Base class containing the logic for constructing DWARF expressions independently of whether they are emitted into a DIE or into a .debug_loc entry. More...

#include "CodeGen/AsmPrinter/DwarfExpression.h"

Inheritance diagram for llvm::DwarfExpression:

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Collaboration diagram for llvm::DwarfExpression:

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Classes
struct	Register
	Holds information about all subregisters comprising a register location. More...

Public Member Functions
	DwarfExpression (unsigned DwarfVersion)

void	finalize ()
	This needs to be called last to commit any pending changes. More...

void	addSignedConstant (int64_t Value)
	Emit a signed constant. More...

void	addUnsignedConstant (uint64_t Value)
	Emit an unsigned constant. More...

void	addUnsignedConstant (const APInt &Value)
	Emit an unsigned constant. More...

bool	isMemoryLocation () const

bool	isUnknownLocation () const

void	setMemoryLocationKind ()
	Lock this down to become a memory location description. More...

bool	addMachineRegExpression (const TargetRegisterInfo &TRI, DIExpressionCursor &Expr, unsigned MachineReg, unsigned FragmentOffsetInBits=0)
	Emit a machine register location. More...

void	addExpression (DIExpressionCursor &&Expr, unsigned FragmentOffsetInBits=0)
	Emit all remaining operations in the DIExpressionCursor. More...

void	addFragmentOffset (const DIExpression *Expr)
	If applicable, emit an empty DW_OP_piece / DW_OP_bit_piece to advance to the fragment described by `Expr`. More...

Protected Types
enum	{ Unknown = 0, Register, Memory, Implicit }
	The kind of location description being produced. More...

Protected Member Functions
void	setSubRegisterPiece (unsigned SizeInBits, unsigned OffsetInBits)
	Push a DW_OP_piece / DW_OP_bit_piece for emitting later, if one is needed to represent a subregister. More...

void	maskSubRegister ()
	Add masking operations to stencil out a subregister. More...

virtual void	emitOp (uint8_t Op, const char *Comment=nullptr)=0
	Output a dwarf operand and an optional assembler comment. More...

virtual void	emitSigned (int64_t Value)=0
	Emit a raw signed value. More...

virtual void	emitUnsigned (uint64_t Value)=0
	Emit a raw unsigned value. More...

void	emitConstu (uint64_t Value)
	Emit a normalized unsigned constant. More...

virtual bool	isFrameRegister (const TargetRegisterInfo &TRI, unsigned MachineReg)=0
	Return whether the given machine register is the frame register in the current function. More...

void	addReg (int DwarfReg, const char *Comment=nullptr)
	Emit a DW_OP_reg operation. More...

void	addBReg (int DwarfReg, int Offset)
	Emit a DW_OP_breg operation. More...

void	addFBReg (int Offset)
	Emit DW_OP_fbreg <Offset>. More...

bool	addMachineReg (const TargetRegisterInfo &TRI, unsigned MachineReg, unsigned MaxSize=~1U)
	Emit a partial DWARF register operation. More...

void	addOpPiece (unsigned SizeInBits, unsigned OffsetInBits=0)
	Emit a DW_OP_piece or DW_OP_bit_piece operation for a variable fragment. More...

void	addShr (unsigned ShiftBy)
	Emit a shift-right dwarf operation. More...

void	addAnd (unsigned Mask)
	Emit a bitwise and dwarf operation. More...

void	addStackValue ()
	Emit a DW_OP_stack_value, if supported. More...

	~DwarfExpression ()=default

Protected Attributes
SmallVector< Register, 2 >	DwarfRegs
	The register location, if any. More...

uint64_t	OffsetInBits = 0
	Current Fragment Offset in Bits. More...

unsigned	DwarfVersion

unsigned	SubRegisterSizeInBits = 0
	Sometimes we need to add a DW_OP_bit_piece to describe a subregister. More...

unsigned	SubRegisterOffsetInBits = 0

enum llvm::DwarfExpression:: { ... }	LocationKind = Unknown
	The kind of location description being produced. More...

Detailed Description

Base class containing the logic for constructing DWARF expressions independently of whether they are emitted into a DIE or into a .debug_loc entry.

Definition at line 99 of file DwarfExpression.h.

