| //=======- ARMFrameLowering.cpp - ARM Frame Information --------*- C++ -*-====// |
| // |
| // 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 ARM implementation of TargetFrameLowering class. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "ARMFrameLowering.h" |
| #include "ARMAddressingModes.h" |
| #include "ARMBaseInstrInfo.h" |
| #include "ARMBaseRegisterInfo.h" |
| #include "ARMMachineFunctionInfo.h" |
| #include "llvm/CodeGen/MachineFrameInfo.h" |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/CodeGen/MachineInstrBuilder.h" |
| #include "llvm/CodeGen/MachineRegisterInfo.h" |
| #include "llvm/CodeGen/RegisterScavenging.h" |
| #include "llvm/Target/TargetOptions.h" |
| |
| using namespace llvm; |
| |
| /// hasFP - Return true if the specified function should have a dedicated frame |
| /// pointer register. This is true if the function has variable sized allocas |
| /// or if frame pointer elimination is disabled. |
| bool ARMFrameLowering::hasFP(const MachineFunction &MF) const { |
| const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo(); |
| |
| // Mac OS X requires FP not to be clobbered for backtracing purpose. |
| if (STI.isTargetDarwin()) |
| return true; |
| |
| const MachineFrameInfo *MFI = MF.getFrameInfo(); |
| // Always eliminate non-leaf frame pointers. |
| return ((DisableFramePointerElim(MF) && MFI->hasCalls()) || |
| RegInfo->needsStackRealignment(MF) || |
| MFI->hasVarSizedObjects() || |
| MFI->isFrameAddressTaken()); |
| } |
| |
| /// hasReservedCallFrame - Under normal circumstances, when a frame pointer is |
| /// not required, we reserve argument space for call sites in the function |
| /// immediately on entry to the current function. This eliminates the need for |
| /// add/sub sp brackets around call sites. Returns true if the call frame is |
| /// included as part of the stack frame. |
| bool ARMFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const { |
| const MachineFrameInfo *FFI = MF.getFrameInfo(); |
| unsigned CFSize = FFI->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 << 12) - 1) / 2) // Half of imm12 |
| return false; |
| |
| return !MF.getFrameInfo()->hasVarSizedObjects(); |
| } |
| |
| /// canSimplifyCallFramePseudos - If there is a reserved call frame, the |
| /// call frame pseudos can be simplified. Unlike most targets, having a FP |
| /// is not sufficient here since we still may reference some objects via SP |
| /// even when FP is available in Thumb2 mode. |
| bool |
| ARMFrameLowering::canSimplifyCallFramePseudos(const MachineFunction &MF) const { |
| return hasReservedCallFrame(MF) || MF.getFrameInfo()->hasVarSizedObjects(); |
| } |
| |
| static bool isCalleeSavedRegister(unsigned Reg, const unsigned *CSRegs) { |
| for (unsigned i = 0; CSRegs[i]; ++i) |
| if (Reg == CSRegs[i]) |
| return true; |
| return false; |
| } |
| |
| static bool isCSRestore(MachineInstr *MI, |
| const ARMBaseInstrInfo &TII, |
| const unsigned *CSRegs) { |
| // Integer spill area is handled with "pop". |
| if (MI->getOpcode() == ARM::LDMIA_RET || |
| MI->getOpcode() == ARM::t2LDMIA_RET || |
| MI->getOpcode() == ARM::LDMIA_UPD || |
| MI->getOpcode() == ARM::t2LDMIA_UPD || |
| MI->getOpcode() == ARM::VLDMDIA_UPD) { |
| // The first two operands are predicates. The last two are |
| // imp-def and imp-use of SP. Check everything in between. |
| for (int i = 5, e = MI->getNumOperands(); i != e; ++i) |
| if (!isCalleeSavedRegister(MI->getOperand(i).getReg(), CSRegs)) |
| return false; |
| return true; |
| } |
| if ((MI->getOpcode() == ARM::LDR_POST || |
| MI->getOpcode() == ARM::t2LDR_POST) && |
| isCalleeSavedRegister(MI->getOperand(0).getReg(), CSRegs) && |
| MI->getOperand(1).getReg() == ARM::SP) |
| return true; |
| |
| return false; |
| } |
| |
| static void |
| emitSPUpdate(bool isARM, |
| MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI, |
| DebugLoc dl, const ARMBaseInstrInfo &TII, |
| int NumBytes, |
| ARMCC::CondCodes Pred = ARMCC::AL, unsigned PredReg = 0) { |
| if (isARM) |
| emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes, |
| Pred, PredReg, TII); |
| else |
| emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes, |
| Pred, PredReg, TII); |
| } |
| |
| void ARMFrameLowering::emitPrologue(MachineFunction &MF) const { |
| MachineBasicBlock &MBB = MF.front(); |
| MachineBasicBlock::iterator MBBI = MBB.begin(); |
| MachineFrameInfo *MFI = MF.getFrameInfo(); |
| ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); |
| const ARMBaseRegisterInfo *RegInfo = |
| static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo()); |
| const ARMBaseInstrInfo &TII = |
