class TransferTracker

Declaration

class TransferTracker { /* full declaration omitted */ };

Description

Tracker for converting machine value locations and variable values into variable locations (the output of LiveDebugValues), recorded as DBG_VALUEs specifying block live-in locations and transfers within blocks. Operating on a per-block basis, this class takes a (pre-loaded) MLocTracker and must be initialized with the set of variable values that are live-in to the block. The caller then repeatedly calls process(). TransferTracker picks out variable locations for the live-in variable values (if there _is_ a location) and creates the corresponding DBG_VALUEs. Then, as the block is stepped through, transfers of values between machine locations are identified and if profitable, a DBG_VALUE created. This is where debug use-before-defs would be resolved: a variable with an unavailable value could materialize in the middle of a block, when the value becomes available. Or, we could detect clobbers and re-specify the variable in a backup location. (XXX these are unimplemented).

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:174

Member Variables

public const llvm::TargetInstrInfo* TII

public const llvm::TargetLowering* TLI

public LiveDebugValues::MLocTracker* MTracker

This machine location tracker is assumed to always contain the up-to-date value mapping for all machine locations. TransferTracker only reads information from it. (XXX make it const?)

public llvm::MachineFunction& MF

public bool ShouldEmitDebugEntryValues

public SmallVector<TransferTracker::Transfer, 32> Transfers

Collection of transfers (DBG_VALUEs) to be inserted.

public SmallVector<LiveDebugValues::ValueIDNum, 32> VarLocs

Local cache of what-value-is-in-what-LocIdx. Used to identify differences between TransferTrackers view of variable locations and MLocTrackers. For example, MLocTracker observes all clobbers, but TransferTracker lazily does not.

public DenseMap<LiveDebugValues::LocIdx, SmallSet<llvm::DebugVariable, 4>> ActiveMLocs

Map from LocIdxes to which DebugVariables are based that location. Mantained while stepping through the block. Not accurate if VarLocs[Idx] != MTracker->LocIdxToIDNum[Idx].

public DenseMap<llvm::DebugVariable, TransferTracker::LocAndProperties> ActiveVLocs

Map from DebugVariable to it's current location and qualifying meta information. To be used in conjunction with ActiveMLocs to construct enough information for the DBG_VALUEs for a particular LocIdx.

public SmallVector<llvm::MachineInstr*, 4> PendingDbgValues

Temporary cache of DBG_VALUEs to be entered into the Transfers collection.

public DenseMap< unsigned int, SmallVector<TransferTracker::UseBeforeDef, 1>> UseBeforeDefs

Map from instruction index (within the block) to the set of UseBeforeDefs that become defined at that instruction.

public DenseSet<llvm::DebugVariable> UseBeforeDefVariables

The set of variables that are in UseBeforeDefs and can become a location once the relevant value is defined. An element being erased from this collection prevents the use-before-def materializing.

public const llvm::TargetRegisterInfo& TRI

public const llvm::BitVector& CalleeSavedRegs

Method Overview

• public TransferTracker(const llvm::TargetInstrInfo * TII, LiveDebugValues::MLocTracker * MTracker, llvm::MachineFunction & MF, const llvm::TargetRegisterInfo & TRI, const llvm::BitVector & CalleeSavedRegs, const llvm::TargetPassConfig & TPC)
• public void addUseBeforeDef(const llvm::DebugVariable & Var, const LiveDebugValues::DbgValueProperties & Properties, LiveDebugValues::ValueIDNum ID)
• public void checkInstForNewValues(unsigned int Inst, MachineBasicBlock::iterator pos)
• public void clobberMloc(LiveDebugValues::LocIdx MLoc, MachineBasicBlock::iterator Pos, bool MakeUndef = true)
• public void clobberMloc(LiveDebugValues::LocIdx MLoc, LiveDebugValues::ValueIDNum OldValue, MachineBasicBlock::iterator Pos, bool MakeUndef = true)
• public llvm::MachineInstrBuilder emitMOLoc(const llvm::MachineOperand & MO, const llvm::DebugVariable & Var, const LiveDebugValues::DbgValueProperties & Properties)
• public void flushDbgValues(MachineBasicBlock::iterator Pos, llvm::MachineBasicBlock * MBB)
• public bool isEntryValueValue(const LiveDebugValues::ValueIDNum & Val) const
• public bool isEntryValueVariable(const llvm::DebugVariable & Var, const llvm::DIExpression * Expr) const
• public void loadInlocs(llvm::MachineBasicBlock & MBB, LiveDebugValues::ValueTable & MLocs, const SmallVectorImpl<std::pair<DebugVariable, DbgValue>> & VLocs, unsigned int NumLocs)
• public bool recoverAsEntryValue(const llvm::DebugVariable & Var, const LiveDebugValues::DbgValueProperties & Prop, const LiveDebugValues::ValueIDNum & Num)
• public void redefVar(const llvm::MachineInstr & MI)
• public void redefVar(const llvm::MachineInstr & MI, const LiveDebugValues::DbgValueProperties & Properties, Optional<LiveDebugValues::LocIdx> OptNewLoc)
• public void transferMlocs(LiveDebugValues::LocIdx Src, LiveDebugValues::LocIdx Dst, MachineBasicBlock::iterator Pos)

Methods

¶TransferTracker(
    const llvm::TargetInstrInfo* TII,
    LiveDebugValues::MLocTracker* MTracker,
    llvm::MachineFunction& MF,
    const llvm::TargetRegisterInfo& TRI,
    const llvm::BitVector& CalleeSavedRegs,
    const llvm::TargetPassConfig& TPC)

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:245

Parameters

const llvm::TargetInstrInfo* TII

LiveDebugValues::MLocTracker* MTracker

llvm::MachineFunction& MF

const llvm::TargetRegisterInfo& TRI

const llvm::BitVector& CalleeSavedRegs

const llvm::TargetPassConfig& TPC

¶void addUseBeforeDef(
    const llvm::DebugVariable& Var,
    const LiveDebugValues::DbgValueProperties&
        Properties,
    LiveDebugValues::ValueIDNum ID)

Description

Record that \p Var has value \p ID, a value that becomes available later in the function.

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:354

Parameters

const llvm::DebugVariable& Var

const LiveDebugValues::DbgValueProperties& Properties

LiveDebugValues::ValueIDNum ID

¶void checkInstForNewValues(
    unsigned int Inst,
    MachineBasicBlock::iterator pos)

Description

After the instruction at index \p Inst and position \p pos has been processed, check whether it defines a variable value in a use-before-def. If so, and the variable value hasn't changed since the start of the block, create a DBG_VALUE.

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:365

Parameters

unsigned int Inst

MachineBasicBlock::iterator pos

¶void clobberMloc(LiveDebugValues::LocIdx MLoc,
                 MachineBasicBlock::iterator Pos,
                 bool MakeUndef = true)

Description

Account for a location \p mloc being clobbered. Examine the variable locations that will be terminated: and try to recover them by using another location. Optionally, given \p MakeUndef, emit a DBG_VALUE to explicitly terminate a location if it can't be recovered.

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:531

Parameters

LiveDebugValues::LocIdx MLoc

MachineBasicBlock::iterator Pos

bool MakeUndef = true

¶void clobberMloc(
    LiveDebugValues::LocIdx MLoc,
    LiveDebugValues::ValueIDNum OldValue,
    MachineBasicBlock::iterator Pos,
    bool MakeUndef = true)

Description

Overload that takes an explicit value \p OldValue for when the value in\p MLoc has changed and the TransferTracker's locations have not been updated yet.

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:544

Parameters

LiveDebugValues::LocIdx MLoc

LiveDebugValues::ValueIDNum OldValue

MachineBasicBlock::iterator Pos

bool MakeUndef = true

¶llvm::MachineInstrBuilder emitMOLoc(
    const llvm::MachineOperand& MO,
    const llvm::DebugVariable& Var,
    const LiveDebugValues::DbgValueProperties&
        Properties)

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:644

Parameters

const llvm::MachineOperand& MO

const llvm::DebugVariable& Var

const LiveDebugValues::DbgValueProperties& Properties

¶void flushDbgValues(
    MachineBasicBlock::iterator Pos,
    llvm::MachineBasicBlock* MBB)

Description

Helper to move created DBG_VALUEs into Transfers collection.

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:391

Parameters

MachineBasicBlock::iterator Pos

llvm::MachineBasicBlock* MBB

¶bool isEntryValueValue(
    const LiveDebugValues::ValueIDNum& Val) const

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:420

Parameters

const LiveDebugValues::ValueIDNum& Val

¶bool isEntryValueVariable(
    const llvm::DebugVariable& Var,
    const llvm::DIExpression* Expr) const

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:406

Parameters

const llvm::DebugVariable& Var

const llvm::DIExpression* Expr

¶void loadInlocs(
    llvm::MachineBasicBlock& MBB,
    LiveDebugValues::ValueTable& MLocs,
    const SmallVectorImpl<
        std::pair<DebugVariable, DbgValue>>&
        VLocs,
    unsigned int NumLocs)

Description

Load object with live-in variable values. \p mlocs contains the live-in values in each machine location, while \p vlocs the live-in variable values. This method picks variable locations for the live-in variables, creates DBG_VALUEs and puts them in #Transfers, then prepares the other object fields to track variable locations as we step through the block. FIXME: could just examine mloctracker instead of passing in \p mlocs?

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:262

Parameters

llvm::MachineBasicBlock& MBB

LiveDebugValues::ValueTable& MLocs

const SmallVectorImpl< std::pair<DebugVariable, DbgValue>>& VLocs

unsigned int NumLocs

¶bool recoverAsEntryValue(
    const llvm::DebugVariable& Var,
    const LiveDebugValues::DbgValueProperties&
        Prop,
    const LiveDebugValues::ValueIDNum& Num)

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:435

Parameters

const llvm::DebugVariable& Var

const LiveDebugValues::DbgValueProperties& Prop

const LiveDebugValues::ValueIDNum& Num

¶void redefVar(const llvm::MachineInstr& MI)

Description

Change a variable value after encountering a DBG_VALUE inside a block.

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:462

Parameters

const llvm::MachineInstr& MI

¶void redefVar(
    const llvm::MachineInstr& MI,
    const LiveDebugValues::DbgValueProperties&
        Properties,
    Optional<LiveDebugValues::LocIdx> OptNewLoc)

Description

Handle a change in variable location within a block. Terminate the variables current location, and record the value it now refers to, so that we can detect location transfers later on.

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:489

Parameters

const llvm::MachineInstr& MI

const LiveDebugValues::DbgValueProperties& Properties

Optional<LiveDebugValues::LocIdx> OptNewLoc

¶void transferMlocs(
    LiveDebugValues::LocIdx Src,
    LiveDebugValues::LocIdx Dst,
    MachineBasicBlock::iterator Pos)

Description

Transfer variables based on \p Src to be based on \p Dst. This handles both register copies as well as spills and restores. Creates DBG_VALUEs describing the movement.

Declared at: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp:611

Parameters

LiveDebugValues::LocIdx Src

LiveDebugValues::LocIdx Dst

MachineBasicBlock::iterator Pos