+++ /dev/null
-\section[StgMiniInt]{The ``mini-interpreter'' that drives the STG machine}
-
-% this file is part of the C-as-assembler document
-
-\begin{code}
-#include "rtsdefs.h"
-\end{code}
-
-For portable~C, there really is a mini-interpreter that repeatedly
-grabs the continuation from each code fragment and jumps to it.
-
-In portable~C, we also have a ``debugging'' version of the
-mini-interpreter which does ``hygiene-checking'' of the stacks/heap(?)
-each time it regains control. This is deeply wonderful when the
-compiler's generating duff code and things are badly broken!
-
-For optimised~C, the mini-interpreter really {\em doesn't} do anything
-remotely interpretive. It just jumps off into a Haskell Threaded
-World, dropping a label for \tr{_miniInterpretEnd} so we'll have a
-place to eventually come back to.
-
-A complication in optimised~C: Because we completely nuke C-stack
-activity (pushing/popping frames, moving register-windows) within the
-Haskell-threaded world, we need to ensure there is enough C-stack
-space actually present to satisfy the code that GCC generated.
-
-IMPORTANT POINT: the mini-interpreter is supposed to be {\em generic}.
-It is not only for the Haskell Threaded World---the storage manager
-may use it as well. So: whatever threaded world is in operation has
-to handle its own register saving/restoring, and such grimy details.
-For an example, see the @startStgWorld@, @stopStgWorld@ pair of
-routines.
-
-%************************************************************************
-%* *
-\subsection[StgMiniInt-optimised]{Mini-interpreter for ``optimised~C''}
-%* *
-%************************************************************************
-
-Unusually, for mini-interpreters, the ``optimised~C'' case involves
-less code.
-
-\begin{code}
-#if defined(__STG_TAILJUMPS__) && defined(__GNUC__)
-
-void
-miniInterpret(start_cont)
- StgFunPtr start_cont;
-{
- /*
- * MINI_INTERPRETER_SETUP _must_ save _all_ callee-saves registers, because
- * the caller expects them to be saved if they are used, but the threaded
- * code never saaves anything (all function prologues have been removed).
- */
-
- MINI_INTERPRETER_SETUP
-
- /*
- * starts Haskell world by _calling_ "start_cont"
- *
- * Make this a JMP_ and dead code elimination will make you unhappy.
- *
- * You will be even more unhappy with a registerized HP build, because
- * the continuation passed in here is actually the address of a function
- * ADT, and not the address where the function really begins.
- */
- (start_cont)();
-
- /*
- * and drops a label for "miniInterpretEnd" right here, along
- * with any cleanup that has to be done before we return.
- *
- * _Always_ RESUME_(miniInterpretEnd). Never JMP_(miniInterpretEnd).
- */
-
- MINI_INTERPRETER_END
-
- return;
-}
-\end{code}
-
-%************************************************************************
-%* *
-\subsection[StgMiniInt-portable]{Mini-interpreter for ``portable~C''}
-%* *
-%************************************************************************
-
-\begin{code}
-#else /* ! (__STG_TAILJUMPS__ && __GNUC__) */
-
-#include <setjmp.h>
-/* by which we mean the Standard C Library stuff */
-\end{code}
-
-%************************************************************************
-%* *
-\subsubsection[StgMiniInt-portable-normal]{Normal mini-interpreter for ``portable~C''}
-%* *
-%************************************************************************
-
-The static @jmp_environment@ variable allows @miniInterpret@ to
-communicate with @miniInterpretEnd@.
-
-Because @miniInterpret@ may be used recursively, we carefully
-save and restore the whole of @jmp_environment@.
-
-\begin{code}
-static jmp_buf jmp_environment;
-
-void bcopy PROTO((char *, char *, int)); /*ToDo: properly?*/
-
-void
-miniInterpret(start_cont)
- StgFunPtr start_cont;
-{
- StgFunPtr continuation = (StgFunPtr) start_cont;
- jmp_buf save_buf;
- bcopy((char *) jmp_environment, (char *) save_buf, sizeof(jmp_buf));
- /* Save jmp_environment for previous call to miniInterpret */
-
- if (setjmp(jmp_environment) == 0) {
-
- while ( 1 ) {
- /* unrolled for a little speed */
- continuation = (StgFunPtr) (continuation)();
- continuation = (StgFunPtr) (continuation)();
- continuation = (StgFunPtr) (continuation)();
- continuation = (StgFunPtr) (continuation)();
- continuation = (StgFunPtr) (continuation)();
- }
- }
-
-
- /* Restore jmp_environment for previous call */
- bcopy((char *) save_buf, (char *) jmp_environment, sizeof(jmp_buf));
-
- /* ToDo: restore real registers ... (see longjmp) */
- return;
- /*
- Note that on returning (after miniInterpretEnd is called)
- the values variables declared as real machine registers
- will be undefined.
- */
-}
-
-void miniInterpretEnd(STG_NO_ARGS)
-{
- /* ToDo: save real register in something somewhere */
- longjmp(jmp_environment, 1);
-}
-
-#endif /* ! __STG_TAILJUMPS__ */
-\end{code}
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