Merge pull request #5076 from ethereum/exprBreaker

[Yul] Expression breaker.

5 files changed, 477 insertions, 0 deletions

diff --git a/libdevcore/CommonData.h b/libdevcore/CommonData.h
index e410af5c..98136b44 100644
--- a/libdevcore/CommonData.h
+++ b/libdevcore/CommonData.h
@@ -25,11 +25,14 @@
 
 #include <libdevcore/Common.h>
 
+#include <boost/optional.hpp>
+
 #include <vector>
 #include <type_traits>
 #include <cstring>
 #include <string>
 #include <set>
+#include <functional>
 
 namespace dev
 {
@@ -229,6 +232,36 @@ bool contains(T const& _t, V const& _v)
 	return std::end(_t) != std::find(std::begin(_t), std::end(_t), _v);
 }
 
+
+/// Function that iterates over a vector, calling a function on each of its
+/// elements. If that function returns a vector, the element is replaced by
+/// the returned vector. During the iteration, the original vector is only valid
+/// on the current element and after that. The actual replacement takes
+/// place at the end, but already visited elements might be invalidated.
+/// If nothing is replaced, no copy is performed.
+template <class T>
+void iterateReplacing(std::vector<T>& _vector, std::function<boost::optional<std::vector<T>>(T&)> _f)
+{
+	bool useModified = false;
+	std::vector<T> modifiedVector;
+	for (size_t i = 0; i < _vector.size(); ++i)
+	{
+		if (boost::optional<std::vector<T>> r = _f(_vector[i]))
+		{
+			if (!useModified)
+			{
+				std::move(_vector.begin(), _vector.begin() + i, back_inserter(modifiedVector));
+				useModified = true;
+			}
+			modifiedVector += std::move(*r);
+		}
+		else if (useModified)
+			modifiedVector.emplace_back(std::move(_vector[i]));
+	}
+	if (useModified)
+		_vector = std::move(modifiedVector);
+}
+
 /// @returns true iff @a _str passess the hex address checksum test.
 /// @param _strict if false, hex strings with only uppercase or only lowercase letters
 /// are considered valid.
diff --git a/libjulia/optimiser/ExpressionBreaker.cpp b/libjulia/optimiser/ExpressionBreaker.cpp
new file mode 100644
index 00000000..2273fa98
--- /dev/null
+++ b/libjulia/optimiser/ExpressionBreaker.cpp
@@ -0,0 +1,105 @@
+/*
+	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 turns complex expressions into multiple variable
+ * declarations.
+ */
+
+#include <libjulia/optimiser/ExpressionBreaker.h>
+
+#include <libjulia/optimiser/ASTWalker.h>
+
+#include <libsolidity/inlineasm/AsmData.h>
+
+#include <libdevcore/CommonData.h>
+
+#include <boost/range/adaptor/reversed.hpp>
+
+using namespace std;
+using namespace dev;
+using namespace dev::julia;
+using namespace dev::solidity;
+
+void ExpressionBreaker::operator()(FunctionalInstruction& _instruction)
+{
+	for (auto& arg: _instruction.arguments | boost::adaptors::reversed)
+		outlineExpression(arg);
+}
+
+void ExpressionBreaker::operator()(FunctionCall& _funCall)
+{
+	for (auto& arg: _funCall.arguments | boost::adaptors::reversed)
+		outlineExpression(arg);
+}
+
+void ExpressionBreaker::operator()(If& _if)
+{
+	outlineExpression(*_if.condition);
+	(*this)(_if.body);
+}
+
+void ExpressionBreaker::operator()(Switch& _switch)
+{
+	outlineExpression(*_switch.expression);
+	for (auto& _case: _switch.cases)
+		// Do not visit the case expression, nothing to break there.
+		(*this)(_case.body);
+}
+
+void ExpressionBreaker::operator()(ForLoop& _loop)
+{
+	(*this)(_loop.pre);
+	// Do not visit the condition because we cannot break expressions there.
+	(*this)(_loop.post);
+	(*this)(_loop.body);
+}
+
+void ExpressionBreaker::operator()(Block& _block)
+{
+	vector<Statement> saved;
+	swap(saved, m_statementsToPrefix);
+
+	function<boost::optional<vector<Statement>>(Statement&)> f =
+			[&](Statement& _statement) -> boost::optional<vector<Statement>> {
+		m_statementsToPrefix.clear();
+		visit(_statement);
+		if (m_statementsToPrefix.empty())
+			return {};
+		m_statementsToPrefix.emplace_back(std::move(_statement));
+		return std::move(m_statementsToPrefix);
+	};
+	iterateReplacing(_block.statements, f);
+
+	swap(saved, m_statementsToPrefix);
+}
+
+void ExpressionBreaker::outlineExpression(Expression& _expr)
