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Diffstat (limited to 'contrib/llvm/lib/Target/ARM/ARMFrameLowering.cpp')
| -rw-r--r-- | contrib/llvm/lib/Target/ARM/ARMFrameLowering.cpp | 2179 |
1 files changed, 2179 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Target/ARM/ARMFrameLowering.cpp b/contrib/llvm/lib/Target/ARM/ARMFrameLowering.cpp new file mode 100644 index 0000000..45c2c30 --- /dev/null +++ b/contrib/llvm/lib/Target/ARM/ARMFrameLowering.cpp @@ -0,0 +1,2179 @@ +//===-- ARMFrameLowering.cpp - ARM Frame 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 ARM implementation of TargetFrameLowering class. +// +//===----------------------------------------------------------------------===// + +#include "ARMFrameLowering.h" +#include "ARMBaseInstrInfo.h" +#include "ARMBaseRegisterInfo.h" +#include "ARMConstantPoolValue.h" +#include "ARMMachineFunctionInfo.h" +#include "MCTargetDesc/ARMAddressingModes.h" +#include "llvm/CodeGen/MachineFrameInfo.h" +#include "llvm/CodeGen/MachineFunction.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineModuleInfo.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/CodeGen/RegisterScavenging.h" +#include "llvm/IR/CallingConv.h" +#include "llvm/IR/Function.h" +#include "llvm/MC/MCContext.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Target/TargetOptions.h" + +using namespace llvm; + +static cl::opt<bool> +SpillAlignedNEONRegs("align-neon-spills", cl::Hidden, cl::init(true), + cl::desc("Align ARM NEON spills in prolog and epilog")); + +static MachineBasicBlock::iterator +skipAlignedDPRCS2Spills(MachineBasicBlock::iterator MI, + unsigned NumAlignedDPRCS2Regs); + +ARMFrameLowering::ARMFrameLowering(const ARMSubtarget &sti) + : TargetFrameLowering(StackGrowsDown, sti.getStackAlignment(), 0, 4), + STI(sti) {} + +/// 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.getSubtarget().getRegisterInfo(); + + // iOS requires FP not to be clobbered for backtracing purpose. + if (STI.isTargetIOS()) + return true; + + const MachineFrameInfo *MFI = MF.getFrameInfo(); + // Always eliminate non-leaf frame pointers. + return ((MF.getTarget().Options.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 isCSRestore(MachineInstr *MI, + const ARMBaseInstrInfo &TII, + const MCPhysReg *CSRegs) { + // Integer spill area is handled with "pop". + if (isPopOpcode(MI->getOpcode())) { + // 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_IMM || + MI->getOpcode() == ARM::LDR_POST_REG || + MI->getOpcode() == ARM::t2LDR_POST) && + isCalleeSavedRegister(MI->getOperand(0).getReg(), CSRegs) && + MI->getOperand(1).getReg() == ARM::SP) + return true; + + return false; +} + +static void emitRegPlusImmediate(bool isARM, MachineBasicBlock &MBB, + MachineBasicBlock::iterator &MBBI, DebugLoc dl, + const ARMBaseInstrInfo &TII, unsigned DestReg, + unsigned SrcReg, int NumBytes, + unsigned MIFlags = MachineInstr::NoFlags, + ARMCC::CondCodes Pred = ARMCC::AL, + unsigned PredReg = 0) { + if (isARM) + emitARMRegPlusImmediate(MBB, MBBI, dl, DestReg, SrcReg, NumBytes, + Pred, PredReg, TII, MIFlags); + else + emitT2RegPlusImmediate(MBB, MBBI, dl, DestReg, SrcReg, NumBytes, + Pred, PredReg, TII, MIFlags); +} + +static void emitSPUpdate(bool isARM, MachineBasicBlock &MBB, + MachineBasicBlock::iterator &MBBI, DebugLoc dl, + const ARMBaseInstrInfo &TII, int NumBytes, + unsigned MIFlags = MachineInstr::NoFlags, + ARMCC::CondCodes Pred = ARMCC::AL, + unsigned PredReg = 0) { + emitRegPlusImmediate(isARM, MBB, MBBI, dl, TII, ARM::SP, ARM::SP, NumBytes, + MIFlags, Pred, PredReg); +} + +static int sizeOfSPAdjustment(const MachineInstr *MI) { + int RegSize; + switch (MI->getOpcode()) { + case ARM::VSTMDDB_UPD: + RegSize = 8; + break; + case ARM::STMDB_UPD: + case ARM::t2STMDB_UPD: + RegSize = 4; + break; + case ARM::t2STR_PRE: + case ARM::STR_PRE_IMM: + return 4; + default: + llvm_unreachable("Unknown push or pop like instruction"); + } + + int count = 0; + // ARM and Thumb2 push/pop insts have explicit "sp, sp" operands (+ + // pred) so the list starts at 4. + for (int i = MI->getNumOperands() - 1; i >= 4; --i) + count += RegSize; + return count; +} + +static bool WindowsRequiresStackProbe(const MachineFunction &MF, + size_t StackSizeInBytes) { + const MachineFrameInfo *MFI = MF.getFrameInfo(); + if (MFI->getStackProtectorIndex() > 0) + return StackSizeInBytes >= 4080; + return StackSizeInBytes >= 4096; +} + +namespace { +struct StackAdjustingInsts { + struct InstInfo { + MachineBasicBlock::iterator I; + unsigned SPAdjust; + bool BeforeFPSet; + }; + + SmallVector<InstInfo, 4> Insts; + + void addInst(MachineBasicBlock::iterator I, unsigned SPAdjust, + bool BeforeFPSet = false) { + InstInfo Info = {I, SPAdjust, BeforeFPSet}; + Insts.push_back(Info); + } + + void addExtraBytes(const MachineBasicBlock::iterator I, unsigned ExtraBytes) { + auto Info = std::find_if(Insts.begin(), Insts.end(), + [&](InstInfo &Info) { return Info.I == I; }); + assert(Info != Insts.end() && "invalid sp adjusting instruction"); + Info->SPAdjust += ExtraBytes; + } + + void emitDefCFAOffsets(MachineModuleInfo &MMI, MachineBasicBlock &MBB, + DebugLoc dl, const ARMBaseInstrInfo &TII, bool HasFP) { + unsigned CFAOffset = 0; + for (auto &Info : Insts) { + if (HasFP && !Info.BeforeFPSet) + return; + + CFAOffset -= Info.SPAdjust; + unsigned CFIIndex = MMI.addFrameInst( + MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset)); + BuildMI(MBB, std::next(Info.I), dl, + TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex) + .setMIFlags(MachineInstr::FrameSetup); + } + } +}; +} + +/// Emit an instruction sequence that will align the address in +/// register Reg by zero-ing out the lower bits. For versions of the +/// architecture that support Neon, this must be done in a single +/// instruction, since skipAlignedDPRCS2Spills assumes it is done in a +/// single instruction. That function only gets called when optimizing +/// spilling of D registers on a core with the Neon instruction set +/// present. +static void emitAligningInstructions(MachineFunction &MF, ARMFunctionInfo *AFI, + const TargetInstrInfo &TII, + MachineBasicBlock &MBB, + MachineBasicBlock::iterator MBBI, + DebugLoc DL, const unsigned Reg, + const unsigned Alignment, + const bool MustBeSingleInstruction) { + const ARMSubtarget &AST = MF.getTarget().getSubtarget<ARMSubtarget>(); + const bool CanUseBFC = AST.hasV6T2Ops() || AST.hasV7Ops(); + const unsigned AlignMask = Alignment - 1; + const unsigned NrBitsToZero = countTrailingZeros(Alignment); + assert(!AFI->isThumb1OnlyFunction() && "Thumb1 not supported"); + if (!AFI->isThumbFunction()) { + // if the BFC instruction is available, use that to zero the lower + // bits: + // bfc Reg, #0, log2(Alignment) + // otherwise use BIC, if the mask to zero the required number of bits + // can be encoded in the bic immediate field + // bic Reg, Reg, Alignment-1 + // otherwise, emit + // lsr Reg, Reg, log2(Alignment) + // lsl Reg, Reg, log2(Alignment) + if (CanUseBFC) { + AddDefaultPred(BuildMI(MBB, MBBI, DL, TII.get(ARM::BFC), Reg) + .addReg(Reg, RegState::Kill) + .addImm(~AlignMask)); + } else if (AlignMask <= 255) { + AddDefaultCC( + AddDefaultPred(BuildMI(MBB, MBBI, DL, TII.get(ARM::BICri), Reg) + .addReg(Reg, RegState::Kill) + .addImm(AlignMask))); + } else { + assert(!MustBeSingleInstruction && + "Shouldn't call emitAligningInstructions demanding a single " + "instruction to be emitted for large stack alignment for a target " + "without BFC."); + AddDefaultCC(AddDefaultPred( + BuildMI(MBB, MBBI, DL, TII.get(ARM::MOVsi), Reg) + .addReg(Reg, RegState::Kill) + .addImm(ARM_AM::getSORegOpc(ARM_AM::lsr, NrBitsToZero)))); + AddDefaultCC(AddDefaultPred( + BuildMI(MBB, MBBI, DL, TII.get(ARM::MOVsi), Reg) + .addReg(Reg, RegState::Kill) + .addImm(ARM_AM::getSORegOpc(ARM_AM::lsl, NrBitsToZero)))); + } + } else { + // Since this is only reached for Thumb-2 targets, the BFC instruction + // should always be available. + assert(CanUseBFC); + AddDefaultPred(BuildMI(MBB, MBBI, DL, TII.get(ARM::t2BFC), Reg) + .addReg(Reg, RegState::Kill) + .addImm(~AlignMask)); + } +} + +void ARMFrameLowering::emitPrologue(MachineFunction &MF) const { + MachineBasicBlock &MBB = MF.front(); + MachineBasicBlock::iterator MBBI = MBB.begin(); + MachineFrameInfo *MFI = MF.getFrameInfo(); + ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); + MachineModuleInfo &MMI = MF.getMMI(); + MCContext &Context = MMI.getContext(); + const TargetMachine &TM = MF.getTarget(); + const MCRegisterInfo *MRI = Context.getRegisterInfo(); + const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>( + TM.getSubtargetImpl()->getRegisterInfo()); + const ARMBaseInstrInfo &TII = *static_cast<const ARMBaseInstrInfo *>( + TM.getSubtargetImpl()->getInstrInfo()); + assert(!AFI->isThumb1OnlyFunction() && + "This emitPrologue does not support Thumb1!"); + bool isARM = !AFI->isThumbFunction(); + unsigned Align = + TM.getSubtargetImpl()->getFrameLowering()->getStackAlignment(); + unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(Align); + 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; + int D8SpillFI = 0; + + // All calls are tail calls in GHC calling conv, and functions have no + // prologue/epilogue. + if (MF.getFunction()->getCallingConv() == CallingConv::GHC) + return; + + StackAdjustingInsts DefCFAOffsetCandidates; + + // Allocate the vararg register save area. + if (ArgRegsSaveSize) { + emitSPUpdate(isARM, MBB, MBBI, dl, TII, -ArgRegsSaveSize, + MachineInstr::FrameSetup); + DefCFAOffsetCandidates.addInst(std::prev(MBBI), ArgRegsSaveSize, true); + } + + if (!AFI->hasStackFrame() && + (!STI.isTargetWindows() || !WindowsRequiresStackProbe(MF, NumBytes))) { + if (NumBytes - ArgRegsSaveSize != 0) { + emitSPUpdate(isARM, MBB, MBBI, dl, TII, -(NumBytes - ArgRegsSaveSize), + MachineInstr::FrameSetup); + DefCFAOffsetCandidates.addInst(std::prev(MBBI), + NumBytes - ArgRegsSaveSize, true); + } + return; + } + + // Determine spill area sizes. + 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: + case ARM::R12: + if (STI.isTargetDarwin()) { + GPRCS2Size += 4; + break; + } + // 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: + if (Reg == FramePtr) + FramePtrSpillFI = FI; + GPRCS1Size += 4; + break; + default: + // This is a DPR. Exclude the aligned DPRCS2 spills. + if (Reg == ARM::D8) + D8SpillFI = FI; + if (Reg < ARM::D8 || Reg >= ARM::D8 + AFI->getNumAlignedDPRCS2Regs()) + DPRCSSize += 8; + } + } + + // Move past area 1. + MachineBasicBlock::iterator LastPush = MBB.end(), GPRCS1Push, GPRCS2Push; + if (GPRCS1Size > 0) { + GPRCS1Push = LastPush = MBBI++; + DefCFAOffsetCandidates.addInst(LastPush, GPRCS1Size, true); + } + + // Determine starting offsets of spill areas. + bool HasFP = hasFP(MF); + unsigned GPRCS1Offset = NumBytes - ArgRegsSaveSize - GPRCS1Size; + unsigned GPRCS2Offset = GPRCS1Offset - GPRCS2Size; + unsigned DPRAlign = DPRCSSize ? std::min(8U, Align) : 4U; + unsigned DPRGapSize = (GPRCS1Size + GPRCS2Size + ArgRegsSaveSize) % DPRAlign; + unsigned DPRCSOffset = GPRCS2Offset - DPRGapSize - DPRCSSize; + int FramePtrOffsetInPush = 0; + if (HasFP) { + FramePtrOffsetInPush = + MFI->getObjectOffset(FramePtrSpillFI) + ArgRegsSaveSize; + AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) + + NumBytes); + } + AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset); + AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset); + AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset); + + // Move past area 2. + if (GPRCS2Size > 0) { + GPRCS2Push = LastPush = MBBI++; + DefCFAOffsetCandidates.addInst(LastPush, GPRCS2Size); + } + + // Prolog/epilog inserter assumes we correctly align DPRs on the stack, so our + // .cfi_offset operations will reflect that. + if (DPRGapSize) { + assert(DPRGapSize == 4 && "unexpected alignment requirements for DPRs"); + if (tryFoldSPUpdateIntoPushPop(STI, MF, LastPush, DPRGapSize)) + DefCFAOffsetCandidates.addExtraBytes(LastPush, DPRGapSize); + else { + emitSPUpdate(isARM, MBB, MBBI, dl, TII, -DPRGapSize, + MachineInstr::FrameSetup); + DefCFAOffsetCandidates.addInst(std::prev(MBBI), DPRGapSize); + } + } + + // Move past area 3. + if (DPRCSSize > 0) { + // Since vpush register list cannot have gaps, there may be multiple vpush + // instructions in the prologue. + while (MBBI->getOpcode() == ARM::VSTMDDB_UPD) { + DefCFAOffsetCandidates.addInst(MBBI, sizeOfSPAdjustment(MBBI)); + LastPush = MBBI++; + } + } + + // Move past the aligned DPRCS2 area. + if (AFI->getNumAlignedDPRCS2Regs() > 0) { + MBBI = skipAlignedDPRCS2Spills(MBBI, AFI->getNumAlignedDPRCS2Regs()); + // The code inserted by emitAlignedDPRCS2Spills realigns the stack, and + // leaves the stack pointer pointing to the DPRCS2 area. + // + // Adjust NumBytes to represent the stack slots below the DPRCS2 area. + NumBytes += MFI->getObjectOffset(D8SpillFI); + } else + NumBytes = DPRCSOffset; + + if (STI.isTargetWindows() && WindowsRequiresStackProbe(MF, NumBytes)) { + uint32_t NumWords = NumBytes >> 2; + + if (NumWords < 65536) + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi16), ARM::R4) + .addImm(NumWords) + .setMIFlags(MachineInstr::FrameSetup)); + else + BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi32imm), ARM::R4) + .addImm(NumWords) + .setMIFlags(MachineInstr::FrameSetup); + + switch (TM.getCodeModel()) { + case CodeModel::Small: + case CodeModel::Medium: + case CodeModel::Default: + case CodeModel::Kernel: + BuildMI(MBB, MBBI, dl, TII.get(ARM::tBL)) + .addImm((unsigned)ARMCC::AL).addReg(0) + .addExternalSymbol("__chkstk") + .addReg(ARM::R4, RegState::Implicit) + .setMIFlags(MachineInstr::FrameSetup); + break; + case CodeModel::Large: + case CodeModel::JITDefault: + BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi32imm), ARM::R12) + .addExternalSymbol("__chkstk") + .setMIFlags(MachineInstr::FrameSetup); + + BuildMI(MBB, MBBI, dl, TII.get(ARM::tBLXr)) + .addImm((unsigned)ARMCC::AL).addReg(0) + .addReg(ARM::R12, RegState::Kill) + .addReg(ARM::R4, RegState::Implicit) + .setMIFlags(MachineInstr::FrameSetup); + break; + } + + AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::t2SUBrr), + ARM::SP) + .addReg(ARM::SP, RegState::Define) + .addReg(ARM::R4, RegState::Kill) + .setMIFlags(MachineInstr::FrameSetup))); + NumBytes = 0; + } + + if (NumBytes) { + // Adjust SP after all the callee-save spills. + if (tryFoldSPUpdateIntoPushPop(STI, MF, LastPush, NumBytes)) + DefCFAOffsetCandidates.addExtraBytes(LastPush, NumBytes); + else { + emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes, + MachineInstr::FrameSetup); + DefCFAOffsetCandidates.addInst(std::prev(MBBI), 