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diff --git a/libyul/backends/evm/AbstractAssembly.h b/libyul/backends/evm/AbstractAssembly.h
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+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @date 2017
+ * Abstract assembly interface, subclasses of which are to be used with the generic
+ * bytecode generator.
+ */
+
+#pragma once
+
+#include <libdevcore/CommonData.h>
+
+#include <functional>
+
+namespace dev
+{
+struct SourceLocation;
+namespace solidity
+{
+enum class Instruction: uint8_t;
+namespace assembly
+{
+struct Instruction;
+struct Identifier;
+}
+}
+namespace yul
+{
+
+///
+/// Assembly class that abstracts both the libevmasm assembly and the new Yul assembly.
+///
+class AbstractAssembly
+{
+public:
+	using LabelID = size_t;
+
+	virtual ~AbstractAssembly() {}
+
+	/// Set a new source location valid starting from the next instruction.
+	virtual void setSourceLocation(SourceLocation const& _location) = 0;
+	/// Retrieve the current height of the stack. This does not have to be zero
+	/// at the beginning.
+	virtual int stackHeight() const = 0;
+	/// Append an EVM instruction.
+	virtual void appendInstruction(solidity::Instruction _instruction) = 0;
+	/// Append a constant.
+	virtual void appendConstant(u256 const& _constant) = 0;
+	/// Append a label.
+	virtual void appendLabel(LabelID _labelId) = 0;
+	/// Append a label reference.
+	virtual void appendLabelReference(LabelID _labelId) = 0;
+	/// Generate a new unique label.
+	virtual LabelID newLabelId() = 0;
+	/// Returns a label identified by the given name. Creates it if it does not yet exist.
+	virtual LabelID namedLabel(std::string const& _name) = 0;
+	/// Append a reference to a to-be-linked symbol.
+	/// Currently, we assume that the value is always a 20 byte number.
+	virtual void appendLinkerSymbol(std::string const& _name) = 0;
+
+	/// Append a jump instruction.
+	/// @param _stackDiffAfter the stack adjustment after this instruction.
+	/// This is helpful to stack height analysis if there is no continuing control flow.
+	virtual void appendJump(int _stackDiffAfter) = 0;
+
+	/// Append a jump-to-immediate operation.
+	/// @param _stackDiffAfter the stack adjustment after this instruction.
+	virtual void appendJumpTo(LabelID _labelId, int _stackDiffAfter = 0) = 0;
+	/// Append a jump-to-if-immediate operation.
+	virtual void appendJumpToIf(LabelID _labelId) = 0;
+	/// Start a subroutine identified by @a _labelId that takes @a _arguments
+	/// stack slots as arguments.
+	virtual void appendBeginsub(LabelID _labelId, int _arguments) = 0;
+	/// Call a subroutine identified by @a _labelId, taking @a _arguments from the
+	/// stack upon call and putting @a _returns arguments onto the stack upon return.
+	virtual void appendJumpsub(LabelID _labelId, int _arguments, int _returns) = 0;
+	/// Return from a subroutine.
+	/// @param _stackDiffAfter the stack adjustment after this instruction.
+	virtual void appendReturnsub(int _returns, int _stackDiffAfter = 0) = 0;
+
+	/// Append the assembled size as a constant.
+	virtual void appendAssemblySize() = 0;
+};
+
+enum class IdentifierContext { LValue, RValue };
+
+/// Object that is used to resolve references and generate code for access to identifiers external
+/// to inline assembly (not used in standalone assembly mode).
+struct ExternalIdentifierAccess
+{
+	using Resolver = std::function<size_t(solidity::assembly::Identifier const&, IdentifierContext, bool /*_crossesFunctionBoundary*/)>;
+	/// Resolve an external reference given by the identifier in the given context.
+	/// @returns the size of the value (number of stack slots) or size_t(-1) if not found.
+	Resolver resolve;
+	using CodeGenerator = std::function<void(solidity::assembly::Identifier const&, IdentifierContext, yul::AbstractAssembly&)>;
+	/// Generate code for retrieving the value (rvalue context) or storing the value (lvalue context)
+	/// of an identifier. The code should be appended to the assembly. In rvalue context, the value is supposed
+	/// to be put onto the stack, in lvalue context, the value is assumed to be at the top of the stack.
+	CodeGenerator generateCode;
+};
+
+
+
+}
+}