document tail call elimination

jkotlinski · Aug 12, 2015 · 51993b8 · 51993b8
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diff --git a/docs/anatomy.tex b/docs/anatomy.tex
@@ -28,7 +28,7 @@ \section{Header}
 
 The first two bytes contain a back-pointer to the previous word, starting at \$4bed. The next byte, "02", is the length of "bg" name string. After that, the string "bg" follows. (42 = 'b', 47 = 'g')
 
-The name length byte is also used to store special attributes of the word. Bit 7 is "immediate" flag, which means that the word should execute immediately instead of being compiled into word definitions. ("(" is such an example of an immediate word that does not get compiled.) Bit 6 is "hidden" flag, which makes a word unfindable. Since bg is neither immediate nor hidden, bits 7-6 are both clear.
+The name length byte is also used to store special attributes of the word. Bit 7 is "immediate" flag, which means that the word should execute immediately instead of being compiled into word definitions. ("(" is such an example of an immediate word that does not get compiled.) Bit 6 is "hidden" flag, which makes a word unfindable. Bit 5 is the "no-tail-call-elimination" flag, which makes sure that tail call elimination (the practice of replacing jsr/rts with jmp) is not performed if this word is the jsr target. Since bg does not have these flags set, bits 7-5 are all clear.
 
 \section{Code}
 

diff --git a/docs/forth.tex b/docs/forth.tex
@@ -178,6 +178,7 @@ \section{Compiling}
 \item[[ ( -- )] Leave compile mode. Execute the following words immediately instead of compiling them.
 \item[{]} ( -- )] Return to compile mode.
 \item[immediate] Mark the word being compiled as immediate (i.e. inside colon definitions, it will be executed immediately instead of compiled).
+\item[no-tce] Do not perform tail call elimination (the practice of substituting jsr/rts with jmp) if this word is the jsr target.
 \item[{[']} name ( -- xt )] Place name's execution token xt on the stack. The execution token returned by the compiled phrase \texttt{['] x} is the same value returned by \texttt{' x} outside of compilation state. Typical use: \texttt{: x ... {[}'{]} name ... ;}
 \item[compile, ( xt -- )] Append \texttt{jsr xt} to the word being compiled. Typical use: \texttt{: recurse immed latest @ >cfa compile, ;}
 \item[postpone xxx] Compile the compilation semantics (instead of interpretation semantics) of xxx. Typical use: