Merge pull request #3456 from ethereum/simplifier

Use simplification rules also for IULIA

8 files changed, 533 insertions, 0 deletions

diff --git a/libjulia/optimiser/ExpressionSimplifier.cpp b/libjulia/optimiser/ExpressionSimplifier.cpp
new file mode 100644
index 00000000..3d471cb3
--- /dev/null
+++ b/libjulia/optimiser/ExpressionSimplifier.cpp
@@ -0,0 +1,50 @@
+/*
+	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/>.
+*/
+/**
+ * Optimiser component that uses the simplification rules to simplify expressions.
+ */
+
+#include <libjulia/optimiser/ExpressionSimplifier.h>
+
+#include <libjulia/optimiser/SimplificationRules.h>
+#include <libjulia/optimiser/Semantics.h>
+
+#include <libsolidity/inlineasm/AsmData.h>
+
+#include <libsolidity/interface/Exceptions.h>
+
+#include <libdevcore/CommonData.h>
+
+using namespace std;
+using namespace dev;
+using namespace dev::julia;
+using namespace dev::solidity;
+
+
+void ExpressionSimplifier::visit(Expression& _expression)
+{
+	ASTModifier::visit(_expression);
+	while (auto match = SimplificationRules::findFirstMatch(_expression))
+	{
+		// Do not apply the rule if it removes non-constant parts of the expression.
+		// TODO: The check could actually be less strict than "movable".
+		// We only require "Does not cause side-effects".
+		if (match->removesNonConstants && !MovableChecker(_expression).movable())
+			return;
+		_expression = match->action().toExpression(locationOf(_expression));
+	}
+}
diff --git a/libjulia/optimiser/ExpressionSimplifier.h b/libjulia/optimiser/ExpressionSimplifier.h
new file mode 100644
index 00000000..8a9e0e20
--- /dev/null
+++ b/libjulia/optimiser/ExpressionSimplifier.h
@@ -0,0 +1,45 @@
+/*
+	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/>.
+*/
+/**
+ * Optimiser component that uses the simplification rules to simplify expressions.
+ */
+
+#pragma once
+
+#include <libjulia/ASTDataForward.h>
+
+#include <libjulia/optimiser/ASTWalker.h>
+
+namespace dev
+{
+namespace julia
+{
+
+/**
+ * Applies simplification rules to all expressions.
+ */
+class ExpressionSimplifier: public ASTModifier
+{
+public:
+	using ASTModifier::operator();
+	virtual void visit(Expression& _expression);
+
+private:
+};
+
+}
+}
diff --git a/libjulia/optimiser/README.md b/libjulia/optimiser/README.md
index 24ee429c..e7134440 100644
--- a/libjulia/optimiser/README.md
+++ b/libjulia/optimiser/README.md
@@ -78,3 +78,12 @@ a loop or conditional, the first one is not inside), the first assignment is rem
 
