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Created: Sat, Mar 14, 12:21 AM

CGCall.h
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	//===----- CGCall.h - Encapsulate calling convention details ----- C++ --===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// These classes wrap the information about a call or function
	// definition used to handle ABI compliancy.
	//
	//===----------------------------------------------------------------------===//

	#ifndef LLVM_CLANG_LIB_CODEGEN_CGCALL_H
	#define LLVM_CLANG_LIB_CODEGEN_CGCALL_H

	#include "CGValue.h"
	#include "EHScopeStack.h"
	#include "clang/AST/CanonicalType.h"
	#include "clang/AST/Type.h"
	#include "llvm/ADT/FoldingSet.h"
	#include "llvm/IR/Value.h"

	// FIXME: Restructure so we don't have to expose so much stuff.
	#include "ABIInfo.h"

	namespace llvm {
	class AttributeSet;
	class Function;
	class Type;
	class Value;
	}

	namespace clang {
	class ASTContext;
	class Decl;
	class FunctionDecl;
	class ObjCMethodDecl;
	class VarDecl;

	namespace CodeGen {
	typedef SmallVector<llvm::AttributeSet, 8> AttributeListType;

	struct CallArg {
	RValue RV;
	QualType Ty;
	bool NeedsCopy;
	CallArg(RValue rv, QualType ty, bool needscopy)
	: RV(rv), Ty(ty), NeedsCopy(needscopy)
	{ }
	};

	/// CallArgList - Type for representing both the value and type of
	/// arguments in a call.
	class CallArgList :
	public SmallVector<CallArg, 16> {
	public:
	CallArgList() : StackBase(nullptr) {}

	struct Writeback {
	/// The original argument. Note that the argument l-value
	/// is potentially null.
	LValue Source;

	/// The temporary alloca.
	Address Temporary;

	/// A value to "use" after the writeback, or null.
	llvm::Value *ToUse;
	};

	struct CallArgCleanup {
	EHScopeStack::stable_iterator Cleanup;

	/// The "is active" insertion point. This instruction is temporary and
	/// will be removed after insertion.
	llvm::Instruction *IsActiveIP;
	};

	void add(RValue rvalue, QualType type, bool needscopy = false) {
	push_back(CallArg(rvalue, type, needscopy));
	}

	void addFrom(const CallArgList &other) {
	insert(end(), other.begin(), other.end());
	Writebacks.insert(Writebacks.end(),
	other.Writebacks.begin(), other.Writebacks.end());
	}

	void addWriteback(LValue srcLV, Address temporary,
	llvm::Value *toUse) {
	Writeback writeback = { srcLV, temporary, toUse };
	Writebacks.push_back(writeback);
	}

	bool hasWritebacks() const { return !Writebacks.empty(); }

	typedef llvm::iterator_range<SmallVectorImpl<Writeback>::const_iterator>
	writeback_const_range;

	writeback_const_range writebacks() const {
	return writeback_const_range(Writebacks.begin(), Writebacks.end());
	}

	void addArgCleanupDeactivation(EHScopeStack::stable_iterator Cleanup,
	llvm::Instruction *IsActiveIP) {
	CallArgCleanup ArgCleanup;
	ArgCleanup.Cleanup = Cleanup;
	ArgCleanup.IsActiveIP = IsActiveIP;
	CleanupsToDeactivate.push_back(ArgCleanup);
	}

	ArrayRef<CallArgCleanup> getCleanupsToDeactivate() const {
	return CleanupsToDeactivate;
	}

	void allocateArgumentMemory(CodeGenFunction &CGF);
	llvm::Instruction *getStackBase() const { return StackBase; }
	void freeArgumentMemory(CodeGenFunction &CGF) const;

	/// \brief Returns if we're using an inalloca struct to pass arguments in
	/// memory.
	bool isUsingInAlloca() const { return StackBase; }

	private:
	SmallVector<Writeback, 1> Writebacks;

	/// Deactivate these cleanups immediately before making the call. This
	/// is used to cleanup objects that are owned by the callee once the call
	/// occurs.
	SmallVector<CallArgCleanup, 1> CleanupsToDeactivate;

	/// The stacksave call. It dominates all of the argument evaluation.
	llvm::CallInst *StackBase;

	/// The iterator pointing to the stack restore cleanup. We manually run and
	/// deactivate this cleanup after the call in the unexceptional case because
	/// it doesn't run in the normal order.
	EHScopeStack::stable_iterator StackCleanup;
	};

	/// FunctionArgList - Type for representing both the decl and type
	/// of parameters to a function. The decl must be either a
	/// ParmVarDecl or ImplicitParamDecl.
	class FunctionArgList : public SmallVector<const VarDecl*, 16> {
	};

	/// ReturnValueSlot - Contains the address where the return value of a
	/// function can be stored, and whether the address is volatile or not.
	class ReturnValueSlot {
	llvm::PointerIntPair<llvm::Value *, 2, unsigned int> Value;
	CharUnits Alignment;

	// Return value slot flags
	enum Flags {
	IS_VOLATILE = 0x1,
	IS_UNUSED = 0x2,
	};

	public:
	ReturnValueSlot() {}
	ReturnValueSlot(Address Addr, bool IsVolatile, bool IsUnused = false)
	: Value(Addr.isValid() ? Addr.getPointer() : nullptr,
	(IsVolatile ? IS_VOLATILE : 0) \| (IsUnused ? IS_UNUSED : 0)),
	Alignment(Addr.isValid() ? Addr.getAlignment() : CharUnits::Zero()) {}

	bool isNull() const { return !getValue().isValid(); }

	bool isVolatile() const { return Value.getInt() & IS_VOLATILE; }
	Address getValue() const { return Address(Value.getPointer(), Alignment); }
	bool isUnused() const { return Value.getInt() & IS_UNUSED; }
	};

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

	#endif

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