//===- Thumb1FrameLowering.cpp - Thumb1 Frame Information -----------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This file contains the Thumb1 implementation of TargetFrameLowering class. // //===----------------------------------------------------------------------===// #include "Thumb1FrameLowering.h" #include "ARMBaseInstrInfo.h" #include "ARMBaseRegisterInfo.h" #include "ARMMachineFunctionInfo.h" #include "ARMSubtarget.h" #include "Thumb1InstrInfo.h" #include "ThumbRegisterInfo.h" #include "Utils/ARMBaseInfo.h" #include "llvm/ADT/BitVector.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/SmallVector.h" #include "llvm/CodeGen/LivePhysRegs.h" #include "llvm/CodeGen/MachineBasicBlock.h" #include "llvm/CodeGen/MachineFrameInfo.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/CodeGen/MachineInstr.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/MachineModuleInfo.h" #include "llvm/CodeGen/MachineOperand.h" #include "llvm/CodeGen/MachineRegisterInfo.h" #include "llvm/CodeGen/TargetInstrInfo.h" #include "llvm/CodeGen/TargetOpcodes.h" #include "llvm/CodeGen/TargetSubtargetInfo.h" #include "llvm/IR/DebugLoc.h" #include "llvm/MC/MCContext.h" #include "llvm/MC/MCDwarf.h" #include "llvm/MC/MCRegisterInfo.h" #include "llvm/Support/Compiler.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/MathExtras.h" #include #include #include #include using namespace llvm; Thumb1FrameLowering::Thumb1FrameLowering(const ARMSubtarget &sti) : ARMFrameLowering(sti) {} bool Thumb1FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const{ const MachineFrameInfo &MFI = MF.getFrameInfo(); unsigned CFSize = MFI.getMaxCallFrameSize(); // It's not always a good idea to include the call frame as part of the // stack frame. ARM (especially Thumb) has small immediate offset to // address the stack frame. So a large call frame can cause poor codegen // and may even makes it impossible to scavenge a register. if (CFSize >= ((1 << 8) - 1) * 4 / 2) // Half of imm8 * 4 return false; return !MFI.hasVarSizedObjects(); } static void emitPrologueEpilogueSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI, const TargetInstrInfo &TII, const DebugLoc &dl, const ThumbRegisterInfo &MRI, int NumBytes, unsigned ScratchReg, unsigned MIFlags) { // If it would take more than three instructions to adjust the stack pointer // using tADDspi/tSUBspi, load an immediate instead. if (std::abs(NumBytes) > 508 * 3) { // We use a different codepath here from the normal // emitThumbRegPlusImmediate so we don't have to deal with register // scavenging. (Scavenging could try to use the emergency spill slot // before we've actually finished setting up the stack.) if (ScratchReg == ARM::NoRegister) report_fatal_error("Failed to emit Thumb1 stack adjustment"); MachineFunction &MF = *MBB.getParent(); const ARMSubtarget &ST = MF.getSubtarget(); if (ST.genExecuteOnly()) { BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi32imm), ScratchReg) .addImm(NumBytes).setMIFlags(MIFlags); } else { MRI.emitLoadConstPool(MBB, MBBI, dl, ScratchReg, 0, NumBytes, ARMCC::AL, 0, MIFlags); } BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDhirr), ARM::SP) .addReg(ARM::SP) .addReg(ScratchReg, RegState::Kill) .add(predOps(ARMCC::AL)) .setMIFlags(MIFlags); return; } // FIXME: This is assuming the heuristics in emitThumbRegPlusImmediate // won't change. emitThumbRegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes, TII, MRI, MIFlags); } static void emitCallSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI, const TargetInstrInfo &TII, const DebugLoc &dl, const ThumbRegisterInfo &MRI, int NumBytes, unsigned MIFlags = MachineInstr::NoFlags) { emitThumbRegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes, TII, MRI, MIFlags); } MachineBasicBlock::iterator Thumb1FrameLowering:: eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB, MachineBasicBlock::iterator I) const { const Thumb1InstrInfo &TII = *static_cast(STI.getInstrInfo()); const ThumbRegisterInfo *RegInfo = static_cast(STI.getRegisterInfo()); if (!hasReservedCallFrame(MF)) { // If we have alloca, convert as follows: // ADJCALLSTACKDOWN -> sub, sp, sp, amount // ADJCALLSTACKUP -> add, sp, sp, amount MachineInstr &Old = *I; DebugLoc dl = Old.getDebugLoc(); unsigned Amount = TII.getFrameSize(Old); if (Amount != 0) { // We need to keep the stack aligned properly. To do this, we round the // amount of space needed for the outgoing arguments up to the next // alignment boundary. Amount = alignTo(Amount, getStackAlign()); // Replace the pseudo instruction with a new instruction... unsigned Opc = Old.getOpcode(); if (Opc == ARM::ADJCALLSTACKDOWN || Opc == ARM::tADJCALLSTACKDOWN) { emitCallSPUpdate(MBB, I, TII, dl, *RegInfo, -Amount); } else { assert(Opc == ARM::ADJCALLSTACKUP || Opc == ARM::tADJCALLSTACKUP); emitCallSPUpdate(MBB, I, TII, dl, *RegInfo, Amount); } } } return MBB.erase(I); } void Thumb1FrameLowering::emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const { MachineBasicBlock::iterator MBBI = MBB.begin(); MachineFrameInfo &MFI = MF.getFrameInfo(); ARMFunctionInfo *AFI = MF.getInfo(); MachineModuleInfo &MMI = MF.getMMI(); const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo(); const ThumbRegisterInfo *RegInfo = static_cast(STI.getRegisterInfo()); const Thumb1InstrInfo &TII = *static_cast(STI.getInstrInfo()); unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(); unsigned NumBytes = MFI.getStackSize(); assert(NumBytes >= ArgRegsSaveSize && "ArgRegsSaveSize is included in NumBytes"); const std::vector &CSI = MFI.getCalleeSavedInfo(); // Debug location must be unknown since the first debug location is used // to determine the end of the prologue. DebugLoc dl; Register FramePtr = RegInfo->getFrameRegister(MF); unsigned BasePtr = RegInfo->getBaseRegister(); int CFAOffset = 0; // Thumb add/sub sp, imm8 instructions implicitly multiply the offset by 4. NumBytes = (NumBytes + 3) & ~3; MFI.setStackSize(NumBytes); // Determine the sizes of each callee-save spill areas and record which frame // belongs to which callee-save spill areas. unsigned GPRCS1Size = 0, GPRCS2Size = 0, DPRCSSize = 0; int FramePtrSpillFI = 0; if (ArgRegsSaveSize) { emitPrologueEpilogueSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -ArgRegsSaveSize, ARM::NoRegister, MachineInstr::FrameSetup); CFAOffset += ArgRegsSaveSize; unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, CFAOffset)); BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) .addCFIIndex(CFIIndex) .setMIFlags(MachineInstr::FrameSetup); } if (!AFI->hasStackFrame()) { if (NumBytes - ArgRegsSaveSize != 0) { emitPrologueEpilogueSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -(NumBytes - ArgRegsSaveSize), ARM::NoRegister, MachineInstr::FrameSetup); CFAOffset += NumBytes - ArgRegsSaveSize; unsigned CFIIndex = MF.addFrameInst( MCCFIInstruction::cfiDefCfaOffset(nullptr, CFAOffset)); BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) .addCFIIndex(CFIIndex) .setMIFlags(MachineInstr::FrameSetup); } return; } for (unsigned i = 0, e = CSI.size(); i != e; ++i) { unsigned Reg = CSI[i].getReg(); int FI = CSI[i].getFrameIdx(); switch (Reg) { case ARM::R8: case ARM::R9: case ARM::R10: case ARM::R11: if (STI.splitFramePushPop(MF)) { GPRCS2Size += 4; break; } LLVM_FALLTHROUGH; case ARM::R4: case ARM::R5: case ARM::R6: case ARM::R7: case ARM::LR: if (Reg == FramePtr) FramePtrSpillFI = FI; GPRCS1Size += 4; break; default: DPRCSSize += 8; } } if (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tPUSH) { ++MBBI; } // Determine starting offsets of spill areas. unsigned DPRCSOffset = NumBytes - ArgRegsSaveSize - (GPRCS1Size + GPRCS2Size + DPRCSSize); unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize; unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size; bool HasFP = hasFP(MF); if (HasFP) AFI->setFramePtrSpillOffset(MFI.getObjectOffset(FramePtrSpillFI) + NumBytes); AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset); AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset); AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset); NumBytes = DPRCSOffset; int FramePtrOffsetInBlock = 0; unsigned adjustedGPRCS1Size = GPRCS1Size; if (GPRCS1Size > 0 && GPRCS2Size == 0 && tryFoldSPUpdateIntoPushPop(STI, MF, &*std::prev(MBBI), NumBytes)) { FramePtrOffsetInBlock = NumBytes; adjustedGPRCS1Size += NumBytes; NumBytes = 0; } if (adjustedGPRCS1Size) { CFAOffset += adjustedGPRCS1Size; unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, CFAOffset)); BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) .addCFIIndex(CFIIndex) .setMIFlags(MachineInstr::FrameSetup); } for (std::vector::const_iterator I = CSI.begin(), E = CSI.end(); I != E; ++I) { unsigned Reg = I->getReg(); int FI = I->getFrameIdx(); switch (Reg) { case ARM::R8: case ARM::R9: case ARM::R10: case ARM::R11: case ARM::R12: if (STI.splitFramePushPop(MF)) break; LLVM_FALLTHROUGH; case ARM::R0: case ARM::R1: case ARM::R2: case ARM::R3: case ARM::R4: case ARM::R5: case ARM::R6: case ARM::R7: case ARM::LR: unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset( nullptr, MRI->getDwarfRegNum(Reg, true), MFI.getObjectOffset(FI))); BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) .addCFIIndex(CFIIndex) .setMIFlags(MachineInstr::FrameSetup); break; } } // Adjust FP so it point to the stack slot that contains the previous FP. if (HasFP) { FramePtrOffsetInBlock += MFI.getObjectOffset(FramePtrSpillFI) + GPRCS1Size + ArgRegsSaveSize; BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDrSPi), FramePtr) .addReg(ARM::SP) .addImm(FramePtrOffsetInBlock / 4) .setMIFlags(MachineInstr::FrameSetup) .add(predOps(ARMCC::AL)); if(FramePtrOffsetInBlock) { CFAOffset -= FramePtrOffsetInBlock; unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfa( nullptr, MRI->getDwarfRegNum(FramePtr, true), CFAOffset)); BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) .addCFIIndex(CFIIndex) .setMIFlags(MachineInstr::FrameSetup); } else { unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createDefCfaRegister( nullptr, MRI->getDwarfRegNum(FramePtr, true))); BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) .addCFIIndex(CFIIndex) .setMIFlags(MachineInstr::FrameSetup); } if (NumBytes > 508) // If offset is > 508 then sp cannot be adjusted in a single instruction, // try restoring from fp instead. AFI->setShouldRestoreSPFromFP(true); } // Skip past the spilling of r8-r11, which could consist of multiple tPUSH // and tMOVr instructions. We don't need to add any call frame information // in-between these instructions, because they do not modify the high // registers. while (true) { MachineBasicBlock::iterator OldMBBI = MBBI; // Skip a run of tMOVr instructions while (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tMOVr) MBBI++; if (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tPUSH) { MBBI++; } else { // We have reached an instruction which is not a push, so the previous // run of tMOVr instructions (which may have been empty) was not part of // the prologue. Reset MBBI back to the last PUSH of the prologue. MBBI = OldMBBI; break; } } // Emit call frame information for the callee-saved high registers. for (auto &I : CSI) { unsigned Reg = I.getReg(); int FI = I.getFrameIdx(); switch (Reg) { case ARM::R8: case ARM::R9: case ARM::R10: case ARM::R11: case ARM::R12: { unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset( nullptr, MRI->getDwarfRegNum(Reg, true), MFI.getObjectOffset(FI))); BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) .addCFIIndex(CFIIndex) .setMIFlags(MachineInstr::FrameSetup); break; } default: break; } } if (NumBytes) { // Insert it after all the callee-save spills. // // For a large stack frame, we might need a scratch register to store // the size of the frame. We know all callee-save registers are free // at this point in the prologue, so pick one. unsigned ScratchRegister = ARM::NoRegister; for (auto &I : CSI) { unsigned Reg = I.getReg(); if (isARMLowRegister(Reg) && !(HasFP && Reg == FramePtr)) { ScratchRegister = Reg; break; } } emitPrologueEpilogueSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -NumBytes, ScratchRegister, MachineInstr::FrameSetup); if (!HasFP) { CFAOffset += NumBytes; unsigned CFIIndex = MF.addFrameInst( MCCFIInstruction::cfiDefCfaOffset(nullptr, CFAOffset)); BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) .addCFIIndex(CFIIndex) .setMIFlags(MachineInstr::FrameSetup); } } if (STI.isTargetELF() && HasFP) MFI.setOffsetAdjustment(MFI.getOffsetAdjustment() - AFI->getFramePtrSpillOffset()); AFI->setGPRCalleeSavedArea1Size(GPRCS1Size); AFI->setGPRCalleeSavedArea2Size(GPRCS2Size); AFI->setDPRCalleeSavedAreaSize(DPRCSSize); if (RegInfo->hasStackRealignment(MF)) { const unsigned NrBitsToZero = Log2(MFI.getMaxAlign()); // Emit the following sequence, using R4 as a temporary, since we cannot use // SP as a source or