 
 ## Function Unifier
+
+## Expression Simplifier
+
+This step can only be applied for the EVM-flavoured dialect of iulia. It applies
+simple rules like ``x + 0 == x`` to simplify expressions.
+
+## Ineffective Statement Remover
+
+This step removes statements that have no side-effects.
diff --git a/libjulia/optimiser/SimplificationRules.cpp b/libjulia/optimiser/SimplificationRules.cpp
new file mode 100644
index 00000000..a439caef
--- /dev/null
+++ b/libjulia/optimiser/SimplificationRules.cpp
@@ -0,0 +1,182 @@
+/*
+	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/>.
+*/
+/**
+ * Module for applying replacement rules against Expressions.
+ */
+
+#include <libjulia/optimiser/SimplificationRules.h>
+
+#include <libjulia/optimiser/Utilities.h>
+#include <libjulia/optimiser/ASTCopier.h>
+#include <libjulia/optimiser/Semantics.h>
+#include <libjulia/optimiser/SyntacticalEquality.h>
+
+#include <libsolidity/inlineasm/AsmData.h>
+
+#include <libevmasm/RuleList.h>
+
+using namespace std;
+using namespace dev;
+using namespace dev::julia;
+
+
+SimplificationRule<Pattern> const* SimplificationRules::findFirstMatch(Expression const& _expr)
+{
+	if (_expr.type() != typeid(FunctionalInstruction))
+		return nullptr;
+
+	static SimplificationRules rules;
+
+	FunctionalInstruction const& instruction = boost::get<FunctionalInstruction const&>(_expr);
+	for (auto const& rule: rules.m_rules[byte(instruction.instruction)])
+	{
+		rules.resetMatchGroups();
+		if (rule.pattern.matches(_expr))
+			return &rule;
+	}
+	return nullptr;
+}
+
+void SimplificationRules::addRules(vector<SimplificationRule<Pattern>> const& _rules)
+{
+	for (auto const& r: _rules)
+		addRule(r);
+}
+
+void SimplificationRules::addRule(SimplificationRule<Pattern> const& _rule)
+{
+	m_rules[byte(_rule.pattern.instruction())].push_back(_rule);
+}
+
+SimplificationRules::SimplificationRules()
+{
+	// Multiple occurences of one of these inside one rule must match the same equivalence class.
+	// Constants.
+	Pattern A(PatternKind::Constant);
+	Pattern B(PatternKind::Constant);
+	Pattern C(PatternKind::Constant);
+	// Anything.
+	Pattern X;
+	Pattern Y;
+	A.setMatchGroup(1, m_matchGroups);
+	B.setMatchGroup(2, m_matchGroups);
+	C.setMatchGroup(3, m_matchGroups);
+	X.setMatchGroup(4, m_matchGroups);
+	Y.setMatchGroup(5, m_matchGroups);
+
+	addRules(simplificationRuleList(A, B, C, X, Y));
+}
+
+Pattern::Pattern(solidity::Instruction _instruction, vector<Pattern> const& _arguments):
+	m_kind(PatternKind::Operation),
+	m_instruction(_instruction),
+	m_arguments(_arguments)
+{
+}
+
+void Pattern::setMatchGroup(unsigned _group, map<unsigned, Expression const*>& _matchGroups)
+{
+	m_matchGroup = _group;
+	m_matchGroups = &_matchGroups;
+}
+
+bool Pattern::matches(Expression const& _expr) const
+{
+	if (m_kind == PatternKind::Constant)
+	{
+		if (_expr.type() != typeid(Literal))
+			return false;
+		Literal const& literal = boost::get<Literal const&>(_expr);
+		if (literal.kind != assembly::LiteralKind::Number)
+			return false;
+		if (m_data && *m_data != u256(literal.value))
+			return false;
+		assertThrow(m_arguments.empty(), OptimizerException, "");
+	}
+	else if (m_kind == PatternKind::Operation)
+	{
+		if (_expr.type() != typeid(FunctionalInstruction))
+			return false;
+		FunctionalInstruction const& instr = boost::get<FunctionalInstruction const&>(_expr);
+		if (m_instruction != instr.instruction)
+			return false;
+		assertThrow(m_arguments.size() == instr.arguments.size(), OptimizerException, "");
+		for (size_t i = 0; i < m_arguments.size(); ++i)
+			if (!m_arguments[i].matches(instr.arguments.at(i)))
+				return false;
+	}
+	else
+	{
+		assertThrow(m_arguments.empty(), OptimizerException, "");
+	}
+	// We support matching multiple expressions that require the same value
+	// based on identical ASTs, which have to be movable.
+	if (m_matchGroup)
+	{
+		if (m_matchGroups->count(m_matchGroup))
+		{
+			Expression const* firstMatch = (*m_matchGroups)[m_matchGroup];
+			assertThrow(firstMatch, OptimizerException, "Match set but to null.");
