CGValue.h
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CGValue.h
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	//===-- CGValue.h - LLVM CodeGen wrappers for llvm::Value* ------- C++ --===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// These classes implement wrappers around llvm::Value in order to
	// fully represent the range of values for C L- and R- values.
	//
	//===----------------------------------------------------------------------===//

	#ifndef LLVM_CLANG_LIB_CODEGEN_CGVALUE_H
	#define LLVM_CLANG_LIB_CODEGEN_CGVALUE_H

	#include "clang/AST/ASTContext.h"
	#include "clang/AST/Type.h"
	#include "llvm/IR/Value.h"
	#include "llvm/IR/Type.h"
	#include "Address.h"

	namespace llvm {
	class Constant;
	class MDNode;
	}

	namespace clang {
	namespace CodeGen {
	class AggValueSlot;
	struct CGBitFieldInfo;

	/// RValue - This trivial value class is used to represent the result of an
	/// expression that is evaluated. It can be one of three things: either a
	/// simple LLVM SSA value, a pair of SSA values for complex numbers, or the
	/// address of an aggregate value in memory.
	class RValue {
	enum Flavor { Scalar, Complex, Aggregate };

	// The shift to make to an aggregate's alignment to make it look
	// like a pointer.
	enum { AggAlignShift = 4 };

	// Stores first value and flavor.
	llvm::PointerIntPair<llvm::Value *, 2, Flavor> V1;
	// Stores second value and volatility.
	llvm::PointerIntPair<llvm::Value *, 1, bool> V2;

	public:
	bool isScalar() const { return V1.getInt() == Scalar; }
	bool isComplex() const { return V1.getInt() == Complex; }
	bool isAggregate() const { return V1.getInt() == Aggregate; }

	bool isVolatileQualified() const { return V2.getInt(); }

	/// getScalarVal() - Return the Value* of this scalar value.
	llvm::Value *getScalarVal() const {
	assert(isScalar() && "Not a scalar!");
	return V1.getPointer();
	}

	/// getComplexVal - Return the real/imag components of this complex value.
	///
	std::pair<llvm::Value , llvm::Value > getComplexVal() const {
	return std::make_pair(V1.getPointer(), V2.getPointer());
	}

	/// getAggregateAddr() - Return the Value* of the address of the aggregate.
	Address getAggregateAddress() const {
	assert(isAggregate() && "Not an aggregate!");
	auto align = reinterpret_cast<uintptr_t>(V2.getPointer()) >> AggAlignShift;
	return Address(V1.getPointer(), CharUnits::fromQuantity(align));
	}
	llvm::Value *getAggregatePointer() const {
	assert(isAggregate() && "Not an aggregate!");
	return V1.getPointer();
	}

	static RValue getIgnored() {
	// FIXME: should we make this a more explicit state?
	return get(nullptr);
	}

	static RValue get(llvm::Value *V) {
	RValue ER;
	ER.V1.setPointer(V);
	ER.V1.setInt(Scalar);
	ER.V2.setInt(false);
	return ER;
	}
	static RValue getComplex(llvm::Value V1, llvm::Value V2) {
	RValue ER;
	ER.V1.setPointer(V1);
	ER.V2.setPointer(V2);
	ER.V1.setInt(Complex);
	ER.V2.setInt(false);
	return ER;
	}
	static RValue getComplex(const std::pair<llvm::Value , llvm::Value > &C) {
	return getComplex(C.first, C.second);
	}
	// FIXME: Aggregate rvalues need to retain information about whether they are
	// volatile or not. Remove default to find all places that probably get this
	// wrong.
	static RValue getAggregate(Address addr, bool isVolatile = false) {
	RValue ER;
	ER.V1.setPointer(addr.getPointer());
	ER.V1.setInt(Aggregate);

	auto align = static_cast<uintptr_t>(addr.getAlignment().getQuantity());
	ER.V2.setPointer(reinterpret_cast<llvm::Value*>(align << AggAlignShift));
	ER.V2.setInt(isVolatile);
	return ER;
	}
	};

	/// Does an ARC strong l-value have precise lifetime?
	enum ARCPreciseLifetime_t {
	ARCImpreciseLifetime, ARCPreciseLifetime
	};