Member Enumeration Documentation

◆ anonymous enum

anonymous enum

protected

The kind of location description being produced.

Enumerator
Unknown
Register
Memory
Implicit

Definition at line 120 of file DwarfExpression.h.

Constructor & Destructor Documentation

◆ ~DwarfExpression()

llvm::DwarfExpression::~DwarfExpression ( )

protecteddefault

◆ DwarfExpression()

llvm::DwarfExpression::DwarfExpression ( unsigned DwarfVersion )

inline

Definition at line 203 of file DwarfExpression.h.

References finalize.

Member Function Documentation

◆ addAnd()

void DwarfExpression::addAnd ( unsigned Mask )

protected

Emit a bitwise and dwarf operation.

Definition at line 93 of file DwarfExpression.cpp.

References emitConstu(), and emitOp().

Referenced by maskSubRegister().

◆ addBReg()

void DwarfExpression::addBReg	(	int	DwarfReg,
		int	Offset
	)

protected

Emit a DW_OP_breg operation.

Definition at line 54 of file DwarfExpression.cpp.

References assert(), emitOp(), emitSigned(), emitUnsigned(), and LocationKind.

Referenced by addMachineRegExpression().

◆ addExpression()

void DwarfExpression::addExpression	(	DIExpressionCursor &&	Expr,
		unsigned	FragmentOffsetInBits = `0`
	)

Emit all remaining operations in the DIExpressionCursor.

Parameters

FragmentOffsetInBits If this is one fragment out of multiple locations, this is the offset of the fragment inside the entire variable.

Definition at line 314 of file DwarfExpression.cpp.

References addOpPiece(), addStackValue(), assert(), llvm::dwarf::DW_OP_LLVM_fragment, emitConstu(), emitOp(), emitUnsigned(), Implicit, isMemoryLocation(), llvm_unreachable, LocationKind, maskSubRegister(), Memory, N, OffsetInBits, setSubRegisterPiece(), SubRegisterOffsetInBits, SubRegisterSizeInBits, and Unknown.

Referenced by llvm::DwarfCompileUnit::addAddress(), llvm::DwarfCompileUnit::addComplexAddress(), llvm::DwarfCompileUnit::constructLabelDIE(), and emitDebugLocValue().

◆ addFBReg()

void DwarfExpression::addFBReg ( int Offset )

protected

Emit DW_OP_fbreg <Offset>.

Definition at line 66 of file DwarfExpression.cpp.

References emitOp(), and emitSigned().

Referenced by addMachineRegExpression().

◆ addFragmentOffset()

void DwarfExpression::addFragmentOffset ( const DIExpression * Expr )

If applicable, emit an empty DW_OP_piece / DW_OP_bit_piece to advance to the fragment described by Expr.

Definition at line 429 of file DwarfExpression.cpp.

References addOpPiece(), assert(), llvm::DIExpression::getFragmentInfo(), llvm::DIExpression::isFragment(), and OffsetInBits.

Referenced by llvm::DwarfCompileUnit::addComplexAddress(), llvm::DwarfCompileUnit::constructLabelDIE(), and emitDebugLocValue().

◆ addMachineReg()

bool DwarfExpression::addMachineReg	(	const TargetRegisterInfo &	TRI,
		unsigned	MachineReg,
		unsigned	MaxSize = `~1U`
	)

protected

Emit a partial DWARF register operation.

Parameters

MachineReg	The register number.
MaxSize	If the register must be composed from sub-registers this is an upper bound for how many bits the emitted DW_OP_piece may cover.

If size and offset is zero an operation for the entire register is emitted: Some targets do not provide a DWARF register number for every register. If this is the case, this function will attempt to emit a DWARF register by emitting a fragment of a super-register or by piecing together multiple subregisters that alias the register.

Returns: false if no DWARF register exists for MachineReg.

Definition at line 98 of file DwarfExpression.cpp.

References DwarfRegs, llvm::MCRegisterInfo::getDwarfRegNum(), llvm::TargetRegisterInfo::getMinimalPhysRegClass(), llvm::TargetRegisterInfo::getRegSizeInBits(), llvm::MCRegisterInfo::getSubRegIdxOffset(), llvm::MCRegisterInfo::getSubRegIdxSize(), llvm::MCRegisterInfo::getSubRegIndex(), isFrameRegister(), llvm::TargetRegisterInfo::isPhysicalRegister(), llvm::MCRegisterInfo::DiffListIterator::isValid(), Reg, llvm::SmallBitVector::set(), setSubRegisterPiece(), Size, and llvm::SmallBitVector::test().