destination register for the shifts: // mov r4, sp // lsrs r4, r4, #NrBitsToZero // lsls r4, r4, #NrBitsToZero // mov sp, r4 BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R4) .addReg(ARM::SP, RegState::Kill) .add(predOps(ARMCC::AL)); BuildMI(MBB, MBBI, dl, TII.get(ARM::tLSRri), ARM::R4) .addDef(ARM::CPSR) .addReg(ARM::R4, RegState::Kill) .addImm(NrBitsToZero) .add(predOps(ARMCC::AL)); BuildMI(MBB, MBBI, dl, TII.get(ARM::tLSLri), ARM::R4) .addDef(ARM::CPSR) .addReg(ARM::R4, RegState::Kill) .addImm(NrBitsToZero) .add(predOps(ARMCC::AL)); BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP) .addReg(ARM::R4, RegState::Kill) .add(predOps(ARMCC::AL)); AFI->setShouldRestoreSPFromFP(true); } // If we need a base pointer, set it up here. It's whatever the value // of the stack pointer is at this point. Any variable size objects // will be allocated after this, so we can still use the base pointer // to reference locals. if (RegInfo->hasBasePointer(MF)) BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), BasePtr) .addReg(ARM::SP) .add(predOps(ARMCC::AL)); // If the frame has variable sized objects then the epilogue must restore // the sp from fp. We can assume there's an FP here since hasFP already // checks for hasVarSizedObjects. if (MFI.hasVarSizedObjects()) AFI->setShouldRestoreSPFromFP(true); // In some cases, virtual registers have been introduced, e.g. by uses of // emitThumbRegPlusImmInReg. MF.getProperties().reset(MachineFunctionProperties::Property::NoVRegs); } static bool isCSRestore(MachineInstr &MI, const MCPhysReg *CSRegs) { if (MI.getOpcode() == ARM::tLDRspi && MI.getOperand(1).isFI() && isCalleeSavedRegister(MI.getOperand(0).getReg(), CSRegs)) return true; else if (MI.getOpcode() == ARM::tPOP) { return true; } else if (MI.getOpcode() == ARM::tMOVr) { Register Dst = MI.getOperand(0).getReg(); Register Src = MI.getOperand(1).getReg(); return ((ARM::tGPRRegClass.contains(Src) || Src == ARM::LR) && ARM::hGPRRegClass.contains(Dst)); } return false; } void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const { MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator(); DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc(); MachineFrameInfo &MFI = MF.getFrameInfo(); ARMFunctionInfo *AFI = MF.getInfo(); const ThumbRegisterInfo *RegInfo = static_cast(STI.getRegisterInfo()); const Thumb1InstrInfo &TII = *static_cast(STI.getInstrInfo()); unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(); int NumBytes = (int)MFI.getStackSize(); assert((unsigned)NumBytes >= ArgRegsSaveSize && "ArgRegsSaveSize is included in NumBytes"); const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&MF); Register FramePtr = RegInfo->getFrameRegister(MF); if (!AFI->hasStackFrame()) { if (NumBytes - ArgRegsSaveSize != 0) emitPrologueEpilogueSPUpdate(MBB, MBBI, TII, dl, *RegInfo, NumBytes - ArgRegsSaveSize, ARM::NoRegister, MachineInstr::NoFlags); } else { // Unwind MBBI to point to first LDR / VLDRD. if (MBBI != MBB.begin()) { do --MBBI; while (MBBI != MBB.begin() && isCSRestore(*MBBI, CSRegs)); if (!isCSRestore(*MBBI, CSRegs)) ++MBBI; } // Move SP to start of FP callee save spill area. NumBytes -= (AFI->getGPRCalleeSavedArea1Size() + AFI->getGPRCalleeSavedArea2Size() + AFI->getDPRCalleeSavedAreaSize() + ArgRegsSaveSize); if (AFI->shouldRestoreSPFromFP()) { NumBytes = AFI->getFramePtrSpillOffset() - NumBytes; // Reset SP based on frame pointer only if the stack frame extends beyond // frame pointer stack slot, the target is ELF and the function has FP, or // the target uses var sized objects. if (NumBytes) { assert(!MFI.getPristineRegs(MF).test(ARM::R4) && "No scratch register to restore SP from FP!"); emitThumbRegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes, TII, *RegInfo); BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP) .addReg(ARM::R4) .add(predOps(ARMCC::AL)); } else BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP) .addReg(FramePtr) .add(predOps(ARMCC::AL)); } else { // For a large stack frame, we might need a scratch register to store // the size of the frame. We know all callee-save registers are free // at this point in the epilogue, so pick one. unsigned ScratchRegister = ARM::NoRegister; bool HasFP = hasFP(MF); for (auto &I : MFI.getCalleeSavedInfo()) { unsigned Reg = I.getReg(); if (isARMLowRegister(Reg) && !