	/// The source of the alignment of an l-value; an expression of
	/// confidence in the alignment actually matching the estimate.
	enum class AlignmentSource {
	/// The l-value was an access to a declared entity or something
	/// equivalently strong, like the address of an array allocated by a
	/// language runtime.
	Decl,

	/// The l-value was considered opaque, so the alignment was
	/// determined from a type, but that type was an explicitly-aligned
	/// typedef.
	AttributedType,

	/// The l-value was considered opaque, so the alignment was
	/// determined from a type.
	Type
	};

	/// Given that the base address has the given alignment source, what's
	/// our confidence in the alignment of the field?
	static inline AlignmentSource getFieldAlignmentSource(AlignmentSource Source) {
	// For now, we don't distinguish fields of opaque pointers from
	// top-level declarations, but maybe we should.
	return AlignmentSource::Decl;
	}

	/// LValue - This represents an lvalue references. Because C/C++ allow
	/// bitfields, this is not a simple LLVM pointer, it may be a pointer plus a
	/// bitrange.
	class LValue {
	enum {
	Simple, // This is a normal l-value, use getAddress().
	VectorElt, // This is a vector element l-value (V[i]), use getVector*
	BitField, // This is a bitfield l-value, use getBitfield*.
	ExtVectorElt, // This is an extended vector subset, use getExtVectorComp
	GlobalReg // This is a register l-value, use getGlobalReg()
	} LVType;

	llvm::Value *V;

	union {
	// Index into a vector subscript: V[i]
	llvm::Value *VectorIdx;

	// ExtVector element subset: V.xyx
	llvm::Constant *VectorElts;

	// BitField start bit and size
	const CGBitFieldInfo *BitFieldInfo;
	};

	QualType Type;

	// 'const' is unused here
	Qualifiers Quals;

	// The alignment to use when accessing this lvalue. (For vector elements,
	// this is the alignment of the whole vector.)
	int64_t Alignment;

	// objective-c's ivar
	bool Ivar:1;

	// objective-c's ivar is an array
	bool ObjIsArray:1;

	// LValue is non-gc'able for any reason, including being a parameter or local
	// variable.
	bool NonGC: 1;

	// Lvalue is a global reference of an objective-c object
	bool GlobalObjCRef : 1;

	// Lvalue is a thread local reference
	bool ThreadLocalRef : 1;

	// Lvalue has ARC imprecise lifetime. We store this inverted to try
	// to make the default bitfield pattern all-zeroes.
	bool ImpreciseLifetime : 1;

	unsigned AlignSource : 2;

	// This flag shows if a nontemporal load/stores should be used when accessing
	// this lvalue.
	bool Nontemporal : 1;

	Expr *BaseIvarExp;

	/// Used by struct-path-aware TBAA.
	QualType TBAABaseType;
	/// Offset relative to the base type.
	uint64_t TBAAOffset;

	/// TBAAInfo - TBAA information to attach to dereferences of this LValue.
	llvm::MDNode *TBAAInfo;

	private:
	void Initialize(QualType Type, Qualifiers Quals,
	CharUnits Alignment, AlignmentSource AlignSource,
	llvm::MDNode *TBAAInfo = nullptr) {
	assert((!Alignment.isZero() \|\| Type->isIncompleteType()) &&
	"initializing l-value with zero alignment!");
	this->Type = Type;
	this->Quals = Quals;
	this->Alignment = Alignment.getQuantity();
	assert(this->Alignment == Alignment.getQuantity() &&
	"Alignment exceeds allowed max!");
	this->AlignSource = unsigned(AlignSource);

	// Initialize Objective-C flags.
	this->Ivar = this->ObjIsArray = this->NonGC = this->GlobalObjCRef = false;
	this->ImpreciseLifetime = false;
	this->Nontemporal = false;
	this->ThreadLocalRef = false;
	this->BaseIvarExp = nullptr;

