Method overflowCheckedIntMulFunction

libsolidity/codegen/YulUtilFunctions.cpp:780–832

}

std::string YulUtilFunctions::overflowCheckedIntMulFunction(IntegerType const& _type)
{
	std::string functionName = "checked_mul_" + _type.identifier();
	return m_functionCollector.createFunction(functionName, [&]() {
		return
			// Multiplication by zero could be treated separately and directly return zero.
			Whiskers(R"(
			function <functionName>(x, y) -> product {
				x := <cleanupFunction>(x)
				y := <cleanupFunction>(y)
				let product_raw := mul(x, y)
				product := <cleanupFunction>(product_raw)
				<?signed>
					<?gt128bit>
						<?256bit>
							// special case
							if and(slt(x, 0), eq(y, <minValue>)) { <panic>() }
						</256bit>
						// overflow, if x != 0 and y != product/x
						if iszero(
							or(
								iszero(x),
								eq(y, sdiv(product, x))
							)
						) { <panic>() }
					<!gt128bit>
						if iszero(eq(product, product_raw)) { <panic>() }
					</gt128bit>
				<!signed>
					<?gt128bit>
						// overflow, if x != 0 and y != product/x
						if iszero(
							or(
								iszero(x),
								eq(y, div(product, x))
							)
						) { <panic>() }
					<!gt128bit>
						if iszero(eq(product, product_raw)) { <panic>() }
					</gt128bit>
				</signed>
			}
			)")
			("functionName", functionName)
			("signed", _type.isSigned())
			("cleanupFunction", cleanupFunction(_type))
			("panic", panicFunction(PanicCode::UnderOverflow))
			("minValue", toCompactHexWithPrefix(u256(_type.minValue())))
			("256bit", _type.numBits() == 256)
			("gt128bit", _type.numBits() > 128)
			.render();
	});
}

std::string YulUtilFunctions::wrappingIntMulFunction(IntegerType const& _type)
{