The following lines of assembly code are not optimized, but they can be optimized very easily. Can you find a way to optimize these lines?
Callee clean-up
When the callee cleans the arguments from the stack it needs to be known at compile time how many bytes the stack needs to be adjusted. Therefore, these calling conventions are not compatible with variable argument lists, eg. printf(). They may be, however, slightly more efficient as the code needed to unwind the stack does not need to be generated by the calling code.
Caller clean-up
In these conventions the caller cleans the arguments from the stack, which allows for variable argument lists, eg. printf().
Duff’s device
The famous “Duff’s device” in C makes use of the fact that a case statement is still legal within a sub-block of its matching switch statement. Tom Duff used this for an optimised output loop. Duff’s device is an optimized implementation of a serial copy that uses a technique widely applied in assembly language for loop unwinding. It is perhaps the most dramatic use of case label fall-through in the C programming language to date.