cerc-io/solidity
16
0
Fork 0
mirror of https://github.com/ethereum/solidity synced 2023-10-03 13:03:40 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Merge pull request #5649 from ethereum/returnsAreZero

Browse Source 
[Yul] Consider return variables to be zero initially.
This commit is contained in:
chriseth 2018-12-13 16:46:48 +01:00 committed by GitHub
commit 633dd44576
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 79 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
libyul/optimiser/DataFlowAnalyzer.cpp
View File

@ -96,7 +96,10 @@ void DataFlowAnalyzer::operator()(FunctionDefinition& _fun)
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);
handleAssignment({var.name}, nullptr);
}
ASTModifier::operator()(_fun);
popScope();

13
libyul/optimiser/SSAValueTracker.cpp
View File

@ -33,12 +33,18 @@ void SSAValueTracker::operator()(Assignment const& _assignment)
m_values.erase(var.name);
}
void SSAValueTracker::operator()(FunctionDefinition const& _funDef)
{
for (auto const& var: _funDef.returnVariables)
setValue(var.name, nullptr);
ASTWalker::operator()(_funDef);
}
void SSAValueTracker::operator()(VariableDeclaration const& _varDecl)
{
static Expression const zero{Literal{{}, LiteralKind::Number, YulString{"0"}, {}}};
if (!_varDecl.value)
for (auto const& var: _varDecl.variables)
setValue(var.name, &zero);
setValue(var.name, nullptr);
else if (_varDecl.variables.size() == 1)
setValue(_varDecl.variables.front().name, _varDecl.value.get());
}
@ -50,5 +56,8 @@ void SSAValueTracker::setValue(YulString _name, Expression const* _value)
OptimizerException,
"Source needs to be disambiguated."
);
static Expression const zero{Literal{{}, LiteralKind::Number, YulString{"0"}, {}}};
if (!_value)
_value = &zero;
m_values[_name] = _value;
}

1
libyul/optimiser/SSAValueTracker.h
View File

@ -41,6 +41,7 @@ class SSAValueTracker: public ASTWalker
{
public:
using ASTWalker::operator();
void operator()(FunctionDefinition const& _funDef) override;
void operator()(VariableDeclaration const& _varDecl) override;
void operator()(Assignment const& _assignment) override;

23
test/libyul/yulOptimizerTests/commonSubexpressionEliminator/unassigned_return.yul Normal file
View File

@ -0,0 +1,23 @@
{
function f() -> x {
// can re-use x
let y := 0
mstore(y, 7)
}
let a
// can re-use a
let b := 0
sstore(a, b)
}
// ----
// commonSubexpressionEliminator
// {
// function f() -> x
// {
// let y := x
// mstore(x, 7)
// }
// let a
// let b := a
// sstore(a, a)
// }

14
test/libyul/yulOptimizerTests/expressionSimplifier/return_vars_zero.yul Normal file
View File

@ -0,0 +1,14 @@
// return variables are assumed to be zero initially.
{
function f() -> c, d {
let y := add(d, add(c, 7))
}
}
// ----
// expressionSimplifier
// {
// function f() -> c, d
// {
// let y := 7
// }
// }