| *static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo()); |
| assert(!AFI->isThumb1OnlyFunction() && |
| "This emitPrologue does not support Thumb1!"); |
| bool isARM = !AFI->isThumbFunction(); |
| unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize(); |
| unsigned NumBytes = MFI->getStackSize(); |
| const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo(); |
| DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc(); |
| unsigned FramePtr = RegInfo->getFrameRegister(MF); |
| |
| // 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; |
| |
| // Allocate the vararg register save area. This is not counted in NumBytes. |
| if (VARegSaveSize) |
| emitSPUpdate(isARM, MBB, MBBI, dl, TII, -VARegSaveSize); |
| |
| if (!AFI->hasStackFrame()) { |
| if (NumBytes != 0) |
| emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes); |
| 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::R4: |
| case ARM::R5: |
| case ARM::R6: |
| case ARM::R7: |
| case ARM::LR: |
| if (Reg == FramePtr) |
| FramePtrSpillFI = FI; |
| AFI->addGPRCalleeSavedArea1Frame(FI); |
| GPRCS1Size += 4; |
| break; |
| case ARM::R8: |
| case ARM::R9: |
| case ARM::R10: |
| case ARM::R11: |
| if (Reg == FramePtr) |
| FramePtrSpillFI = FI; |
| if (STI.isTargetDarwin()) { |
| AFI->addGPRCalleeSavedArea2Frame(FI); |
| GPRCS2Size += 4; |
| } else { |
| AFI->addGPRCalleeSavedArea1Frame(FI); |
| GPRCS1Size += 4; |
| } |
| break; |
| default: |
| AFI->addDPRCalleeSavedAreaFrame(FI); |
| DPRCSSize += 8; |
| } |
| } |
| |
| // Move past area 1. |
| if (GPRCS1Size > 0) MBBI++; |
| |
| // Set FP to point to the stack slot that contains the previous FP. |
| // For Darwin, FP is R7, which has now been stored in spill area 1. |
| // Otherwise, if this is not Darwin, all the callee-saved registers go |
| // into spill area 1, including the FP in R11. In either case, it is |
| // now safe to emit this assignment. |
| bool HasFP = hasFP(MF); |
| if (HasFP) { |
| unsigned ADDriOpc = !AFI->isThumbFunction() ? ARM::ADDri : ARM::t2ADDri; |
| MachineInstrBuilder MIB = |
| BuildMI(MBB, MBBI, dl, TII.get(ADDriOpc), FramePtr) |
| .addFrameIndex(FramePtrSpillFI).addImm(0); |
| AddDefaultCC(AddDefaultPred(MIB)); |
| } |
| |
| // Move past area 2. |
| if (GPRCS2Size > 0) MBBI++; |
| |
| // Determine starting offsets of spill areas. |
| unsigned DPRCSOffset = NumBytes - (GPRCS1Size + GPRCS2Size + DPRCSSize); |
| unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize; |
| unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size; |
| if (HasFP) |
| AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) + |
| NumBytes); |
| AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset); |
| AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset); |
| AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset); |
| |
| // Move past area 3. |
| if (DPRCSSize > 0) { |
| MBBI++; |
| // Since vpush register list cannot have gaps, there may be multiple vpush |
| // instructions in the epilogue. |
| while (MBBI->getOpcode() == ARM::VSTMDDB_UPD) |
| MBBI++; |
| } |
| |
| NumBytes = DPRCSOffset; |
| if (NumBytes) { |
| // Adjust SP after all the callee-save spills. |
| emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes); |
| if (HasFP && isARM) |
| // Restore from fp only in ARM mode: e.g. sub sp, r7, #24 |
| // Note it's not safe to do this in Thumb2 mode because it would have |
| // taken two instructions: |
| // mov sp, r7 |
| // sub sp, #24 |
| // If an interrupt is taken between the two instructions, then sp is in |
| // an inconsistent state (pointing to the middle of callee-saved area). |
| // The interrupt handler can end up clobbering the registers. |
| AFI->setShouldRestoreSPFromFP(true); |
| } |
| |
| if (STI.isTargetELF() && hasFP(MF)) |
| MFI->setOffsetAdjustment(MFI->getOffsetAdjustment() - |
| AFI->getFramePtrSpillOffset()); |
| |
| AFI->setGPRCalleeSavedArea1Size(GPRCS1Size); |
| AFI->setGPRCalleeSavedArea2Size(GPRCS2Size); |
| AFI->setDPRCalleeSavedAreaSize(DPRCSSize); |
| |
| // If we need dynamic stack realignment, do it here. Be paranoid and make |
| // sure if we also have VLAs, we have a base pointer for frame access. |
| if (RegInfo->needsStackRealignment(MF)) { |
| unsigned MaxAlign = MFI->getMaxAlignment(); |
| assert (!AFI->isThumb1OnlyFunction()); |
| if (!AFI->isThumbFunction()) { |
| // Emit bic sp, sp, MaxAlign |
| AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl, |
| TII.get(ARM::BICri), ARM::SP) |
| .addReg(ARM::SP, RegState::Kill) |
| .addImm(MaxAlign-1))); |
| } else { |
| // We cannot use sp as source/dest register here, thus we're emitting the |
| // following sequence: |
