Implemented FunctionSpecializer

Optimiser step that specializes the function with its literal arguments.

libsolutil/CommonData.h

@@ -93,10 +93,8 @@ template <class T>
 inline std::vector<T> operator+(std::vector<T>&& _a, std::vector<T>&& _b)
 {
 	std::vector<T> ret(std::move(_a));
-	if (&_a == &_b)
+	assert(&_a != &_b);
-		ret += ret;
+	ret += std::move(_b);
-	else
-		ret += std::move(_b);
 	return ret;
 }
 

libyul/CMakeLists.txt

@@ -131,6 +131,8 @@ add_library(yul
 	optimiser/FunctionGrouper.h
 	optimiser/FunctionHoister.cpp
 	optimiser/FunctionHoister.h
+	optimiser/FunctionSpecializer.cpp
+	optimiser/FunctionSpecializer.h
 	optimiser/InlinableExpressionFunctionFinder.cpp
 	optimiser/InlinableExpressionFunctionFinder.h
 	optimiser/KnowledgeBase.cpp

libyul/optimiser/FunctionSpecializer.cpp

@@ -0,0 +1,150 @@
+/*
+	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/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+
+#include <libyul/optimiser/FunctionSpecializer.h>
+
+#include <libyul/optimiser/ASTCopier.h>
+#include <libyul/optimiser/NameCollector.h>
+#include <libyul/optimiser/NameDispenser.h>
+
+#include <libyul/AST.h>
+#include <libyul/YulString.h>
+#include <libsolutil/CommonData.h>
+
+#include <range/v3/algorithm/any_of.hpp>
+#include <range/v3/view/enumerate.hpp>
+
+#include <variant>
+
+using namespace std;
+using namespace solidity::util;
+using namespace solidity::yul;
+
+FunctionSpecializer::LiteralArguments FunctionSpecializer::specializableArguments(
+	FunctionCall const& _f
+)
+{
+	auto heuristic = [&](Expression const& _e) -> optional<Expression>
+	{
+		if (holds_alternative<Literal>(_e))
+			return ASTCopier{}.translate(_e);
+		return nullopt;
+	};
+
+	return applyMap(_f.arguments, heuristic);
+}
+
+void FunctionSpecializer::operator()(FunctionCall& _f)
+{
+	ASTModifier::operator()(_f);
+
+	if (m_dialect.builtin(_f.functionName.name))
+		return;
+
+	LiteralArguments arguments = specializableArguments(_f);
+
+	if (ranges::any_of(arguments, [](auto& _a) { return _a.has_value(); }))
+	{
+		YulString oldName = move(_f.functionName.name);
+		auto newName = m_nameDispenser.newName(oldName);
+
+		m_oldToNewMap[oldName].emplace_back(make_pair(newName, arguments));
+
+		_f.functionName.name = newName;
+		_f.arguments = util::filter(
+			_f.arguments,
+			applyMap(arguments, [](auto& _a) { return !_a; })
+		);
+	}
+}
+
+FunctionDefinition FunctionSpecializer::specialize(
+	FunctionDefinition const& _f,
+	YulString _newName,
+	FunctionSpecializer::LiteralArguments _arguments
+)
+{
+	yulAssert(_arguments.size() == _f.parameters.size(), "");
+
+	map<YulString, YulString> translatedNames = applyMap(
+		NameCollector{_f, NameCollector::OnlyVariables}.names(),
+		[&](auto& _name) -> pair<YulString, YulString>
+		{
+			return make_pair(_name, m_nameDispenser.newName(_name));
+		},
+		map<YulString, YulString>{}
+	);
+
+	FunctionDefinition newFunction = get<FunctionDefinition>(FunctionCopier{translatedNames}(_f));
+
+	// Function parameters that will be specialized inside the body are converted into variable
+	// declarations.
+	vector<Statement> missingVariableDeclarations;
+	for (auto&& [index, argument]: _arguments | ranges::views::enumerate)
+		if (argument)
+			missingVariableDeclarations.emplace_back(
+				VariableDeclaration{
+					_f.location,
+					vector<TypedName>{newFunction.parameters[index]},
+					make_unique<Expression>(move(*argument))
+				}
+			);
+
+	newFunction.body.statements =
+		move(missingVariableDeclarations) + move(newFunction.body.statements);
+
+	// Only take those indices where optional in arguments in nullopt
+	newFunction.parameters =
+		util::filter(
+			newFunction.parameters,
+			applyMap(_arguments, [&](auto const& _v) { return !_v; })
+		);
+
+	newFunction.name = move(_newName);
+
+	return newFunction;
+}
+
+void FunctionSpecializer::run(OptimiserStepContext& _context, Block& _ast)
+{
+	// Finds all function calls that can be replaced.
+	FunctionSpecializer f{_context.dispenser, _context.dialect};
+	f(_ast);
+
+	iterateReplacing(_ast.statements, [&](Statement& _s) -> optional<vector<Statement>>
+	{
+		if (holds_alternative<FunctionDefinition>(_s))
+		{
+			auto& functionDefinition = get<FunctionDefinition>(_s);
+
+			if (f.m_oldToNewMap.count(functionDefinition.name))
+			{
+				vector<Statement> out = applyMap(
+					f.m_oldToNewMap.at(functionDefinition.name),
+					[&](auto& _p) -> Statement
+					{
+						return f.specialize(functionDefinition, move(_p.first), move(_p.second));
+					}
+				);
+				return move(out) + make_vector<Statement>(move(functionDefinition));
+			}
+		}
+
+		return nullopt;
+	});
+}

