15 lines
1.3 KiB
TeX
15 lines
1.3 KiB
TeX
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% Problems and solutions. Summary of problems you encountered and how you solved them (max. two
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% pages).
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\subsection{Function calls within parameters}
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Each function call requires an AR. When new ARs are allocated at a static offset relative to the current AR, this may lead to problems with function calls of the form \verb|f(g(h))| or \verb|f(a, g(h))|: the AR of \verb|f| must not be overwritten during the call to \verb|g|. There are multiple solutions to this problem:
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\begin{enumerate}
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\item dynamically allocating the AR (requires a dynamic allocator)
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\item generating different offsets for nested function calls (e.g. the AR of \verb|h| in \verb|f(g(h()))| must be allocated at \verb|ARP+f_AR+g_AR|)
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\item allocating the AR after evaluating its parameters (requires a temporary storage for the parameters)
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\end{enumerate}
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The third option was chosen, namely by pushing each parameter value to the stack, then allocating the AR for the outer function call and popping the values into it.
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\subsection{Register saves}
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When calling a function, some registers must be saved by the caller or callee in order to not lose their value when executing the callee. The choice was made to use caller-saves and to keep track of all the registers that are required for future instructions.
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