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Access output memory area so that we do not pay for resize during call.

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chriseth
2016-09-17 11:29:54 +02:00
parent dd2f878e59
commit 5a45990458
2 changed files with 14 additions and 5 deletions
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libsolidity/codegen/ExpressionCompiler.cpp
+13 -4
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@@ -1476,6 +1476,18 @@ void ExpressionCompiler::appendExternalFunctionCall(
utils().storeFreeMemoryPointer();
}
// Touch the end of the output area so that we do not pay for memory resize during the call
// (which we would have to subtract from the gas left)
// We could also just use MLOAD; POP right before the gas calculation, but the optimizer
// would remove that, so we use MSTORE here.
if (!_functionType.gasSet() && retSize > 0)
{
m_context << u256(0);
utils().fetchFreeMemoryPointer();
// This touches too much, but that way we save some rounding arithmetics
m_context << u256(retSize) << Instruction::ADD << Instruction::MSTORE;
}
// Copy function identifier to memory.
utils().fetchFreeMemoryPointer();
if (!_functionType.isBareCall() || manualFunctionId)
@@ -1551,10 +1563,7 @@ void ExpressionCompiler::appendExternalFunctionCall(
gasNeededByCaller += eth::GasCosts::callValueTransferGas;
if (!isCallCode && !isDelegateCall && !existenceChecked)
gasNeededByCaller += eth::GasCosts::callNewAccountGas; // we never know
m_context <<
gasNeededByCaller <<
Instruction::GAS <<
Instruction::SUB;
m_context << gasNeededByCaller << Instruction::GAS << Instruction::SUB;
}
if (isDelegateCall)
m_context << Instruction::DELEGATECALL;