	// Initialize fields for TBAA.
	this->TBAABaseType = Type;
	this->TBAAOffset = 0;
	this->TBAAInfo = TBAAInfo;
	}

	public:
	bool isSimple() const { return LVType == Simple; }
	bool isVectorElt() const { return LVType == VectorElt; }
	bool isBitField() const { return LVType == BitField; }
	bool isExtVectorElt() const { return LVType == ExtVectorElt; }
	bool isGlobalReg() const { return LVType == GlobalReg; }

	bool isVolatileQualified() const { return Quals.hasVolatile(); }
	bool isRestrictQualified() const { return Quals.hasRestrict(); }
	unsigned getVRQualifiers() const {
	return Quals.getCVRQualifiers() & ~Qualifiers::Const;
	}

	QualType getType() const { return Type; }

	Qualifiers::ObjCLifetime getObjCLifetime() const {
	return Quals.getObjCLifetime();
	}

	bool isObjCIvar() const { return Ivar; }
	void setObjCIvar(bool Value) { Ivar = Value; }

	bool isObjCArray() const { return ObjIsArray; }
	void setObjCArray(bool Value) { ObjIsArray = Value; }

	bool isNonGC () const { return NonGC; }
	void setNonGC(bool Value) { NonGC = Value; }

	bool isGlobalObjCRef() const { return GlobalObjCRef; }
	void setGlobalObjCRef(bool Value) { GlobalObjCRef = Value; }

	bool isThreadLocalRef() const { return ThreadLocalRef; }
	void setThreadLocalRef(bool Value) { ThreadLocalRef = Value;}

	ARCPreciseLifetime_t isARCPreciseLifetime() const {
	return ARCPreciseLifetime_t(!ImpreciseLifetime);
	}
	void setARCPreciseLifetime(ARCPreciseLifetime_t value) {
	ImpreciseLifetime = (value == ARCImpreciseLifetime);
	}
	bool isNontemporal() const { return Nontemporal; }
	void setNontemporal(bool Value) { Nontemporal = Value; }

	bool isObjCWeak() const {
	return Quals.getObjCGCAttr() == Qualifiers::Weak;
	}
	bool isObjCStrong() const {
	return Quals.getObjCGCAttr() == Qualifiers::Strong;
	}

	bool isVolatile() const {
	return Quals.hasVolatile();
	}

	Expr *getBaseIvarExp() const { return BaseIvarExp; }
	void setBaseIvarExp(Expr *V) { BaseIvarExp = V; }

	QualType getTBAABaseType() const { return TBAABaseType; }
	void setTBAABaseType(QualType T) { TBAABaseType = T; }

	uint64_t getTBAAOffset() const { return TBAAOffset; }
	void setTBAAOffset(uint64_t O) { TBAAOffset = O; }

	llvm::MDNode *getTBAAInfo() const { return TBAAInfo; }
	void setTBAAInfo(llvm::MDNode *N) { TBAAInfo = N; }

	const Qualifiers &getQuals() const { return Quals; }
	Qualifiers &getQuals() { return Quals; }

	unsigned getAddressSpace() const { return Quals.getAddressSpace(); }

	CharUnits getAlignment() const { return CharUnits::fromQuantity(Alignment); }
	void setAlignment(CharUnits A) { Alignment = A.getQuantity(); }

	AlignmentSource getAlignmentSource() const {
	return AlignmentSource(AlignSource);
	}
	void setAlignmentSource(AlignmentSource Source) {
	AlignSource = unsigned(Source);
	}

	// simple lvalue
	llvm::Value *getPointer() const {
	assert(isSimple());
	return V;
	}
	Address getAddress() const { return Address(getPointer(), getAlignment()); }
	void setAddress(Address address) {
	assert(isSimple());
	V = address.getPointer();
	Alignment = address.getAlignment().getQuantity();
	}

	// vector elt lvalue
	Address getVectorAddress() const {
	return Address(getVectorPointer(), getAlignment());
	}
	llvm::Value *getVectorPointer() const { assert(isVectorElt()); return V; }
	llvm::Value *getVectorIdx() const { assert(isVectorElt()); return VectorIdx; }

