/* ----------------------------------------------------------------------------
- * $Id: InfoTables.h,v 1.28 2002/12/11 15:36:37 simonmar Exp $
+ * $Id: InfoTables.h,v 1.31 2003/11/14 09:27:00 stolz Exp $
*
* (c) The GHC Team, 1998-2002
*
Ticky info
-------------------------------------------------------------------------- */
+#if defined(SUPPORTS_EMPTY_STRUCTS)
typedef struct {
/* empty */
} StgTickyInfo;
+#endif
/* -----------------------------------------------------------------------------
Debugging info
#else /* !DEBUG_CLOSURE */
-typedef struct {
+# if defined(SUPPORTS_EMPTY_STRUCTS)
+typedef struct StgDebugInfo {
/* empty */
} StgDebugInfo;
+# endif
#endif /* DEBUG_CLOSURE */
the layout of a PAP to the GC).
-------------------------------------------------------------------------- */
-//
-// Small bitmaps: for a small bitmap, we store the size and bitmap in
-// the same word, using the following macros. If the bitmap doesn't
-// fit in a single word, we use a pointer to an StgLargeBitmap below.
-//
+/*
+ Small bitmaps: for a small bitmap, we store the size and bitmap in
+ the same word, using the following macros. If the bitmap doesn't
+ fit in a single word, we use a pointer to an StgLargeBitmap below.
+*/
#define MK_SMALL_BITMAP(size,bits) (((bits)<<BITMAP_BITS_SHIFT) | (size))
#define BITMAP_SIZE(bitmap) ((bitmap) & BITMAP_SIZE_MASK)
#define BITMAP_BITS(bitmap) ((bitmap) >> BITMAP_BITS_SHIFT)
-//
-// A large bitmap.
-//
+/*
+ A large bitmap.
+*/
typedef struct {
StgWord size;
StgWord bitmap[FLEXIBLE_ARRAY];
} StgLargeBitmap;
+/* -----------------------------------------------------------------------------
+ SRTs (Static Reference Tables)
+
+ These tables are used to keep track of the static objects referred
+ to by the code for a closure or stack frame, so that we can follow
+ static data references from code and thus accurately
+ garbage-collect CAFs.
+ -------------------------------------------------------------------------- */
+
+/* An SRT is just an array of closure pointers: */
+typedef StgClosure* StgSRT[];
+
+/* Each info table refers to some subset of the closure pointers in an
+ SRT. It does this using a pair of an StgSRT pointer and a
+ half-word bitmap. If the half-word bitmap isn't large enough, then
+ we fall back to a large SRT, including an unbounded bitmap. If the
+ half-word bitmap is set to all ones (0xffff), then the StgSRT
+ pointer instead points to an StgLargeSRT: */
+typedef struct StgLargeSRT_ {
+ StgSRT *srt;
+ StgLargeBitmap l;
+} StgLargeSRT;
+
/* ----------------------------------------------------------------------------
Info Tables
------------------------------------------------------------------------- */
-//
-// Stuff describing the closure layout. Well, actually, it might
-// contain the selector index for a THUNK_SELECTOR. This union is one
-// word long.
-//
+/*
+ Stuff describing the closure layout. Well, actually, it might
+ contain the selector index for a THUNK_SELECTOR. This union is one
+ word long.
+*/
typedef union {
- struct { // Heap closure payload layout:
- StgHalfWord ptrs; // number of pointers
- StgHalfWord nptrs; // number of non-pointers
+ struct { /* Heap closure payload layout: */
+ StgHalfWord ptrs; /* number of pointers */
+ StgHalfWord nptrs; /* number of non-pointers */
} payload;
- StgWord bitmap; // word-sized bit pattern describing
- // a stack frame: see below
+ StgWord bitmap; /* word-sized bit pattern describing */
+ /* a stack frame: see below */
- StgLargeBitmap* large_bitmap; // pointer to large bitmap structure
+ StgLargeBitmap* large_bitmap; /* pointer to large bitmap structure */
- StgWord selector_offset; // used in THUNK_SELECTORs
+ StgWord selector_offset; /* used in THUNK_SELECTORs */
} StgClosureInfo;
-//
-// An SRT.
