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@@ -26,7 +26,7 @@
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\def\racketEd{0}
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\def\pythonEd{1}
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-\def\edition{0}
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+\def\edition{1}
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% material that is specific to the Racket edition of the book
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\newcommand{\racket}[1]{{\if\edition\racketEd{#1}\fi}}
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@@ -3898,7 +3898,7 @@ programs.
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The \code{patch\_instructions} pass compiles from \LangXVar{} to
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\LangXInt{} by making sure that each instruction adheres to the
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restriction that at most one argument of an instruction may be a
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-memory reference.
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+memory reference.
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We return to the following example.\\
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\begin{minipage}{0.5\textwidth}
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@@ -3945,6 +3945,12 @@ from \key{rax} to the destination location, as follows.
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movq %rax, -16(%rbp)
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\end{lstlisting}
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+There is a similar corner case that also needs to be dealt with. If
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+one argument is an immediate integer larger than $2^{16}$ and the
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+other is a memory reference, then the instruction is invalid. One can
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+fix this, for example, by first moving the immediate integer into
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+\key{rax} and then using \key{rax} in place of the integer.
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+
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\begin{exercise}
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\normalfont\normalsize Implement the \key{patch\_instructions} pass in
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\racket{\code{compiler.rkt}}\python{\code{compiler.py}}.
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Jeremy G. Siek