nursery

gc.c
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			#include "gc.h"
			#include "arena.h"
			#include "internal.h"
			#include "common.h"
			#include "modules/timer.h"

			#include <string.h>
			#include <stdlib.h>
			#include <stdio.h>
			#include <time.h>

			#ifdef _WIN32
			#include <windows.h>
			static inline void *gc_mmap(size_t size) {
			return VirtualAlloc(NULL, size, MEM_COMMIT \| MEM_RESERVE, PAGE_READWRITE);
			}
			static inline void gc_munmap(void *ptr, size_t size) {
			(void)size;
			VirtualFree(ptr, 0, MEM_RELEASE);
			}
			#else
			#include <sys/mman.h>
			static inline void *gc_mmap(size_t size) {
			void *p = mmap(NULL, size, PROT_READ \| PROT_WRITE, MAP_PRIVATE \| MAP_ANON, -1, 0);
			return (p == MAP_FAILED) ? NULL : p;
			}
			static inline void gc_munmap(void *ptr, size_t size) {
			munmap(ptr, size);
			}
			#endif

			#define MCO_API extern
			#include "minicoro.h"

			static uint8_t *gc_scratch_buf = NULL;
			static size_t gc_scratch_size = 0;
			static time_t gc_last_run_time = 0;

			static bool gc_throttled = false;
			void js_gc_throttle(bool enabled) { gc_throttled = enabled; }

			#define FWD_EMPTY ((jsoff_t)~0)
			#define FWD_TOMBSTONE ((jsoff_t)~1)

			#ifdef _WIN32
			#define RELEASE_PAGES(p, sz) VirtualAlloc(p, sz, MEM_RESET, PAGE_READWRITE)
			#else
			#define RELEASE_PAGES(p, sz) madvise(p, sz, MADV_DONTNEED)
			#endif

			typedef struct {
			jsoff_t *old_offs;
			jsoff_t *new_offs;
			size_t count;
			size_t capacity;
			size_t mask;
			} gc_forward_table_t;

			typedef struct {
			jsoff_t *items;
			size_t count;
			size_t capacity;
			} gc_work_queue_t;

			typedef struct {
			ant_t *js;
			uint8_t *new_mem;
			uint8_t *mark_bits;
			gc_forward_table_t fwd;
			gc_work_queue_t work;
			jsoff_t new_brk;
			jsoff_t new_size;
			bool failed;
			} gc_ctx_t;

			static jsval_t gc_update_val(gc_ctx_t *ctx, jsval_t val);

			static inline void mark_set(gc_ctx_t *ctx, jsoff_t off) {
			jsoff_t idx = off >> 3;
			ctx->mark_bits[idx >> 3] \|= (1 << (idx & 7));
			}

			static inline size_t next_pow2(size_t n) {
			n--;
			n \|= n >> 1; n \|= n >> 2; n \|= n >> 4;
			n \|= n >> 8; n \|= n >> 16;
			#if SIZE_MAX > 0xFFFFFFFF
			n \|= n >> 32;
			#endif
			return n + 1;
			}

			static bool fwd_init(gc_forward_table_t *fwd, size_t estimated) {
			size_t cap = next_pow2(estimated < 64 ? 64 : estimated);
			size_t size = cap * sizeof(jsoff_t);

			fwd->old_offs = (jsoff_t *)gc_mmap(size);
			fwd->new_offs = (jsoff_t *)gc_mmap(size);

			if (!fwd->old_offs \|\| !fwd->new_offs) {
			if (fwd->old_offs) gc_munmap(fwd->old_offs, size);
			if (fwd->new_offs) gc_munmap(fwd->new_offs, size);
			return false;
			}

			for (size_t i = 0; i < cap; i++) fwd->old_offs[i] = FWD_EMPTY;

			fwd->count = 0;
			fwd->capacity = cap;
			fwd->mask = cap - 1;

			return true;
			}

			static bool fwd_grow(gc_forward_table_t *fwd) {
			size_t new_cap = fwd->capacity * 2;
			size_t new_mask = new_cap - 1;
			size_t new_size = new_cap * sizeof(jsoff_t);
			size_t old_size = fwd->capacity * sizeof(jsoff_t);

			jsoff_t new_old = (jsoff_t )gc_mmap(new_size);
			jsoff_t new_new = (jsoff_t )gc_mmap(new_size);

			if (!new_old \|\| !new_new) {
			if (new_old) gc_munmap(new_old, new_size);
			if (new_new) gc_munmap(new_new, new_size);
			return false;
			}

			for (size_t i = 0; i < new_cap; i++) new_old[i] = FWD_EMPTY;

			for (size_t i = 0; i < fwd->capacity; i++) {
			jsoff_t key = fwd->old_offs[i];
			if (key == FWD_EMPTY \|\| key == FWD_TOMBSTONE) continue;
			size_t h = (key >> 3) & new_mask;
			while (new_old[h] != FWD_EMPTY) h = (h + 1) & new_mask;
			new_old[h] = key;
			new_new[h] = fwd->new_offs[i];
			}

			gc_munmap(fwd->old_offs, old_size);
			gc_munmap(fwd->new_offs, old_size);

			fwd->old_offs = new_old;
			fwd->new_offs = new_new;
			fwd->capacity = new_cap;
			fwd->mask = new_mask;

			return true;
			}

			static inline bool fwd_add(gc_forward_table_t *fwd, jsoff_t old_off, jsoff_t new_off) {
			if (fwd->count * 100 >= fwd->capacity * GC_FWD_LOAD_FACTOR) {
			if (!fwd_grow(fwd)) return false;
			}

			size_t h = (old_off >> 3) & fwd->mask;
			while (fwd->old_offs[h] != FWD_EMPTY && fwd->old_offs[h] != FWD_TOMBSTONE) {
			if (fwd->old_offs[h] == old_off) {
			fwd->new_offs[h] = new_off;
			return true;
			}
			h = (h + 1) & fwd->mask;
			}

			fwd->old_offs[h] = old_off;
			fwd->new_offs[h] = new_off;
			fwd->count++;

			return true;
			}

			static inline jsoff_t fwd_lookup(gc_forward_table_t *fwd, jsoff_t old_off) {
			size_t h = (old_off >> 3) & fwd->mask;
			for (size_t i = 0; i < fwd->capacity; i++) {
			jsoff_t key = fwd->old_offs[h];
			if (key == FWD_EMPTY) return (jsoff_t)~0;
			if (key == old_off) return fwd->new_offs[h];
			h = (h + 1) & fwd->mask;
			}
			return (jsoff_t)~0;
			}

			static void fwd_free(gc_forward_table_t *fwd) {
			size_t size = fwd->capacity * sizeof(jsoff_t);
			if (fwd->old_offs) gc_munmap(fwd->old_offs, size);
			if (fwd->new_offs) gc_munmap(fwd->new_offs, size);

			fwd->old_offs = NULL;
			fwd->new_offs = NULL;
			fwd->count = 0;
			fwd->capacity = 0;
			}

			static bool work_init(gc_work_queue_t *work, size_t initial) {
			size_t size = initial * sizeof(jsoff_t);
			work->items = (jsoff_t *)gc_mmap(size);
			if (!work->items) return false;
			work->count = 0;
			work->capacity = initial;
			return true;
			}

			static inline bool work_push(gc_work_queue_t *work, jsoff_t off) {
			if (work->count >= work->capacity) {
			size_t new_cap = work->capacity * 2;
			size_t new_size = new_cap * sizeof(jsoff_t);
			size_t old_size = work->capacity * sizeof(jsoff_t);

			jsoff_t new_items = (jsoff_t )gc_mmap(new_size);
			if (!new_items) return false;

			memcpy(new_items, work->items, work->count * sizeof(jsoff_t));
			gc_munmap(work->items, old_size);

			work->items = new_items;
			work->capacity = new_cap;
			}

			work->items[work->count++] = off;
			return true;
			}

			static inline jsoff_t work_pop(gc_work_queue_t *work) {
			if (work->count == 0) return (jsoff_t)~0;
			return work->items[--work->count];
			}

			static void work_free(gc_work_queue_t *work) {
			size_t size = work->capacity * sizeof(jsoff_t);
			if (work->items) gc_munmap(work->items, size);

			work->items = NULL;
			work->count = 0;
			work->capacity = 0;
			}

			static inline jsoff_t gc_loadoff(uint8_t *mem, jsoff_t off) {
			jsoff_t val;
			memcpy(&val, &mem[off], sizeof(val));
			return val;
			}

