Merge pull request #3351 from ethereum/remove_unused

Remove unused variables and functions

8 files changed, 431 insertions, 3 deletions

diff --git a/libjulia/optimiser/ASTWalker.h b/libjulia/optimiser/ASTWalker.h
index dbf8194b..97891381 100644
--- a/libjulia/optimiser/ASTWalker.h
+++ b/libjulia/optimiser/ASTWalker.h
@@ -71,8 +71,8 @@ protected:
 	template <class T>
 	void walkVector(T const& _statements)
 	{
-		for (auto const& st: _statements)
-			visit(st);
+		for (auto const& statement: _statements)
+			visit(statement);
 	}
 };
 
diff --git a/libjulia/optimiser/NameCollector.cpp b/libjulia/optimiser/NameCollector.cpp
index 7b4c4793..f94104b7 100644
--- a/libjulia/optimiser/NameCollector.cpp
+++ b/libjulia/optimiser/NameCollector.cpp
@@ -42,3 +42,28 @@ void NameCollector::operator ()(FunctionDefinition const& _funDef)
 		m_names.insert(ret.name);
 	ASTWalker::operator ()(_funDef);
 }
+
+void ReferencesCounter::operator()(Identifier const& _identifier)
+{
+	++m_references[_identifier.name];
+}
+
+void ReferencesCounter::operator()(FunctionCall const& _funCall)
+{
+	++m_references[_funCall.functionName.name];
+	ASTWalker::operator()(_funCall);
+}
+
+map<string, size_t> ReferencesCounter::countReferences(Block const& _block)
+{
+	ReferencesCounter counter;
+	counter(_block);
+	return counter.references();
+}
+
+map<string, size_t> ReferencesCounter::countReferences(Expression const& _expression)
+{
+	ReferencesCounter counter;
+	counter.visit(_expression);
+	return counter.references();
+}
diff --git a/libjulia/optimiser/NameCollector.h b/libjulia/optimiser/NameCollector.h
index b7e38f46..7fe386f7 100644
--- a/libjulia/optimiser/NameCollector.h
+++ b/libjulia/optimiser/NameCollector.h
@@ -15,7 +15,7 @@
 	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
 */
 /**
- * Specific AST walker that collects all defined names.
+ * Specific AST walkers that collect facts about identifiers and definitions.
  */
 
 #pragma once
@@ -48,5 +48,23 @@ private:
 	std::map<std::string, FunctionDefinition const*> m_functions;
 };
 
