[Yul] Implements a pass to rewrite for-loop's pre block into the parent's Block.

libyul/optimiser/ForLoopInitRewriter.cpp

@@ -0,0 +1,43 @@
+/*
+	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/>.
+*/
+#include <libyul/optimiser/ForLoopInitRewriter.h>
+#include <libsolidity/inlineasm/AsmData.h>
+#include <libdevcore/CommonData.h>
+#include <functional>
+
+using namespace std;
+using namespace dev;
+using namespace dev::yul;
+
+void ForLoopInitRewriter::operator()(Block& _block)
+{
+	iterateReplacing(
+		_block.statements,
+		[](Statement& _stmt) -> boost::optional<vector<Statement>>
+		{
+			if (_stmt.type() == typeid(ForLoop))
+			{
+				auto& forLoop = boost::get<ForLoop>(_stmt);
+				vector<Statement> rewrite;
+				swap(rewrite, forLoop.pre.statements);
+				rewrite.emplace_back(move(forLoop));
+				return rewrite;
+			}
+			return {};
+		}
+	);
+}

libyul/optimiser/ForLoopInitRewriter.h

@@ -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/>.
+*/
+#pragma once
+
+#include <libyul/optimiser/ASTWalker.h>
+
+namespace dev
+{
+namespace yul
+{
+
+/**
+ * Rewrites ForLoop by moving the pre statement block in front of the ForLoop.
+ * Requirements:
+ * - The Disambiguator must be run upfront.
+ */
+class ForLoopInitRewriter: public ASTModifier
+{
+public:
+	using ASTModifier::operator();
+	void operator()(Block& _block) override;
+};
+
+}
+}

libyul/optimiser/Suite.cpp

@@ -27,6 +27,7 @@
 #include <libyul/optimiser/ExpressionJoiner.h>
 #include <libyul/optimiser/ExpressionInliner.h>
 #include <libyul/optimiser/FullInliner.h>
+#include <libyul/optimiser/ForLoopInitRewriter.h>
 #include <libyul/optimiser/Rematerialiser.h>
 #include <libyul/optimiser/UnusedPruner.h>
 #include <libyul/optimiser/ExpressionSimplifier.h>
@@ -58,6 +59,7 @@ void OptimiserSuite::run(
 
 	(FunctionHoister{})(ast);
 	(FunctionGrouper{})(ast);
+	(ForLoopInitRewriter{})(ast);
 
 	NameDispenser dispenser{ast};