	// extended vector elements.
	Address getExtVectorAddress() const {
	return Address(getExtVectorPointer(), getAlignment());
	}
	llvm::Value *getExtVectorPointer() const {
	assert(isExtVectorElt());
	return V;
	}
	llvm::Constant *getExtVectorElts() const {
	assert(isExtVectorElt());
	return VectorElts;
	}

	// bitfield lvalue
	Address getBitFieldAddress() const {
	return Address(getBitFieldPointer(), getAlignment());
	}
	llvm::Value *getBitFieldPointer() const { assert(isBitField()); return V; }
	const CGBitFieldInfo &getBitFieldInfo() const {
	assert(isBitField());
	return *BitFieldInfo;
	}

	// global register lvalue
	llvm::Value *getGlobalReg() const { assert(isGlobalReg()); return V; }

	static LValue MakeAddr(Address address, QualType type,
	ASTContext &Context,
	AlignmentSource alignSource,
	llvm::MDNode *TBAAInfo = nullptr) {
	Qualifiers qs = type.getQualifiers();
	qs.setObjCGCAttr(Context.getObjCGCAttrKind(type));

	LValue R;
	R.LVType = Simple;
	assert(address.getPointer()->getType()->isPointerTy());
	R.V = address.getPointer();
	R.Initialize(type, qs, address.getAlignment(), alignSource, TBAAInfo);
	return R;
	}

	static LValue MakeVectorElt(Address vecAddress, llvm::Value *Idx,
	QualType type, AlignmentSource alignSource) {
	LValue R;
	R.LVType = VectorElt;
	R.V = vecAddress.getPointer();
	R.VectorIdx = Idx;
	R.Initialize(type, type.getQualifiers(), vecAddress.getAlignment(),
	alignSource);
	return R;
	}

	static LValue MakeExtVectorElt(Address vecAddress, llvm::Constant *Elts,
	QualType type, AlignmentSource alignSource) {
	LValue R;
	R.LVType = ExtVectorElt;
	R.V = vecAddress.getPointer();
	R.VectorElts = Elts;
	R.Initialize(type, type.getQualifiers(), vecAddress.getAlignment(),
	alignSource);
	return R;
	}

	/// \brief Create a new object to represent a bit-field access.
	///
	/// \param Addr - The base address of the bit-field sequence this
	/// bit-field refers to.
	/// \param Info - The information describing how to perform the bit-field
	/// access.
	static LValue MakeBitfield(Address Addr,
	const CGBitFieldInfo &Info,
	QualType type,
	AlignmentSource alignSource) {
	LValue R;
	R.LVType = BitField;
	R.V = Addr.getPointer();
	R.BitFieldInfo = &Info;
	R.Initialize(type, type.getQualifiers(), Addr.getAlignment(), alignSource);
	return R;
	}

	static LValue MakeGlobalReg(Address Reg, QualType type) {
	LValue R;
	R.LVType = GlobalReg;
	R.V = Reg.getPointer();
	R.Initialize(type, type.getQualifiers(), Reg.getAlignment(),
	AlignmentSource::Decl);
	return R;
	}

	RValue asAggregateRValue() const {
	return RValue::getAggregate(getAddress(), isVolatileQualified());
	}
	};

	/// An aggregate value slot.
	class AggValueSlot {
	/// The address.
	llvm::Value *Addr;

	// Qualifiers
	Qualifiers Quals;

	unsigned short Alignment;

	/// DestructedFlag - This is set to true if some external code is
	/// responsible for setting up a destructor for the slot. Otherwise
	/// the code which constructs it should push the appropriate cleanup.
	bool DestructedFlag : 1;

	/// ObjCGCFlag - This is set to true if writing to the memory in the
	/// slot might require calling an appropriate Objective-C GC
	/// barrier. The exact interaction here is unnecessarily mysterious.
	bool ObjCGCFlag : 1;

	/// ZeroedFlag - This is set to true if the memory in the slot is
	/// known to be zero before the assignment into it. This means that
	/// zero fields don't need to be set.
	bool ZeroedFlag : 1;

