From 25c41546ee03f9567d67068dcc636c09367e9a32 Mon Sep 17 00:00:00 2001
From: chriseth <chris@ethereum.org>
Date: Wed, 3 Nov 2021 11:08:45 +0100
Subject: [PATCH] Function reference resolver.

---
 libyul/CMakeLists.txt                |  2 +
 libyul/FunctionReferenceResolver.cpp | 60 ++++++++++++++++++++++++++++
 libyul/FunctionReferenceResolver.h   | 48 ++++++++++++++++++++++
 3 files changed, 110 insertions(+)
 create mode 100644 libyul/FunctionReferenceResolver.cpp
 create mode 100644 libyul/FunctionReferenceResolver.h

diff --git a/libyul/CMakeLists.txt b/libyul/CMakeLists.txt
index 3c980fbb8..039e24ea9 100644
--- a/libyul/CMakeLists.txt
+++ b/libyul/CMakeLists.txt
@@ -40,6 +40,8 @@ add_library(yul
 	Dialect.cpp
 	Dialect.h
 	Exceptions.h
+	FunctionReferenceResolver.cpp
+	FunctionReferenceResolver.h
 	Object.cpp
 	Object.h
 	ObjectParser.cpp
diff --git a/libyul/FunctionReferenceResolver.cpp b/libyul/FunctionReferenceResolver.cpp
new file mode 100644
index 000000000..5df94237a
--- /dev/null
+++ b/libyul/FunctionReferenceResolver.cpp
@@ -0,0 +1,60 @@
+/*
+	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/FunctionReferenceResolver.h>
+
+#include <libyul/AST.h>
+#include <libsolutil/CommonData.h>
+
+#include <range/v3/view/reverse.hpp>
+
+using namespace std;
+using namespace solidity::yul;
+using namespace solidity::util;
+
+FunctionReferenceResolver::FunctionReferenceResolver(Block const& _ast)
+{
+	(*this)(_ast);
+	yulAssert(m_scopes.empty());
+}
+
+void FunctionReferenceResolver::operator()(FunctionCall const& _functionCall)
+{
+	for (auto&& scope: m_scopes | ranges::views::reverse)
+		if (FunctionDefinition const** function = util::valueOrNullptr(scope, _functionCall.functionName.name))
+		{
+			m_functionReferences[&_functionCall] = *function;
+			break;
+		}
+
+	// If we did not find anything, it was a builtin call.
+
+	ASTWalker::operator()(_functionCall);
+}
+
+void FunctionReferenceResolver::operator()(Block const& _block)
+{
+	m_scopes.emplace_back();
+	for (auto const& statement: _block.statements)
+		if (auto const* function = get_if<FunctionDefinition>(&statement))
+			m_scopes.back()[function->name] = function;
+
+	ASTWalker::operator()(_block);
+
+	m_scopes.pop_back();
+}
diff --git a/libyul/FunctionReferenceResolver.h b/libyul/FunctionReferenceResolver.h
new file mode 100644
index 000000000..8c1385adb
--- /dev/null
+++ b/libyul/FunctionReferenceResolver.h
@@ -0,0 +1,48 @@
+/*
+	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>
+
+namespace solidity::yul
+{
+
+/**
+ * Resolves references to user-defined functions in function calls.
+ * Assumes the code is correct, i.e. does not check for references to be valid or unique.
+ *
+ * Be careful not to iterate over the result - it is not deterministic.
+ */
+class FunctionReferenceResolver: private ASTWalker
+{
+public:
+	explicit FunctionReferenceResolver(Block const& _ast);
+	std::map<FunctionCall const*, FunctionDefinition const*> const& references() const { return m_functionReferences; }
+
+private:
+	using ASTWalker::operator();
+	void operator()(FunctionCall const& _functionCall) override;
+	void operator()(Block const& _block) override;
+
+	std::map<FunctionCall const*, FunctionDefinition const*> m_functionReferences;
+	std::vector<std::map<YulString, FunctionDefinition const*>> m_scopes;
+};
+
+
+}