			static inline jsval_t gc_loadval(uint8_t *mem, jsoff_t off) {
			jsval_t val;
			memcpy(&val, &mem[off], sizeof(val));
			return val;
			}

			static inline void gc_saveoff(uint8_t *mem, jsoff_t off, jsoff_t val) {
			memcpy(&mem[off], &val, sizeof(val));
			}

			static inline void gc_saveval(uint8_t *mem, jsoff_t off, jsval_t val) {
			memcpy(&mem[off], &val, sizeof(val));
			}

			static jsoff_t gc_alloc(gc_ctx_t *ctx, size_t size) {
			size = (size + 7) / 8 * 8;
			if (ctx->new_brk + size > ctx->new_size) {
			ctx->failed = true;
			return (jsoff_t)~0;
			}
			jsoff_t off = ctx->new_brk;
			ctx->new_brk += (jsoff_t)size;
			return off;
			}

			static inline bool gc_is_tagged(jsval_t v) {
			return (v >> 53) == NANBOX_PREFIX_CHK;
			}

			static inline uint8_t gc_vtype(jsval_t v) {
			return gc_is_tagged(v) ? ((v >> NANBOX_TYPE_SHIFT) & NANBOX_TYPE_MASK) : 255;
			}

			static inline size_t gc_vdata(jsval_t v) {
			return (size_t)(v & NANBOX_DATA_MASK);
			}

			static inline jsval_t gc_mkval(uint8_t type, uint64_t data) {
			return NANBOX_PREFIX \| ((jsval_t)(type & NANBOX_TYPE_MASK) << NANBOX_TYPE_SHIFT) \| (data & NANBOX_DATA_MASK);
			}

			static jsoff_t gc_copy_string(gc_ctx_t *ctx, jsoff_t old_off) {
			if (old_off >= ctx->js->brk) return old_off;

			jsoff_t new_off = fwd_lookup(&ctx->fwd, old_off);
			if (new_off != (jsoff_t)~0) return new_off;

			jsoff_t header = gc_loadoff(ctx->js->mem, old_off);
			if ((header & 3) != T_STR) return old_off;

			bool is_rope_str = (header & ROPE_FLAG) != 0;
			jsoff_t size;

			if (is_rope_str) {
			size = sizeof(rope_node_t);
			} else size = esize(header);

			if (size == (jsoff_t)~0) return old_off;

			new_off = gc_alloc(ctx, size);
			if (new_off == (jsoff_t)~0) return old_off;

			memcpy(&ctx->new_mem[new_off], &ctx->js->mem[old_off], size);
			if (!fwd_add(&ctx->fwd, old_off, new_off)) ctx->failed = true;
			mark_set(ctx, old_off);

			if (is_rope_str) {
			jsval_t left, right, cached;
			memcpy(&left, &ctx->js->mem[old_off + offsetof(rope_node_t, left)], sizeof(jsval_t));
			memcpy(&right, &ctx->js->mem[old_off + offsetof(rope_node_t, right)], sizeof(jsval_t));
			memcpy(&cached, &ctx->js->mem[old_off + offsetof(rope_node_t, cached)], sizeof(jsval_t));

			jsval_t new_left = gc_update_val(ctx, left);
			jsval_t new_right = gc_update_val(ctx, right);
			jsval_t new_cached = gc_update_val(ctx, cached);

			memcpy(&ctx->new_mem[new_off + offsetof(rope_node_t, left)], &new_left, sizeof(jsval_t));
			memcpy(&ctx->new_mem[new_off + offsetof(rope_node_t, right)], &new_right, sizeof(jsval_t));
			memcpy(&ctx->new_mem[new_off + offsetof(rope_node_t, cached)], &new_cached, sizeof(jsval_t));
			}

			return new_off;
			}

			static jsoff_t gc_copy_bigint(gc_ctx_t *ctx, jsoff_t old_off) {
			if (old_off >= ctx->js->brk) return old_off;

			jsoff_t new_off = fwd_lookup(&ctx->fwd, old_off);
			if (new_off != (jsoff_t)~0) return new_off;

			jsoff_t header = gc_loadoff(ctx->js->mem, old_off);
			size_t total = (header >> 4) + sizeof(jsoff_t);
			total = (total + 7) / 8 * 8;

			new_off = gc_alloc(ctx, total);
			if (new_off == (jsoff_t)~0) return old_off;