	/// AliasedFlag - This is set to true if the slot might be aliased
	/// and it's not undefined behavior to access it through such an
	/// alias. Note that it's always undefined behavior to access a C++
	/// object that's under construction through an alias derived from
	/// outside the construction process.
	///
	/// This flag controls whether calls that produce the aggregate
	/// value may be evaluated directly into the slot, or whether they
	/// must be evaluated into an unaliased temporary and then memcpy'ed
	/// over. Since it's invalid in general to memcpy a non-POD C++
	/// object, it's important that this flag never be set when
	/// evaluating an expression which constructs such an object.
	bool AliasedFlag : 1;

	public:
	enum IsAliased_t { IsNotAliased, IsAliased };
	enum IsDestructed_t { IsNotDestructed, IsDestructed };
	enum IsZeroed_t { IsNotZeroed, IsZeroed };
	enum NeedsGCBarriers_t { DoesNotNeedGCBarriers, NeedsGCBarriers };

	/// ignored - Returns an aggregate value slot indicating that the
	/// aggregate value is being ignored.
	static AggValueSlot ignored() {
	return forAddr(Address::invalid(), Qualifiers(), IsNotDestructed,
	DoesNotNeedGCBarriers, IsNotAliased);
	}

	/// forAddr - Make a slot for an aggregate value.
	///
	/// \param quals - The qualifiers that dictate how the slot should
	/// be initialied. Only 'volatile' and the Objective-C lifetime
	/// qualifiers matter.
	///
	/// \param isDestructed - true if something else is responsible
	/// for calling destructors on this object
	/// \param needsGC - true if the slot is potentially located
	/// somewhere that ObjC GC calls should be emitted for
	static AggValueSlot forAddr(Address addr,
	Qualifiers quals,
	IsDestructed_t isDestructed,
	NeedsGCBarriers_t needsGC,
	IsAliased_t isAliased,
	IsZeroed_t isZeroed = IsNotZeroed) {
	AggValueSlot AV;
	if (addr.isValid()) {
	AV.Addr = addr.getPointer();
	AV.Alignment = addr.getAlignment().getQuantity();
	} else {
	AV.Addr = nullptr;
	AV.Alignment = 0;
	}
	AV.Quals = quals;
	AV.DestructedFlag = isDestructed;
	AV.ObjCGCFlag = needsGC;
	AV.ZeroedFlag = isZeroed;
	AV.AliasedFlag = isAliased;
	return AV;
	}

	static AggValueSlot forLValue(const LValue &LV,
	IsDestructed_t isDestructed,
	NeedsGCBarriers_t needsGC,
	IsAliased_t isAliased,
	IsZeroed_t isZeroed = IsNotZeroed) {
	return forAddr(LV.getAddress(),
	LV.getQuals(), isDestructed, needsGC, isAliased, isZeroed);
	}

	IsDestructed_t isExternallyDestructed() const {
	return IsDestructed_t(DestructedFlag);
	}
	void setExternallyDestructed(bool destructed = true) {
	DestructedFlag = destructed;
	}

	Qualifiers getQualifiers() const { return Quals; }

	bool isVolatile() const {
	return Quals.hasVolatile();
	}

	void setVolatile(bool flag) {
	Quals.setVolatile(flag);
	}

	Qualifiers::ObjCLifetime getObjCLifetime() const {
	return Quals.getObjCLifetime();
	}

	NeedsGCBarriers_t requiresGCollection() const {
	return NeedsGCBarriers_t(ObjCGCFlag);
	}

	llvm::Value *getPointer() const {
	return Addr;
	}

	Address getAddress() const {
	return Address(Addr, getAlignment());
	}

	bool isIgnored() const {
	return Addr == nullptr;
	}

	CharUnits getAlignment() const {
	return CharUnits::fromQuantity(Alignment);
	}

	IsAliased_t isPotentiallyAliased() const {
	return IsAliased_t(AliasedFlag);
	}

	RValue asRValue() const {
	if (isIgnored()) {
	return RValue::getIgnored();
	} else {
	return RValue::getAggregate(getAddress(), isVolatile());
	}
	}

	void setZeroed(bool V = true) { ZeroedFlag = V; }
	IsZeroed_t isZeroed() const {
	return IsZeroed_t(ZeroedFlag);
	}
	};

	} // end namespace CodeGen
	} // end namespace clang

	#endif

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