Common subexpression eliminator.

2 files changed, 93 insertions, 0 deletions

diff --git a/libjulia/optimiser/CommonSubexpressionEliminator.cpp b/libjulia/optimiser/CommonSubexpressionEliminator.cpp
new file mode 100644
index 00000000..229bd35e
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+++ b/libjulia/optimiser/CommonSubexpressionEliminator.cpp
@@ -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/>.
+*/
+/**
+ * Optimisation stage that replaces expressions known to be the current value of a variable
+ * in scope by a reference to that variable.
+ */
+
+#include <libjulia/optimiser/CommonSubexpressionEliminator.h>
+
+#include <libjulia/optimiser/Metrics.h>
+#include <libjulia/optimiser/SyntacticalEquality.h>
+
+#include <libsolidity/inlineasm/AsmData.h>
+
+using namespace std;
+using namespace dev;
+using namespace dev::julia;
+
+void CommonSubexpressionEliminator::visit(Expression& _e)
+{
+	// Single exception for substitution: We do not substitute one variable for another.
+	if (_e.type() != typeid(Identifier))
+		// TODO this search rather inefficient.
+		for (auto const& var: m_value)
+		{
+			solAssert(var.second, "");
+			if (SyntacticalEqualityChecker::equal(_e, *var.second))
+			{
+				_e = Identifier{locationOf(_e), var.first};
+				break;
+			}
+		}
+	DataFlowAnalyzer::visit(_e);
+}
diff --git a/libjulia/optimiser/CommonSubexpressionEliminator.h b/libjulia/optimiser/CommonSubexpressionEliminator.h
new file mode 100644
index 00000000..a8ca3abb
--- /dev/null
+++ b/libjulia/optimiser/CommonSubexpressionEliminator.h
@@ -0,0 +1,45 @@
+/*
+	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 expressions known to be the current value of a variable
+ * in scope by a reference to that variable.
+ */
+
+#pragma once
+
+#include <libjulia/optimiser/DataFlowAnalyzer.h>
+
+namespace dev
+{
+namespace julia
+{
+
+/**
+ * Optimisation stage that replaces expressions known to be the current value of a variable
+ * in scope by a reference to that variable.
+ *
+ * Prerequisite: Disambiguator
+ */
+class CommonSubexpressionEliminator: public DataFlowAnalyzer
+{
+protected:
+	using ASTModifier::visit;
+	virtual void visit(Expression& _e) override;
+};
+
+}
+}