| // mov r4, sp |
| // bic r4, r4, MaxAlign |
| // mov sp, r4 |
| // FIXME: It will be better just to find spare register here. |
| BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2tgpr), ARM::R4) |
| .addReg(ARM::SP, RegState::Kill); |
| AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl, |
| TII.get(ARM::t2BICri), ARM::R4) |
| .addReg(ARM::R4, RegState::Kill) |
| .addImm(MaxAlign-1))); |
| BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::SP) |
| .addReg(ARM::R4, RegState::Kill); |
| } |
| |
| 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)) { |
| if (isARM) |
| BuildMI(MBB, MBBI, dl, |
| TII.get(ARM::MOVr), RegInfo->getBaseRegister()) |
| .addReg(ARM::SP) |
| .addImm((unsigned)ARMCC::AL).addReg(0).addReg(0); |
| else |
| BuildMI(MBB, MBBI, dl, |
| TII.get(ARM::tMOVgpr2gpr), RegInfo->getBaseRegister()) |
| .addReg(ARM::SP); |
| } |
| |
| // 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); |
| } |
| |
| void ARMFrameLowering::emitEpilogue(MachineFunction &MF, |
| MachineBasicBlock &MBB) const { |
| MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr(); |
| assert(MBBI->getDesc().isReturn() && |
| "Can only insert epilog into returning blocks"); |
| unsigned RetOpcode = MBBI->getOpcode(); |
| DebugLoc dl = MBBI->getDebugLoc(); |
| MachineFrameInfo *MFI = MF.getFrameInfo(); |
| ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); |
| const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo(); |
| const ARMBaseInstrInfo &TII = |
| *static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo()); |
| assert(!AFI->isThumb1OnlyFunction() && |
| "This emitEpilogue does not support Thumb1!"); |
| bool isARM = !AFI->isThumbFunction(); |
| |
| unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize(); |
| int NumBytes = (int)MFI->getStackSize(); |
| unsigned FramePtr = RegInfo->getFrameRegister(MF); |
| |
| if (!AFI->hasStackFrame()) { |
| if (NumBytes != 0) |
| emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes); |
| } else { |
| // Unwind MBBI to point to first LDR / VLDRD. |
| const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(); |
| if (MBBI != MBB.begin()) { |
| do |
| --MBBI; |
| while (MBBI != MBB.begin() && isCSRestore(MBBI, TII, CSRegs)); |
| if (!isCSRestore(MBBI, TII, CSRegs)) |
| ++MBBI; |
| } |
| |
| // Move SP to start of FP callee save spill area. |
| NumBytes -= (AFI->getGPRCalleeSavedArea1Size() + |
| AFI->getGPRCalleeSavedArea2Size() + |
| AFI->getDPRCalleeSavedAreaSize()); |
| |
| // Reset SP based on frame pointer only if the stack frame extends beyond |
| // frame pointer stack slot or target is ELF and the function has FP. |
| if (AFI->shouldRestoreSPFromFP()) { |
| NumBytes = AFI->getFramePtrSpillOffset() - NumBytes; |
| if (NumBytes) { |
| if (isARM) |
| emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, FramePtr, -NumBytes, |
| ARMCC::AL, 0, TII); |
| else { |
| // It's not possible to restore SP from FP in a single instruction. |
| // For Darwin, this looks like: |
| // mov sp, r7 |
| // sub sp, #24 |
| // This is bad, if an interrupt is taken after the mov, sp is in an |
| // inconsistent state. |
| // Use the first callee-saved register as a scratch register. |
| assert(MF.getRegInfo().isPhysRegUsed(ARM::R4) && |
| "No scratch register to restore SP from FP!"); |
| emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes, |
| ARMCC::AL, 0, TII); |
| BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2gpr), ARM::SP) |
| .addReg(ARM::R4); |
| } |
| } else { |
| // Thumb2 or ARM. |
| if (isARM) |
| BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), ARM::SP) |
| .addReg(FramePtr).addImm((unsigned)ARMCC::AL).addReg(0).addReg(0); |
| else |
| BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2gpr), ARM::SP) |
| .addReg(FramePtr); |
| } |
| } else if (NumBytes) |
| emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes); |
| |
| // Increment past our save areas. |
| if (AFI->getDPRCalleeSavedAreaSize()) { |
| MBBI++; |
| // Since vpop register list cannot have gaps, there may be multiple vpop |
| // instructions in the epilogue. |
| while (MBBI->getOpcode() == ARM::VLDMDIA_UPD) |
| MBBI++; |
| } |
| if (AFI->getGPRCalleeSavedArea2Size()) MBBI++; |
| if (AFI->getGPRCalleeSavedArea1Size()) MBBI++; |
| } |
| |
| if (RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNdiND || |
| RetOpcode == ARM::TCRETURNri || RetOpcode == ARM::TCRETURNriND) { |
| // Tail call return: adjust the stack pointer and jump to callee. |
| MBBI = MBB.getLastNonDebugInstr(); |
| MachineOperand &JumpTarget = MBBI->getOperand(0); |
| |
| // Jump to label or value in register. |
