move libevmasm

1 files changed, 190 insertions, 0 deletions

diff --git a/libevmasm/ExpressionClasses.h b/libevmasm/ExpressionClasses.h
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+++ b/libevmasm/ExpressionClasses.h
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+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum 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.
+
+	cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @file ExpressionClasses.h
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ * Container for equivalence classes of expressions for use in common subexpression elimination.
+ */
+
+#pragma once
+
+#include <vector>
+#include <map>
+#include <memory>
+#include <libdevcore/Common.h>
+#include <libevmasm/AssemblyItem.h>
+
+namespace dev
+{
+namespace eth
+{
+
+class Pattern;
+struct ExpressionTemplate;
+
+/**
+ * Collection of classes of equivalent expressions that can also determine the class of an expression.
+ * Identifiers are contiguously assigned to new classes starting from zero.
+ */
+class ExpressionClasses
+{
+public:
+	using Id = unsigned;
+	using Ids = std::vector<Id>;
+
+	struct Expression
+	{
+		Id id;
+		AssemblyItem const* item = nullptr;
+		Ids arguments;
+		/// Storage modification sequence, only used for storage and memory operations.
+		unsigned sequenceNumber = 0;
+		/// Behaves as if this was a tuple of (item->type(), item->data(), arguments, sequenceNumber).
+		bool operator<(Expression const& _other) const;
+	};
+
+	/// Retrieves the id of the expression equivalence class resulting from the given item applied to the
+	/// given classes, might also create a new one.
+	/// @param _copyItem if true, copies the assembly item to an internal storage instead of just
+	/// keeping a pointer.
+	/// The @a _sequenceNumber indicates the current storage or memory access sequence.
+	Id find(
+		AssemblyItem const& _item,
+		Ids const& _arguments = {},
+		bool _copyItem = true,
+		unsigned _sequenceNumber = 0
+	);
+	/// @returns the canonical representative of an expression class.
+	Expression const& representative(Id _id) const { return m_representatives.at(_id); }
+	/// @returns the number of classes.
+	Id size() const { return m_representatives.size(); }
+
+	/// Forces the given @a _item with @a _arguments to the class @a _id. This can be used to
+	/// add prior knowledge e.g. about CALLDATA, but has to be used with caution. Will not work as
+	/// expected if @a _item applied to @a _arguments already exists.
+	void forceEqual(Id _id, AssemblyItem const& _item, Ids const& _arguments, bool _copyItem = true);
+
+	/// @returns the id of a new class which is different to all other classes.
+	Id newClass(SourceLocation const& _location);
+
+	/// @returns true if the values of the given classes are known to be different (on every input).
+	/// @note that this function might still return false for some different inputs.
+	bool knownToBeDifferent(Id _a, Id _b);
+	/// Similar to @a knownToBeDifferent but require that abs(_a - b) >= 32.
+	bool knownToBeDifferentBy32(Id _a, Id _b);
+	/// @returns true if the value of the given class is known to be zero.
+	/// @note that this is not the negation of knownNonZero
+	bool knownZero(Id _c);
+	/// @returns true if the value of the given class is known to be nonzero.
+	/// @note that this is not the negation of knownZero
+	bool knownNonZero(Id _c);
+	/// @returns a pointer to the value if the given class is known to be a constant,
+	/// and a nullptr otherwise.
+	u256 const* knownConstant(Id _c);
+
+	/// Stores a copy of the given AssemblyItem and returns a pointer to the copy that is valid for
+	/// the lifetime of the ExpressionClasses object.
+	AssemblyItem const* storeItem(AssemblyItem const& _item);
+
+	std::string fullDAGToString(Id _id) const;
+
+private:
+	/// Tries to simplify the given expression.
+	/// @returns its class if it possible or Id(-1) otherwise.
+	/// @param _secondRun is set to true for the second run where arguments of commutative expressions are reversed
+	Id tryToSimplify(Expression const& _expr, bool _secondRun = false);
+
+	/// Rebuilds an expression from a (matched) pattern.
+	Id rebuildExpression(ExpressionTemplate const& _template);
+
+	std::vector<std::pair<Pattern, std::function<Pattern()>>> createRules() const;
+
+	/// Expression equivalence class representatives - we only store one item of an equivalence.
+	std::vector<Expression> m_representatives;
+	/// All expression ever encountered.
+	std::set<Expression> m_expressions;
+	std::vector<std::shared_ptr<AssemblyItem>> m_spareAssemblyItems;
+};
+
+/**
+ * Pattern to match against an expression.
+ * Also stores matched expressions to retrieve them later, for constructing new expressions using
+ * ExpressionTemplate.
+ */
+class Pattern
+{
+public:
+	using Expression = ExpressionClasses::Expression;
+	using Id = ExpressionClasses::Id;
+
+	// Matches a specific constant value.
+	Pattern(unsigned _value): Pattern(u256(_value)) {}
+	// Matches a specific constant value.
+	Pattern(u256 const& _value): m_type(Push), m_requireDataMatch(true), m_data(_value) {}
+	// Matches a specific assembly item type or anything if not given.
+	Pattern(AssemblyItemType _type = UndefinedItem): m_type(_type) {}
+	// Matches a given instruction with given arguments
+	Pattern(Instruction _instruction, std::vector<Pattern> const& _arguments = {});
+	/// Sets this pattern to be part of the match group with the identifier @a _group.
+	/// Inside one rule, all patterns in the same match group have to match expressions from the
+	/// same expression equivalence class.
+	void setMatchGroup(unsigned _group, std::map<unsigned, Expression const*>& _matchGroups);
+	unsigned matchGroup() const { return m_matchGroup; }
+	bool matches(Expression const& _expr, ExpressionClasses const& _classes) const;
+
+	AssemblyItem toAssemblyItem(SourceLocation const& _location) const;
+	std::vector<Pattern> arguments() const { return m_arguments; }
+
+	/// @returns the id of the matched expression if this pattern is part of a match group.
+	Id id() const { return matchGroupValue().id; }
+	/// @returns the data of the matched expression if this pattern is part of a match group.
+	u256 const& d() const { return matchGroupValue().item->data(); }
+
+	std::string toString() const;
+
+private:
+	bool matchesBaseItem(AssemblyItem const* _item) const;
+	Expression const& matchGroupValue() const;
+
+	AssemblyItemType m_type;
+	bool m_requireDataMatch = false;
+	u256 m_data = 0;
+	std::vector<Pattern> m_arguments;
+	unsigned m_matchGroup = 0;
+	std::map<unsigned, Expression const*>* m_matchGroups = nullptr;
+};
+
+/**
+ * Template for a new expression that can be built from matched patterns.
+ */
+struct ExpressionTemplate
+{
+	using Expression = ExpressionClasses::Expression;
+	using Id = ExpressionClasses::Id;
+	explicit ExpressionTemplate(Pattern const& _pattern, SourceLocation const& _location);
+	std::string toString() const;
+	bool hasId = false;
+	/// Id of the matched expression, if available.
+	Id id = Id(-1);
+	// Otherwise, assembly item.
+	AssemblyItem item = UndefinedItem;
+	std::vector<ExpressionTemplate> arguments;
+};
+
+}
+}