Method overflowCheckedIntSubFunction

libsolidity/codegen/YulUtilFunctions.cpp:922–964

}

std::string YulUtilFunctions::overflowCheckedIntSubFunction(IntegerType const& _type)
{
	std::string functionName = "checked_sub_" + _type.identifier();
	return m_functionCollector.createFunction(functionName, [&] {
		return
			Whiskers(R"(
			function <functionName>(x, y) -> diff {
				x := <cleanupFunction>(x)
				y := <cleanupFunction>(y)
				diff := sub(x, y)
				<?signed>
					<?256bit>
						// underflow, if y >= 0 and diff > x
						// overflow, if y < 0 and diff < x
						if or(
							and(iszero(slt(y, 0)), sgt(diff, x)),
							and(slt(y, 0), slt(diff, x))
						) { <panic>() }
					<!256bit>
						if or(
							slt(diff, <minValue>),
							sgt(diff, <maxValue>)
						) { <panic>() }
					</256bit>
				<!signed>
					<?256bit>
						if gt(diff, x) { <panic>() }
					<!256bit>
						if gt(diff, <maxValue>) { <panic>() }
					</256bit>
				</signed>
			}
			)")
			("functionName", functionName)
			("signed", _type.isSigned())
			("maxValue", toCompactHexWithPrefix(u256(_type.maxValue())))
			("minValue", toCompactHexWithPrefix(u256(_type.minValue())))
			("cleanupFunction", cleanupFunction(_type))
			("panic", panicFunction(PanicCode::UnderOverflow))
			("256bit", _type.numBits() == 256)
			.render();
	});
}

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