| if (RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNdiND) { |
| unsigned TCOpcode = (RetOpcode == ARM::TCRETURNdi) |
| ? (STI.isThumb() ? ARM::TAILJMPdt : ARM::TAILJMPd) |
| : (STI.isThumb() ? ARM::TAILJMPdNDt : ARM::TAILJMPdND); |
| MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(TCOpcode)); |
| if (JumpTarget.isGlobal()) |
| MIB.addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(), |
| JumpTarget.getTargetFlags()); |
| else { |
| assert(JumpTarget.isSymbol()); |
| MIB.addExternalSymbol(JumpTarget.getSymbolName(), |
| JumpTarget.getTargetFlags()); |
| } |
| } else if (RetOpcode == ARM::TCRETURNri) { |
| BuildMI(MBB, MBBI, dl, TII.get(ARM::TAILJMPr)). |
| addReg(JumpTarget.getReg(), RegState::Kill); |
| } else if (RetOpcode == ARM::TCRETURNriND) { |
| BuildMI(MBB, MBBI, dl, TII.get(ARM::TAILJMPrND)). |
| addReg(JumpTarget.getReg(), RegState::Kill); |
| } |
| |
| MachineInstr *NewMI = prior(MBBI); |
| for (unsigned i = 1, e = MBBI->getNumOperands(); i != e; ++i) |
| NewMI->addOperand(MBBI->getOperand(i)); |
| |
| // Delete the pseudo instruction TCRETURN. |
| MBB.erase(MBBI); |
| } |
| |
| if (VARegSaveSize) |
| emitSPUpdate(isARM, MBB, MBBI, dl, TII, VARegSaveSize); |
| } |
| |
| /// getFrameIndexReference - Provide a base+offset reference to an FI slot for |
| /// debug info. It's the same as what we use for resolving the code-gen |
| /// references for now. FIXME: This can go wrong when references are |
| /// SP-relative and simple call frames aren't used. |
| int |
| ARMFrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI, |
| unsigned &FrameReg) const { |
| return ResolveFrameIndexReference(MF, FI, FrameReg, 0); |
| } |
| |
| int |
| ARMFrameLowering::ResolveFrameIndexReference(const MachineFunction &MF, |
| int FI, |
| unsigned &FrameReg, |
| int SPAdj) const { |
| const MachineFrameInfo *MFI = MF.getFrameInfo(); |
| const ARMBaseRegisterInfo *RegInfo = |
| static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo()); |
| const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); |
| int Offset = MFI->getObjectOffset(FI) + MFI->getStackSize(); |
| int FPOffset = Offset - AFI->getFramePtrSpillOffset(); |
| bool isFixed = MFI->isFixedObjectIndex(FI); |
| |
| FrameReg = ARM::SP; |
| Offset += SPAdj; |
| if (AFI->isGPRCalleeSavedArea1Frame(FI)) |
| return Offset - AFI->getGPRCalleeSavedArea1Offset(); |
| else if (AFI->isGPRCalleeSavedArea2Frame(FI)) |
| return Offset - AFI->getGPRCalleeSavedArea2Offset(); |
| else if (AFI->isDPRCalleeSavedAreaFrame(FI)) |
| return Offset - AFI->getDPRCalleeSavedAreaOffset(); |
| |
| // When dynamically realigning the stack, use the frame pointer for |
| // parameters, and the stack/base pointer for locals. |
| if (RegInfo->needsStackRealignment(MF)) { |
| assert (hasFP(MF) && "dynamic stack realignment without a FP!"); |
| if (isFixed) { |
| FrameReg = RegInfo->getFrameRegister(MF); |
| Offset = FPOffset; |
| } else if (MFI->hasVarSizedObjects()) { |
| assert(RegInfo->hasBasePointer(MF) && |
| "VLAs and dynamic stack alignment, but missing base pointer!"); |
| FrameReg = RegInfo->getBaseRegister(); |
| } |
| return Offset; |
| } |
| |
| // If there is a frame pointer, use it when we can. |
| if (hasFP(MF) && AFI->hasStackFrame()) { |
| // Use frame pointer to reference fixed objects. Use it for locals if |
| // there are VLAs (and thus the SP isn't reliable as a base). |
| if (isFixed || (MFI->hasVarSizedObjects() && |
| !RegInfo->hasBasePointer(MF))) { |
| FrameReg = RegInfo->getFrameRegister(MF); |
| return FPOffset; |
| } else if (MFI->hasVarSizedObjects()) { |
| assert(RegInfo->hasBasePointer(MF) && "missing base pointer!"); |
| // Try to use the frame pointer if we can, else use the base pointer |
| // since it's available. This is handy for the emergency spill slot, in |
| // particular. |
| if (AFI->isThumb2Function()) { |
| if (FPOffset >= -255 && FPOffset < 0) { |
| FrameReg = RegInfo->getFrameRegister(MF); |
| return FPOffset; |
| } |
| } else |
| FrameReg = RegInfo->getBaseRegister(); |
| } else if (AFI->isThumb2Function()) { |
| // In Thumb2 mode, the negative offset is very limited. Try to avoid |
| // out of range references. |
| if (FPOffset >= -255 && FPOffset < 0) { |
| FrameReg = RegInfo->getFrameRegister(MF); |
| return FPOffset; |
| } |
| } else if (Offset > (FPOffset < 0 ? -FPOffset : FPOffset)) { |
| // Otherwise, use SP or FP, whichever is closer to the stack slot. |
| FrameReg = RegInfo->getFrameRegister(MF); |
| return FPOffset; |
| } |
| } |
| // Use the base pointer if we have one. |
| if (RegInfo->hasBasePointer(MF)) |
| FrameReg = RegInfo->getBaseRegister(); |
| return Offset; |
