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Whippet reserves a bit in object kind for forwarding

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Tags without the bit are forwarding addresses.
This commit is contained in:
Andy Wingo 2022-06-06 16:58:53 +02:00
parent 8409383ee1
commit a8214af467
1 changed files with 10 additions and 4 deletions
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14
whippet.h
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@ -251,14 +251,20 @@ static inline size_t size_to_granules(size_t size) {
return (size + GRANULE_SIZE - 1) >> GRANULE_SIZE_LOG_2; return (size + GRANULE_SIZE - 1) >> GRANULE_SIZE_LOG_2;
} }
// Alloc kind is in bits 0-7, for live objects. // Alloc kind is in bits 1-7, for live objects.
static const uintptr_t gcobj_alloc_kind_mask = 0xff; static const uintptr_t gcobj_alloc_kind_mask = 0x7f;
static const uintptr_t gcobj_alloc_kind_shift = 0; static const uintptr_t gcobj_alloc_kind_shift = 1;
static const uintptr_t gcobj_forwarded_mask = 0x1;
static const uintptr_t gcobj_not_forwarded_bit = 0x1;
static inline uint8_t tag_live_alloc_kind(uintptr_t tag) { static inline uint8_t tag_live_alloc_kind(uintptr_t tag) {
return (tag >> gcobj_alloc_kind_shift) & gcobj_alloc_kind_mask; return (tag >> gcobj_alloc_kind_shift) & gcobj_alloc_kind_mask;
} }
static inline uintptr_t tag_live(uint8_t alloc_kind) { static inline uintptr_t tag_live(uint8_t alloc_kind) {
return ((uintptr_t)alloc_kind << gcobj_alloc_kind_shift); return ((uintptr_t)alloc_kind << gcobj_alloc_kind_shift)
| gcobj_not_forwarded_bit;
}
static inline uintptr_t tag_forwarded(struct gcobj *new_addr) {
return (uintptr_t)new_addr;
} }
struct gcobj { struct gcobj {