Skip to main content ☰ Contents Index You! < Prev ^ Up Next > \(\newcommand{\powerset}[1]{\mathcal{P}(#1)}
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Section C.6 M3: Function Calls
Synopsis.
Explain function call mechanism. jal and jr and the return address.
Mention the problem that we want to preserve values over calls (first and foremost the return address).
Such values have to be saved somewhere; registers may be overwritten by called function.
So we need a convention which registers are preserved and which can be overwritten.
Overwritten registers must be saved somewhere. Global data not possible because recursive calls would overwrite saved values.
Need call stack. Explain allocation/deallocation of stack frame, usage of stack pointer. Show how saving/restoring is done (relative addressing to stack pointer.)
Discuss recursion and tail recursion in this context. Live code factorial recursively and tail recursively. Step through program and show the difference.
Goal is to understand that recursion requires book keeping and has an overhead.