+			return
+				SyntacticalEqualityChecker::equal(*firstMatch, _expr) &&
+				MovableChecker(_expr).movable();
+		}
+		else
+			(*m_matchGroups)[m_matchGroup] = &_expr;
+	}
+	return true;
+}
+
+solidity::Instruction Pattern::instruction() const
+{
+	assertThrow(m_kind == PatternKind::Operation, OptimizerException, "");
+	return m_instruction;
+}
+
+Expression Pattern::toExpression(SourceLocation const& _location) const
+{
+	if (matchGroup())
+		return ASTCopier().translate(matchGroupValue());
+	if (m_kind == PatternKind::Constant)
+	{
+		assertThrow(m_data, OptimizerException, "No match group and no constant value given.");
+		return Literal{_location, assembly::LiteralKind::Number, m_data->str(), ""};
+	}
+	else if (m_kind == PatternKind::Operation)
+	{
+		vector<Expression> arguments;
+		for (auto const& arg: m_arguments)
+			arguments.emplace_back(arg.toExpression(_location));
+		return FunctionalInstruction{_location, m_instruction, std::move(arguments)};
+	}
+	assertThrow(false, OptimizerException, "Pattern of kind 'any', but no match group.");
+}
+
+u256 Pattern::d() const
+{
+	Literal const& literal = boost::get<Literal const&>(matchGroupValue());
+	assertThrow(literal.kind == assembly::LiteralKind::Number, OptimizerException, "");
+	return u256(literal.value);
+}
+
+Expression const& Pattern::matchGroupValue() const
+{
+	assertThrow(m_matchGroup > 0, OptimizerException, "");
+	assertThrow(!!m_matchGroups, OptimizerException, "");
+	assertThrow((*m_matchGroups)[m_matchGroup], OptimizerException, "");
+	return *(*m_matchGroups)[m_matchGroup];
+}
diff --git a/libjulia/optimiser/SimplificationRules.h b/libjulia/optimiser/SimplificationRules.h
new file mode 100644
index 00000000..68b640b1
--- /dev/null
+++ b/libjulia/optimiser/SimplificationRules.h
@@ -0,0 +1,117 @@
+/*
+	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/>.
+*/
+/**
+ * Module for applying replacement rules against Expressions.
+ */
+
+#pragma once
+
+#include <libevmasm/ExpressionClasses.h>
+#include <libevmasm/SimplificationRule.h>
+
+#include <libjulia/ASTDataForward.h>
+
+#include <libsolidity/inlineasm/AsmData.h>
+
+#include <boost/noncopyable.hpp>
+
+#include <functional>
+#include <vector>
+
+namespace dev
+{
+namespace julia
+{
+
+class Pattern;
+
+/**
+ * Container for all simplification rules.
+ */
+class SimplificationRules: public boost::noncopyable
+{
+public:
+	SimplificationRules();
+
+	/// @returns a pointer to the first matching pattern and sets the match
+	/// groups accordingly.
+	static SimplificationRule<Pattern> const* findFirstMatch(Expression const& _expr);
+
+private:
+	void addRules(std::vector<SimplificationRule<Pattern>> const& _rules);
+	void addRule(SimplificationRule<Pattern> const& _rule);
+
+	void resetMatchGroups() { m_matchGroups.clear(); }
+
+	std::map<unsigned, Expression const*> m_matchGroups;
+	std::vector<SimplificationRule<Pattern>> m_rules[256];
+};
+
+enum class PatternKind
+{
+	Operation,
+	Constant,
+	Any
+};
+
+/**
+ * Pattern to match against an expression.
+ * Also stores matched expressions to retrieve them later, for constructing new expressions using
+ * ExpressionTemplate.
+ */
+class Pattern
+{
+public:
+	/// Matches any expression.
+	Pattern(PatternKind _kind = PatternKind::Any): m_kind(_kind) {}
+	// Matches a specific constant value.
+	Pattern(unsigned _value): Pattern(u256(_value)) {}
+	// Matches a specific constant value.
+	Pattern(u256 const& _value): m_kind(PatternKind::Constant), m_data(std::make_shared<u256>(_value)) {}
+	// Matches a given instruction with given arguments
+	Pattern(solidity::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) const;
+
+	std::vector<Pattern> arguments() const { return m_arguments; }
+
+	/// @returns the data of the matched expression if this pattern is part of a match group.
+	u256 d() const;
+
+	solidity::Instruction instruction() const;
+
+	/// Turns this pattern into an actual expression. Should only be called
+	/// for patterns resulting from an action, i.e. with match groups assigned.
+	Expression toExpression(SourceLocation const& _location) const;