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); + } + + // Set FP to point to the stack slot that contains the previous FP. + // For iOS, FP is R7, which has now been stored in spill area 1. + // Otherwise, if this is not iOS, all the callee-saved registers go + // into spill area 1, including the FP in R11. In either case, it + // is in area one and the adjustment needs to take place just after + // that push. + if (HasFP) { + MachineBasicBlock::iterator AfterPush = std::next(GPRCS1Push); + unsigned PushSize = sizeOfSPAdjustment(GPRCS1Push); + emitRegPlusImmediate(!AFI->isThumbFunction(), MBB, AfterPush, + dl, TII, FramePtr, ARM::SP, + PushSize + FramePtrOffsetInPush, + MachineInstr::FrameSetup); + if (FramePtrOffsetInPush + PushSize != 0) { + unsigned CFIIndex = MMI.addFrameInst(MCCFIInstruction::createDefCfa( + nullptr, MRI->getDwarfRegNum(FramePtr, true), + -(ArgRegsSaveSize - FramePtrOffsetInPush))); + BuildMI(MBB, AfterPush, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex) + .setMIFlags(MachineInstr::FrameSetup); + } else { + unsigned CFIIndex = + MMI.addFrameInst(MCCFIInstruction::createDefCfaRegister( + nullptr, MRI->getDwarfRegNum(FramePtr, true))); + BuildMI(MBB, AfterPush, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex) + .setMIFlags(MachineInstr::FrameSetup); + } + } + + // Now that the prologue's actual instructions are finalised, we can insert + // the necessary DWARF cf instructions to describe the situation. Start by + // recording where each register ended up: + if (GPRCS1Size > 0) { + MachineBasicBlock::iterator Pos = std::next(GPRCS1Push); + int CFIIndex; + for (const auto &Entry : CSI) { + unsigned Reg = Entry.getReg(); + int FI = Entry.getFrameIdx(); + switch (Reg) { + case ARM::R8: + case ARM::R9: + case ARM::R10: + case ARM::R11: + case ARM::R12: + if (STI.isTargetDarwin()) + break; + // 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: + CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset( + nullptr, MRI->getDwarfRegNum(Reg, true), MFI->getObjectOffset(FI))); + BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex) + .setMIFlags(MachineInstr::FrameSetup); + break; + } + } + } + + if (GPRCS2Size > 0) { + MachineBasicBlock::iterator Pos = std::next(GPRCS2Push); + for (const auto &Entry : CSI) { + unsigned Reg = Entry.getReg(); + int FI = Entry.getFrameIdx(); + switch (Reg) { + case ARM::R8: + case ARM::R9: + case ARM::R10: + case ARM::R11: + case ARM::R12: + if (STI.isTargetDarwin()) { + unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true); + unsigned Offset = MFI->getObjectOffset(FI); + unsigned CFIIndex = MMI.addFrameInst( + MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset)); + BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex) + .setMIFlags(MachineInstr::FrameSetup); + } + break; + } + } + } + + if (DPRCSSize > 0) { + // Since vpush register list cannot have gaps, there may be multiple vpush + // instructions in the prologue. + MachineBasicBlock::iterator Pos = std::next(LastPush); + for (const auto &Entry : CSI) { + unsigned Reg = Entry.getReg(); + int FI = Entry.getFrameIdx(); + if ((Reg >= ARM::D0 && Reg <= ARM::D31) && + (Reg < ARM::D8 || Reg >= ARM::D8 + AFI->getNumAlignedDPRCS2Regs())) { + unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true); + unsigned Offset = MFI->getObjectOffset(FI); + unsigned CFIIndex = MMI.addFrameInst( + MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset)); + BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex) + .setMIFlags(MachineInstr::FrameSetup); + } + } + } + + // Now we can emit descriptions of where the canonical frame address was + // throughout the process. If we have a frame pointer, it takes over the job + // half-way through, so only the first few .cfi_def_cfa_offset instructions + // actually get emitted. + DefCFAOffsetCandidates.emitDefCFAOffsets(MMI, MBB, dl, TII, HasFP); + + if (STI.isTargetELF() && hasFP(MF)) + MFI->setOffsetAdjustment(MFI->getOffsetAdjustment() - + AFI->getFramePtrSpillOffset()); + + AFI->setGPRCalleeSavedArea1Size(GPRCS1Size); + AFI->setGPRCalleeSavedArea2Size(GPRCS2Size); + AFI->setDPRCalleeSavedGapSize(DPRGapSize); + 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 aligned NEON registers were spilled, the stack has already been + // realigned. + if (!AFI->getNumAlignedDPRCS2Regs() && RegInfo->needsStackRealignment(MF)) { + unsigned MaxAlign = MFI->getMaxAlignment(); + assert(!AFI->isThumb1OnlyFunction()); + if (!AFI->isThumbFunction()) { + emitAligningInstructions(MF, AFI, TII, MBB, MBBI, dl, ARM::SP, MaxAlign, + false); + } else { + // We cannot use sp as source/dest register here, thus we're using r4 to + // perform the calculations. We're emitting the following sequence: + // mov r4, sp + // -- use emitAligningInstructions to produce best sequence to zero + // -- out lower bits in r4 + // mov sp, r4 + // FIXME: It will be better just to find spare register here. + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R4) + .addReg(ARM::SP, RegState::Kill)); + emitAligningInstructions(MF, AFI, TII, MBB, MBBI, dl, ARM::R4, MaxAlign, + false); + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), 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. + // FIXME: Clarify FrameSetup flags here. + 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 + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), + 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); +} + +// Resolve TCReturn pseudo-instruction +void ARMFrameLowering::fixTCReturn(MachineFunction &MF, + MachineBasicBlock &MBB) const { + MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr(); + assert(MBBI->isReturn() && "Can only insert epilog into returning blocks"); + unsigned RetOpcode = MBBI->getOpcode(); + DebugLoc dl = MBBI->getDebugLoc(); + const ARMBaseInstrInfo &TII = + *static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo()); + + if (!(RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNri)) + return; + + // 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) { + unsigned TCOpcode = STI.isThumb() ? + (STI.isTargetMachO() ? ARM::tTAILJMPd : ARM::tTAILJMPdND) : + ARM::TAILJMPd; + 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()); + } + + // Add the default predicate in Thumb mode. + if (STI.isThumb()) MIB.addImm(ARMCC::AL).addReg(0); + } else if (RetOpcode == ARM::TCRETURNri) { + BuildMI(MBB, MBBI, dl, + TII.get(STI.isThumb() ? ARM::tTAILJMPr : ARM::TAILJMPr)). + addReg(JumpTarget.getReg(), RegState::Kill); + } + + MachineInstr *NewMI = std::prev(MBBI); + for (unsigned i = 1, e = MBBI->getNumOperands(); i != e; ++i) + NewMI->addOperand(MBBI->getOperand(i)); + + // Delete the pseudo instruction TCRETURN. + MBB.erase(MBBI); + MBBI = NewMI; +} + +void ARMFrameLowering::emitEpilogue(MachineFunction &MF, + MachineBasicBlock &MBB) const { + MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr(); + assert(MBBI->isReturn() && "Can only insert epilog into returning blocks"); + DebugLoc dl = MBBI->getDebugLoc(); + MachineFrameInfo *MFI = MF.getFrameInfo(); + ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); + const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo(); + const ARMBaseInstrInfo &TII = + *static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo()); + assert(!AFI->isThumb1OnlyFunction() && + "This emitEpilogue does not support Thumb1!"); + bool isARM = !AFI->isThumbFunction(); + + unsigned Align = MF.getTarget() + .getSubtargetImpl() + ->getFrameLowering() + ->getStackAlignment(); + unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(Align); + int NumBytes = (int)MFI->getStackSize(); + unsigned FramePtr = RegInfo->getFrameRegister(MF); + + // All calls are tail calls in GHC calling conv, and functions have no + // prologue/epilogue. + if (MF.getFunction()->getCallingConv() == CallingConv::GHC) { + fixTCReturn(MF, MBB); + return; + } + + if (!AFI->hasStackFrame()) { + if (NumBytes - ArgRegsSaveSize != 0) + emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes - ArgRegsSaveSize); + } else { + // Unwind MBBI to point to first LDR / VLDRD. + const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&MF); + 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 -= (ArgRegsSaveSize + + AFI->getGPRCalleeSavedArea1Size() + + AFI->getGPRCalleeSavedArea2Size() + + AFI->getDPRCalleeSavedGapSize() + + 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 iOS, 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); + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), + 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 + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), + ARM::SP) + .addReg(FramePtr)); + } + } else if (NumBytes && + !tryFoldSPUpdateIntoPushPop(STI, MF, MBBI, 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->getDPRCalleeSavedGapSize()) { + assert(AFI->getDPRCalleeSavedGapSize() == 4 && + "unexpected DPR alignment gap"); + emitSPUpdate(isARM, MBB, MBBI, dl, TII, AFI->getDPRCalleeSavedGapSize()); + } + + if (AFI->getGPRCalleeSavedArea2Size()) MBBI++; + if (AFI->getGPRCalleeSavedArea1Size()) MBBI++; + } + + fixTCReturn(MF, MBB); + + if (ArgRegsSaveSize) + emitSPUpdate(isARM, MBB, MBBI, dl, TII, ArgRegsSaveSize); +} + +/// 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.getSubtarget().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; + + // SP can move around if there are allocas. We may also lose track of SP + // when emergency spilling inside a non-reserved call frame setup. + bool hasMovingSP = !hasReservedCallFrame(MF); + + // 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 (hasMovingSP) { + 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 || (hasMovingSP && !RegInfo->hasBasePointer(MF))) { + FrameReg = RegInfo->getFrameRegister(MF); + return FPOffset; + } else if (hasMovingSP) { + assert(RegInfo->hasBasePointer(MF) && "missing base pointer!"); + if (AFI->isThumb2Function()) { + // 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 (FPOffset >= -255 && FPOffset < 0) { + FrameReg = RegInfo->getFrameRegister(MF); + return FPOffset; + } + } + } else if (AFI->isThumb2Function()) { + // Use add <rd>, sp, #<imm8> + // ldr <rd>, [sp, #<imm8>] + // if at all possible to save space. + if (Offset >= 0 && (Offset & 3) == 0 && Offset <= 1020) + return Offset; + // In Thumb2 mode, the negative offset is very limited. Try to avoid + // out of range references. ldr <rt>,[<rn>, #-<imm8>] + 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), + unsigned NumAlignedDPRCS2Regs, + unsigned MIFlags) const { + MachineFunction &MF = *MBB.getParent(); + const TargetInstrInfo &TII = *MF.getSubtarget().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; + + // D-registers in the aligned area DPRCS2 are NOT spilled here. + if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs) + 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).setMIFlags(MIFlags)); + 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).setMIFlags(MIFlags) + .addImm(-4); + AddDefaultPred(MIB); + } + Regs.clear(); + + // Put any subsequent vpush instructions before this one: they will refer to + // higher register numbers so need to be pushed first in order to preserve + // monotonicity. + --MI; + } +} + +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), + unsigned NumAlignedDPRCS2Regs) const { + MachineFunction &MF = *MBB.getParent(); + const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); + ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); + DebugLoc DL = MI->getDebugLoc(); + unsigned RetOpcode = MI->getOpcode(); + bool isTailCall = (RetOpcode == ARM::TCRETURNdi || + RetOpcode == ARM::TCRETURNri); + bool isInterrupt = + RetOpcode == ARM::SUBS_PC_LR || RetOpcode == ARM::t2SUBS_PC_LR; + + 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; + + // The aligned reloads from area DPRCS2 are not inserted here. + if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs) + continue; + + if (Reg == ARM::LR && !isTailCall && !isVarArg && !isInterrupt && + 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) { + MIB.copyImplicitOps(&*MI); + 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_REG || LdrOpc == ARM::LDR_POST_IMM) { + MIB.addReg(0); + MIB.addImm(ARM_AM::getAM2Opc(ARM_AM::add, 4, ARM_AM::no_shift)); + } else + MIB.addImm(4); + AddDefaultPred(MIB); + } + Regs.clear(); + + // Put any subsequent vpop instructions after this one: they will refer to + // higher register numbers so need to be popped afterwards. + ++MI; + } +} + +/// Emit aligned spill instructions for NumAlignedDPRCS2Regs D-registers +/// starting from d8. Also insert stack realignment code and leave the stack +/// pointer pointing to the d8 spill slot. +static void emitAlignedDPRCS2Spills(MachineBasicBlock &MBB, + MachineBasicBlock::iterator MI, + unsigned NumAlignedDPRCS2Regs, + const std::vector<CalleeSavedInfo> &CSI, + const TargetRegisterInfo *TRI) { + MachineFunction &MF = *MBB.getParent(); + ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); + DebugLoc DL = MI->getDebugLoc(); + const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); + MachineFrameInfo &MFI = *MF.getFrameInfo(); + + // Mark the D-register spill slots as properly aligned. Since MFI computes + // stack slot layout backwards, this can actually mean that the d-reg stack + // slot offsets can be wrong. The offset for d8 will always be correct. + for (unsigned i = 0, e = CSI.size(); i != e; ++i) { + unsigned DNum = CSI[i].getReg() - ARM::D8; + if (DNum >= 8) + continue; + int FI = CSI[i].getFrameIdx(); + // The even-numbered registers will be 16-byte aligned, the odd-numbered + // registers will be 8-byte aligned. + MFI.setObjectAlignment(FI, DNum % 2 ? 