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[SPCA] more assembly

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RobinB27
2026-01-10 19:57:50 +01:00
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6 changed files with 37 additions and 2 deletions
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semester3/spca/parts/00_asm/03_operations.tex
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\subsection{Operations}
Assembly operations include performing arithmetic or logic functions on registers or memory data,
transferring data between memory and registers and transferring control (conditional or unconditional jumps)
transferring data between memory and registers and transferring control (conditional or unconditional jumps).\\
Note that \verb|move| instructions \textit{cannot} move data directly from memory to memory.
Most of the memory-related instructions in \texttt{x86} assembly have the format
\mint{asm}|movq dest, src|
whereas arithmetic / logic operations have the format inversed (below \texttt{X} is to be replced with size postfix).
Arithmetic / logic operations have the format inversed (below \texttt{X} is to be replced with size postfix).
\begin{tables}{lll}{Mnemonic & Format & Computation}
\texttt{addl} & \texttt{Src, Dest} & \texttt{Dest} $\gets$ \texttt{Dest + Src} \\
\texttt{subX} & \texttt{Src, Dest} & \texttt{Dest} $\gets$ \texttt{Dest - Src} \\

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semester3/spca/parts/00_asm/04_control-flow.tex Normal file
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\newpage
\subsection{Control Flow}
Control flow structures from \verb|C| like \verb|if/else| or \verb|for| are compiled into assembly mainly using jumps and conditional \verb|move|.
By the nature of Assembly and thanks to compilers optimizing aggressively, there is no \textit{single} definitive translation of the \verb|C| control structures: The compiler may translate it very differently depending on the context of the program.
\subsubsection{Conditional statements}
A function using an \verb|if/else| construct to choose the maximum of $2$ numbers might compile like this:
\inputcodewithfilename{gas}{code-examples/01_asm/}{02_max.s}
A function computing the absolute difference $|x-y|$ using an \verb|if/else| construct, might use a conditional \verb|move| instead:
\inputcodewithfilename{gas}{code-examples/01_asm/}{03_absdiff.s}