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+ <title>The GHC Commentary - Spineless Tagless C</title>
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+ <h1>The GHC Commentary - Spineless Tagless C</h1>
+ <p>
+ The C code generated by GHC doesn't use higher-level features of C to be
+ able to control as precisely as possible what code is generated.
+ Moreover, it uses special features of gcc (such as, first class labels)
+ to produce more efficient code.
+ <p>
+ STG C makes ample use of C's macro language to define idioms, which also
+ reduces the size of the generated C code (thus, reducing I/O times).
+ These macros are defined in the C headers located in GHC's <a
+ href="http://cvs.haskell.org/cgi-bin/cvsweb.cgi/fptools/ghc/includes/"><code>includes</code></a>
+ directory.
+
+ <h4><code>TailCalls.h</code></h4>
+ <p>
+ <a
+ href="http://cvs.haskell.org/cgi-bin/cvsweb.cgi/fptools/ghc/includes/TailCalls.h"><code>TailCalls.h</code></a>
+ defines how tail calls are implemented - and in particular - optimised
+ in GHC generated code. The default case, for an architecture for which
+ GHC is not optimised, is to use the mini interpreter described in the <a
+ href="http://research.microsoft.com/copyright/accept.asp?path=/users/simonpj/papers/spineless-tagless-gmachine.ps.gz&pub=34">STG paper.</a>
+ <p>
+ For supported architectures, various tricks are used to generate
+ assembler implementing proper tail calls. On i386, gcc's first class
+ labels are used to directly jump to a function pointer. Furthermore,
+ markers of the form <code>--- BEGIN ---</code> and <code>--- END
+ ---</code> are added to the assembly right after the function prologue
+ and before the epilogue. These markers are used by <a
+ href="../the-beast/mangler.html">the Evil Mangler.</a>
+
+ <p><small>
+<!-- hhmts start -->
+Last modified: Wed Aug 8 19:28:29 EST 2001
+<!-- hhmts end -->
+ </small>
+ </body>
+</html>
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