Merge pull request #5325 from ethereum/fixDataFlow

[Yul] Fix data flow analyzer for function definitions.

libyul/optimiser/DataFlowAnalyzer.cpp

@@ -84,13 +84,26 @@ void DataFlowAnalyzer::operator()(Switch& _switch)
 
 void DataFlowAnalyzer::operator()(FunctionDefinition& _fun)
 {
+	// Save all information. We might rather reinstantiate this class,
+	// but this could be difficult if it is subclassed.
+	map<YulString, Expression const*> value;
+	map<YulString, set<YulString>> references;
+	map<YulString, set<YulString>> referencedBy;
+	m_value.swap(value);
+	m_references.swap(references);
+	m_referencedBy.swap(referencedBy);
 	pushScope(true);
+
 	for (auto const& parameter: _fun.parameters)
 		m_variableScopes.back().variables.emplace(parameter.name);
 	for (auto const& var: _fun.returnVariables)
 		m_variableScopes.back().variables.emplace(var.name);
 	ASTModifier::operator()(_fun);
+
 	popScope();
+	m_value.swap(value);
+	m_references.swap(references);
+	m_referencedBy.swap(referencedBy);
 }
 
 void DataFlowAnalyzer::operator()(ForLoop& _for)

test/libyul/yulOptimizerTests/commonSubexpressionEliminator/case2.yul

@@ -0,0 +1,52 @@
+{
+    let _13 := 0x20
+    let _14 := allocate(_13)
+    pop(_14)
+    let _15 := 2
+    let _16 := 3
+    let _17 := 0x40
+    let _18 := allocate(_17)
+    let _19 := array_index_access(_18, _16)
+    mstore(_19, _15)
+    function allocate(size) -> p
+    {
+        let _1 := 0x40
+        let p_2 := mload(_1)
+        p := p_2
+        let _20 := add(p_2, size)
+        mstore(_1, _20)
+    }
+    function array_index_access(array, index) -> p_1
+    {
+        let _21 := 0x20
+        let _22 := mul(index, _21)
+        p_1 := add(array, _22)
+    }
+}
+// ----
+// commonSubexpressionEliminator
+// {
+//     let _13 := 0x20
+//     let _14 := allocate(_13)
+//     pop(_14)
+//     let _15 := 2
+//     let _16 := 3
+//     let _17 := 0x40
+//     let _18 := allocate(_17)
+//     let _19 := array_index_access(_18, _16)
+//     mstore(_19, _15)
+//     function allocate(size) -> p
+//     {
+//         let _1 := 0x40
+//         let p_2 := mload(_1)
+//         p := p_2
+//         let _20 := add(p_2, size)
+//         mstore(_1, _20)
+//     }
+//     function array_index_access(array, index) -> p_1
+//     {
+//         let _21 := 0x20
+//         let _22 := mul(index, _21)
+//         p_1 := add(array, _22)
+//     }
+// }

test/libyul/yulOptimizerTests/commonSubexpressionEliminator/function_scopes.yul

@@ -0,0 +1,52 @@
+{
+    function allocate(size) -> p
+    {
+        let _1 := 0x40
+        p := mload(_1)
+        let _2 := add(p, size)
+        let _3 := 0x40
+        mstore(_3, _2)
+    }
+    function array_index_access(array, index) -> p_1
+    {
+        let _4 := 0x20
+        let _5 := mul(index, _4)
+        p_1 := add(array, _5)
+    }
+    let _6 := 0x20
+    let _7 := allocate(_6)
+    pop(_7)
+    let _8 := 0x40
+    let x := allocate(_8)
+    let _9 := 2
+    let _10 := 3
+    let _11 := array_index_access(x, _10)
+    mstore(_11, _9)
+}
+// ----
+// commonSubexpressionEliminator
+// {
+//     function allocate(size) -> p
+//     {
+//         let _1 := 0x40
+//         p := mload(_1)
+//         let _2 := add(p, size)
+//         let _3 := _1
+//         mstore(_1, _2)
+//     }
+//     function array_index_access(array, index) -> p_1
+//     {
+//         let _4 := 0x20
+//         let _5 := mul(index, _4)
+//         p_1 := add(array, _5)
+//     }
+//     let _6 := 0x20
+//     let _7 := allocate(_6)
+//     pop(_7)
+//     let _8 := 0x40
+//     let x := allocate(_8)
+//     let _9 := 2
+//     let _10 := 3
+//     let _11 := array_index_access(x, _10)
+//     mstore(_11, _9)
+// }