//===- AArch64RegisterInfo.cpp - AArch64 Register Information -------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file contains the AArch64 implementation of the TargetRegisterInfo // class. // //===----------------------------------------------------------------------===// #include "AArch64RegisterInfo.h" #include "AArch64FrameLowering.h" #include "AArch64InstrInfo.h" #include "AArch64Subtarget.h" #include "MCTargetDesc/AArch64AddressingModes.h" #include "llvm/ADT/BitVector.h" #include "llvm/CodeGen/MachineFrameInfo.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/MachineRegisterInfo.h" #include "llvm/CodeGen/RegisterScavenging.h" #include "llvm/IR/Function.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/raw_ostream.h" #include "llvm/Target/TargetFrameLowering.h" #include "llvm/Target/TargetOptions.h" using namespace llvm; #define GET_REGINFO_TARGET_DESC #include "AArch64GenRegisterInfo.inc" AArch64RegisterInfo::AArch64RegisterInfo(const AArch64InstrInfo *tii, const AArch64Subtarget *sti) : AArch64GenRegisterInfo(AArch64::LR), TII(tii), STI(sti) {} const MCPhysReg * AArch64RegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const { assert(MF && "Invalid MachineFunction pointer."); if (MF->getFunction()->getCallingConv() == CallingConv::AnyReg) return CSR_AArch64_AllRegs_SaveList; else return CSR_AArch64_AAPCS_SaveList; } const uint32_t * AArch64RegisterInfo::getCallPreservedMask(CallingConv::ID CC) const { if (CC == CallingConv::AnyReg) return CSR_AArch64_AllRegs_RegMask; else return CSR_AArch64_AAPCS_RegMask; } const uint32_t *AArch64RegisterInfo::getTLSCallPreservedMask() const { if (STI->isTargetDarwin()) return CSR_AArch64_TLS_Darwin_RegMask; assert(STI->isTargetELF() && "only expect Darwin or ELF TLS"); return CSR_AArch64_TLS_ELF_RegMask; } const uint32_t * AArch64RegisterInfo::getThisReturnPreservedMask(CallingConv::ID) const { // This should return a register mask that is the same as that returned by // getCallPreservedMask but that additionally preserves the register used for // the first i64 argument (which must also be the register used to return a // single i64 return value) // // In case that the calling convention does not use the same register for // both, the function should return NULL (does not currently apply) return CSR_AArch64_AAPCS_ThisReturn_RegMask; } BitVector AArch64RegisterInfo::getReservedRegs(const MachineFunction &MF) const { const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering(); // FIXME: avoid re-calculating this every time. BitVector Reserved(getNumRegs()); Reserved.set(AArch64::SP); Reserved.set(AArch64::XZR); Reserved.set(AArch64::WSP); Reserved.set(AArch64::WZR); if (TFI->hasFP(MF) || STI->isTargetDarwin()) { Reserved.set(AArch64::FP); Reserved.set(AArch64::W29); } if (STI->isTargetDarwin()) { Reserved.set(AArch64::X18); // Platform register Reserved.set(AArch64::W18); } if (hasBasePointer(MF)) { Reserved.set(AArch64::X19); Reserved.set(AArch64::W19); } return Reserved; } bool AArch64RegisterInfo::isReservedReg(const MachineFunction &MF, unsigned Reg) const { const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering(); switch (Reg) { default: break; case AArch64::SP: case AArch64::XZR: case AArch64::WSP: case AArch64::WZR: return true; case AArch64::X18: case AArch64::W18: return STI->isTargetDarwin(); case AArch64::FP: case AArch64::W29: return TFI->hasFP(MF) || STI->isTargetDarwin(); case AArch64::W19: case AArch64::X19: return hasBasePointer(MF); } return false; } const TargetRegisterClass * AArch64RegisterInfo::getPointerRegClass(const MachineFunction &MF, unsigned Kind) const { return &AArch64::GPR64RegClass; } const TargetRegisterClass * AArch64RegisterInfo::getCrossCopyRegClass(const TargetRegisterClass *RC) const { if (RC == &AArch64::CCRRegClass) return &AArch64::GPR64RegClass; // Only MSR & MRS copy NZCV. return RC; } unsigned AArch64RegisterInfo::getBaseRegister() const { return AArch64::X19; } bool AArch64RegisterInfo::hasBasePointer(const MachineFunction &MF) const { const MachineFrameInfo *MFI = MF.getFrameInfo(); // In the presence of variable sized objects, if the fixed stack size is // large enough that referencing from the FP won't result in things being // in range relatively often, we can use a base pointer to allow access // from the other direction like the SP normally works. if (MFI->hasVarSizedObjects()) { // Conservatively estimate whether the negative offset from the frame // pointer will be sufficient to reach. If a function has a