+{
+	if (_expr.type() != typeid(FunctionalInstruction) && _expr.type() != typeid(FunctionCall))
+		return;
+
+	visit(_expr);
+
+	SourceLocation location = locationOf(_expr);
+	string var = m_nameDispenser.newName("");
+	m_statementsToPrefix.emplace_back(VariableDeclaration{
+		location,
+		{{TypedName{location, var, ""}}},
+		make_shared<Expression>(std::move(_expr))
+	});
+	_expr = Identifier{location, var};
+}
diff --git a/libjulia/optimiser/ExpressionBreaker.h b/libjulia/optimiser/ExpressionBreaker.h
new file mode 100644
index 00000000..28cfdbc9
--- /dev/null
+++ b/libjulia/optimiser/ExpressionBreaker.h
@@ -0,0 +1,86 @@
+/*
+	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 turns complex expressions into multiple variable
+ * declarations.
+ */
+#pragma once
+
+#include <libjulia/ASTDataForward.h>
+
+#include <libjulia/optimiser/ASTWalker.h>
+#include <libjulia/optimiser/NameDispenser.h>
+
+#include <vector>
+
+namespace dev
+{
+namespace julia
+{
+
+class NameCollector;
+
+
+/**
+ * Optimiser component that modifies an AST in place, turning complex
+ * expressions into simple expressions and multiple variable declarations.
+ *
+ * Code of the form
+ *
+ * sstore(mul(x, 4), mload(y))
+ *
+ * is transformed into
+ *
+ * let a1 := mload(y)
+ * let a2 := mul(x, 4)
+ * sstore(a2, a1)
+ *
+ * The transformation is not applied to loop conditions, because the loop control flow
+ * does not allow "outlining" the inner expressions in all cases.
+ *
+ * The final program should be in a form such that with the exception of a loop condition,
+ * function calls can only appear in the right-hand side of a variable declaration,
+ * assignments or expression statements and all arguments have to be constants or variables.
+ */
+class ExpressionBreaker: public ASTModifier
+{
+public:
+	explicit ExpressionBreaker(NameDispenser& _nameDispenser):
+		m_nameDispenser(_nameDispenser)
+	{ }
+
+	virtual void operator()(FunctionalInstruction&) override;
+	virtual void operator()(FunctionCall&) override;
+	virtual void operator()(If&) override;
+	virtual void operator()(Switch&) override;
+	virtual void operator()(ForLoop&) override;
+	virtual void operator()(Block& _block) override;
+
+private:
+	/// Replaces the expression by a variable if it is a function call or functional
+	/// instruction. The declaration of the variable is appended to m_statementsToPrefix.
+	/// Recurses via visit().
+	void outlineExpression(Expression& _expr);
+
+	/// List of statements that should go in front of the currently visited AST element,
+	/// at the statement level.
+	std::vector<Statement> m_statementsToPrefix;
+	NameDispenser& m_nameDispenser;
+};
+
+}
+}
diff --git a/test/libdevcore/IterateReplacing.cpp b/test/libdevcore/IterateReplacing.cpp
new file mode 100644
index 00000000..08cd1e22
--- /dev/null
+++ b/test/libdevcore/IterateReplacing.cpp
@@ -0,0 +1,97 @@
+/*
+	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/>.
+*/
+/**
+ * Unit tests for the iterateReplacing function
+ */
+
+#include <libdevcore/CommonData.h>
+
+#include <test/Options.h>
+
+using namespace std;
+
+namespace dev
+{
+namespace test
+{
+
+BOOST_AUTO_TEST_SUITE(IterateReplacing)
+
+BOOST_AUTO_TEST_CASE(no_replacement)
+{
+	vector<string> v{"abc", "def", "ghi"};
+	function<boost::optional<vector<string>>(string&)> f = [](string&) -> boost::optional<vector<string>> { return {}; };
+	iterateReplacing(v, f);
+	vector<string> expectation{"abc", "def", "ghi"};
+	BOOST_CHECK(v == expectation);
+}
+
+BOOST_AUTO_TEST_CASE(empty_input)
+{
+	vector<string> v;
+	function<boost::optional<vector<string>>(string&)> f = [](string&) -> boost::optional<vector<string>> { return {}; };
+	iterateReplacing(v, f);
+	vector<string> expectation;
+	BOOST_CHECK(v == expectation);
+}
+
+BOOST_AUTO_TEST_CASE(delete_some)
+{
+	vector<string> v{"abc", "def", "ghi"};
+	function<boost::optional<vector<string>>(string&)> f = [](string& _s) -> boost::optional<vector<string>> {
+		if (_s == "def")
+			return vector<string>();
+		else
+			return {};
+	};
+	iterateReplacing(v, f);
