pairs in the region.
 414   BitVector PhysClobbered(getNumRegs());
 415   for (MachineBasicBlock::iterator MII = FirstMI,
 416                                    MEE = std::next(LastMI->getIterator());
 417        MII != MEE; ++MII)
 418     for (const MachineOperand &MO : MII->operands())
 419       if (MO.isReg() && MO.getReg().isPhysical()) {
 420         for (MCPhysReg SI : superregs_inclusive(MO.getReg()))
 421           if (NewRC->contains(SI)) {
 422             PhysClobbered.set(SI);
 423             break;
 424           }
 425       }
 426
 427   // Demand an arbitrary margin of free regs.
 428   unsigned const DemandedFreeGR128 = 3;
 429   if (PhysClobbered.count() > (NewRC->getNumRegs() - DemandedFreeGR128))
 430     return false;
 431
 432   return true;
 433 }
 434
 435 Register
 436 SystemZRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
 437   const SystemZFrameLowering *TFI = getFrameLowering(MF);
 438   const SystemZSubtarget *Subtarget = &MF.getSubtarget<SystemZSubtarget>();
 439   SystemZCallingConventionRegisters *Regs = Subtarget->getSpecialRegisters();
 440
 441   return TFI->hasFP(MF) ? Regs->getFramePointerRegister()
 442                         : Regs->getStackPointerRegister();
 443 }
 444
 445 const TargetRegisterClass *
 446 SystemZRegisterInfo::getCrossCopyRegClass(const TargetRegisterClass *RC) const {
 447   if (RC == &SystemZ::CCRRegClass)
 448     return &SystemZ::GR32BitRegClass;
 449   return RC;
 450 }
 451