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Merge pull request #6197 from ethereum/yul-opt-switch-rem-6189

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YulOpt: Remove empty cases
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chriseth 2019-03-06 18:40:04 +01:00 committed by GitHub
commit 08146c76c9
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5 changed files with 94 additions and 5 deletions
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32
libyul/optimiser/StructuralSimplifier.cpp
View File

@ -21,6 +21,9 @@
#include <libdevcore/CommonData.h>
#include <libdevcore/Visitor.h>
#include <boost/range/algorithm_ext/erase.hpp>
#include <boost/range/algorithm/find_if.hpp>
using namespace std;
using namespace dev;
using namespace yul;
@ -83,9 +86,11 @@ void StructuralSimplifier::simplify(std::vector<yul::Statement>& _statements)
return {};
},
[&](Switch& _switchStmt) -> OptionalStatements {
if (_switchStmt.cases.size() == 1)
auto& cases = _switchStmt.cases;
if (cases.size() == 1)
{
auto& switchCase = _switchStmt.cases.front();
auto& switchCase = cases.front();
auto loc = locationOf(*_switchStmt.expression);
if (switchCase.value)
{
@ -107,12 +112,14 @@ void StructuralSimplifier::simplify(std::vector<yul::Statement>& _statements)
return s;
}
}
// Replace the whole switch with the resulting case body if arg. is
// a constant
else if (boost::optional<u256> const constExprVal = hasLiteralValue(*_switchStmt.expression))
{
Block* matchingCaseBlock = nullptr;
Case* defaultCase = nullptr;
for (auto& _case: _switchStmt.cases)
for (auto& _case: cases)
{
if (_case.value && valueOfLiteral(*_case.value) == constExprVal)
{
@ -133,8 +140,23 @@ void StructuralSimplifier::simplify(std::vector<yul::Statement>& _statements)
return s;
}
else
return {};
// Remove cases with empty body if no default case exists
auto const defaultCase = boost::find_if(
cases,
[](Case const& _case) { return !_case.value; });
if (
(defaultCase != cases.end() &&
defaultCase->body.statements.empty()) ||
defaultCase == cases.end()
)
boost::remove_erase_if(
cases,
[](Case const& _case) { return _case.body.statements.empty(); }
);
return {};
},
[&](ForLoop& _forLoop) -> OptionalStatements {
if (expressionAlwaysFalse(*_forLoop.condition))

21
test/libyul/yulOptimizerTests/structuralSimplifier/switch_no_remove_empty_case.yul Normal file
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@ -0,0 +1,21 @@
{
let y := 200
switch y
case 0 { }
case 1 { y := 9 }
default { y := 100 }
}
// ----
// structuralSimplifier
// {
// let y := 200
// switch y
// case 0 {
// }
// case 1 {
// y := 9
// }
// default {
// y := 100
// }
// }

15
test/libyul/yulOptimizerTests/structuralSimplifier/switch_remove_empty_case.yul Normal file
View File

@ -0,0 +1,15 @@
{
let y := 200
switch y
case 0 { }
case 1 { y := 9 }
}
// ----
// structuralSimplifier
// {
// let y := 200
// switch y
// case 1 {
// y := 9
// }
// }

16
test/libyul/yulOptimizerTests/structuralSimplifier/switch_remove_empty_cases.yul Normal file
View File

@ -0,0 +1,16 @@
{
let y := 200
switch y
case 0 { }
case 1 { y := 9 }
default { }
}
// ----
// structuralSimplifier
// {
// let y := 200
// switch y
// case 1 {
// y := 9
// }
// }

15
test/libyul/yulOptimizerTests/structuralSimplifier/switch_remove_empty_default_case.yul Normal file
View File

@ -0,0 +1,15 @@
{
let y := 200
switch y
case 1 { y := 9 }
default { }
}
// ----
// structuralSimplifier
// {
// let y := 200
// switch y
// case 1 {
// y := 9
// }
// }