| } |
| |
| int ARMFrameLowering::getFrameIndexOffset(const MachineFunction &MF, |
| int FI) const { |
| unsigned FrameReg; |
| return getFrameIndexReference(MF, FI, FrameReg); |
| } |
| |
| void ARMFrameLowering::emitPushInst(MachineBasicBlock &MBB, |
| MachineBasicBlock::iterator MI, |
| const std::vector<CalleeSavedInfo> &CSI, |
| unsigned StmOpc, unsigned StrOpc, |
| bool NoGap, |
| bool(*Func)(unsigned, bool)) const { |
| MachineFunction &MF = *MBB.getParent(); |
| const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo(); |
| |
| DebugLoc DL; |
| if (MI != MBB.end()) DL = MI->getDebugLoc(); |
| |
| SmallVector<std::pair<unsigned,bool>, 4> Regs; |
| unsigned i = CSI.size(); |
| while (i != 0) { |
| unsigned LastReg = 0; |
| for (; i != 0; --i) { |
| unsigned Reg = CSI[i-1].getReg(); |
| if (!(Func)(Reg, STI.isTargetDarwin())) continue; |
| |
| // Add the callee-saved register as live-in unless it's LR and |
| // @llvm.returnaddress is called. If LR is returned for |
| // @llvm.returnaddress then it's already added to the function and |
| // entry block live-in sets. |
| bool isKill = true; |
| if (Reg == ARM::LR) { |
| if (MF.getFrameInfo()->isReturnAddressTaken() && |
| MF.getRegInfo().isLiveIn(Reg)) |
| isKill = false; |
| } |
| |
| if (isKill) |
| MBB.addLiveIn(Reg); |
| |
| // If NoGap is true, push consecutive registers and then leave the rest |
| // for other instructions. e.g. |
| // vpush {d8, d10, d11} -> vpush {d8}, vpush {d10, d11} |
| if (NoGap && LastReg && LastReg != Reg-1) |
| break; |
| LastReg = Reg; |
| Regs.push_back(std::make_pair(Reg, isKill)); |
| } |
| |
| if (Regs.empty()) |
| continue; |
| if (Regs.size() > 1 || StrOpc== 0) { |
| MachineInstrBuilder MIB = |
| AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(StmOpc), ARM::SP) |
| .addReg(ARM::SP)); |
| for (unsigned i = 0, e = Regs.size(); i < e; ++i) |
| MIB.addReg(Regs[i].first, getKillRegState(Regs[i].second)); |
| } else if (Regs.size() == 1) { |
| MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(StrOpc), |
| ARM::SP) |
| .addReg(Regs[0].first, getKillRegState(Regs[0].second)) |
| .addReg(ARM::SP); |
| // ARM mode needs an extra reg0 here due to addrmode2. Will go away once |
| // that refactoring is complete (eventually). |
| if (StrOpc == ARM::STR_PRE) { |
| MIB.addReg(0); |
| MIB.addImm(ARM_AM::getAM2Opc(ARM_AM::sub, 4, ARM_AM::no_shift)); |
| } else |
| MIB.addImm(-4); |
| AddDefaultPred(MIB); |
| } |
| Regs.clear(); |
| } |
| } |
| |
| void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB, |
| MachineBasicBlock::iterator MI, |
| const std::vector<CalleeSavedInfo> &CSI, |
| unsigned LdmOpc, unsigned LdrOpc, |
| bool isVarArg, bool NoGap, |
| bool(*Func)(unsigned, bool)) const { |
| MachineFunction &MF = *MBB.getParent(); |
| const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo(); |
| ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); |
| DebugLoc DL = MI->getDebugLoc(); |
| unsigned RetOpcode = MI->getOpcode(); |
| bool isTailCall = (RetOpcode == ARM::TCRETURNdi || |
| RetOpcode == ARM::TCRETURNdiND || |
| RetOpcode == ARM::TCRETURNri || |
| RetOpcode == ARM::TCRETURNriND); |
| |
| SmallVector<unsigned, 4> Regs; |
| unsigned i = CSI.size(); |
| while (i != 0) { |
| unsigned LastReg = 0; |
| bool DeleteRet = false; |
| for (; i != 0; --i) { |
| unsigned Reg = CSI[i-1].getReg(); |
| if (!(Func)(Reg, STI.isTargetDarwin())) continue; |
| |
| if (Reg == ARM::LR && !isTailCall && !isVarArg && STI.hasV5TOps()) { |
| Reg = ARM::PC; |
| LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET; |
| // Fold the return instruction into the LDM. |
| DeleteRet = true; |
| } |
| |
| // If NoGap is true, pop consecutive registers and then leave the rest |
| // for other instructions. e.g. |
| // vpop {d8, d10, d11} -> vpop {d8}, vpop {d10, d11} |
| if (NoGap && LastReg && LastReg != Reg-1) |
| break; |
| |
| LastReg = Reg; |
| Regs.push_back(Reg); |
| } |
| |
| if (Regs.empty()) |
| continue; |
| if (Regs.size() > 1 || LdrOpc == 0) { |
| MachineInstrBuilder MIB = |
| AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(LdmOpc), ARM::SP) |
| .addReg(ARM::SP)); |
| for (unsigned i = 0, e = Regs.size(); i < e; ++i) |
| MIB.addReg(Regs[i], getDefRegState(true)); |
| if (DeleteRet) |
| MI->eraseFromParent(); |
| MI = MIB; |
| } else if (Regs.size() == 1) { |
| // If we adjusted the reg to PC from LR above, switch it back here. We |
| // only do that for LDM. |
| if (Regs[0] == ARM::PC) |
| Regs[0] = ARM::LR; |
| MachineInstrBuilder MIB = |
| BuildMI(MBB, MI, DL, TII.get(LdrOpc), Regs[0]) |
| .addReg(ARM::SP, RegState::Define) |
| .addReg(ARM::SP); |