8 : 16); + + // The stack slot for D8 needs to be maximally aligned because this is + // actually the point where we align the stack pointer. MachineFrameInfo + // computes all offsets relative to the incoming stack pointer which is a + // bit weird when realigning the stack. Any extra padding for this + // over-alignment is not realized because the code inserted below adjusts + // the stack pointer by numregs * 8 before aligning the stack pointer. + if (DNum == 0) + MFI.setObjectAlignment(FI, MFI.getMaxAlignment()); + } + + // Move the stack pointer to the d8 spill slot, and align it at the same + // time. Leave the stack slot address in the scratch register r4. + // + // sub r4, sp, #numregs * 8 + // bic r4, r4, #align - 1 + // mov sp, r4 + // + bool isThumb = AFI->isThumbFunction(); + assert(!AFI->isThumb1OnlyFunction() && "Can't realign stack for thumb1"); + AFI->setShouldRestoreSPFromFP(true); + + // sub r4, sp, #numregs * 8 + // The immediate is <= 64, so it doesn't need any special encoding. + unsigned Opc = isThumb ? ARM::t2SUBri : ARM::SUBri; + AddDefaultCC(AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4) + .addReg(ARM::SP) + .addImm(8 * NumAlignedDPRCS2Regs))); + + unsigned MaxAlign = MF.getFrameInfo()->getMaxAlignment(); + // We must set parameter MustBeSingleInstruction to true, since + // skipAlignedDPRCS2Spills expects exactly 3 instructions to perform + // stack alignment. Luckily, this can always be done since all ARM + // architecture versions that support Neon also support the BFC + // instruction. + emitAligningInstructions(MF, AFI, TII, MBB, MI, DL, ARM::R4, MaxAlign, true); + + // mov sp, r4 + // The stack pointer must be adjusted before spilling anything, otherwise + // the stack slots could be clobbered by an interrupt handler. + // Leave r4 live, it is used below. + Opc = isThumb ? ARM::tMOVr : ARM::MOVr; + MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(Opc), ARM::SP) + .addReg(ARM::R4); + MIB = AddDefaultPred(MIB); + if (!isThumb) + AddDefaultCC(MIB); + + // Now spill NumAlignedDPRCS2Regs registers starting from d8. + // r4 holds the stack slot address. + unsigned NextReg = ARM::D8; + + // 16-byte aligned vst1.64 with 4 d-regs and address writeback. + // The writeback is only needed when emitting two vst1.64 instructions. + if (NumAlignedDPRCS2Regs >= 6) { + unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, + &ARM::QQPRRegClass); + MBB.addLiveIn(SupReg); + AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VST1d64Qwb_fixed), + ARM::R4) + .addReg(ARM::R4, RegState::Kill).addImm(16) + .addReg(NextReg) + .addReg(SupReg, RegState::ImplicitKill)); + NextReg += 4; + NumAlignedDPRCS2Regs -= 4; + } + + // We won't modify r4 beyond this point. It currently points to the next + // register to be spilled. + unsigned R4BaseReg = NextReg; + + // 16-byte aligned vst1.64 with 4 d-regs, no writeback. + if (NumAlignedDPRCS2Regs >= 4) { + unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, + &ARM::QQPRRegClass); + MBB.addLiveIn(SupReg); + AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VST1d64Q)) + .addReg(ARM::R4).addImm(16).addReg(NextReg) + .addReg(SupReg, RegState::ImplicitKill)); + NextReg += 4; + NumAlignedDPRCS2Regs -= 4; + } + + // 16-byte aligned vst1.64 with 2 d-regs. + if (NumAlignedDPRCS2Regs >= 2) { + unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, + &ARM::QPRRegClass); + MBB.addLiveIn(SupReg); + AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VST1q64)) + .addReg(ARM::R4).addImm(16).addReg(SupReg)); + NextReg += 2; + NumAlignedDPRCS2Regs -= 2; + } + + // Finally, use a vanilla vstr.64 for the odd last register. + if (NumAlignedDPRCS2Regs) { + MBB.addLiveIn(NextReg); + // vstr.64 uses addrmode5 which has an offset scale of 4. + AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VSTRD)) + .addReg(NextReg) + .addReg(ARM::R4).addImm((NextReg-R4BaseReg)*2)); + } + + // The last spill instruction inserted should kill the scratch register r4. + std::prev(MI)->addRegisterKilled(ARM::R4, TRI); +} + +/// Skip past the code inserted by emitAlignedDPRCS2Spills, and return an +/// iterator to the following instruction. +static MachineBasicBlock::iterator +skipAlignedDPRCS2Spills(MachineBasicBlock::iterator MI, + unsigned NumAlignedDPRCS2Regs) { + // sub r4, sp, #numregs * 8 + // bic r4, r4, #align - 1 + // mov sp, r4 + ++MI; ++MI; ++MI; + assert(MI->mayStore() && "Expecting spill instruction"); + + // These switches all fall through. + switch(NumAlignedDPRCS2Regs) { + case 7: + ++MI; + assert(MI->mayStore() && "Expecting spill instruction"); + default: + ++MI; + assert(MI->mayStore() && "Expecting spill instruction"); + case 1: + case 2: + case 4: + assert(MI->killsRegister(ARM::R4) && "Missed kill flag"); + ++MI; + } + return MI; +} + +/// Emit aligned reload instructions for NumAlignedDPRCS2Regs D-registers +/// starting from d8. These instructions are assumed to execute while the +/// stack is still aligned, unlike the code inserted by emitPopInst. +static void emitAlignedDPRCS2Restores(MachineBasicBlock &MBB, + MachineBasicBlock::iterator MI, + unsigned NumAlignedDPRCS2Regs, + const std::vector<CalleeSavedInfo> &CSI, + const TargetRegisterInfo *TRI) { + MachineFunction &MF = *MBB.getParent(); + ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); + DebugLoc DL = MI->getDebugLoc(); + const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); + + // Find the frame index assigned to d8. + int D8SpillFI = 0; + for (unsigned i = 0, e = CSI.size(); i != e; ++i) + if (CSI[i].getReg() == ARM::D8) { + D8SpillFI = CSI[i].getFrameIdx(); + break; + } + + // Materialize the address of the d8 spill slot into the scratch register r4. + // This can be fairly complicated if the stack frame is large, so just use + // the normal frame index elimination mechanism to do it. This code runs as + // the initial part of the epilog where the stack and base pointers haven't + // been changed yet. + bool isThumb = AFI->isThumbFunction(); + assert(!AFI->isThumb1OnlyFunction() && "Can't realign stack for thumb1"); + + unsigned Opc = isThumb ? ARM::t2ADDri : ARM::ADDri; + AddDefaultCC(AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4) + .addFrameIndex(D8SpillFI).addImm(0))); + + // Now restore NumAlignedDPRCS2Regs registers starting from d8. + unsigned NextReg = ARM::D8; + + // 16-byte aligned vld1.64 with 4 d-regs and writeback. + if (NumAlignedDPRCS2Regs >= 6) { + unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, + &ARM::QQPRRegClass); + AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLD1d64Qwb_fixed), NextReg) + .addReg(ARM::R4, RegState::Define) + .addReg(ARM::R4, RegState::Kill).addImm(16) + .addReg(SupReg, RegState::ImplicitDefine)); + NextReg += 4; + NumAlignedDPRCS2Regs -= 4; + } + + // We won't modify r4 beyond this point. It currently points to the next + // register to be spilled. + unsigned R4BaseReg = NextReg; + + // 16-byte aligned vld1.64 with 4 d-regs, no writeback. + if (NumAlignedDPRCS2Regs >= 4) { + unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, + &ARM::QQPRRegClass); + AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLD1d64Q), NextReg) + .addReg(ARM::R4).addImm(16) + .addReg(SupReg, RegState::ImplicitDefine)); + NextReg += 4; + NumAlignedDPRCS2Regs -= 4; + } + + // 16-byte aligned vld1.64 with 2 d-regs. + if (NumAlignedDPRCS2Regs >= 2) { + unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, + &ARM::QPRRegClass); + AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLD1q64), SupReg) + .addReg(ARM::R4).addImm(16)); + NextReg += 2; + NumAlignedDPRCS2Regs -= 2; + } + + // Finally, use a vanilla vldr.64 for the remaining odd register. + if (NumAlignedDPRCS2Regs) + AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLDRD), NextReg) + .addReg(ARM::R4).addImm(2*(NextReg-R4BaseReg))); + + // Last store kills r4. + std::prev(MI)->addRegisterKilled(ARM::R4, TRI); +} + +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_IMM; + unsigned FltOpc = ARM::VSTMDDB_UPD; + unsigned NumAlignedDPRCS2Regs = AFI->getNumAlignedDPRCS2Regs(); + emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea1Register, 