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@@ -118,7 +118,21 @@ primary concern, this is not a big problem.
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\subsubsection*{Constant folding}
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+Another optimization is to do constant folding. Constant folding is replacing
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+a expensive step like addition with a more simple step like loading a constant.
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+Of course, this is not always possible. It is possible in cases where you apply
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+an operation on two constants, or a constant and a variable of which you know
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+for sure that it always has a certain value at that point. For example:
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+\begin{verbatim}
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+li $regA, 1 li $regA, 1
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+addu $regB, $regA, 2 -> li $regB, 3
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+\end{verbatim}
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+Of course, if \texttt{\$regA} is not used after this, it can be removed, which
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+will be done by the dead code elimination.
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+One problem we encountered with this is that the use of a \texttt{li} is that
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+the program often also stores this in the memory, so we had to check whether
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+this was necessary here as well.
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\subsubsection*{Copy propagation}
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@@ -145,12 +159,11 @@ of the move operation.
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An example would be the following:
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\begin{verbatim}
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-move $regA, $regB move $regA, $regB
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-... ...
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-Code not writing $regA, -> ...
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-$regB ...
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-... ...
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-addu $regC, $regA, ... addu $regC, $regB, ...
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+move $regA, $regB move $regA, $regB
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+... ...
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+Code not writing $regA, $regB -> ...
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+... ...
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+addu $regC, $regA, ... addu $regC, $regB, ...
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\end{verbatim}
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This code shows that \texttt{\$regA} is replaced with \texttt{\$regB}. This
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way, the move instruction might have become useless, and it will then be
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Jayke Meijer