			memcpy(&ctx->new_mem[new_off], &ctx->js->mem[old_off], total);
			if (!fwd_add(&ctx->fwd, old_off, new_off)) ctx->failed = true;
			mark_set(ctx, old_off);

			return new_off;
			}

			static jsoff_t gc_reserve_object(gc_ctx_t *ctx, jsoff_t old_off) {
			if (old_off >= ctx->js->brk) return old_off;

			jsoff_t new_off = fwd_lookup(&ctx->fwd, old_off);
			if (new_off != (jsoff_t)~0) return new_off;

			jsoff_t header = gc_loadoff(ctx->js->mem, old_off);
			if ((header & 3) != T_OBJ) return old_off;

			jsoff_t size = esize(header);
			if (size == (jsoff_t)~0) return old_off;

			new_off = gc_alloc(ctx, size);
			if (new_off == (jsoff_t)~0) return old_off;

			memcpy(&ctx->new_mem[new_off], &ctx->js->mem[old_off], size);
			if (!fwd_add(&ctx->fwd, old_off, new_off)) ctx->failed = true;
			mark_set(ctx, old_off);
			if (!work_push(&ctx->work, old_off)) ctx->failed = true;

			return new_off;
			}

			static jsoff_t gc_reserve_prop(gc_ctx_t *ctx, jsoff_t old_off) {
			if (old_off >= ctx->js->brk) return old_off;

			jsoff_t new_off = fwd_lookup(&ctx->fwd, old_off);
			if (new_off != (jsoff_t)~0) return new_off;

			jsoff_t header = gc_loadoff(ctx->js->mem, old_off);
			if ((header & 3) != T_PROP) return old_off;

			jsoff_t size = esize(header);
			if (size == (jsoff_t)~0) return old_off;

			new_off = gc_alloc(ctx, size);
			if (new_off == (jsoff_t)~0) return old_off;

			memcpy(&ctx->new_mem[new_off], &ctx->js->mem[old_off], size);
			if (!fwd_add(&ctx->fwd, old_off, new_off)) ctx->failed = true;
			mark_set(ctx, old_off);
			if (!work_push(&ctx->work, old_off)) ctx->failed = true;

			return new_off;
			}

			static void gc_process_prop(gc_ctx_t *ctx, jsoff_t old_off) {
			jsoff_t new_off = fwd_lookup(&ctx->fwd, old_off);
			if (new_off == (jsoff_t)~0) return;

			jsoff_t header = gc_loadoff(ctx->js->mem, old_off);

			jsoff_t next_prop = header & ~(3ULL \| FLAGMASK);
			if (next_prop != 0 && next_prop < ctx->js->brk) {
			jsoff_t new_next = gc_reserve_prop(ctx, next_prop);
			jsoff_t new_header = (new_next & ~3ULL) \| (header & (3ULL \| FLAGMASK));
			gc_saveoff(ctx->new_mem, new_off, new_header);
			}

			bool is_slot = (header & SLOTMASK) != 0;

			if (!is_slot) {
			jsoff_t key_off = gc_loadoff(ctx->js->mem, old_off + sizeof(jsoff_t));
			if (key_off < ctx->js->brk) {
			jsoff_t new_key = gc_copy_string(ctx, key_off);
			gc_saveoff(ctx->new_mem, new_off + sizeof(jsoff_t), new_key);
			}
			}

			jsval_t val = gc_loadval(ctx->js->mem, old_off + sizeof(jsoff_t) + sizeof(jsoff_t));
			jsval_t new_val = gc_update_val(ctx, val);
			gc_saveval(ctx->new_mem, new_off + sizeof(jsoff_t) + sizeof(jsoff_t), new_val);
			}

			static void gc_process_object(gc_ctx_t *ctx, jsoff_t old_off) {
			jsoff_t new_off = fwd_lookup(&ctx->fwd, old_off);
			if (new_off == (jsoff_t)~0) return;

			jsoff_t header = gc_loadoff(ctx->js->mem, old_off);

			jsoff_t first_prop = header & ~(3ULL \| FLAGMASK);
			if (first_prop != 0 && first_prop < ctx->js->brk) {
			jsoff_t new_first = gc_reserve_prop(ctx, first_prop);
			jsoff_t new_header = (new_first & ~3ULL) \| (header & (3ULL \| FLAGMASK));
			gc_saveoff(ctx->new_mem, new_off, new_header);
			}

