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ffi/target/release/build/mlua-sys-6a99a2ae50f12319/out/luajit-build/build/src/lj_obj.h  view on Meta::CPAN

#define GCHeader	GCRef nextgc; uint8_t marked; uint8_t gct
/* This occupies 6 bytes, so use the next 2 bytes for non-32 bit fields. */

#if LJ_GC64
#define gcref(r)	((GCobj *)(r).gcptr64)
#define gcrefp(r, t)	((t *)(void *)(r).gcptr64)
#define gcrefu(r)	((r).gcptr64)
#define gcrefeq(r1, r2)	((r1).gcptr64 == (r2).gcptr64)

#define setgcref(r, gc)	((r).gcptr64 = (uint64_t)&(gc)->gch)
#define setgcreft(r, gc, it) \
  (r).gcptr64 = (uint64_t)&(gc)->gch | (((uint64_t)(it)) << 47)
#define setgcrefp(r, p)	((r).gcptr64 = (uint64_t)(p))
#define setgcrefnull(r)	((r).gcptr64 = 0)
#define setgcrefr(r, v)	((r).gcptr64 = (v).gcptr64)
#else
#define gcref(r)	((GCobj *)(uintptr_t)(r).gcptr32)
#define gcrefp(r, t)	((t *)(void *)(uintptr_t)(r).gcptr32)
#define gcrefu(r)	((r).gcptr32)
#define gcrefeq(r1, r2)	((r1).gcptr32 == (r2).gcptr32)

#define setgcref(r, gc)	((r).gcptr32 = (uint32_t)(uintptr_t)&(gc)->gch)
#define setgcrefp(r, p)	((r).gcptr32 = (uint32_t)(uintptr_t)(p))
#define setgcrefnull(r)	((r).gcptr32 = 0)
#define setgcrefr(r, v)	((r).gcptr32 = (v).gcptr32)
#endif

#define gcnext(gc)	(gcref((gc)->gch.nextgc))

/* IMPORTANT NOTE:
**
** All uses of the setgcref* macros MUST be accompanied with a write barrier.
**
** This is to ensure the integrity of the incremental GC. The invariant
** to preserve is that a black object never points to a white object.
** I.e. never store a white object into a field of a black object.
**
** It's ok to LEAVE OUT the write barrier ONLY in the following cases:
** - The source is not a GC object (NULL).
** - The target is a GC root. I.e. everything in global_State.
** - The target is a lua_State field (threads are never black).
** - The target is a stack slot, see setgcV et al.
** - The target is an open upvalue, i.e. pointing to a stack slot.
** - The target is a newly created object (i.e. marked white). But make
**   sure nothing invokes the GC inbetween.
** - The target and the source are the same object (self-reference).
** - The target already contains the object (e.g. moving elements around).
**
** The most common case is a store to a stack slot. All other cases where
** a barrier has been omitted are annotated with a NOBARRIER comment.
**
** The same logic applies for stores to table slots (array part or hash
** part). ALL uses of lj_tab_set* require a barrier for the stored value
** *and* the stored key, based on the above rules. In practice this means
** a barrier is needed if *either* of the key or value are a GC object.
**
** It's ok to LEAVE OUT the write barrier in the following special cases:
** - The stored value is nil. The key doesn't matter because it's either
**   not resurrected or lj_tab_newkey() will take care of the key barrier.
** - The key doesn't matter if the *previously* stored value is guaranteed
**   to be non-nil (because the key is kept alive in the table).
** - The key doesn't matter if it's guaranteed not to be part of the table,
**   since lj_tab_newkey() takes care of the key barrier. This applies
**   trivially to new tables, but watch out for resurrected keys. Storing
**   a nil value leaves the key in the table!
**
** In case of doubt use lj_gc_anybarriert() as it's rather cheap. It's used
** by the interpreter for all table stores.
**
** Note: In contrast to Lua's GC, LuaJIT's GC does *not* specially mark
** dead keys in tables. The reference is left in, but it's guaranteed to
** be never dereferenced as long as the value is nil. It's ok if the key is
** freed or if any object subsequently gets the same address.
**
** Not destroying dead keys helps to keep key hash slots stable. This avoids
** specialization back-off for HREFK when a value flips between nil and
** non-nil and the GC gets in the way. It also allows safely hoisting
** HREF/HREFK across GC steps. Dead keys are only removed if a table is
** resized (i.e. by NEWREF) and xREF must not be CSEd across a resize.
**
** The trade-off is that a write barrier for tables must take the key into
** account, too. Implicitly resurrecting the key by storing a non-nil value
** may invalidate the incremental GC invariant.
*/

/* -- Common type definitions --------------------------------------------- */

/* Types for handling bytecodes. Need this here, details in lj_bc.h. */
typedef uint32_t BCIns;  /* Bytecode instruction. */
typedef uint32_t BCPos;  /* Bytecode position. */
typedef uint32_t BCReg;  /* Bytecode register. */
typedef int32_t BCLine;  /* Bytecode line number. */

/* Internal assembler functions. Never call these directly from C. */
typedef void (*ASMFunction)(void);

/* Resizable string buffer. Need this here, details in lj_buf.h. */
#define SBufHeader	char *w, *e, *b; MRef L
typedef struct SBuf {
  SBufHeader;
} SBuf;

/* -- Tags and values ----------------------------------------------------- */

/* Frame link. */
typedef union {
  int32_t ftsz;		/* Frame type and size of previous frame. */
  MRef pcr;		/* Or PC for Lua frames. */
} FrameLink;

/* Tagged value. */
typedef LJ_ALIGN(8) union TValue {
  uint64_t u64;		/* 64 bit pattern overlaps number. */
  lua_Number n;		/* Number object overlaps split tag/value object. */
#if LJ_GC64
  GCRef gcr;		/* GCobj reference with tag. */
  int64_t it64;
  struct {
    LJ_ENDIAN_LOHI(
      int32_t i;	/* Integer value. */
    , uint32_t it;	/* Internal object tag. Must overlap MSW of number. */