61
test/libyul/yulOptimizerTests/fullSuite/abi_example1.yul
View File

@ -463,11 +463,12 @@
// let _2 := 0
// let _485 := mload(_2)
// let abi_encode_pos := _1
// let abi_encode_end_67_610
// let abi_encode_length_68 := mload(_485)
// mstore(_1, abi_encode_length_68)
// abi_encode_pos := 64
// let abi_encode_srcPtr := add(_485, _1)
// let abi_encode_i_69 := _2
// let abi_encode_i_69 := abi_encode_end_67_610
// for {
// }
// lt(abi_encode_i_69, abi_encode_length_68)
@ -475,21 +476,21 @@
// abi_encode_i_69 := add(abi_encode_i_69, 1)
// }
// {
// let _854 := mload(abi_encode_srcPtr)
// let abi_encode_pos_71_961 := abi_encode_pos
// let abi_encode_length_72_962 := 0x3
// let abi_encode_srcPtr_73_963 := _854
// let abi_encode_i_74_964 := _2
// let _857 := mload(abi_encode_srcPtr)
// let abi_encode_pos_71_965 := abi_encode_pos
// let abi_encode_length_72_966 := 0x3
// let abi_encode_srcPtr_73_967 := _857
// let abi_encode_i_74_968 := _2
// for {
// }
// lt(abi_encode_i_74_964, abi_encode_length_72_962)
// lt(abi_encode_i_74_968, abi_encode_length_72_966)
// {
// abi_encode_i_74_964 := add(abi_encode_i_74_964, 1)
// abi_encode_i_74_968 := add(abi_encode_i_74_968, 1)
// }
// {
// mstore(abi_encode_pos_71_961, and(mload(abi_encode_srcPtr_73_963), 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF))
// abi_encode_srcPtr_73_963 := add(abi_encode_srcPtr_73_963, _1)
// abi_encode_pos_71_961 := add(abi_encode_pos_71_961, _1)
// mstore(abi_encode_pos_71_965, and(mload(abi_encode_srcPtr_73_967), 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF))
// abi_encode_srcPtr_73_967 := add(abi_encode_srcPtr_73_967, _1)
// abi_encode_pos_71_965 := add(abi_encode_pos_71_965, _1)
// }
// abi_encode_srcPtr := add(abi_encode_srcPtr, _1)
// abi_encode_pos := add(abi_encode_pos, 0x60)
@ -503,8 +504,7 @@
// {
// if iszero(slt(add(offset_3, 0x1f), end_4))
// {
// let _33 := 0
// revert(_33, _33)
// revert(array_5, array_5)
// }
// let length_6 := calldataload(offset_3)
// let array_5_254 := allocateMemory(array_allocation_size_t_array$_t_array$_t_uint256_$2_memory_$dyn_memory_ptr(length_6))
@ -538,17 +538,16 @@
// {
// if iszero(slt(add(offset_11, 0x1f), end_12))
// {
// let _52 := 0
// revert(_52, _52)
// revert(array_13, array_13)
// }
// let length_14 := 0x2
// let array_allo__558 := 0x20
// let array_allo_size_95_604 := 64
// let array_13_263 := allocateMemory(array_allo_size_95_604)
// let array_allo__559 := 0x20
// let array_allo_size_95_605 := 64
// let array_13_263 := allocateMemory(array_allo_size_95_605)
// array_13 := array_13_263
// let dst_15 := array_13_263
// let src_16 := offset_11
// if gt(add(offset_11, array_allo_size_95_604), end_12)
// if gt(add(offset_11, array_allo_size_95_605), end_12)
// {
// let _59 := 0
// revert(_59, _59)
@ -562,16 +561,15 @@
// }
// {
// mstore(dst_15, calldataload(src_16))
// dst_15 := add(dst_15, array_allo__558)
// src_16 := add(src_16, array_allo__558)
// dst_15 := add(dst_15, array_allo__559)
// src_16 := add(src_16, array_allo__559)
// }
// }
// function abi_decode_t_array$_t_uint256_$dyn_memory_ptr(offset_27, end_28) -> array_29
// {
// if iszero(slt(add(offset_27, 0x1f), end_28))
// {
// let _88 := 0
// revert(_88, _88)
// revert(array_29, array_29)
// }
// let length_30 := calldataload(offset_27)
// let array_29_279 := allocateMemory(array_allocation_size_t_array$_t_uint256_$dyn_memory_ptr(length_30))
@ -604,11 +602,10 @@
// {
// if slt(sub(dataEnd_59, headStart_58), 128)
// {
// let _159 := 0
// revert(_159, _159)
// revert(value2, value2)
// }
// {
// value0_60 := calldataload(headStart_58)
// value0_60 := calldataload(add(headStart_58, value2))
// }
// {
// value1_61 := calldataload(add(headStart_58, 32))
@ -617,8 +614,7 @@
// let offset_64 := calldataload(add(headStart_58, 64))
// if gt(offset_64, 0xffffffffffffffff)
// {
// let _167 := 0
// revert(_167, _167)
// revert(value2, value2)
// }
// value2 := abi_decode_t_array$_t_uint256_$dyn_memory_ptr(add(headStart_58, offset_64), dataEnd_59)
// }
@ -626,8 +622,7 @@
// let offset_65 := calldataload(add(headStart_58, 96))
// if gt(offset_65, 0xffffffffffffffff)
// {
// let _174 := 0
// revert(_174, _174)
// revert(value3, value3)
// }
// value3 := abi_decode_t_array$_t_array$_t_uint256_$2_memory_$dyn_memory_ptr(add(headStart_58, offset_65), dataEnd_59)
// }
@ -649,8 +644,7 @@
// {
// if gt(length_92, 0xffffffffffffffff)
// {
// let _215 := 0
// revert(_215, _215)
// revert(size_93, size_93)
// }
// let _217 := 0x20
// size_93 := add(mul(length_92, _217), _217)
@ -659,8 +653,7 @@
// {
// if gt(length_98, 0xffffffffffffffff)
// {
// let _232 := 0
// revert(_232, _232)
// revert(size_99, size_99)
// }
// let _234 := 0x20
// size_99 := add(mul(length_98, _234), _234)