+
+private:
+	Expression const& matchGroupValue() const;
+
+	PatternKind m_kind = PatternKind::Any;
+	solidity::Instruction m_instruction; ///< Only valid if m_kind is Operation
+	std::shared_ptr<u256> m_data; ///< Only valid if m_kind is Constant
+	std::vector<Pattern> m_arguments;
+	unsigned m_matchGroup = 0;
+	std::map<unsigned, Expression const*>* m_matchGroups = nullptr;
+};
+
+}
+}
diff --git a/libjulia/optimiser/SyntacticalEquality.cpp b/libjulia/optimiser/SyntacticalEquality.cpp
new file mode 100644
index 00000000..2b90b091
--- /dev/null
+++ b/libjulia/optimiser/SyntacticalEquality.cpp
@@ -0,0 +1,75 @@
+/*(
+	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/>.
+*/
+/**
+ * Component that can compare ASTs for equality on a syntactic basis.
+ */
+
+#include <libjulia/optimiser/SyntacticalEquality.h>
+
+#include <libsolidity/inlineasm/AsmData.h>
+#include <libsolidity/interface/Exceptions.h>
+
+#include <libdevcore/CommonData.h>
+
+using namespace std;
+using namespace dev;
+using namespace dev::julia;
+
+bool SyntacticalEqualityChecker::equal(Expression const& _e1, Expression const& _e2)
+{
+	if (_e1.type() != _e2.type())
+		return false;
+
+	// TODO This should be replaced by some kind of AST walker as soon as it gets
+	// more complex.
+	if (_e1.type() == typeid(FunctionalInstruction))
+	{
+		auto const& e1 = boost::get<FunctionalInstruction>(_e1);
+		auto const& e2 = boost::get<FunctionalInstruction>(_e2);
+		return
+			e1.instruction == e2.instruction &&
+			equalVector(e1.arguments, e2.arguments);
+	}
+	else if (_e1.type() == typeid(FunctionCall))
+	{
+		auto const& e1 = boost::get<FunctionCall>(_e1);
+		auto const& e2 = boost::get<FunctionCall>(_e2);
+		return
+			equal(e1.functionName, e2.functionName) &&
+			equalVector(e1.arguments, e2.arguments);
+	}
+	else if (_e1.type() == typeid(Identifier))
+		return boost::get<Identifier>(_e1).name == boost::get<Identifier>(_e2).name;
+	else if (_e1.type() == typeid(Literal))
+	{
+		auto const& e1 = boost::get<Literal>(_e1);
+		auto const& e2 = boost::get<Literal>(_e2);
+		return e1.kind == e2.kind && e1.value == e2.value && e1.type == e2.type;
+	}
+	else
+	{
+		solAssert(false, "Invlid expression");
+	}
+	return false;
+}
+
+bool SyntacticalEqualityChecker::equalVector(vector<Expression> const& _e1, vector<Expression> const& _e2)
+{
+	return _e1.size() == _e2.size() &&
+		std::equal(begin(_e1), end(_e1), begin(_e2), SyntacticalEqualityChecker::equal);
+
+}
diff --git a/libjulia/optimiser/SyntacticalEquality.h b/libjulia/optimiser/SyntacticalEquality.h
new file mode 100644
index 00000000..b7c09330
--- /dev/null
+++ b/libjulia/optimiser/SyntacticalEquality.h
@@ -0,0 +1,50 @@
+/*
+	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/>.
+*/
+/**
+ * Component that can compare ASTs for equality on a syntactic basis.
+ */
+
+#pragma once
+
+#include <libjulia/ASTDataForward.h>
+
+#include <vector>
+
+namespace dev
+{
+namespace julia
+{
+
+/**
+ * Component that can compare ASTs for equality on a syntactic basis.
+ * Ignores source locations but requires exact matches otherwise.
+ *
+ * TODO: Only implemented for Expressions for now.
+ * A future version might also recognize renamed variables and thus could be used to
+ * remove duplicate functions.
+ */
+class SyntacticalEqualityChecker
+{
+public:
+	static bool equal(Expression const& _e1, Expression const& _e2);
+
+protected:
+	static bool equalVector(std::vector<Expression> const& _e1, std::vector<Expression> const& _e2);
+};
+
+}
+}
diff --git a/libjulia/optimiser/Utilities.h b/libjulia/optimiser/Utilities.h
index 88ba3f47..e3b4b087 100644
--- a/libjulia/optimiser/Utilities.h
+++ b/libjulia/optimiser/Utilities.h
@@ -22,11 +22,16 @@
 
 #include <libjulia/ASTDataForward.h>
 
+#include <libdevcore/Exceptions.h>
+
 namespace dev
 {
 namespace julia
 {
 
+struct IuliaException: virtual Exception {};
+struct OptimizerException: virtual IuliaException {};
+
 /// Removes statements that are just empty blocks (non-recursive).
 void removeEmptyBlocks(Block& _block);