| // ARM mode needs an extra reg0 here due to addrmode2. Will go away once |
| // that refactoring is complete (eventually). |
| if (LdrOpc == ARM::LDR_POST) { |
| MIB.addReg(0); |
| MIB.addImm(ARM_AM::getAM2Opc(ARM_AM::add, 4, ARM_AM::no_shift)); |
| } else |
| MIB.addImm(4); |
| AddDefaultPred(MIB); |
| } |
| Regs.clear(); |
| } |
| } |
| |
| bool ARMFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB, |
| MachineBasicBlock::iterator MI, |
| const std::vector<CalleeSavedInfo> &CSI, |
| const TargetRegisterInfo *TRI) const { |
| if (CSI.empty()) |
| return false; |
| |
| MachineFunction &MF = *MBB.getParent(); |
| ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); |
| |
| unsigned PushOpc = AFI->isThumbFunction() ? ARM::t2STMDB_UPD : ARM::STMDB_UPD; |
| unsigned PushOneOpc = AFI->isThumbFunction() ? ARM::t2STR_PRE : ARM::STR_PRE; |
| unsigned FltOpc = ARM::VSTMDDB_UPD; |
| emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea1Register); |
| emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea2Register); |
| emitPushInst(MBB, MI, CSI, FltOpc, 0, true, &isARMArea3Register); |
| |
| return true; |
| } |
| |
| bool ARMFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB, |
| MachineBasicBlock::iterator MI, |
| const std::vector<CalleeSavedInfo> &CSI, |
| const TargetRegisterInfo *TRI) const { |
| if (CSI.empty()) |
| return false; |
| |
| MachineFunction &MF = *MBB.getParent(); |
| ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); |
| bool isVarArg = AFI->getVarArgsRegSaveSize() > 0; |
| |
| unsigned PopOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_UPD : ARM::LDMIA_UPD; |
| unsigned LdrOpc = AFI->isThumbFunction() ? ARM::t2LDR_POST : ARM::LDR_POST; |
| unsigned FltOpc = ARM::VLDMDIA_UPD; |
| emitPopInst(MBB, MI, CSI, FltOpc, 0, isVarArg, true, &isARMArea3Register); |
| emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false, |
| &isARMArea2Register); |
| emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false, |
| &isARMArea1Register); |
| |
| return true; |
| } |
| |
| // FIXME: Make generic? |
| static unsigned GetFunctionSizeInBytes(const MachineFunction &MF, |
| const ARMBaseInstrInfo &TII) { |
| unsigned FnSize = 0; |
| for (MachineFunction::const_iterator MBBI = MF.begin(), E = MF.end(); |
| MBBI != E; ++MBBI) { |
| const MachineBasicBlock &MBB = *MBBI; |
| for (MachineBasicBlock::const_iterator I = MBB.begin(),E = MBB.end(); |
| I != E; ++I) |
| FnSize += TII.GetInstSizeInBytes(I); |
| } |
| return FnSize; |
| } |
| |
| /// estimateStackSize - Estimate and return the size of the frame. |
| /// FIXME: Make generic? |
| static unsigned estimateStackSize(MachineFunction &MF) { |
| const MachineFrameInfo *FFI = MF.getFrameInfo(); |
| int Offset = 0; |
| for (int i = FFI->getObjectIndexBegin(); i != 0; ++i) { |
| int FixedOff = -FFI->getObjectOffset(i); |
| if (FixedOff > Offset) Offset = FixedOff; |
| } |
| for (unsigned i = 0, e = FFI->getObjectIndexEnd(); i != e; ++i) { |
| if (FFI->isDeadObjectIndex(i)) |
| continue; |
| Offset += FFI->getObjectSize(i); |
| unsigned Align = FFI->getObjectAlignment(i); |
| // Adjust to alignment boundary |
| Offset = (Offset+Align-1)/Align*Align; |
| } |
| return (unsigned)Offset; |
| } |
| |
| /// estimateRSStackSizeLimit - Look at each instruction that references stack |
| /// frames and return the stack size limit beyond which some of these |
| /// instructions will require a scratch register during their expansion later. |
| // FIXME: Move to TII? |
| static unsigned estimateRSStackSizeLimit(MachineFunction &MF, |
| const TargetFrameLowering *TFI) { |
| const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); |
| unsigned Limit = (1 << 12) - 1; |
| for (MachineFunction::iterator BB = MF.begin(),E = MF.end(); BB != E; ++BB) { |
| for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end(); |
| I != E; ++I) { |
| for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { |
| if (!I->getOperand(i).isFI()) continue; |
| |
| // When using ADDri to get the address of a stack object, 255 is the |
| // largest offset guaranteed to fit in the immediate offset. |
| if (I->getOpcode() == ARM::ADDri) { |
| Limit = std::min(Limit, (1U << 8) - 1); |
| break; |
| } |
| |
| // Otherwise check the addressing mode. |
| switch (I->getDesc().TSFlags & ARMII::AddrModeMask) { |
| case ARMII::AddrMode3: |
| case ARMII::AddrModeT2_i8: |
| Limit = std::min(Limit, (1U << 8) - 1); |
| break; |
| case ARMII::AddrMode5: |
| case ARMII::AddrModeT2_i8s4: |
| Limit = std::min(Limit, ((1U << 8) - 1) * 4); |
| break; |
| case ARMII::AddrModeT2_i12: |
| // i12 supports only positive offset so these will be converted to |