			jsoff_t parent_off = gc_loadoff(ctx->js->mem, old_off + sizeof(jsoff_t));
			if (parent_off < ctx->js->brk) {
			jsoff_t new_parent = gc_reserve_object(ctx, parent_off);
			gc_saveoff(ctx->new_mem, new_off + sizeof(jsoff_t), new_parent);
			}

			jsoff_t tail_off = gc_loadoff(ctx->js->mem, old_off + sizeof(jsoff_t) + sizeof(jsoff_t));
			if (tail_off != 0 && tail_off < ctx->js->brk) {
			jsoff_t new_tail = fwd_lookup(&ctx->fwd, tail_off);
			if (new_tail == (jsoff_t)~0) new_tail = gc_reserve_prop(ctx, tail_off);
			gc_saveoff(ctx->new_mem, new_off + sizeof(jsoff_t) + sizeof(jsoff_t), new_tail);
			}
			}

			static void gc_drain_work_queue(gc_ctx_t *ctx) {
			jsoff_t off;
			while ((off = work_pop(&ctx->work)) != (jsoff_t)~0) {
			jsoff_t header = gc_loadoff(ctx->js->mem, off);
			switch (header & 3) {
			case T_OBJ: gc_process_object(ctx, off); break;
			case T_PROP: gc_process_prop(ctx, off); break;
			default: break;
			}
			}
			}

			static jsval_t gc_update_val(gc_ctx_t *ctx, jsval_t val) {
			if (!gc_is_tagged(val)) return val;

			uint8_t type = gc_vtype(val);
			jsoff_t old_off = (jsoff_t)gc_vdata(val);

			switch (type) {
			case T_OBJ:
			case T_FUNC:
			case T_ARR:
			case T_PROMISE:
			case T_GENERATOR: {
			if (old_off >= ctx->js->brk) return val;
			jsoff_t new_off = gc_reserve_object(ctx, old_off);
			if (new_off != (jsoff_t)~0) return gc_mkval(type, new_off);
			break;
			}
			case T_STR: {
			if (old_off >= ctx->js->brk) return val;
			jsoff_t new_off = gc_copy_string(ctx, old_off);
			if (new_off != (jsoff_t)~0) return gc_mkval(type, new_off);
			break;
			}
			case T_PROP: {
			if (old_off >= ctx->js->brk) return val;
			jsoff_t new_off = gc_reserve_prop(ctx, old_off);
			if (new_off != (jsoff_t)~0) return gc_mkval(type, new_off);
			break;
			}
			case T_BIGINT: {
			if (old_off >= ctx->js->brk) return val;
			jsoff_t new_off = gc_copy_bigint(ctx, old_off);
			if (new_off != (jsoff_t)~0) return gc_mkval(type, new_off);
			break;
			}
			default: break;
			}

			return val;
			}

			static jsoff_t gc_fwd_off_callback(void *ctx_ptr, jsoff_t old_off) {
			gc_ctx_t ctx = (gc_ctx_t )ctx_ptr;
			if (old_off == 0) return 0;
			if (old_off >= ctx->js->brk) return old_off;

			jsoff_t new_off = fwd_lookup(&ctx->fwd, old_off);
			if (new_off != (jsoff_t)~0) return new_off;

			static const void *dispatch[] = { &&l_obj, &&l_prop, &&l_str, &&l_default };
			jsoff_t header = gc_loadoff(ctx->js->mem, old_off);
			goto *dispatch[header & 3];

			l_obj: new_off = gc_reserve_object(ctx, old_off); goto l_done;
			l_prop: new_off = gc_reserve_prop(ctx, old_off); goto l_done;
			l_str: new_off = gc_copy_string(ctx, old_off); goto l_done;
			l_default: return old_off;

			l_done: return (new_off != (jsoff_t)~0) ? new_off : old_off;
			}

			static jsval_t gc_fwd_val_callback(void *ctx_ptr, jsval_t val) {
			gc_ctx_t ctx = (gc_ctx_t )ctx_ptr;
			return gc_update_val(ctx, val);
			}

			static jsoff_t gc_apply_off_callback(void *ctx_ptr, jsoff_t old_off) {
			gc_ctx_t ctx = (gc_ctx_t )ctx_ptr;
			if (old_off == 0) return 0;
			if (old_off >= ctx->js->brk) return old_off;