libyul/optimiser/FunctionSpecializer.h

@@ -0,0 +1,106 @@
+/*
+	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/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+
+#pragma once
+
+#include <libyul/optimiser/ASTWalker.h>
+#include <libyul/optimiser/NameDispenser.h>
+#include <libyul/optimiser/OptimiserStep.h>
+
+#include <libyul/ASTForward.h>
+#include <libyul/Dialect.h>
+
+#include <map>
+#include <optional>
+#include <vector>
+
+namespace solidity::yul
+{
+
+/**
+ * FunctionSpecializer: Optimiser step that specializes the function with its literal arguments.
+ *
+ * If a function, say, `function f(a, b) { sstore (a, b)}`, is called with literal arguments, for
+ * example, `f(x, 5)`, where `x` is an identifier, it could be specialized by creating a new
+ * function `f_1` that takes only one argument, i.e.,
+ *
+ *   function f_1(a_1) {
+ *     let b_1 := 5
+ *     sstore(a_1, b_1)
+ *   }
+ *
+ * Other optimization steps will be able to make more simplifications to the function. The
+ * optimization step is mainly useful for functions that would not be inlined.
+ *
+ * Prerequisites: Disambiguator, FunctionHoister
+ *
+ * LiteralRematerialiser is recommended as a prerequisite, even though it's not required for
+ * correctness.
+ */
+class FunctionSpecializer: public ASTModifier
+{
+public:
+	/// A vector of function-call arguments. An element 'has value' if it's a literal, and the
+	/// corresponding Expression would be the literal.
+	using LiteralArguments = std::vector<std::optional<Expression>>;
+
+	static constexpr char const* name{"FunctionSpecializer"};
+	static void run(OptimiserStepContext& _context, Block& _ast);
+
+	using ASTModifier::operator();
+	void operator()(FunctionCall& _f) override;
+
+private:
+	explicit FunctionSpecializer(NameDispenser& _nameDispenser, Dialect const& _dialect):
+		m_nameDispenser(_nameDispenser),
+		m_dialect(_dialect)
+	{}
+	/// Returns a vector of Expressions, where the index `i` is an expression if the function's
+	/// `i`-th argument can be specialized, nullopt otherwise.
+	LiteralArguments specializableArguments(FunctionCall const& _f);
+	/// Given a function definition `_f` and its arguments `_arguments`, of which, at least one is a
+	/// literal, this function returns a new function with the literal arguments specialized.
+	///
+	/// Note that the returned function definition will have new (and unique) names, for both the
+	/// function and variable declarations to retain the properties enforced by the Disambiguator.
+	///
+	/// For example, if `_f` is the function `function f(a, b, c) -> d { sstore(a, b) }`,
+	/// `_arguments` is the vector of literals `{1, 2, nullopt}` and the @param, `_newName` has
+	/// value `f_1`, the returned function could be:
+	///
+	///   function f_1(c_2) -> d_3 {
+	///     let a_4 := 1
+	///     let b_5 := 2
+	///     sstore(a_4, b_5)
+	///   }
+	///
+	FunctionDefinition specialize(
+		FunctionDefinition const& _f,
+		YulString _newName,
+		FunctionSpecializer::LiteralArguments _arguments
+	);
+
+	/// A mapping between the old function name and a pair of new function name and its arguments.
+	/// Note that at least one of the argument will have a literal value.
+	std::map<YulString, std::vector<std::pair<YulString, LiteralArguments>>> m_oldToNewMap;
+
+	NameDispenser& m_nameDispenser;
+	Dialect const& m_dialect;
+};
+
+}