(HasFP && Reg == FramePtr)) { ScratchRegister = Reg; break; } } if (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tBX_RET && &MBB.front() != &*MBBI && std::prev(MBBI)->getOpcode() == ARM::tPOP) { MachineBasicBlock::iterator PMBBI = std::prev(MBBI); if (!tryFoldSPUpdateIntoPushPop(STI, MF, &*PMBBI, NumBytes)) emitPrologueEpilogueSPUpdate(MBB, PMBBI, TII, dl, *RegInfo, NumBytes, ScratchRegister, MachineInstr::NoFlags); } else if (!tryFoldSPUpdateIntoPushPop(STI, MF, &*MBBI, NumBytes)) emitPrologueEpilogueSPUpdate(MBB, MBBI, TII, dl, *RegInfo, NumBytes, ScratchRegister, MachineInstr::NoFlags); } } if (needPopSpecialFixUp(MF)) { bool Done = emitPopSpecialFixUp(MBB, /* DoIt */ true); (void)Done; assert(Done && "Emission of the special fixup failed!?"); } } bool Thumb1FrameLowering::canUseAsEpilogue(const MachineBasicBlock &MBB) const { if (!needPopSpecialFixUp(*MBB.getParent())) return true; MachineBasicBlock *TmpMBB = const_cast(&MBB); return emitPopSpecialFixUp(*TmpMBB, /* DoIt */ false); } bool Thumb1FrameLowering::needPopSpecialFixUp(const MachineFunction &MF) const { ARMFunctionInfo *AFI = const_cast(&MF)->getInfo(); if (AFI->getArgRegsSaveSize()) return true; // LR cannot be encoded with Thumb1, i.e., it requires a special fix-up. for (const CalleeSavedInfo &CSI : MF.getFrameInfo().getCalleeSavedInfo()) if (CSI.getReg() == ARM::LR) return true; return false; } static void findTemporariesForLR(const BitVector &GPRsNoLRSP, const BitVector &PopFriendly, const LivePhysRegs &UsedRegs, unsigned &PopReg, unsigned &TmpReg) { PopReg = TmpReg = 0; for (auto Reg : GPRsNoLRSP.set_bits()) { if (!UsedRegs.contains(Reg)) { // Remember the first pop-friendly register and exit. if (PopFriendly.test(Reg)) { PopReg = Reg; TmpReg = 0; break; } // Otherwise, remember that the register will be available to // save a pop-friendly register. TmpReg = Reg; } } } bool Thumb1FrameLowering::emitPopSpecialFixUp(MachineBasicBlock &MBB, bool DoIt) const { MachineFunction &MF = *MBB.getParent(); ARMFunctionInfo *AFI = MF.getInfo(); unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(); const TargetInstrInfo &TII = *STI.getInstrInfo(); const ThumbRegisterInfo *RegInfo = static_cast(STI.getRegisterInfo()); // If MBBI is a return instruction, or is a tPOP followed by a return // instruction in the successor BB, we may be able to directly restore // LR in the PC. // This is only possible with v5T ops (v4T can't change the Thumb bit via // a POP PC instruction), and only if we do not need to emit any SP update. // Otherwise, we need a temporary register to pop the value // and copy that value into LR. auto MBBI = MBB.getFirstTerminator(); bool CanRestoreDirectly = STI.hasV5TOps() && !ArgRegsSaveSize; if (CanRestoreDirectly) { if (MBBI != MBB.end() && MBBI->getOpcode() != ARM::tB) CanRestoreDirectly = (MBBI->getOpcode() == ARM::tBX_RET || MBBI->getOpcode() == ARM::tPOP_RET); else { auto MBBI_prev = MBBI; MBBI_prev--; assert(MBBI_prev->getOpcode() == ARM::tPOP); assert(MBB.succ_size() == 1); if ((*MBB.succ_begin())->begin()->getOpcode() == ARM::tBX_RET) MBBI = MBBI_prev; // Replace the final tPOP with a tPOP_RET. else CanRestoreDirectly = false; } } if (CanRestoreDirectly) { if (!DoIt || MBBI->getOpcode() == ARM::tPOP_RET) return true; MachineInstrBuilder MIB = BuildMI(MBB, MBBI, MBBI->getDebugLoc(), TII.get(ARM::tPOP_RET)) .add(predOps(ARMCC::AL)); // Copy implicit ops and popped registers, if any. for (auto MO: MBBI->operands()) if (MO.isReg() && (MO.isImplicit() || MO.isDef())) MIB.add(MO); MIB.addReg(ARM::PC, RegState::Define); // Erase the old instruction (tBX_RET or tPOP). MBB.erase(MBBI); return true; } // Look for a temporary register to use. // First, compute the liveness information. const TargetRegisterInfo &TRI = *STI.getRegisterInfo(); LivePhysRegs UsedRegs(TRI); UsedRegs.addLiveOuts(MBB); // The semantic of pristines changed recently and now, // the callee-saved registers that are touched in the function // are not part of the pristines set anymore. // Add those callee-saved now. const MCPhysReg *CSRegs = TRI.getCalleeSavedRegs(&MF); for (unsigned i = 0; CSRegs[i]; ++i) UsedRegs.addReg(CSRegs[i]); DebugLoc dl = DebugLoc(); if (MBBI != MBB.end()) { dl = MBBI->getDebugLoc(); auto