| // i8 opcodes. See llvm::rewriteT2FrameIndex. |
| if (TFI->hasFP(MF) && AFI->hasStackFrame()) |
| Limit = std::min(Limit, (1U << 8) - 1); |
| break; |
| case ARMII::AddrMode4: |
| case ARMII::AddrMode6: |
| // Addressing modes 4 & 6 (load/store) instructions can't encode an |
| // immediate offset for stack references. |
| return 0; |
| default: |
| break; |
| } |
| break; // At most one FI per instruction |
| } |
| } |
| } |
| |
| return Limit; |
| } |
| |
| void |
| ARMFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF, |
| RegScavenger *RS) const { |
| // This tells PEI to spill the FP as if it is any other callee-save register |
| // to take advantage the eliminateFrameIndex machinery. This also ensures it |
| // is spilled in the order specified by getCalleeSavedRegs() to make it easier |
| // to combine multiple loads / stores. |
| bool CanEliminateFrame = true; |
| bool CS1Spilled = false; |
| bool LRSpilled = false; |
| unsigned NumGPRSpills = 0; |
| SmallVector<unsigned, 4> UnspilledCS1GPRs; |
| SmallVector<unsigned, 4> UnspilledCS2GPRs; |
| const ARMBaseRegisterInfo *RegInfo = |
| static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo()); |
| const ARMBaseInstrInfo &TII = |
| *static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo()); |
| ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); |
| MachineFrameInfo *MFI = MF.getFrameInfo(); |
| unsigned FramePtr = RegInfo->getFrameRegister(MF); |
| |
| // Spill R4 if Thumb2 function requires stack realignment - it will be used as |
| // scratch register. Also spill R4 if Thumb2 function has varsized objects, |
| // since it's not always possible to restore sp from fp in a single |
| // instruction. |
| // FIXME: It will be better just to find spare register here. |
| if (AFI->isThumb2Function() && |
| (MFI->hasVarSizedObjects() || RegInfo->needsStackRealignment(MF))) |
| MF.getRegInfo().setPhysRegUsed(ARM::R4); |
| |
| if (AFI->isThumb1OnlyFunction()) { |
| // Spill LR if Thumb1 function uses variable length argument lists. |
| if (AFI->getVarArgsRegSaveSize() > 0) |
| MF.getRegInfo().setPhysRegUsed(ARM::LR); |
| |
| // Spill R4 if Thumb1 epilogue has to restore SP from FP since |
| // FIXME: It will be better just to find spare register here. |
| if (MFI->hasVarSizedObjects()) |
| MF.getRegInfo().setPhysRegUsed(ARM::R4); |
| } |
| |
| // Spill the BasePtr if it's used. |
| if (RegInfo->hasBasePointer(MF)) |
| MF.getRegInfo().setPhysRegUsed(RegInfo->getBaseRegister()); |
| |
| // Don't spill FP if the frame can be eliminated. This is determined |
| // by scanning the callee-save registers to see if any is used. |
| const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(); |
| for (unsigned i = 0; CSRegs[i]; ++i) { |
| unsigned Reg = CSRegs[i]; |
| bool Spilled = false; |
| if (MF.getRegInfo().isPhysRegUsed(Reg)) { |
| Spilled = true; |
| CanEliminateFrame = false; |
| } else { |
| // Check alias registers too. |
| for (const unsigned *Aliases = |
| RegInfo->getAliasSet(Reg); *Aliases; ++Aliases) { |
| if (MF.getRegInfo().isPhysRegUsed(*Aliases)) { |
| Spilled = true; |
| CanEliminateFrame = false; |
| } |
| } |
| } |
| |
| if (!ARM::GPRRegisterClass->contains(Reg)) |
| continue; |
| |
| if (Spilled) { |
| NumGPRSpills++; |
| |
| if (!STI.isTargetDarwin()) { |
| if (Reg == ARM::LR) |
| LRSpilled = true; |
| CS1Spilled = true; |
| continue; |
| } |
| |
| // Keep track if LR and any of R4, R5, R6, and R7 is spilled. |
| switch (Reg) { |
| case ARM::LR: |
| LRSpilled = true; |
| // Fallthrough |
| case ARM::R4: case ARM::R5: |
| case ARM::R6: case ARM::R7: |
| CS1Spilled = true; |
| break; |
| default: |
| break; |
| } |
| } else { |
| if (!STI.isTargetDarwin()) { |
| UnspilledCS1GPRs.push_back(Reg); |
| continue; |
| } |
| |
| switch (Reg) { |
| case ARM::R4: case ARM::R5: |
| case ARM::R6: case ARM::R7: |
| case ARM::LR: |
| UnspilledCS1GPRs.push_back(Reg); |
| break; |
| default: |
| UnspilledCS2GPRs.push_back(Reg); |
| break; |
| } |
| } |
| } |
| |
| bool ForceLRSpill = false; |
| if (!LRSpilled && AFI->isThumb1OnlyFunction()) { |
| unsigned FnSize = GetFunctionSizeInBytes(MF, TII); |
| // Force LR to be spilled if the Thumb function size is > 2048. This enables |
| // use of BL to implement far jump. If it turns out that it's not needed |
| // then the branch fix up path will undo it. |
| if (FnSize >= (1 << 11)) { |
| CanEliminateFrame = false; |
| ForceLRSpill = true; |
| } |
| } |
| |
| // If any of the stack slot references may be out of range of an immediate |
| // offset, make sure a register (or a spill slot) is available for the |