+	vector<string> expectation{"abc", "ghi"};
+	BOOST_CHECK(v == expectation);
+}
+
+BOOST_AUTO_TEST_CASE(inject_some_start)
+{
+	vector<string> v{"abc", "def", "ghi"};
+	function<boost::optional<vector<string>>(string&)> f = [](string& _s) -> boost::optional<vector<string>> {
+		if (_s == "abc")
+			return vector<string>{"x", "y"};
+		else
+			return {};
+	};
+	iterateReplacing(v, f);
+	vector<string> expectation{"x", "y", "def", "ghi"};
+	BOOST_CHECK(v == expectation);
+}
+
+BOOST_AUTO_TEST_CASE(inject_some_end)
+{
+	vector<string> v{"abc", "def", "ghi"};
+	function<boost::optional<vector<string>>(string&)> f = [](string& _s) -> boost::optional<vector<string>> {
+		if (_s == "ghi")
+			return vector<string>{"x", "y"};
+		else
+			return {};
+	};
+	iterateReplacing(v, f);
+	vector<string> expectation{"abc", "def", "x", "y"};
+	BOOST_CHECK(v == expectation);
+}
+
+BOOST_AUTO_TEST_SUITE_END()
+
+}
+}
diff --git a/test/libjulia/ExpressionBreaker.cpp b/test/libjulia/ExpressionBreaker.cpp
new file mode 100644
index 00000000..de8d2251
--- /dev/null
+++ b/test/libjulia/ExpressionBreaker.cpp
@@ -0,0 +1,156 @@
+/*
+	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/>.
+*/
+/**
+ * Unit tests for the expression breaker.
+ */
+
+#include <test/libjulia/Common.h>
+
+#include <libjulia/optimiser/ExpressionBreaker.h>
+#include <libjulia/optimiser/NameCollector.h>
+
+#include <libsolidity/inlineasm/AsmPrinter.h>
+
+#include <boost/test/unit_test.hpp>
+
+#include <boost/range/adaptors.hpp>
+#include <boost/algorithm/string/join.hpp>
+
+using namespace std;
+using namespace dev;
+using namespace dev::julia;
+using namespace dev::julia::test;
+using namespace dev::solidity;
+
+
+#define CHECK(_original, _expectation)\
+do\
+{\
+	auto result = parse(_original, false);\
+	NameDispenser nameDispenser;\
+	nameDispenser.m_usedNames = NameCollector(*result.first).names();\
+	ExpressionBreaker{nameDispenser}(*result.first);\
+	BOOST_CHECK_EQUAL(assembly::AsmPrinter{}(*result.first), format(_expectation, false));\
+}\
+while(false)
+
+BOOST_AUTO_TEST_SUITE(YulExpressionBreaker)
+
+BOOST_AUTO_TEST_CASE(smoke_test)
+{
+	CHECK("{ }", "{ }");
+}
+
+BOOST_AUTO_TEST_CASE(trivial)
+{
+	CHECK(
+		"{ mstore(add(calldataload(2), mload(3)), 8) }",
+		"{ let _1 := mload(3) let _2 := calldataload(2) let _3 := add(_2, _1) mstore(_3, 8) }"
+	);
+}
+
+BOOST_AUTO_TEST_CASE(control_flow)
+{
+	string input = R"({
+		let x := calldataload(0)
+		if mul(add(x, 2), 3) {
+			for { let a := 2 } lt(a, mload(a)) { a := add(a, mul(a, 2)) } {
+				let b := mul(add(a, 2), 4)
+				sstore(b, mul(b, 2))
+			}
+		}
+	})";
+	string expectation = R"({
+		let x := calldataload(0)
+		let _1 := add(x, 2)
+		let _2 := mul(_1, 3)
+		if _2
+		{
+			for { let a := 2 } lt(a, mload(a))
+				{
+					let _3 := mul(a, 2)
+					a := add(a, _3)
+				}
+			{
+				let _4 := add(a, 2)
+				let b := mul(_4, 4)
+				let _5 := mul(b, 2)
+				sstore(b, _5)
+			}
+		}
+	})";
+	CHECK(input, expectation);
+}
+
+BOOST_AUTO_TEST_CASE(switch_)
+{
+	string input = R"({
+		let x := 8
+		switch add(2, calldataload(0))
+		case 0 { sstore(0, mload(2)) }
+		default { mstore(0, mload(3)) }
+		x := add(mload(3), 4)
+	})";
+	string expectation = R"({
+		let x := 8
+		let _1 := calldataload(0)
+		let _2 := add(2, _1)
+		switch _2
+		case 0 {
+			let _3 := mload(2)
+			sstore(0, _3)
+		}
+		default {
+			let _4 := mload(3)
+			mstore(0, _4)
+		}
+		let _5 := mload(3)
+		x := add(_5, 4)
+	})";
+
+	CHECK(input, expectation);
+}
+
+BOOST_AUTO_TEST_CASE(inside_function)
+{
+	string input = R"({
+		let x := mul(f(0, mload(7)), 3)
+		function f(a, b) -> c {
+			c := mul(a, mload(add(b, c)))
+		}
+		sstore(x, f(mload(2), mload(2)))
+	})";
+	string expectation = R"({
+		let _1 := mload(7)
+		let _2 := f(0, _1)
+		let x := mul(_2, 3)
+		function f(a, b) -> c
+		{
+			let _3 := add(b, c)
+			let _4 := mload(_3)
+			c := mul(a, _4)
+		}
+		let _5 := mload(2)
+		let _6 := mload(2)
+		let _7 := f(_6, _5)
+		sstore(x, _7)
+	})";
+
+	CHECK(input, expectation);
+}
+
+BOOST_AUTO_TEST_SUITE_END()