			jsoff_t new_off = fwd_lookup(&ctx->fwd, old_off);
			return (new_off != (jsoff_t)~0) ? new_off : old_off;
			}

			static jsval_t gc_apply_val(gc_ctx_t *ctx, jsval_t val) {
			if (!gc_is_tagged(val)) return val;

			uint8_t type = gc_vtype(val);
			jsoff_t old_off = (jsoff_t)gc_vdata(val);
			if (old_off >= ctx->js->brk) return val;

			switch (type) {
			case T_OBJ:
			case T_FUNC:
			case T_ARR:
			case T_PROMISE:
			case T_GENERATOR:
			case T_STR:
			case T_PROP:
			case T_BIGINT: {
			jsoff_t new_off = fwd_lookup(&ctx->fwd, old_off);
			if (new_off != (jsoff_t)~0) return gc_mkval(type, new_off);
			break;
			}
			default: break;
			}

			return val;
			}

			static jsval_t gc_apply_val_callback(void *ctx_ptr, jsval_t val) {
			gc_ctx_t ctx = (gc_ctx_t )ctx_ptr;
			return gc_apply_val(ctx, val);
			}

			static jsoff_t gc_weak_off_callback(void *ctx_ptr, jsoff_t old_off) {
			gc_ctx_t ctx = (gc_ctx_t )ctx_ptr;
			if (old_off >= ctx->js->brk) return old_off;
			return fwd_lookup(&ctx->fwd, old_off);
			}

			size_t js_gc_compact(ant_t *js) {
			if (!js \|\| js->brk == 0) return 0;
			if (js->brk < 2 * 1024 * 1024) return 0;

			mco_coro *running = mco_running();
			int in_coroutine = (running != NULL && running->stack_base != NULL);

			if (in_coroutine) {
			js->needs_gc = true;
			return 0;
			}

			time_t now = time(NULL);
			if (now != (time_t)-1 && gc_last_run_time != 0) {
			double elapsed = difftime(now, gc_last_run_time);
			double cooldown;

			if (js->brk > 64 * 1024 * 1024) cooldown = 0.5;
			else if (js->brk > 16 * 1024 * 1024) cooldown = 1.0;
			else if (js->brk > 4 * 1024 * 1024) cooldown = 2.0;
			else cooldown = 4.0;

			if (elapsed >= 0.0
			&& elapsed < cooldown
			&& js->gc_alloc_since < js->brk / 4
			) return 0;
			}
			if (now != (time_t)-1) gc_last_run_time = now;

			size_t old_brk = js->brk;
			size_t new_size = js->size;

			if (new_size > gc_scratch_size) {
			if (gc_scratch_buf) gc_munmap(gc_scratch_buf, gc_scratch_size);
			gc_scratch_buf = (uint8_t *)gc_mmap(new_size);
			gc_scratch_size = gc_scratch_buf ? new_size : 0;
			}

			if (!gc_scratch_buf) return 0;
			uint8_t *new_mem = gc_scratch_buf;

			size_t bitmap_size = (js->brk / 8 + 7) / 8 + 1;
			uint8_t mark_bits = (uint8_t )calloc(1, bitmap_size);
			if (!mark_bits) return 0;

			size_t estimated_objs = js->brk / 64;
			if (estimated_objs < 256) estimated_objs = 256;

			gc_ctx_t ctx;
			ctx.js = js;
			ctx.new_mem = new_mem;
			ctx.new_brk = 0;
			ctx.new_size = (jsoff_t)new_size;
			ctx.mark_bits = mark_bits;

			if (!fwd_init(&ctx.fwd, estimated_objs)) {
			free(mark_bits);
			return 0;
			}

			if (!work_init(&ctx.work, estimated_objs / 4 < 64 ? 64 : estimated_objs / 4)) {
			fwd_free(&ctx.fwd);
			free(mark_bits);
			return 0;
			}

			ctx.failed = false;

			if (js->brk > 0) {
			jsoff_t header_at_0 = gc_loadoff(js->mem, 0);
			if ((header_at_0 & 3) == T_OBJ) gc_reserve_object(&ctx, 0);
			}

			js_gc_reserve_roots(js,
			gc_fwd_off_callback,
			gc_fwd_val_callback,
			&ctx
			); gc_drain_work_queue(&ctx);

			if (ctx.failed) {
			free(mark_bits);
			work_free(&ctx.work);
			fwd_free(&ctx.fwd);
			return 0;
			}

