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Optimize across MLOAD if MSIZE is not used.

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This commit is contained in:
chriseth
2018-04-03 14:34:32 +02:00
parent d21382157c
commit 6777f7a57f
10 changed files with 87 additions and 35 deletions
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libsolidity/codegen/ExpressionCompiler.cpp
+4 -17
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@@ -850,8 +850,6 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
}
case FunctionType::Kind::ObjectCreation:
{
// Will allocate at the end of memory (MSIZE) and not write at all unless the base
// type is dynamically sized.
ArrayType const& arrayType = dynamic_cast<ArrayType const&>(*_functionCall.annotation().type);
_functionCall.expression().accept(*this);
solAssert(arguments.size() == 1, "");
@@ -861,15 +859,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
utils().convertType(*arguments[0]->annotation().type, IntegerType(256));
// Stack: requested_length
// Allocate at max(MSIZE, freeMemoryPointer)
utils().fetchFreeMemoryPointer();
m_context << Instruction::DUP1 << Instruction::MSIZE;
m_context << Instruction::LT;
auto initialise = m_context.appendConditionalJump();
// Free memory pointer does not point to empty memory, use MSIZE.
m_context << Instruction::POP;
m_context << Instruction::MSIZE;
m_context << initialise;
// Stack: requested_length memptr
m_context << Instruction::SWAP1;
@@ -894,13 +884,10 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
// Check if length is zero
m_context << Instruction::DUP1 << Instruction::ISZERO;
auto skipInit = m_context.appendConditionalJump();
// We only have to initialise if the base type is a not a value type.
if (dynamic_cast<ReferenceType const*>(arrayType.baseType().get()))
{
m_context << Instruction::DUP2 << u256(32) << Instruction::ADD;
utils().zeroInitialiseMemoryArray(arrayType);
}
// Always initialize because the free memory pointer might point at
// a dirty memory area.
m_context << Instruction::DUP2 << u256(32) << Instruction::ADD;
utils().zeroInitialiseMemoryArray(arrayType);
m_context << skipInit;
m_context << Instruction::POP;
break;