diff options
10 files changed, 65 insertions, 13 deletions
diff --git a/libyul/optimiser/DataFlowAnalyzer.cpp b/libyul/optimiser/DataFlowAnalyzer.cpp index 64c67b38..7bff2c89 100644 --- a/libyul/optimiser/DataFlowAnalyzer.cpp +++ b/libyul/optimiser/DataFlowAnalyzer.cpp @@ -136,17 +136,22 @@ void DataFlowAnalyzer::operator()(Block& _block) void DataFlowAnalyzer::handleAssignment(set<YulString> const& _variables, Expression* _value) { + static Expression const zero{Literal{{}, LiteralKind::Number, YulString{"0"}, {}}}; clearValues(_variables); MovableChecker movableChecker; if (_value) movableChecker.visit(*_value); - if (_variables.size() == 1) + else + for (auto const& var: _variables) + m_value[var] = &zero; + + if (_value && _variables.size() == 1) { YulString name = *_variables.begin(); // Expression has to be movable and cannot contain a reference // to the variable that will be assigned to. - if (_value && movableChecker.movable() && !movableChecker.referencedVariables().count(name)) + if (movableChecker.movable() && !movableChecker.referencedVariables().count(name)) m_value[name] = _value; } diff --git a/libyul/optimiser/DataFlowAnalyzer.h b/libyul/optimiser/DataFlowAnalyzer.h index cd134d48..4f12ff6a 100644 --- a/libyul/optimiser/DataFlowAnalyzer.h +++ b/libyul/optimiser/DataFlowAnalyzer.h @@ -36,6 +36,8 @@ namespace yul * Tracks assignments and is used as base class for both Rematerialiser and * Common Subexpression Eliminator. * + * A special zero constant expression is used for the default value of variables. + * * Prerequisite: Disambiguator */ class DataFlowAnalyzer: public ASTModifier diff --git a/libyul/optimiser/SSAValueTracker.cpp b/libyul/optimiser/SSAValueTracker.cpp index ef96c379..a0e44b2b 100644 --- a/libyul/optimiser/SSAValueTracker.cpp +++ b/libyul/optimiser/SSAValueTracker.cpp @@ -35,11 +35,12 @@ void SSAValueTracker::operator()(Assignment const& _assignment) void SSAValueTracker::operator()(VariableDeclaration const& _varDecl) { - if (_varDecl.variables.size() == 1) - setValue(_varDecl.variables.front().name, _varDecl.value.get()); - else if (!_varDecl.value) + static Expression const zero{Literal{{}, LiteralKind::Number, YulString{"0"}, {}}}; + if (!_varDecl.value) for (auto const& var: _varDecl.variables) - setValue(var.name, nullptr); + setValue(var.name, &zero); + else if (_varDecl.variables.size() == 1) + setValue(_varDecl.variables.front().name, _varDecl.value.get()); } void SSAValueTracker::setValue(YulString _name, Expression const* _value) diff --git a/libyul/optimiser/SSAValueTracker.h b/libyul/optimiser/SSAValueTracker.h index efec2200..0a6cde80 100644 --- a/libyul/optimiser/SSAValueTracker.h +++ b/libyul/optimiser/SSAValueTracker.h @@ -33,7 +33,7 @@ namespace yul * Class that walks the AST and stores the initial value of each variable * that is never assigned to. * - * Default value is represented as nullptr. + * A special zero constant expression is used for the default value of variables. * * Prerequisite: Disambiguator */ diff --git a/test/libyul/yulOptimizerTests/commonSubexpressionEliminator/unassigned_variables.yul b/test/libyul/yulOptimizerTests/commonSubexpressionEliminator/unassigned_variables.yul new file mode 100644 index 00000000..a790ca65 --- /dev/null +++ b/test/libyul/yulOptimizerTests/commonSubexpressionEliminator/unassigned_variables.yul @@ -0,0 +1,14 @@ +{ + // This does not replace b by a because there is no + // explicit assignment, even though both hold the same value. + let a + let b + mstore(sub(a, b), 7) +} +// ---- +// commonSubexpressionEliminator +// { +// let a +// let b +// mstore(sub(a, b), 7) +// } diff --git a/test/libyul/yulOptimizerTests/expressionSimplifier/unassigend_vars_multi.yul b/test/libyul/yulOptimizerTests/expressionSimplifier/unassigend_vars_multi.yul index 8c1ad789..f260db0b 100644 --- a/test/libyul/yulOptimizerTests/expressionSimplifier/unassigend_vars_multi.yul +++ b/test/libyul/yulOptimizerTests/expressionSimplifier/unassigend_vars_multi.yul @@ -1,5 +1,4 @@ -// c & d can't be optimized as expression simplifier doesn't handle default -// values yet +// Unassigned variables are assumed to be zero. { let c, d let y := add(d, add(c, 7)) @@ -8,5 +7,5 @@ // expressionSimplifier // { // let c, d -// let y := add(add(d, c), 7) +// let y := 7 // } diff --git a/test/libyul/yulOptimizerTests/expressionSimplifier/unassigned_vars.yul b/test/libyul/yulOptimizerTests/expressionSimplifier/unassigned_vars.yul index 87391b8c..7b1430f3 100644 --- a/test/libyul/yulOptimizerTests/expressionSimplifier/unassigned_vars.yul +++ b/test/libyul/yulOptimizerTests/expressionSimplifier/unassigned_vars.yul @@ -1,5 +1,4 @@ -// c & d can't be optimized as expression simplifier doesn't handle default -// values yet +// Unassigned variables are assumed to be zero. { let c let d @@ -10,5 +9,5 @@ // { // let c // let d -// let y := add(add(d, c), 7) +// let y := 7 // } diff --git a/test/libyul/yulOptimizerTests/fullInliner/large_function_multi_use.yul b/test/libyul/yulOptimizerTests/fullInliner/large_function_multi_use.yul index 0972ac56..ec44dafb 100644 --- a/test/libyul/yulOptimizerTests/fullInliner/large_function_multi_use.yul +++ b/test/libyul/yulOptimizerTests/fullInliner/large_function_multi_use.yul @@ -13,6 +13,9 @@ let r := f(a) // This should be inlined because it is a constant let t := f(a2) + let a3 + // This should be inlined because it is a constant as well (zero) + let s := f(a3) } // ---- // fullInliner @@ -30,6 +33,16 @@ // let f_y := add(f_a, f_x) // sstore(f_y, 10) // let t := f_b +// let a3 +// let f_a_5 := a3 +// let f_b_6 +// let f_x_7 := mload(f_a_5) +// f_b_6 := sload(f_x_7) +// let f_c_8 := 3 +// mstore(mul(f_a_5, f_b_6), mload(f_x_7)) +// let f_y_11 := add(f_a_5, f_x_7) +// sstore(f_y_11, 10) +// let s := f_b_6 // } // function f(a) -> b // { diff --git a/test/libyul/yulOptimizerTests/structuralSimplifier/if_multi_unassigned_condition.yul b/test/libyul/yulOptimizerTests/structuralSimplifier/if_multi_unassigned_condition.yul new file mode 100644 index 00000000..0ece5dbd --- /dev/null +++ b/test/libyul/yulOptimizerTests/structuralSimplifier/if_multi_unassigned_condition.yul @@ -0,0 +1,10 @@ +{ + let x, y + if x { mstore(0, 0) } + if y { mstore(0, 0) } +} +// ---- +// structuralSimplifier +// { +// let x, y +// } diff --git a/test/libyul/yulOptimizerTests/structuralSimplifier/if_unassigned_condition.yul b/test/libyul/yulOptimizerTests/structuralSimplifier/if_unassigned_condition.yul new file mode 100644 index 00000000..a327a882 --- /dev/null +++ b/test/libyul/yulOptimizerTests/structuralSimplifier/if_unassigned_condition.yul @@ -0,0 +1,9 @@ +{ + let x + if x { mstore(0, 0) } +} +// ---- +// structuralSimplifier +// { +// let x +// } |