Referenced by addMachineRegExpression().

◆ addMachineRegExpression()

bool DwarfExpression::addMachineRegExpression	(	const TargetRegisterInfo &	TRI,
		DIExpressionCursor &	Expr,
		unsigned	MachineReg,
		unsigned	FragmentOffsetInBits = `0`
	)

Emit a machine register location.

As an optimization this may also consume the prefix of a DwarfExpression if a more efficient representation for combining the register location and the first operation exists.

Parameters

FragmentOffsetInBits If this is one fragment out of a fragmented location, this is the offset of the fragment inside the entire variable.

Returns: false if no DWARF register exists for MachineReg.

Definition at line 219 of file DwarfExpression.cpp.

References addBReg(), addFBReg(), addMachineReg(), addOpPiece(), addReg(), llvm::any_of(), assert(), llvm::DIExpressionCursor::consume(), llvm::dwarf::DW_OP_LLVM_fragment, DwarfRegs, DwarfVersion, llvm::DIExpression::ExprOperand::getArg(), llvm::DIExpressionCursor::getFragmentInfo(), llvm::DIExpression::ExprOperand::getOp(), isFrameRegister(), LocationKind, N, llvm::DIExpressionCursor::peek(), llvm::DIExpressionCursor::peekNext(), Reg, SubRegisterSizeInBits, llvm::DIExpressionCursor::take(), and Unknown.

Referenced by llvm::DwarfCompileUnit::addAddress(), llvm::DwarfCompileUnit::addComplexAddress(), llvm::DwarfCompileUnit::constructLabelDIE(), and emitDebugLocValue().

◆ addOpPiece()

void DwarfExpression::addOpPiece	(	unsigned	SizeInBits,
		unsigned	OffsetInBits = `0`
	)

protected

Emit a DW_OP_piece or DW_OP_bit_piece operation for a variable fragment.

Parameters

OffsetInBits This is an optional offset into the location that is at the top of the DWARF stack.

Definition at line 71 of file DwarfExpression.cpp.

References emitOp(), and emitUnsigned().

Referenced by addExpression(), addFragmentOffset(), addMachineRegExpression(), addUnsignedConstant(), and finalize().

◆ addReg()

void DwarfExpression::addReg	(	int	DwarfReg,
		const char *	Comment = `nullptr`
	)

protected

Emit a DW_OP_reg operation.

Note that this is only legal inside a DWARF register location description.

Definition at line 41 of file DwarfExpression.cpp.

References assert(), emitOp(), emitUnsigned(), LocationKind, Register, and Unknown.

Referenced by addMachineRegExpression().

◆ addShr()

void DwarfExpression::addShr ( unsigned ShiftBy )

protected

Emit a shift-right dwarf operation.

Definition at line 88 of file DwarfExpression.cpp.

References emitConstu(), and emitOp().

Referenced by maskSubRegister().

◆ addSignedConstant()

void DwarfExpression::addSignedConstant ( int64_t Value )

Emit a signed constant.

Definition at line 186 of file DwarfExpression.cpp.

References assert(), emitOp(), emitSigned(), Implicit, LocationKind, and Unknown.

Referenced by emitDebugLocValue().

◆ addStackValue()

void DwarfExpression::addStackValue ( )

protected

Emit a DW_OP_stack_value, if supported.

The proper way to describe a constant value is DW_OP_constu <const>, DW_OP_stack_value. Unfortunately, DW_OP_stack_value was not available until DWARF 4, so we will continue to generate DW_OP_constu <const> for DWARF 2 and DWARF 3. Technically, this is incorrect since DW_OP_const <const> actually describes a value at a constant address, not a constant value. However, in the past there was no better way to describe a constant value, so the producers and consumers started to rely on heuristics to disambiguate the value vs. location status of the expression. See PR21176 for more details.

Definition at line 181 of file DwarfExpression.cpp.

References DwarfVersion, and emitOp().

Referenced by addExpression(), and addUnsignedConstant().