InstUpToMBBI = MBB.end(); while (InstUpToMBBI != MBBI) // The pre-decrement is on purpose here. // We want to have the liveness right before MBBI. UsedRegs.stepBackward(*--InstUpToMBBI); } // Look for a register that can be directly use in the POP. unsigned PopReg = 0; // And some temporary register, just in case. unsigned TemporaryReg = 0; BitVector PopFriendly = TRI.getAllocatableSet(MF, TRI.getRegClass(ARM::tGPRRegClassID)); // R7 may be used as a frame pointer, hence marked as not generally // allocatable, however there's no reason to not use it as a temporary for // restoring LR. if (STI.getFramePointerReg() == ARM::R7) PopFriendly.set(ARM::R7); assert(PopFriendly.any() && "No allocatable pop-friendly register?!"); // Rebuild the GPRs from the high registers because they are removed // form the GPR reg class for thumb1. BitVector GPRsNoLRSP = TRI.getAllocatableSet(MF, TRI.getRegClass(ARM::hGPRRegClassID)); GPRsNoLRSP |= PopFriendly; GPRsNoLRSP.reset(ARM::LR); GPRsNoLRSP.reset(ARM::SP); GPRsNoLRSP.reset(ARM::PC); findTemporariesForLR(GPRsNoLRSP, PopFriendly, UsedRegs, PopReg, TemporaryReg); // If we couldn't find a pop-friendly register, try restoring LR before // popping the other callee-saved registers, so we could use one of them as a // temporary. bool UseLDRSP = false; if (!PopReg && MBBI != MBB.begin()) { auto PrevMBBI = MBBI; PrevMBBI--; if (PrevMBBI->getOpcode() == ARM::tPOP) { UsedRegs.stepBackward(*PrevMBBI); findTemporariesForLR(GPRsNoLRSP, PopFriendly, UsedRegs, PopReg, TemporaryReg); if (PopReg) { MBBI = PrevMBBI; UseLDRSP = true; } } } if (!DoIt && !PopReg && !TemporaryReg) return false; assert((PopReg || TemporaryReg) && "Cannot get LR"); if (UseLDRSP) { assert(PopReg && "Do not know how to get LR"); // Load the LR via LDR tmp, [SP, #off] BuildMI(MBB, MBBI, dl, TII.get(ARM::tLDRspi)) .addReg(PopReg, RegState::Define) .addReg(ARM::SP) .addImm(MBBI->getNumExplicitOperands() - 2) .add(predOps(ARMCC::AL)); // Move from the temporary register to the LR. BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr)) .addReg(ARM::LR, RegState::Define) .addReg(PopReg, RegState::Kill) .add(predOps(ARMCC::AL)); // Advance past the pop instruction. MBBI++; // Increment the SP. emitPrologueEpilogueSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize + 4, ARM::NoRegister, MachineInstr::NoFlags); return true; } if (TemporaryReg) { assert(!PopReg && "Unnecessary MOV is about to be inserted"); PopReg = PopFriendly.find_first(); BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr)) .addReg(TemporaryReg, RegState::Define) .addReg(PopReg, RegState::Kill) .add(predOps(ARMCC::AL)); } if (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tPOP_RET) { // We couldn't use the direct restoration above, so // perform the opposite conversion: tPOP_RET to tPOP. MachineInstrBuilder MIB = BuildMI(MBB, MBBI, MBBI->getDebugLoc(), TII.get(ARM::tPOP)) .add(predOps(ARMCC::AL)); bool Popped = false; for (auto MO: MBBI->operands()) if (MO.isReg() && (MO.isImplicit() || MO.isDef()) && MO.getReg() != ARM::PC) { MIB.add(MO); if (!MO.isImplicit()) Popped = true; } // Is there anything left to pop? if (!Popped) MBB.erase(MIB.getInstr()); // Erase the old instruction. MBB.erase(MBBI); MBBI = BuildMI(MBB, MBB.end(), dl, TII.get(ARM::tBX_RET)) .add(predOps(ARMCC::AL)); } assert(PopReg && "Do not know how to get LR"); BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP)) .add(predOps(ARMCC::AL)) .addReg(PopReg, RegState::Define); emitPrologueEpilogueSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize, ARM::NoRegister, MachineInstr::NoFlags); BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr)) .addReg(ARM::LR, RegState::Define) .addReg(PopReg, RegState::Kill) .add(predOps(ARMCC::AL)); if (TemporaryReg) BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr)) .addReg(PopReg, RegState::Define) .addReg(TemporaryReg, RegState::Kill) .add(predOps(ARMCC::AL)); return true; } using ARMRegSet = std::bitset; // Return the first iteraror after CurrentReg which is present in EnabledRegs, // or OrderEnd if no further registers are in that set. This does not advance // the iterator fiorst, so returns CurrentReg if it is in EnabledRegs. static const unsigned *findNextOrderedReg(const unsigned *CurrentReg, const ARMRegSet &EnabledRegs, const unsigned *OrderEnd) { while (CurrentReg != OrderEnd && !EnabledRegs[*CurrentReg]) ++CurrentReg; return CurrentReg; } bool Thumb1FrameLowering::spillCalleeSavedRegisters( MachineBasicBlock &MBB, MachineBasicBlock::iterator MI, ArrayRef CSI, const TargetRegisterInfo *TRI) const { if (CSI.empty()) return false; DebugLoc DL; const TargetInstrInfo &TII = *STI.getInstrInfo(); MachineFunction &MF = *MBB.getParent(); const ARMBaseRegisterInfo *RegInfo = static_cast( MF.getSubtarget().getRegisterInfo()); ARMRegSet LoRegsToSave; // r0-r7, lr ARMRegSet HiRegsToSave; // r8-r11 ARMRegSet CopyRegs; // Registers which can be used after pushing // LoRegs for saving HiRegs. for (unsigned i = CSI.size(); i != 0; --i) { unsigned Reg = CSI[i-1].getReg(); if (ARM::tGPRRegClass.contains(Reg) || Reg == ARM::LR) { LoRegsToSave[Reg] = true; } else if (ARM::hGPRRegClass.contains(Reg) && Reg != ARM::LR) { HiRegsToSave[Reg] = true; } else { llvm_unreachable("callee-saved register of unexpected class"); } if ((ARM::tGPRRegClass.contains(Reg) || Reg == ARM::LR) && !MF.getRegInfo().isLiveIn(Reg) && !(hasFP(MF) && Reg == RegInfo->getFrameRegister(MF))) CopyRegs[Reg] = true; } // Unused argument registers can be used for the high register saving. for (unsigned ArgReg : {ARM::R0, ARM::R1, ARM::R2, ARM::R3}) if (!MF.getRegInfo().isLiveIn(ArgReg)) CopyRegs[ArgReg] = true; // Push the low registers and lr const MachineRegisterInfo &MRI = MF.getRegInfo(); if (!LoRegsToSave.none()) { MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(ARM::tPUSH)).add(predOps(ARMCC::AL)); for (unsigned Reg : {ARM::R4, ARM::R5, ARM::R6, ARM::R7, ARM::LR}) { if (LoRegsToSave[Reg]) { bool isKill = !MRI.isLiveIn(Reg); if (isKill && !MRI.isReserved(Reg)) MBB.addLiveIn(Reg); MIB.addReg(Reg, getKillRegState(isKill)); } } MIB.setMIFlags(MachineInstr::FrameSetup); } // Push the high registers. There are no store instructions that can access // these registers directly, so we have to move them to low registers, and // push them. This might take multiple pushes, as it is possible for there to // be fewer low registers available than high registers which need saving. // These are in reverse order so that in the case where we need to use // multiple PUSH instructions, the order of the registers on the stack still // matches the unwind info. They need to be swicthed back to ascending order // before adding to the PUSH instruction. static const unsigned AllCopyRegs[] = {ARM::LR, ARM::R7, ARM::R6, ARM::R5, ARM::R4, ARM::R3, ARM::R2, ARM::R1, ARM::R0}; static const unsigned AllHighRegs[] = {ARM::R11, ARM::R10, ARM::R9, ARM::R8}; const unsigned *AllCopyRegsEnd = std::end(AllCopyRegs); const unsigned *AllHighRegsEnd = std::end(AllHighRegs); // Find the first register to save. const unsigned *HiRegToSave = findNextOrderedReg( std::begin(AllHighRegs), HiRegsToSave, AllHighRegsEnd); while (HiRegToSave != AllHighRegsEnd) { // Find the first low register to use. const unsigned *CopyReg = findNextOrderedReg(std::begin(AllCopyRegs), CopyRegs, AllCopyRegsEnd); // Create the PUSH, but don't insert it yet (the MOVs need to come first). MachineInstrBuilder PushMIB = BuildMI(MF, DL, TII.get(ARM::tPUSH)) .add(predOps(ARMCC::AL)) .setMIFlags(MachineInstr::FrameSetup); SmallVector RegsToPush; while (HiRegToSave != AllHighRegsEnd && CopyReg != AllCopyRegsEnd) { if (HiRegsToSave[*HiRegToSave]) { bool isKill = !MRI.isLiveIn(*HiRegToSave); if (isKill && !MRI.isReserved(*HiRegToSave)) MBB.addLiveIn(*HiRegToSave); // Emit a MOV from the high reg to the low reg. BuildMI(MBB, MI, DL, TII.get(ARM::tMOVr)) .addReg(*CopyReg, RegState::Define) .addReg(*HiRegToSave, getKillRegState(isKill)) .add(predOps(ARMCC::AL)) .setMIFlags(MachineInstr::FrameSetup); // Record the register that must be added to the PUSH. RegsToPush.push_back(*CopyReg); CopyReg = findNextOrderedReg(++CopyReg, CopyRegs, AllCopyRegsEnd); HiRegToSave = findNextOrderedReg(++HiRegToSave, HiRegsToSave, AllHighRegsEnd); } } // Add the low registers to the PUSH, in ascending order. for (unsigned Reg : llvm::reverse(RegsToPush)) PushMIB.addReg(Reg, RegState::Kill); // Insert the PUSH instruction after the MOVs. MBB.insert(MI, PushMIB); } return true; } bool Thumb1FrameLowering::restoreCalleeSavedRegisters( MachineBasicBlock &MBB, MachineBasicBlock::iterator MI, MutableArrayRef CSI, const TargetRegisterInfo *TRI) const { if (CSI.empty()) return false; MachineFunction &MF = *MBB.getParent(); ARMFunctionInfo *AFI = MF.getInfo(); const TargetInstrInfo &TII = *STI.getInstrInfo(); const ARMBaseRegisterInfo *RegInfo = static_cast( MF.getSubtarget().getRegisterInfo()); bool isVarArg = AFI->getArgRegsSaveSize() > 0; DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc() : DebugLoc(); ARMRegSet LoRegsToRestore; ARMRegSet HiRegsToRestore; // Low registers (r0-r7) which can be used to restore the high registers. ARMRegSet CopyRegs; for (CalleeSavedInfo I : CSI) { unsigned Reg = I.getReg(); if (ARM::tGPRRegClass.contains(Reg) || Reg == ARM::LR) { LoRegsToRestore[Reg] = true; } else if (ARM::hGPRRegClass.contains(Reg) && Reg != ARM::LR) { HiRegsToRestore[Reg] = true; } else { llvm_unreachable("callee-saved register of unexpected class"); } // If this is a low register not used as the frame pointer, we may want to // use it for restoring the high registers. if ((ARM::tGPRRegClass.contains(Reg)) && !(hasFP(MF) && Reg == RegInfo->getFrameRegister(MF))) CopyRegs[Reg] = true; } // If this is a return block, we may be able to use some unused return value // registers for restoring the high regs. auto Terminator = MBB.getFirstTerminator(); if (Terminator != MBB.end() && Terminator->getOpcode() == ARM::tBX_RET) { CopyRegs[ARM::R0] = true; CopyRegs[ARM::R1] = true; CopyRegs[ARM::R2] = true; CopyRegs[ARM::R3] = true; for (auto Op : Terminator->implicit_operands()) { if (Op.isReg()) CopyRegs[Op.getReg()] = false; } } static const unsigned AllCopyRegs[] = {ARM::R0, ARM::R1, ARM::R2, ARM::R3, ARM::R4, ARM::R5, ARM::R6, ARM::R7}; static const unsigned AllHighRegs[] = {ARM::R8, ARM::R9, ARM::R10, ARM::R11}; const unsigned *AllCopyRegsEnd = std::end(AllCopyRegs); const unsigned *AllHighRegsEnd = std::end(AllHighRegs); // Find the first register to restore. auto HiRegToRestore = findNextOrderedReg(std::begin(AllHighRegs), HiRegsToRestore, AllHighRegsEnd); while (HiRegToRestore != AllHighRegsEnd) { assert(!CopyRegs.none()); // Find the first low register to use. auto CopyReg = findNextOrderedReg(std::begin(AllCopyRegs), CopyRegs, AllCopyRegsEnd); // Create the POP instruction. MachineInstrBuilder PopMIB = BuildMI(MBB, MI, DL, TII.get(ARM::tPOP)).add(predOps(ARMCC::AL)); while (HiRegToRestore != AllHighRegsEnd && CopyReg != AllCopyRegsEnd) { // Add the low register to the POP. PopMIB.addReg(*CopyReg, RegState::Define); // Create the MOV from low to high register. BuildMI(MBB, MI, DL, TII.get(ARM::tMOVr)) .addReg(*HiRegToRestore, RegState::Define) .addReg(*CopyReg, RegState::Kill) .add(predOps(ARMCC::AL)); CopyReg = findNextOrderedReg(++CopyReg, CopyRegs, AllCopyRegsEnd); HiRegToRestore = findNextOrderedReg(++HiRegToRestore, HiRegsToRestore, AllHighRegsEnd); } } MachineInstrBuilder MIB = BuildMI(MF, DL, TII.get(ARM::tPOP)).add(predOps(ARMCC::AL)); bool NeedsPop = false; for (unsigned i = CSI.size(); i != 0; --i) { CalleeSavedInfo &Info = CSI[i-1]; unsigned Reg = Info.getReg(); // High registers (excluding lr) have already been dealt with if (!(ARM::tGPRRegClass.contains(Reg) || Reg == ARM::LR)) continue; if (Reg == ARM::LR) { Info.setRestored(false); if (!MBB.succ_empty() || MI->getOpcode() == ARM::TCRETURNdi || MI->getOpcode() == ARM::TCRETURNri) // LR may only be popped into PC, as part of return sequence. // If this isn't the return sequence, we'll need emitPopSpecialFixUp // to restore LR the hard way. // FIXME: if we don't pass any stack arguments it would be actually // advantageous *and* correct to do the conversion to an ordinary call // instruction here. continue; // Special epilogue for vararg functions. See emitEpilogue if (isVarArg) continue; // ARMv4T requires BX, see emitEpilogue if (!STI.hasV5TOps()) continue; // CMSE entry functions must return via BXNS, see emitEpilogue. if (AFI->isCmseNSEntryFunction()) continue; // Pop LR into PC. Reg = ARM::PC; (*MIB).setDesc(TII.get(ARM::tPOP_RET)); if (MI != MBB.end()) MIB.copyImplicitOps(*MI); MI = MBB.erase(MI); } MIB.addReg(Reg, getDefRegState(true)); NeedsPop = true; } // It's illegal to emit pop instruction without operands. if (NeedsPop) MBB.insert(MI, &*MIB); else MF.DeleteMachineInstr(MIB); return true; }