Make Yul optimizer not fail for wasm.

2023-10-03 13:03:40 +00:00 · 2019-06-17 18:42:47 +02:00
parent 8260ae1397
commit 6cb6fe35ef
17 changed files with 321 additions and 210 deletions
@@ -0,0 +1,108 @@
+/*
+	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 replaces constants by expressions that compute them.
+ */
+
+#pragma once
+
+#include <libyul/optimiser/ASTWalker.h>
+#include <libyul/YulString.h>
+#include <libyul/Dialect.h>
+#include <libyul/backends/evm/EVMDialect.h>
+#include <libyul/AsmData.h>
+
+#include <liblangutil/SourceLocation.h>
+
+#include <libdevcore/Common.h>
+
+#include <tuple>
+#include <map>
+#include <memory>
+
+namespace yul
+{
+struct Dialect;
+class GasMeter;
+
+/**
+ * Optimisation stage that replaces constants by expressions that compute them.
+ *
+ * Prerequisite: None
+ */
+class ConstantOptimiser: public ASTModifier
+{
+public:
+	ConstantOptimiser(EVMDialect const& _dialect, GasMeter const& _meter):
+		m_dialect(_dialect),
+		m_meter(_meter)
+	{}
+
+	void visit(Expression& _e) override;
+
+	struct Representation
+	{
+		std::unique_ptr<Expression> expression;
+		size_t cost = size_t(-1);
+	};
+
+private:
+	EVMDialect const& m_dialect;
+	GasMeter const& m_meter;
+	std::map<dev::u256, Representation> m_cache;
+};
+
+class RepresentationFinder
+{
+public:
+	using Representation = ConstantOptimiser::Representation;
+	RepresentationFinder(
+		EVMDialect const& _dialect,
+		GasMeter const& _meter,
+		langutil::SourceLocation _location,
+		std::map<dev::u256, Representation>& _cache
+	):
+		m_dialect(_dialect),
+		m_meter(_meter),
+		m_location(std::move(_location)),
+		m_cache(_cache)
+	{}
+
+	/// @returns a cheaper representation for the number than its representation
+	/// as a literal or nullptr otherwise.
+	Expression const* tryFindRepresentation(dev::u256 const& _value);
+
+private:
+	/// Recursively try to find the cheapest representation of the given number,
+	/// literal if necessary.
+	Representation const& findRepresentation(dev::u256 const& _value);
+
+	Representation represent(dev::u256 const& _value) const;
+	Representation represent(YulString _instruction, Representation const& _arg) const;
+	Representation represent(YulString _instruction, Representation const& _arg1, Representation const& _arg2) const;
+
+	Representation min(Representation _a, Representation _b);
+
+	EVMDialect const& m_dialect;
+	GasMeter const& m_meter;
+	langutil::SourceLocation m_location;
+	/// Counter for the complexity of optimization, will stop when it reaches zero.
+	size_t m_maxSteps = 10000;
+	std::map<dev::u256, Representation>& m_cache;
+};
+
+}