[SPCA] more assembly

semester3/spca/code-examples/01_asm/04_factorial.s

@@ -0,0 +1,8 @@
+factorial:
+    movl  $1, %eax      # Setup
+.AGAIN:
+    imull %edi, %eax    # %eax *= %edi
+    subl  $1, %edi      # %edi--
+    cmpl  $1, %edi      # 1 < %edi ?
+    jg    .AGAIN        # go back, if yes
+    ret

semester3/spca/code-examples/01_asm/05_factorial.s

@@ -0,0 +1,9 @@
+factorial:
+    jmp .COMP           # Check condition
+.LOOP: 
+    imull %edx, %eax    # %eax *= %edx
+    decl %edx           # %edx--
+.COMP:
+    cmpl $1, %edx       # 1 < %edx ?
+    jg .LOOP            # if yes, go to loop
+    ret

semester3/spca/parts/00_asm/03_operations.tex

@@ -25,7 +25,7 @@ Arithmetic / logic operations need a size postfix (replace \texttt{X} below with
 \end{tables}
 
 \newpage
-\subsubsection{Condition Codes and jumping}
+\subsubsection{Condition Codes}
 Any arithmetic operation (that is truly part of the arithmetic operations group, so not including \texttt{lea} for example) implicitly sets the \bi{condition codes}.
 The following condition codes were covered in the lecture (operation: \texttt{t = a + b}):
 \begin{itemize}
@@ -68,3 +68,16 @@ and \texttt{SF} is set if \texttt{a \& b < 0}.
     \caption{Condition code postfixes for jump and set instructions}
     \label{tab:condition-codes}
 \end{table}
+
+\content{Conditional Moves}
+
+Similar to \texttt{jX}, the same postfixes can be applied to \texttt{cmovX}, for example:
+
+\begin{minted}{gas}
+    cmpl     %eax, %edx
+    cmovle   %edx, %eax
+\end{minted}
+
+Will move \verb|%edx| into \verb|%eax|, only if \verb|%edx| is less or equal (\verb|le|) \verb|%eax|.
+
+This can be used to, for example, compile ternary expressions from \verb|C| to Assembly. However, this requires evaluating both possible expressions, which may lead to a (significant) performance overhead.

semester3/spca/parts/00_asm/04_control-flow.tex

@@ -13,3 +13,21 @@ A function using an \verb|if/else| construct to choose the maximum of $2$ number
 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}
+
+\subsubsection{While Loops}
+
+A recursive factorial function using a \verb|do while| loop may be compiled like this:
+
+\inputcodewithfilename{gas}{code-examples/01_asm/}{04_factorial.s}
+
+\newpage
+
+The same function, using a \verb|while| loop instead may lead to this:
+
+\inputcodewithfilename{gas}{code-examples/01_asm/}{05_factorial.s}
+
+\subsubsection{For Loops \& Switch}
+
+\verb|for| loops follow the same idea as \verb|while| loops, albeit with a few more jumps.
+
+\verb|switch| statements are implemented differently depending on size and case values: Sparse switch statements are compiled as decision trees, whereas large switch statements may become \textit{jump tables}.

semester3/spca/parts/00_asm/05_stack.tex

@@ -0,0 +1 @@
+\subsection{The Stack}