-//
-typedef StgClosure* StgSRT[];
-
-//
-// The "standard" part of an info table. Every info table has this bit.
-//
+/*
+ The "standard" part of an info table. Every info table has this bit.
+*/
typedef struct _StgInfoTable {
#ifndef TABLES_NEXT_TO_CODE
StgProfInfo prof;
#endif
#ifdef TICKY
- StgTickyInfo ticky;
+ MAYBE_EMPTY_STRUCT(StgTickyInfo,ticky)
#endif
#ifdef DEBUG_CLOSURE
- StgDebugInfo debug;
+ MAYBE_EMPTY_STRUCT(StgDebugInfo,debug)
#endif
- StgClosureInfo layout; // closure layout info (one word)
+ StgClosureInfo layout; /* closure layout info (one word) */
- StgHalfWord type; // closure type
- StgHalfWord srt_len; // number of entries in SRT (or constructor tag)
+ StgHalfWord type; /* closure type */
+ StgHalfWord srt_bitmap; /* number of entries in SRT (or constructor tag) */
#ifdef TABLES_NEXT_TO_CODE
StgCode code[FLEXIBLE_ARRAY];
and bitmap fields may be left out (they are at the end, so omitting
them doesn't affect the layout).
- - If srt_len (in the std info table part) is zero, then the srt
+ - If srt_bitmap (in the std info table part) is zero, then the srt
field may be omitted. This only applies if the slow_apply and
bitmap fields have also been omitted.
-------------------------------------------------------------------------- */
typedef struct _StgFunInfoTable {
#if defined(TABLES_NEXT_TO_CODE)
- StgFun *slow_apply; // apply to args on the stack
- StgWord bitmap; // arg ptr/nonptr bitmap
- StgSRT *srt; // pointer to the SRT table
- StgHalfWord fun_type; // function type
- StgHalfWord arity; // function arity
+ StgFun *slow_apply; /* apply to args on the stack */
+ StgWord bitmap; /* arg ptr/nonptr bitmap */
+ StgSRT *srt; /* pointer to the SRT table */
+ StgHalfWord fun_type; /* function type */
+ StgHalfWord arity; /* function arity */
StgInfoTable i;
#else
StgInfoTable i;
- StgHalfWord fun_type; // function type
- StgHalfWord arity; // function arity
- StgSRT *srt; // pointer to the SRT table
- StgWord bitmap; // arg ptr/nonptr bitmap
- StgFun *slow_apply; // apply to args on the stack
+ StgHalfWord fun_type; /* function type */
+ StgHalfWord arity; /* function arity */
+ StgSRT *srt; /* pointer to the SRT table */
+ StgWord bitmap; /* arg ptr/nonptr bitmap */
+ StgFun *slow_apply; /* apply to args on the stack */
#endif
} StgFunInfoTable;
Return info tables
-------------------------------------------------------------------------- */
-// When info tables are laid out backwards, we can omit the SRT
-// pointer iff srt_len is zero.
+/* When info tables are laid out backwards, we can omit the SRT
+ pointer iff srt_bitmap is zero. */
typedef struct _StgRetInfoTable {
#if !defined(TABLES_NEXT_TO_CODE)
StgInfoTable i;
#endif
- StgSRT *srt; // pointer to the SRT table
+ StgSRT *srt; /* pointer to the SRT table */
#if defined(TABLES_NEXT_TO_CODE)
StgInfoTable i;
#endif
Thunk info tables
-------------------------------------------------------------------------- */
-// When info tables are laid out backwards, we can omit the SRT
-// pointer iff srt_len is zero.
+/* When info tables are laid out backwards, we can omit the SRT
+ pointer iff srt_bitmap is zero. */
typedef struct _StgThunkInfoTable {
#if !defined(TABLES_NEXT_TO_CODE)
StgInfoTable i;
#endif
- StgSRT *srt; // pointer to the SRT table
+ StgSRT *srt; /* pointer to the SRT table */
#if defined(TABLES_NEXT_TO_CODE)
StgInfoTable i;
#endif
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