0, + MachineInstr::FrameSetup); + emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea2Register, 0, + MachineInstr::FrameSetup); + emitPushInst(MBB, MI, CSI, FltOpc, 0, true, &isARMArea3Register, + NumAlignedDPRCS2Regs, MachineInstr::FrameSetup); + + // The code above does not insert spill code for the aligned DPRCS2 registers. + // The stack realignment code will be inserted between the push instructions + // and these spills. + if (NumAlignedDPRCS2Regs) + emitAlignedDPRCS2Spills(MBB, MI, NumAlignedDPRCS2Regs, CSI, TRI); + + 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->getArgRegsSaveSize() > 0; + unsigned NumAlignedDPRCS2Regs = AFI->getNumAlignedDPRCS2Regs(); + + // The emitPopInst calls below do not insert reloads for the aligned DPRCS2 + // registers. Do that here instead. + if (NumAlignedDPRCS2Regs) + emitAlignedDPRCS2Restores(MBB, MI, NumAlignedDPRCS2Regs, CSI, TRI); + + unsigned PopOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_UPD : ARM::LDMIA_UPD; + unsigned LdrOpc = AFI->isThumbFunction() ? ARM::t2LDR_POST :ARM::LDR_POST_IMM; + unsigned FltOpc = ARM::VLDMDIA_UPD; + emitPopInst(MBB, MI, CSI, FltOpc, 0, isVarArg, true, &isARMArea3Register, + NumAlignedDPRCS2Regs); + emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false, + &isARMArea2Register, 0); + emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false, + &isARMArea1Register, 0); + + return true; +} + +// FIXME: Make generic? +static unsigned GetFunctionSizeInBytes(const MachineFunction &MF, + const ARMBaseInstrInfo &TII) { + unsigned FnSize = 0; + for (auto &MBB : MF) { + for (auto &MI : MBB) + FnSize += TII.GetInstSizeInBytes(&MI); + } + return FnSize; +} + +/// 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 (auto &MBB : MF) { + for (auto &MI : MBB) { + for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { + if (!MI.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 (MI.getOpcode() == ARM::ADDri) { + Limit = std::min(Limit, (1U << 8) - 1); + break; + } + + // Otherwise check the addressing mode. + switch (MI.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; +} + +// In functions that realign the stack, it can be an advantage to spill the +// callee-saved vector registers after realigning the stack. The vst1 and vld1 +// instructions take alignment hints that can improve performance. +// +static void checkNumAlignedDPRCS2Regs(MachineFunction &MF) { + MF.getInfo<ARMFunctionInfo>()->setNumAlignedDPRCS2Regs(0); + if (!SpillAlignedNEONRegs) + return; + + // Naked functions don't spill callee-saved registers. + if (MF.getFunction()->getAttributes().hasAttribute(AttributeSet::FunctionIndex, + Attribute::Naked)) + return; + + // We are planning to use NEON instructions vst1 / vld1. + if (!MF.getTarget().getSubtarget<ARMSubtarget>().hasNEON()) + return; + + // Don't bother if the default stack alignment is sufficiently high. + if (MF.getTarget() + .getSubtargetImpl() + ->getFrameLowering() + ->getStackAlignment() >= 8) + return; + + // Aligned spills require stack realignment. + const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>( + MF.getSubtarget().getRegisterInfo()); + if (!RegInfo->canRealignStack(MF)) + return; + + // We always spill contiguous d-registers starting from d8. Count how many + // needs spilling. The register allocator will almost always use the + // callee-saved registers in order, but it can happen that there are holes in + // the range. Registers above the hole will be spilled to the standard DPRCS + // area. + MachineRegisterInfo &MRI = MF.getRegInfo(); + unsigned NumSpills = 0; + for (; NumSpills < 8; ++NumSpills) + if (!MRI.isPhysRegUsed(ARM::D8 + NumSpills)) + break; + + // Don't do this for just one d-register. It's not worth it. + if (NumSpills < 2) + return; + + // Spill the first NumSpills D-registers after realigning the stack. + MF.getInfo<ARMFunctionInfo>()->setNumAlignedDPRCS2Regs(NumSpills); + + // A scratch register is required for the vst1 / vld1 instructions. + MF.getRegInfo().setPhysRegUsed(ARM::R4); +} + +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.getSubtarget().getRegisterInfo()); + const ARMBaseInstrInfo &TII = + *static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo()); + ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); + MachineFrameInfo *MFI = MF.getFrameInfo(); + MachineRegisterInfo &MRI = MF.getRegInfo(); + 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))) + MRI.setPhysRegUsed(ARM::R4); + + if (AFI->isThumb1OnlyFunction()) { + // Spill LR if Thumb1 function uses variable length argument lists. + if (AFI->getArgRegsSaveSize() > 0) + MRI.setPhysRegUsed(ARM::LR); + + // Spill R4 if Thumb1 epilogue has to restore SP from FP. We don't know + // for sure what the stack size will be, but for this, an estimate is good + // enough. If there anything changes it, it'll be a spill, which implies + // we've used all the registers and so R4 is already used, so not marking + // it here will be OK. + // FIXME: It will be better just to find spare register here. + unsigned StackSize = MFI->estimateStackSize(MF); + if (MFI->hasVarSizedObjects() || StackSize > 508) + MRI.setPhysRegUsed(ARM::R4); + } + + // See if we can spill vector registers to aligned stack. + checkNumAlignedDPRCS2Regs(MF); + + // Spill the BasePtr if it's used. + if (RegInfo->hasBasePointer(MF)) + MRI.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 MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&MF); + for (unsigned i = 0; CSRegs[i]; ++i) { + unsigned Reg = CSRegs[i]; + bool Spilled = false; + if (MRI.isPhysRegUsed(Reg)) { + Spilled = true; + CanEliminateFrame = false; + } + + if (!ARM::GPRRegClass.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::R0: case ARM::R1: + case ARM::R2: case ARM::R3: + 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::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: + 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 && + (MFI->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) { + MRI.setPhysRegUsed(ARM::LR); + NumGPRSpills++; + SmallVectorImpl<unsigned>::iterator LRPos; + LRPos = std::find(UnspilledCS1GPRs.begin(), UnspilledCS1GPRs.end(), + (unsigned)ARM::LR); + if (LRPos != UnspilledCS1GPRs.end()) + UnspilledCS1GPRs.erase(LRPos); + + ForceLRSpill = false; + ExtraCSSpill = true; + } + + if (hasFP(MF)) { + MRI.setPhysRegUsed(FramePtr); + auto FPPos = std::find(UnspilledCS1GPRs.begin(), UnspilledCS1GPRs.end(), + FramePtr); + if (FPPos != UnspilledCS1GPRs.end()) + UnspilledCS1GPRs.erase(FPPos); + 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) { + MRI.setPhysRegUsed(Reg); + if (!MRI.isReserved(Reg)) + ExtraCSSpill = true; + break; + } + } + } else if (!UnspilledCS2GPRs.empty() && !AFI->isThumb1OnlyFunction()) { + unsigned Reg = UnspilledCS2GPRs.front(); + MRI.setPhysRegUsed(Reg); + if (!MRI.isReserved(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 (!MRI.isReserved(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 (!MRI.isReserved(Reg)) { + Extras.push_back(Reg); + NumExtras--; + } + } + } + if (Extras.size() && NumExtras == 0) { + for (unsigned i = 0, e = Extras.size(); i != e; ++i) { + MRI.