+/**
+ * Specific AST walker that counts all references to all declarations.
+ */
+class ReferencesCounter: public ASTWalker
+{
+public:
+	using ASTWalker::operator ();
+	virtual void operator()(Identifier const& _identifier);
+	virtual void operator()(FunctionCall const& _funCall);
+
+	static std::map<std::string, size_t> countReferences(Block const& _block);
+	static std::map<std::string, size_t> countReferences(Expression const& _expression);
+
+	std::map<std::string, size_t> const& references() const { return m_references; }
+private:
+	std::map<std::string, size_t> m_references;
+};
+
 }
 }
diff --git a/libjulia/optimiser/UnusedPruner.cpp b/libjulia/optimiser/UnusedPruner.cpp
new file mode 100644
index 00000000..50038431
--- /dev/null
+++ b/libjulia/optimiser/UnusedPruner.cpp
@@ -0,0 +1,116 @@
+/*(
+	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/>.
+*/
+/**
+ * Optimisation stage that removes unused variables and functions.
+ */
+
+#include <libjulia/optimiser/UnusedPruner.h>
+
+#include <libjulia/optimiser/NameCollector.h>
+#include <libjulia/optimiser/Semantics.h>
+#include <libjulia/optimiser/Utilities.h>
+
+#include <libsolidity/inlineasm/AsmData.h>
+
+#include <boost/algorithm/cxx11/none_of.hpp>
+
+using namespace std;
+using namespace dev;
+using namespace dev::julia;
+
+UnusedPruner::UnusedPruner(Block& _ast)
+{
+	ReferencesCounter counter;
+	counter(_ast);
+
+	m_references = counter.references();
+}
+
+void UnusedPruner::operator()(Block& _block)
+{
+	for (auto&& statement: _block.statements)
+		if (statement.type() == typeid(FunctionDefinition))
+		{
+			FunctionDefinition& funDef = boost::get<FunctionDefinition>(statement);
+			if (!used(funDef.name))
+			{
+				subtractReferences(ReferencesCounter::countReferences(funDef.body));
+				statement = Block{std::move(funDef.location), {}};
+			}
+		}
+		else if (statement.type() == typeid(VariableDeclaration))
+		{
+			VariableDeclaration& varDecl = boost::get<VariableDeclaration>(statement);
+			// Multi-variable declarations are special. We can only remove it
+			// if all vairables are unused and the right-hand-side is either
+			// movable or it return a single value. In the latter case, we
+			// replace `let a := f()` by `pop(f())` (in pure IULIA, this will be
+			// `drop(f())`).
+			if (boost::algorithm::none_of(
+				varDecl.variables,
+				[=](TypedName const& _typedName) { return used(_typedName.name); }
+			))
+			{
+				if (!varDecl.value)
+					statement = Block{std::move(varDecl.location), {}};
+				else if (MovableChecker(*varDecl.value).movable())
+				{
+					subtractReferences(ReferencesCounter::countReferences(*varDecl.value));
+					statement = Block{std::move(varDecl.location), {}};
+				}
+				else if (varDecl.variables.size() == 1)
+					// In pure IULIA, this should be replaced by a function call to `drop`
+					// instead of `pop`.
+					statement = ExpressionStatement{varDecl.location, FunctionalInstruction{
+						varDecl.location,
+						solidity::Instruction::POP,
+						{*std::move(varDecl.value)}
+					}};
+			}
+		}
+
+	removeEmptyBlocks(_block);
+
+	ASTModifier::operator()(_block);
+}
+
+void UnusedPruner::runUntilStabilised(Block& _ast)
+{
+	while (true)
+	{
+		UnusedPruner pruner(_ast);
+		pruner(_ast);
+		if (!pruner.shouldRunAgain())
+			return;
+	}
+}
+
+bool UnusedPruner::used(string const& _name) const
+{
+	return m_references.count(_name) && m_references.at(_name) > 0;
+}
+
+void UnusedPruner::subtractReferences(map<string, size_t> const& _subtrahend)
+{
+	for (auto const& ref: _subtrahend)
+	{
+		solAssert(m_references.count(ref.first), "");
+		solAssert(m_references.at(ref.first) >= ref.second, "");
+		m_references[ref.first] -= ref.second;
+		m_shouldRunAgain = true;
+	}
+}
diff --git a/libjulia/optimiser/UnusedPruner.h b/libjulia/optimiser/UnusedPruner.h
new file mode 100644
index 00000000..73e8de7c
--- /dev/null
+++ b/libjulia/optimiser/UnusedPruner.h
@@ -0,0 +1,67 @@
+/*
+	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/>.
+*/
+/**
+ * Optimisation stage that removes unused variables and functions.
+ */
+
+#pragma once
+
+#include <libjulia/optimiser/ASTWalker.h>
+
+#include <string>
+#include <map>
+#include <set>
+
+namespace dev
+{
+namespace julia
+{
+
+/**
+ * Optimisation stage that removes unused variables and functions.
+ *
