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@@ -973,6 +973,8 @@ specified by the label.
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main:
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movq $10, %rax
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addq $32, %rax
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+ movq %rax, %rdi
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+ callq print_int
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retq
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\end{lstlisting}
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\caption{\it An x86-64 program equivalent to $\BINOP{+}{10}{32}$.}
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@@ -991,7 +993,11 @@ the operating system starts executing this program. The instruction
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\lstinline{movq $10, %rax} puts $10$ into register \key{rax}. The
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following instruction \lstinline{addq $32, %rax} adds $32$ to the
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$10$ in \key{rax} and puts the result, $42$, back into
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-\key{rax}. The instruction \key{retq} finishes the \key{main}
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+\key{rax}. The instruction \lstinline{movq %rax, %rdi} moves the value
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+in \key{rax} into another register, \key{rdi}, and
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+\lstinline{callq print_int} calls the external function \code{print\_int}, which
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+prints the value in \key{rdi}.
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+The instruction \key{retq} finishes the \key{main}
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function by returning the integer in \key{rax} to the
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operating system.
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@@ -1008,7 +1014,9 @@ main:
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negq -8(%rbp)
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movq $52, %rax
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addq -8(%rbp), %rax
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-
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+
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+ movq %rax, %rdi
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+ callq print_int
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addq $16, %rsp
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popq %rbp
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retq
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@@ -1084,8 +1092,8 @@ places $52$ in the register \key{rax} and \key{addq -8(\%rbp), \%rax}
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adds the contents of variable $1$ to \key{rax}, at which point
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\key{rax} contains $42$.
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-The last three instructions are the typical \emph{conclusion} of a
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-procedure. These instructions are necessary to get the state of the
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+The last five instructions are the typical \emph{conclusion} of a
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+procedure. The first two print the final result of the program. The latter three are necessary to get the state of the
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machine back to where it was before the current procedure was called.
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The \key{addq \$16, \%rsp} instruction moves the stack pointer back to
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point at the old base pointer. The amount added here needs to match
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@@ -1746,11 +1754,25 @@ stack-allocated variables, for which it is suggest that you compute in
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the \key{assign-homes} pass (Section~\ref{sec:assign-s0}) and store in
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the $\itm{info}$ field of the \key{program} node.
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+Your compiled code should print the result of the program's execution by using the
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+\code{print\_int} function provided in \code{runtime.c}. If your compiler has been implemented correctly so far, this final result should be stored in the \key{rax} register.
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+We'll talk more about
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+how to perform function calls with arguments in general later on, but
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+for now, make sure that your x86 printer includes the following code as part of the conclusion:
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+
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+\begin{lstlisting}
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+ movq %rax, %rdi
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+ callq print_int
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+\end{lstlisting}
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+
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+These lines move the value in \key{rax} into the \key{rdi} register, which
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+stores the first argument to be passed into \key{print\_int}.
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+
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If you want your program to run on Mac OSX, at this stage your code also has to determine whether or not it is running on a Mac, and prepend underscores to labels like \key{main} if it is.
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You can determine the platform your compiler is being run on with the Racket
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call \code{(system-type 'os)}, which returns \code{'macosx}, \code{'unix}, or \code{'windows}.
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In addition to placing underscores on \key{main}, you'll also have to put them in front of
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-\key{callq} labels (so \code{callq read\_int} becomes \code{callq \_read\_int}).
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+\key{callq} labels (so \code{callq print\_int} becomes \code{callq \_print\_int}).
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\begin{exercise}
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\normalfont Implement the \key{print-x86} pass and test it on all of
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Jeremy G. Siek