smallish // frame, it's less likely to have lots of spills and callee saved // space, so it's all more likely to be within range of the frame pointer. // If it's wrong, we'll materialize the constant and still get to the // object; it's just suboptimal. Negative offsets use the unscaled // load/store instructions, which have a 9-bit signed immediate. if (MFI->getLocalFrameSize() < 256) return false; return true; } return false; } unsigned AArch64RegisterInfo::getFrameRegister(const MachineFunction &MF) const { const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering(); return TFI->hasFP(MF) ? AArch64::FP : AArch64::SP; } bool AArch64RegisterInfo::requiresRegisterScavenging( const MachineFunction &MF) const { return true; } bool AArch64RegisterInfo::requiresVirtualBaseRegisters( const MachineFunction &MF) const { return true; } bool AArch64RegisterInfo::useFPForScavengingIndex(const MachineFunction &MF) const { const MachineFrameInfo *MFI = MF.getFrameInfo(); // AArch64FrameLowering::resolveFrameIndexReference() can always fall back // to the stack pointer, so only put the emergency spill slot next to the // FP when there's no better way to access it (SP or base pointer). return MFI->hasVarSizedObjects() && !hasBasePointer(MF); } bool AArch64RegisterInfo::requiresFrameIndexScavenging( const MachineFunction &MF) const { return true; } bool AArch64RegisterInfo::cannotEliminateFrame(const MachineFunction &MF) const { const MachineFrameInfo *MFI = MF.getFrameInfo(); // Only consider eliminating leaf frames. if (MFI->hasCalls() || (MF.getTarget().Options.DisableFramePointerElim(MF) && MFI->adjustsStack())) return true; return MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken(); } /// needsFrameBaseReg - Returns true if the instruction's frame index /// reference would be better served by a base register other than FP /// or SP. Used by LocalStackFrameAllocation to determine which frame index /// references it should create new base registers for. bool AArch64RegisterInfo::needsFrameBaseReg(MachineInstr *MI, int64_t Offset) const { for (unsigned i = 0; !MI->getOperand(i).isFI(); ++i) assert(i < MI->getNumOperands() && "Instr doesn't have FrameIndex operand!"); // It's the load/store FI references that cause issues, as it can be difficult // to materialize the offset if it won't fit in the literal field. Estimate // based on the size of the local frame and some conservative assumptions // about the rest of the stack frame (note, this is pre-regalloc, so // we don't know everything for certain yet) whether this offset is likely // to be out of range of the immediate. Return true if so. // We only generate virtual base registers for loads and stores, so // return false for everything else. if (!MI->mayLoad() && !MI->mayStore()) return false; // Without a virtual base register, if the function has variable sized // objects, all fixed-size local references will be via the frame pointer, // Approximate the offset and see if it's legal for the instruction. // Note that the incoming offset is based on the SP value at function entry, // so it'll be negative. MachineFunction &MF = *MI->getParent()->getParent(); const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering(); MachineFrameInfo *MFI = MF.getFrameInfo(); // Estimate an offset from the frame pointer. // Conservatively assume all GPR callee-saved registers get pushed. // FP, LR, X19-X28, D8-D15. 64-bits each. int64_t FPOffset = Offset - 16 * 20; // Estimate an offset from the stack pointer. // The incoming offset is relating to the SP at the start of the function, // but when we access the local it'll be relative to the SP after local // allocation, so adjust our SP-relative offset by that allocation size. Offset += MFI->getLocalFrameSize(); // Assume that we'll have at least some spill slots allocated. // FIXME: This is a total SWAG number. We should run some statistics // and pick a real one. Offset += 128; // 128 bytes of spill slots // If there is a frame pointer, try using it. // The FP is only available if there is no dynamic realignment. We // don't know for sure yet whether we'll need that, so we guess based // on whether there are any local variables that would trigger it. if (TFI->hasFP(MF) && isFrameOffsetLegal(MI, FPOffset)) return false; // If we can reference via the stack pointer or base pointer, try that. // FIXME: This (and the code that resolves the references) can be improved // to only disallow SP relative references in the live range of // the VLA(s). In