+ * TODO: Also remove intermediate variable assignments from movable expressions
+ * which are not referenced until after the next assignment to the same variable.
+ *
+ * Note that this does not remove circular references.
+ *
+ * Prerequisite: Disambiguator
+ */
+class UnusedPruner: public ASTModifier
+{
+public:
+	explicit UnusedPruner(Block& _ast);
+
+	using ASTModifier::operator();
+	virtual void operator()(Block& _block) override;
+
+	// @returns true iff the code changed in the previous run.
+	bool shouldRunAgain() const { return m_shouldRunAgain; }
+
+	// Run the pruner until the code does not change anymore.
+	static void runUntilStabilised(Block& _ast);
+
+private:
+	bool used(std::string const& _name) const;
+	void subtractReferences(std::map<std::string, size_t> const& _subtrahend);
+
+	bool m_shouldRunAgain = false;
+	std::map<std::string, size_t> m_references;
+};
+
+}
+}
diff --git a/libjulia/optimiser/Utilities.cpp b/libjulia/optimiser/Utilities.cpp
new file mode 100644
index 00000000..ff108b89
--- /dev/null
+++ b/libjulia/optimiser/Utilities.cpp
@@ -0,0 +1,39 @@
+/*(
+	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/>.
+*/
+/**
+ * Some useful snippets for the optimiser.
+ */
+
+#include <libjulia/optimiser/Utilities.h>
+
+#include <libsolidity/inlineasm/AsmData.h>
+
+#include <libdevcore/CommonData.h>
+
+#include <boost/range/algorithm_ext/erase.hpp>
+
+using namespace std;
+using namespace dev;
+using namespace dev::julia;
+
+void dev::julia::removeEmptyBlocks(Block& _block)
+{
+	auto isEmptyBlock = [](Statement const& _st) -> bool {
+		return _st.type() == typeid(Block) && boost::get<Block>(_st).statements.empty();
+	};
+	boost::range::remove_erase_if(_block.statements, isEmptyBlock);
+}
diff --git a/libjulia/optimiser/Utilities.h b/libjulia/optimiser/Utilities.h
new file mode 100644
index 00000000..88ba3f47
--- /dev/null
+++ b/libjulia/optimiser/Utilities.h
@@ -0,0 +1,34 @@
+/*
+	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/>.
+*/
+/**
+ * Small useful snippets for the optimiser.
+ */
+
+#pragma once
+
+#include <libjulia/ASTDataForward.h>
+
+namespace dev
+{
+namespace julia
+{
+
+/// Removes statements that are just empty blocks (non-recursive).
+void removeEmptyBlocks(Block& _block);
+
+}
+}
diff --git a/test/libjulia/UnusedPruner.cpp b/test/libjulia/UnusedPruner.cpp
new file mode 100644
index 00000000..b86a54b3
--- /dev/null
+++ b/test/libjulia/UnusedPruner.cpp
@@ -0,0 +1,129 @@
+/*
+    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
+ * Unit tests for the pruning of unused variables and functions.
+ */
+
+#include <test/libjulia/Common.h>
+
+#include <libjulia/optimiser/UnusedPruner.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\
+{\
+	assembly::AsmPrinter p;\
+	Block b = disambiguate(_original, false);\
+	UnusedPruner::runUntilStabilised(b);\
+	string result = p(b);\
+	BOOST_CHECK_EQUAL(result, format(_expectation, false));\
+}\
+while(false)
+
+BOOST_AUTO_TEST_SUITE(IuliaUnusedPruner)
+
+BOOST_AUTO_TEST_CASE(smoke_test)
+{
+	CHECK("{ }", "{ }");
+}
+
+BOOST_AUTO_TEST_CASE(trivial)
+{
+	CHECK(
+		"{ let a := 1 let b := 1 mstore(0, 1) }",
+		"{ mstore(0, 1) }"
+	);
+}
+
+BOOST_AUTO_TEST_CASE(multi_declarations)
+{
+	CHECK(
+		"{ let x, y }",
+		"{ }"
+	);
+}
+
+BOOST_AUTO_TEST_CASE(multi_assignments)
+{
+	CHECK(
+		"{ let x, y x := 1 y := 2 }",
+		"{ let x, y x := 1 y := 2 }"
+	);
+}
+
+BOOST_AUTO_TEST_CASE(multi_partial_assignments)
+{
+	CHECK(
+		"{ let x, y x := 1 }",
+		"{ let x, y x := 1 }"
+	);
+}
+
+BOOST_AUTO_TEST_CASE(functions)
+{
+	CHECK(
+		"{ function f() { let a := 1 } function g() { f() } }",
+		"{ }"
+	);
+}
+
+BOOST_AUTO_TEST_CASE(intermediate_assignment)
+{
+	CHECK(
+		"{ let a := 1 a := 4 let b := 1 }",
+		"{ let a := 1 a := 4 }"
+	);
+}
+
+BOOST_AUTO_TEST_CASE(intermediate_multi_assignment){
+	CHECK(
+		"{ let a, b function f() -> x { } a := f() b := 1 }",
+		"{ let a, b function f() -> x { } a := f() b := 1 }"
+	);
+}
+
+BOOST_AUTO_TEST_CASE(multi_declare)
+{
+	CHECK(
+		"{ function f() -> x, y { } let a, b := f() }",
+		"{ function f() -> x, y { } let a, b := f() }"
+	);
+}
+
+BOOST_AUTO_TEST_CASE(multi_assign)
+{
+	CHECK(
+		"{ let a let b function f() -> x, y { } a, b := f() }",
+		"{ let a let b function f() -> x, y { } a, b := f() }"
+	);
+}
+
+BOOST_AUTO_TEST_SUITE_END()