added remark about partial eval to avoid comparing two immediates

book.tex

@@ -10027,7 +10027,9 @@ pass.
 The second argument of the \key{cmpq} instruction must not be an
 immediate value (such as an integer). So, if you are comparing two
 immediates, we recommend inserting a \key{movq} instruction to put the
-second argument in \key{rax}.
+second argument in \key{rax}. On the other hand, if you implemented
+the partial evaluator (section~\ref{sec:pe-Lvar}), you could
+update it for \LangIf{} and then this situation would not arise.
 %
 As usual, \key{cmpq} may have at most one memory reference.
 %