describe the nop instruction

part2-nstar.tex

@@ -1065,7 +1065,7 @@ \section{\texttt{ret}}\label{sec:nstar-instructionset-ret}
   \label{fig:nstar-instructionset-ret-typerules}
 \end{figure}
 
-\section{\texttt{push}}\label{fig:nstar-instructionset-push}
+\section{\texttt{push}}\label{sec:nstar-instructionset-push}
 
 The \texttt{push} instruction inserts sized data on top of the stack.
 Grammar for it is given in Figure~\ref{fig:nstar-instructionset-push-grammar} and inference rules are given in Figure~\ref{fig:nstar-instructionset-push-typerules}.
@@ -1095,6 +1095,33 @@ \section{\texttt{push}}\label{fig:nstar-instructionset-push}
   \label{fig:nstar-instructionset-push-typerules}
 \end{figure}
 
+\section{\texttt{nop}}\label{sec:nstar-instructionset-nop}
+
+The \texttt{nop} instruction does absolutely nothing else than skipping a CPU cycle.
+Grammar and type inference rules are respectively given in Figure~\ref{fig:nstar-instructionset-nop-grammar} and Figure~\ref{fig:nstar-instructionset-nop-typerules}.
+
+\begin{figure}[H]
+  \centering
+
+  \scalebox{.5}{
+    \includegraphics{nstar/instructions/nop-grammar}
+  }
+
+  \caption{Grammar for the \texttt{nop} instruction.}
+  \label{fig:nstar-instructionset-nop-grammar}
+\end{figure}
+
+\begin{figure}[H]
+  \centering
+
+  \begin{prooftree}
+    \infer0{\Delta,\Xi\vdash^I$ nop $\dashv\Delta}
+  \end{prooftree}
+
+  \caption{Type inference rules for the \texttt{nop} instruction.}
+  \label{fig:nstar-instructionset-nop-typerules}
+\end{figure}
+
 \chapter{Target-dependent features}\label{chap:nstar-specific}
 
 \section{x86, amd64}\label{sec:nstar-specific-x86amd64}

railroad-diagrams.py

@@ -36,39 +36,46 @@ def mk_diagram(name, nodes):
 
 def character_immediate():
     inner = Sequence(
-	Terminal("'"),
-	Choice(
-	    1,
-	    Sequence(
-		Terminal('\\'),
+		Terminal("'"),
 		Choice(
-		    1,
-		    Sequence(
-			Terminal('x'),
-			NonTerminal('hex-digit'),
-			NonTerminal('hex-digit')
-		    ),
-		    HorizontalChoice(
-			Terminal('n'),
-			Terminal('r'),
-			Terminal('\\'),
-			Terminal('0')
-		    ),
-		    HorizontalChoice(
-			Terminal('t'),
-			Terminal('v'),
-			Terminal('e')
-		    ),
-		)
-	    ),
-	    NonTerminal('ascii-character')
-	),
-	Terminal("'")
+			1,
+			Sequence(
+				Terminal('\\'),
+				Choice(
+					1,
+					Sequence(
+						Terminal('x'),
+						NonTerminal('hex-digit'),
+						NonTerminal('hex-digit')
+					),
+					HorizontalChoice(
+						Terminal('n'),
+						Terminal('r'),
+						Terminal('\\'),
+						Terminal('0')
+					),
+					HorizontalChoice(
+						Terminal('t'),
+						Terminal('v'),
+						Terminal('e')
+					),
+				)
+			),
+			NonTerminal('ascii-character')
+		),
+		Terminal("'")
     )
 
     return mk_diagram('character-immediate', inner)
 
 def character_constant():
     return character_immediate()
 
-character_immediate().writeSvg(sys.stdout.write)
+def nop_instruction():
+	inner = Sequence(
+		Terminal('nop')
+	)
+
+	return mk_diagram('nop-instruction', inner)
+
+nop_instruction().writeSvg(sys.stdout.write)