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::GPRRegClass; + RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(), + RC->getAlignment(), + false)); + } + } + } + + if (ForceLRSpill) { + MRI.setPhysRegUsed(ARM::LR); + AFI->setLRIsSpilledForFarJump(true); + } +} + + +void ARMFrameLowering:: +eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB, + MachineBasicBlock::iterator I) const { + const ARMBaseInstrInfo &TII = + *static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo()); + 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 = Old->getOperand(0).getImm(); + 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. + unsigned Align = getStackAlignment(); + Amount = (Amount+Align-1)/Align*Align; + + ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>(); + assert(!AFI->isThumb1OnlyFunction() && + "This eliminateCallFramePseudoInstr does not support Thumb1!"); + bool isARM = !AFI->isThumbFunction(); + + // Replace the pseudo instruction with a new instruction... + unsigned Opc = Old->getOpcode(); + int PIdx = Old->findFirstPredOperandIdx(); + ARMCC::CondCodes Pred = (PIdx == -1) + ? ARMCC::AL : (ARMCC::CondCodes)Old->getOperand(PIdx).getImm(); + if (Opc == ARM::ADJCALLSTACKDOWN || Opc == ARM::tADJCALLSTACKDOWN) { + // Note: PredReg is operand 2 for ADJCALLSTACKDOWN. + unsigned PredReg = Old->getOperand(2).getReg(); + emitSPUpdate(isARM, MBB, I, dl, TII, -Amount, MachineInstr::NoFlags, + Pred, PredReg); + } else { + // Note: PredReg is operand 3 for ADJCALLSTACKUP. + unsigned PredReg = Old->getOperand(3).getReg(); + assert(Opc == ARM::ADJCALLSTACKUP || Opc == ARM::tADJCALLSTACKUP); + emitSPUpdate(isARM, MBB, I, dl, TII, Amount, MachineInstr::NoFlags, + Pred, PredReg); + } + } + } + MBB.erase(I); +} + +/// Get the minimum constant for ARM that is greater than or equal to the +/// argument. In ARM, constants can have any value that can be produced by +/// rotating an 8-bit value to the right by an even number of bits within a +/// 32-bit word. +static uint32_t alignToARMConstant(uint32_t Value) { + unsigned Shifted = 0; + + if (Value == 0) + return 0; + + while (!(Value & 0xC0000000)) { + Value = Value << 2; + Shifted += 2; + } + + bool Carry = (Value & 0x00FFFFFF); + Value = ((Value & 0xFF000000) >> 24) + Carry; + + if (Value & 0x0000100) + Value = Value & 0x000001FC; + + if (Shifted > 24) + Value = Value >> (Shifted - 24); + else + Value = Value << (24 - Shifted); + + return Value; +} + +// The stack limit in the TCB is set to this many bytes above the actual +// stack limit. +static const uint64_t kSplitStackAvailable = 256; + +// Adjust the function prologue to enable split stacks. This currently only +// supports android and linux. +// +// The ABI of the segmented stack prologue is a little arbitrarily chosen, but +// must be well defined in order to allow for consistent implementations of the +// __morestack helper function. The ABI is also not a normal ABI in that it +// doesn't follow the normal calling conventions because this allows the +// prologue of each function to be optimized further. +// +// Currently, the ABI looks like (when calling __morestack) +// +// * r4 holds the minimum stack size requested for this function call +// * r5 holds the stack size of the arguments to the function +// * the beginning of the function is 3 instructions after the call to +// __morestack +// +// Implementations of __morestack should use r4 to allocate a new stack, r5 to +// place the arguments on to the new stack, and the 3-instruction knowledge to +// jump directly to the body of the function when working on the new stack. +// +// An old (and possibly no longer compatible) implementation of __morestack for +// ARM can be found at [1]. +// +// [1] - https://github.com/mozilla/rust/blob/86efd9/src/rt/arch/arm/morestack.S +void ARMFrameLowering::adjustForSegmentedStacks(MachineFunction &MF) const { + unsigned Opcode; + unsigned CFIIndex; + const ARMSubtarget *ST = &MF.getTarget().getSubtarget<ARMSubtarget>(); + bool Thumb = ST->isThumb(); + + // Sadly, this currently doesn't support varargs, platforms other than + // android/linux. Note that thumb1/thumb2 are support for android/linux. + if (MF.getFunction()->isVarArg()) + report_fatal_error("Segmented stacks do not support vararg functions."); + if (!ST->isTargetAndroid() && !ST->isTargetLinux()) + report_fatal_error("Segmented stacks not supported on this platform."); + + MachineBasicBlock &prologueMBB = MF.front(); + MachineFrameInfo *MFI = MF.getFrameInfo(); + MachineModuleInfo &MMI = MF.getMMI(); + MCContext &Context = MMI.getContext(); + const MCRegisterInfo *MRI = Context.getRegisterInfo(); + const ARMBaseInstrInfo &TII = + *static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo()); + ARMFunctionInfo *ARMFI = MF.getInfo<ARMFunctionInfo>(); + DebugLoc DL; + + uint64_t StackSize = MFI->getStackSize(); + + // Do not generate a prologue for functions with a stack of size zero + if (StackSize == 0) + return; + + // Use R4 and R5 as scratch registers. + // We save R4 and R5 before use and restore them before leaving the function. + unsigned ScratchReg0 = ARM::R4; + unsigned ScratchReg1 = ARM::R5; + uint64_t AlignedStackSize; + + MachineBasicBlock *PrevStackMBB = MF.CreateMachineBasicBlock(); + MachineBasicBlock *PostStackMBB = MF.CreateMachineBasicBlock(); + MachineBasicBlock *AllocMBB = MF.CreateMachineBasicBlock(); + MachineBasicBlock *GetMBB = MF.CreateMachineBasicBlock(); + MachineBasicBlock *McrMBB = MF.CreateMachineBasicBlock(); + + for (MachineBasicBlock::livein_iterator i = prologueMBB.livein_begin(), + e = prologueMBB.livein_end(); + i != e; ++i) { + AllocMBB->addLiveIn(*i); + GetMBB->addLiveIn(*i); + McrMBB->addLiveIn(*i); + PrevStackMBB->addLiveIn(*i); + PostStackMBB->addLiveIn(*i); + } + + MF.push_front(PostStackMBB); + MF.push_front(AllocMBB); + MF.push_front(GetMBB); + MF.push_front(McrMBB); + MF.push_front(PrevStackMBB); + + // The required stack size that is aligned to ARM constant criterion. + AlignedStackSize = alignToARMConstant(StackSize); + + // When the frame size is less than 256 we just compare the stack + // boundary directly to the value of the stack pointer, per gcc. + bool CompareStackPointer = AlignedStackSize < kSplitStackAvailable; + + // We will use two of the callee save registers as scratch registers so we + // need to save those registers onto the stack. + // We will use SR0 to hold stack limit and SR1 to hold the stack size + // requested and arguments for __morestack(). + // SR0: Scratch Register #0 + // SR1: Scratch Register #1 + // push {SR0, SR1} + if (Thumb) { + AddDefaultPred(BuildMI(PrevStackMBB, DL, TII.get(ARM::tPUSH))) + .addReg(ScratchReg0).addReg(ScratchReg1); + } else { + AddDefaultPred(BuildMI(PrevStackMBB, DL, TII.get(ARM::STMDB_UPD)) + .addReg(ARM::SP, RegState::Define).addReg(ARM::SP)) + .addReg(ScratchReg0).addReg(ScratchReg1); + } + + // Emit the relevant DWARF information about the change in stack pointer as + // well as where to find both r4 and r5 (the callee-save registers) + CFIIndex = + MMI.addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, -8)); + BuildMI(PrevStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset( + nullptr, MRI->getDwarfRegNum(ScratchReg1, true), -4)); + BuildMI(PrevStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset( + nullptr, MRI->getDwarfRegNum(ScratchReg0, true), -8)); + BuildMI(PrevStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + + // mov SR1, sp + if (Thumb) { + AddDefaultPred(BuildMI(McrMBB, DL, TII.get(ARM::tMOVr), ScratchReg1) + .addReg(ARM::SP)); + } else if (CompareStackPointer) { + AddDefaultPred(BuildMI(McrMBB, DL, TII.get(ARM::MOVr), ScratchReg1) + .addReg(ARM::SP)).addReg(0); + } + + // sub SR1, sp, #StackSize + if (!CompareStackPointer && Thumb) { + AddDefaultPred( + AddDefaultCC(BuildMI(McrMBB, DL, TII.get(ARM::tSUBi8), ScratchReg1)) + .addReg(ScratchReg1).addImm(AlignedStackSize)); + } else if (!CompareStackPointer) { + AddDefaultPred(BuildMI(McrMBB, DL, TII.get(ARM::SUBri), ScratchReg1) + .addReg(ARM::SP).addImm(AlignedStackSize)).addReg(0); + } + + if (Thumb && ST->isThumb1Only()) { + unsigned PCLabelId = ARMFI->createPICLabelUId(); + ARMConstantPoolValue *NewCPV = ARMConstantPoolSymbol::Create( + MF.getFunction()->getContext(), "__STACK_LIMIT", PCLabelId, 0); + MachineConstantPool *MCP = MF.getConstantPool(); + unsigned CPI = MCP->getConstantPoolIndex(NewCPV, MF.getAlignment()); + + // ldr SR0, [pc, offset(STACK_LIMIT)] + AddDefaultPred(BuildMI(GetMBB, DL, TII.get(ARM::tLDRpci), ScratchReg0) + .addConstantPoolIndex(CPI)); + + // ldr SR0, [SR0] + AddDefaultPred(BuildMI(GetMBB, DL, TII.get(ARM::tLDRi), ScratchReg0) + .addReg(ScratchReg0).addImm(0)); + } else { + // Get TLS base address from the coprocessor + // mrc p15, #0, SR0, c13, c0, #3 + AddDefaultPred(BuildMI(McrMBB, DL, TII.get(ARM::MRC), ScratchReg0) + .addImm(15) + .addImm(0) + .addImm(13) + .addImm(0) + .addImm(3)); + + // Use the last tls slot on android and a private field of the TCP on linux. + assert(ST->isTargetAndroid() || ST->isTargetLinux()); + unsigned TlsOffset = ST->isTargetAndroid() ? 63 : 1; + + // Get the stack limit from the right offset + // ldr SR0, [sr0, #4 * TlsOffset] + AddDefaultPred(BuildMI(GetMBB, DL, TII.get(ARM::LDRi12), ScratchReg0) + .addReg(ScratchReg0).addImm(4 * TlsOffset)); + } + + // Compare stack limit with stack size requested. + // cmp SR0, SR1 + Opcode = Thumb ? ARM::tCMPr : ARM::CMPrr; + AddDefaultPred(BuildMI(GetMBB, DL, TII.get(Opcode)) + .addReg(ScratchReg0) + .addReg(ScratchReg1)); + + // This jump is taken if StackLimit < SP - stack required. + Opcode = Thumb ? ARM::tBcc : ARM::Bcc; + BuildMI(GetMBB, DL, TII.get(Opcode)).addMBB(PostStackMBB) + .addImm(ARMCC::LO) + .addReg(ARM::CPSR); + + + // Calling __morestack(StackSize, Size of stack arguments). + // __morestack knows that the stack size requested is in SR0(r4) + // and amount size of stack arguments is in SR1(r5). + + // Pass first argument for the __morestack by Scratch Register #0. + // The amount size of stack required + if (Thumb) { + AddDefaultPred(AddDefaultCC(BuildMI(AllocMBB, DL, TII.get(ARM::tMOVi8), + ScratchReg0)).addImm(AlignedStackSize)); + } else { + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::MOVi), ScratchReg0) + .addImm(AlignedStackSize)).addReg(0); + } + // Pass second argument for the __morestack by Scratch Register #1. + // The amount size of stack consumed to save function arguments. + if (Thumb) { + AddDefaultPred( + AddDefaultCC(BuildMI(AllocMBB, DL, TII.get(ARM::tMOVi8), ScratchReg1)) + .addImm(alignToARMConstant(ARMFI->getArgumentStackSize()))); + } else { + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::MOVi), ScratchReg1) + .addImm(alignToARMConstant(ARMFI->getArgumentStackSize()))) + .addReg(0); + } + + // push {lr} - Save return address of this function. + if (Thumb) { + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::tPUSH))) + .addReg(ARM::LR); + } else { + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::STMDB_UPD)) + .addReg(ARM::SP, RegState::Define) + .addReg(ARM::SP)) + .addReg(ARM::LR); + } + + // Emit the DWARF info about the change in stack as well as where to find the + // previous link register + CFIIndex = + MMI.addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, -12)); + BuildMI(AllocMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset( + nullptr, MRI->getDwarfRegNum(ARM::LR, true), -12)); + BuildMI(AllocMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + + // Call __morestack(). + if (Thumb) { + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::tBL))) + .addExternalSymbol("__morestack"); + } else { + BuildMI(AllocMBB, DL, TII.get(ARM::BL)) + .addExternalSymbol("__morestack"); + } + + // pop {lr} - Restore return address of this original function. + if (Thumb) { + if (ST->isThumb1Only()) { + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::tPOP))) + .addReg(ScratchReg0); + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::tMOVr), ARM::LR) + .addReg(ScratchReg0)); + } else { + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::t2LDR_POST)) + .addReg(ARM::LR, RegState::Define) + .addReg(ARM::SP, RegState::Define) + .addReg(ARM::SP) + .addImm(4)); + } + } else { + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::LDMIA_UPD)) + .addReg(ARM::SP, RegState::Define) + .addReg(ARM::SP)) + .addReg(ARM::LR); + } + + // Restore SR0 and SR1 in case of __morestack() was called. + // __morestack() will skip PostStackMBB block so we need to restore + // scratch registers from here. + // pop {SR0, SR1} + if (Thumb) { + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::tPOP))) + .addReg(ScratchReg0) + .addReg(ScratchReg1); + } else { + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::LDMIA_UPD)) + .addReg(ARM::SP, RegState::Define) + .addReg(ARM::SP)) + .addReg(ScratchReg0) + .addReg(ScratchReg1); + } + + // Update the CFA offset now that we've popped + CFIIndex = MMI.addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, 0)); + BuildMI(AllocMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + + // bx lr - Return from this function. + Opcode = Thumb ? ARM::tBX_RET : ARM::BX_RET; + AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(Opcode))); + + // Restore SR0 and SR1 in case of __morestack() was not called. + // pop {SR0, SR1} + if (Thumb) { + AddDefaultPred(BuildMI(PostStackMBB, DL, TII.get(ARM::tPOP))) + .addReg(ScratchReg0) + .addReg(ScratchReg1); + } else { + AddDefaultPred(BuildMI(PostStackMBB, DL, TII.get(ARM::LDMIA_UPD)) + .addReg(ARM::SP, RegState::Define) + .addReg(ARM::SP)) + .addReg(ScratchReg0) + .addReg(ScratchReg1); + } + + // Update the CFA offset now that we've popped + CFIIndex = MMI.addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, 0)); + BuildMI(PostStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + + // Tell debuggers that r4 and r5 are now the same as they were in the + // previous function, that they're the "Same Value". + CFIIndex = MMI.addFrameInst(MCCFIInstruction::createSameValue( + nullptr, MRI->getDwarfRegNum(ScratchReg0, true))); + BuildMI(PostStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + CFIIndex = MMI.addFrameInst(MCCFIInstruction::createSameValue( + nullptr, MRI->getDwarfRegNum(ScratchReg1, true))); + BuildMI(PostStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + + // Organizing MBB lists + PostStackMBB->addSuccessor(&prologueMBB); + + AllocMBB->addSuccessor(PostStackMBB); + + GetMBB->addSuccessor(PostStackMBB); + GetMBB->addSuccessor(AllocMBB); + + McrMBB->addSuccessor(GetMBB); + + PrevStackMBB->addSuccessor(McrMBB); + +#ifdef XDEBUG + MF.verify(); +#endif +} |