practice, it's unclear how much difference that // would make, but it may be worth doing. if (isFrameOffsetLegal(MI, Offset)) return false; // The offset likely isn't legal; we want to allocate a virtual base register. return true; } bool AArch64RegisterInfo::isFrameOffsetLegal(const MachineInstr *MI, int64_t Offset) const { assert(Offset <= INT_MAX && "Offset too big to fit in int."); assert(MI && "Unable to get the legal offset for nil instruction."); int SaveOffset = Offset; return isAArch64FrameOffsetLegal(*MI, SaveOffset) & AArch64FrameOffsetIsLegal; } /// Insert defining instruction(s) for BaseReg to be a pointer to FrameIdx /// at the beginning of the basic block. void AArch64RegisterInfo::materializeFrameBaseRegister(MachineBasicBlock *MBB, unsigned BaseReg, int FrameIdx, int64_t Offset) const { MachineBasicBlock::iterator Ins = MBB->begin(); DebugLoc DL; // Defaults to "unknown" if (Ins != MBB->end()) DL = Ins->getDebugLoc(); const MCInstrDesc &MCID = TII->get(AArch64::ADDXri); MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo(); const MachineFunction &MF = *MBB->getParent(); MRI.constrainRegClass(BaseReg, TII->getRegClass(MCID, 0, this, MF)); unsigned Shifter = AArch64_AM::getShifterImm(AArch64_AM::LSL, 0); BuildMI(*MBB, Ins, DL, MCID, BaseReg) .addFrameIndex(FrameIdx) .addImm(Offset) .addImm(Shifter); } void AArch64RegisterInfo::resolveFrameIndex(MachineInstr &MI, unsigned BaseReg, int64_t Offset) const { int Off = Offset; // ARM doesn't need the general 64-bit offsets unsigned i = 0; while (!MI.getOperand(i).isFI()) { ++i; assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!"); } bool Done = rewriteAArch64FrameIndex(MI, i, BaseReg, Off, TII); assert(Done && "Unable to resolve frame index!"); (void)Done; } void AArch64RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II, int SPAdj, unsigned FIOperandNum, RegScavenger *RS) const { assert(SPAdj == 0 && "Unexpected"); MachineInstr &MI = *II; MachineBasicBlock &MBB = *MI.getParent(); MachineFunction &MF = *MBB.getParent(); const AArch64FrameLowering *TFI = static_cast<const AArch64FrameLowering *>( MF.getTarget().getFrameLowering()); int FrameIndex = MI.getOperand(FIOperandNum).getIndex(); unsigned FrameReg; int Offset; // Special handling of dbg_value, stackmap and patchpoint instructions. if (MI.isDebugValue() || MI.getOpcode() == TargetOpcode::STACKMAP || MI.getOpcode() == TargetOpcode::PATCHPOINT) { Offset = TFI->resolveFrameIndexReference(MF, FrameIndex, FrameReg, /*PreferFP=*/true); Offset += MI.getOperand(FIOperandNum + 1).getImm(); MI.getOperand(FIOperandNum).ChangeToRegister(FrameReg, false /*isDef*/); MI.getOperand(FIOperandNum + 1).ChangeToImmediate(Offset); return; } // Modify MI as necessary to handle as much of 'Offset' as possible Offset = TFI->resolveFrameIndexReference(MF, FrameIndex, FrameReg); if (rewriteAArch64FrameIndex(MI, FIOperandNum, FrameReg, Offset, TII)) return; assert((!RS || !RS->isScavengingFrameIndex(FrameIndex)) && "Emergency spill slot is out of reach"); // If we get here, the immediate doesn't fit into the instruction. We folded // as much as possible above. Handle the rest, providing a register that is // SP+LargeImm. unsigned ScratchReg = MF.getRegInfo().createVirtualRegister(&AArch64::GPR64RegClass); emitFrameOffset(MBB, II, MI.getDebugLoc(), ScratchReg, FrameReg, Offset, TII); MI.getOperand(FIOperandNum).ChangeToRegister(ScratchReg, false, false, true); } namespace llvm { unsigned AArch64RegisterInfo::getRegPressureLimit(const TargetRegisterClass *RC, MachineFunction &MF) const { const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering(); switch (RC->getID()) { default: return 0; case AArch64::GPR32RegClassID: case AArch64::GPR32spRegClassID: case AArch64::GPR32allRegClassID: case AArch64::GPR64spRegClassID: case AArch64::GPR64allRegClassID: case AArch64::GPR64RegClassID: case AArch64::GPR32commonRegClassID: case AArch64::GPR64commonRegClassID: return 32 - 1 // XZR/SP - (TFI->hasFP(MF) || STI->isTargetDarwin()) // FP - STI->isTargetDarwin() // X18 reserved as platform register - hasBasePointer(MF); // X19 case AArch64::FPR8RegClassID: case AArch64::FPR16RegClassID: case AArch64::FPR32RegClassID: case AArch64::FPR64RegClassID: case AArch64::FPR128RegClassID: return 32; case AArch64::DDRegClassID: case AArch64::DDDRegClassID: case AArch64::DDDDRegClassID: case AArch64::QQRegClassID: case AArch64::QQQRegClassID: case AArch64::QQQQRegClassID: return 32; case AArch64::FPR128_loRegClassID: return 16; } } } // namespace llvm