| // register scavenger. Note that if we're indexing off the frame pointer, the |
| // effective stack size is 4 bytes larger since the FP points to the stack |
| // slot of the previous FP. Also, if we have variable sized objects in the |
| // function, stack slot references will often be negative, and some of |
| // our instructions are positive-offset only, so conservatively consider |
| // that case to want a spill slot (or register) as well. Similarly, if |
| // the function adjusts the stack pointer during execution and the |
| // adjustments aren't already part of our stack size estimate, our offset |
| // calculations may be off, so be conservative. |
| // FIXME: We could add logic to be more precise about negative offsets |
| // and which instructions will need a scratch register for them. Is it |
| // worth the effort and added fragility? |
| bool BigStack = |
| (RS && |
| (estimateStackSize(MF) + ((hasFP(MF) && AFI->hasStackFrame()) ? 4:0) >= |
| estimateRSStackSizeLimit(MF, this))) |
| || MFI->hasVarSizedObjects() |
| || (MFI->adjustsStack() && !canSimplifyCallFramePseudos(MF)); |
| |
| bool ExtraCSSpill = false; |
| if (BigStack || !CanEliminateFrame || RegInfo->cannotEliminateFrame(MF)) { |
| AFI->setHasStackFrame(true); |
| |
| // If LR is not spilled, but at least one of R4, R5, R6, and R7 is spilled. |
| // Spill LR as well so we can fold BX_RET to the registers restore (LDM). |
| if (!LRSpilled && CS1Spilled) { |
| MF.getRegInfo().setPhysRegUsed(ARM::LR); |
| NumGPRSpills++; |
| UnspilledCS1GPRs.erase(std::find(UnspilledCS1GPRs.begin(), |
| UnspilledCS1GPRs.end(), (unsigned)ARM::LR)); |
| ForceLRSpill = false; |
| ExtraCSSpill = true; |
| } |
| |
| if (hasFP(MF)) { |
| MF.getRegInfo().setPhysRegUsed(FramePtr); |
| NumGPRSpills++; |
| } |
| |
| // If stack and double are 8-byte aligned and we are spilling an odd number |
| // of GPRs, spill one extra callee save GPR so we won't have to pad between |
| // the integer and double callee save areas. |
| unsigned TargetAlign = getStackAlignment(); |
| if (TargetAlign == 8 && (NumGPRSpills & 1)) { |
| if (CS1Spilled && !UnspilledCS1GPRs.empty()) { |
| for (unsigned i = 0, e = UnspilledCS1GPRs.size(); i != e; ++i) { |
| unsigned Reg = UnspilledCS1GPRs[i]; |
| // Don't spill high register if the function is thumb1 |
| if (!AFI->isThumb1OnlyFunction() || |
| isARMLowRegister(Reg) || Reg == ARM::LR) { |
| MF.getRegInfo().setPhysRegUsed(Reg); |
| if (!RegInfo->isReservedReg(MF, Reg)) |
| ExtraCSSpill = true; |
| break; |
| } |
| } |
| } else if (!UnspilledCS2GPRs.empty() && !AFI->isThumb1OnlyFunction()) { |
| unsigned Reg = UnspilledCS2GPRs.front(); |
| MF.getRegInfo().setPhysRegUsed(Reg); |
| if (!RegInfo->isReservedReg(MF, Reg)) |
| ExtraCSSpill = true; |
| } |
| } |
| |
| // Estimate if we might need to scavenge a register at some point in order |
| // to materialize a stack offset. If so, either spill one additional |
| // callee-saved register or reserve a special spill slot to facilitate |
| // register scavenging. Thumb1 needs a spill slot for stack pointer |
| // adjustments also, even when the frame itself is small. |
| if (BigStack && !ExtraCSSpill) { |
| // If any non-reserved CS register isn't spilled, just spill one or two |
| // extra. That should take care of it! |
| unsigned NumExtras = TargetAlign / 4; |
| SmallVector<unsigned, 2> Extras; |
| while (NumExtras && !UnspilledCS1GPRs.empty()) { |
| unsigned Reg = UnspilledCS1GPRs.back(); |
| UnspilledCS1GPRs.pop_back(); |
| if (!RegInfo->isReservedReg(MF, Reg) && |
| (!AFI->isThumb1OnlyFunction() || isARMLowRegister(Reg) || |
| Reg == ARM::LR)) { |
| Extras.push_back(Reg); |
| NumExtras--; |
| } |
| } |
| // For non-Thumb1 functions, also check for hi-reg CS registers |
| if (!AFI->isThumb1OnlyFunction()) { |
| while (NumExtras && !UnspilledCS2GPRs.empty()) { |
| unsigned Reg = UnspilledCS2GPRs.back(); |
| UnspilledCS2GPRs.pop_back(); |
| if (!RegInfo->isReservedReg(MF, Reg)) { |
| Extras.push_back(Reg); |
| NumExtras--; |
| } |
| } |
| } |
| if (Extras.size() && NumExtras == 0) { |
| for (unsigned i = 0, e = Extras.size(); i != e; ++i) { |
| MF.getRegInfo().setPhysRegUsed(Extras[i]); |
| } |
| } else if (!AFI->isThumb1OnlyFunction()) { |
| // note: Thumb1 functions spill to R12, not the stack. Reserve a slot |
| // closest to SP or frame pointer. |
| const TargetRegisterClass *RC = ARM::GPRRegisterClass; |
| RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(), |
| RC->getAlignment(), |
| false)); |
| } |
| } |
| } |
| |
| if (ForceLRSpill) { |
| MF.getRegInfo().setPhysRegUsed(ARM::LR); |
| AFI->setLRIsSpilledForFarJump(true); |
| } |
| } |