			js_gc_update_roots(js,
			gc_apply_off_callback,
			gc_weak_off_callback,
			gc_apply_val_callback,
			&ctx);

			memcpy(js->mem, new_mem, ctx.new_brk);
			js->brk = ctx.new_brk;

			free(mark_bits);
			work_free(&ctx.work);
			fwd_free(&ctx.fwd);

			if (gc_scratch_buf && gc_scratch_size > 0) {
			RELEASE_PAGES(gc_scratch_buf, gc_scratch_size);
			}

			size_t new_brk = ctx.new_brk;
			size_t old_size = js->size;

			if (new_brk < old_size / 2 && old_size > ARENA_GROW_INCREMENT) {
			size_t target = ((new_brk * 2 + ARENA_GROW_INCREMENT - 1) / ARENA_GROW_INCREMENT) * ARENA_GROW_INCREMENT;
			if (target < ARENA_GROW_INCREMENT) target = ARENA_GROW_INCREMENT;
			if (target < old_size) { ant_arena_decommit(js->mem, old_size, target); js->size = (jsoff_t)target; }
			}

			return (old_brk > new_brk ? old_brk - new_brk : 0);
			}

			void js_gc_maybe(ant_t *js) {
			// Nursery scavenge (fast, frequent) - do this first
			if (js->nursery_full && js->nursery) {
			nursery_scavenge(js);
			js->nursery_full = false;
			}

			jsoff_t thresh = js->brk / 4;

			jsoff_t min_thresh = gc_throttled
			? 8 * 1024 * 1024
			: 2 * 1024 * 1024;

			jsoff_t max_thresh = gc_throttled
			? 64 * 1024 * 1024
			: 16 * 1024 * 1024;

			if (thresh < min_thresh) thresh = min_thresh;
			if (thresh > max_thresh) thresh = max_thresh;

			if (js->gc_alloc_since > thresh \|\| js->needs_gc) {
			js->needs_gc = false;
			if (js_gc_compact(js) > 0) js->gc_alloc_since = 0;
			}
			}

			// ============================================================================
			// Generational GC: Nursery Implementation
			// ============================================================================

			bool nursery_init(ant_t *js, size_t size) {
			if (size < NURSERY_SIZE_MIN) size = NURSERY_SIZE_MIN;
			if (size > NURSERY_SIZE_MAX) size = NURSERY_SIZE_MAX;

			js->nursery = (uint8_t *)gc_mmap(size);
			if (!js->nursery) return false;

			js->nursery_ptr = 0;
			js->nursery_size = (jsoff_t)size;
			js->nursery_full = false;
			js->nursery_enabled = false; // enabled after snapshot loads

			js->remembered_set = NULL;
			js->rs_count = 0;
			js->rs_cap = 0;

			return true;
			}

			void nursery_enable(ant_t *js) {
			if (js->nursery) {
			js->nursery_enabled = true;
			}
			}

			void nursery_free(ant_t *js) {
			if (js->nursery) {
			gc_munmap(js->nursery, js->nursery_size);
			js->nursery = NULL;
			js->nursery_ptr = 0;
			js->nursery_size = 0;
			js->nursery_enabled = false;
			}

			if (js->remembered_set) {
			free(js->remembered_set);
			js->remembered_set = NULL;
			js->rs_count = 0;
			js->rs_cap = 0;
			}
			}

			// Add object to remembered set (old→young reference)
			void rs_add(ant_t *js, jsval_t obj) {
			if (js->rs_count >= js->rs_cap) {
			size_t new_cap = js->rs_cap == 0 ? 64 : js->rs_cap * 2;
			jsval_t new_set = (jsval_t )realloc(js->remembered_set, new_cap * sizeof(jsval_t));
			if (!new_set) return;
			js->remembered_set = new_set;
			js->rs_cap = new_cap;
			}
			js->remembered_set[js->rs_count++] = obj;
			}

			void rs_clear(ant_t *js) {
			js->rs_count = 0;
			}

			// Nursery allocation with bump pointer (very fast)
			jsoff_t nursery_alloc(ant_t *js, size_t size) {
			size = (size + 7) & ~(size_t)7; // align to 8 bytes

			if (js->nursery_ptr + size > js->nursery_size) {
			js->nursery_full = true;
			return ~(jsoff_t)0; // signal nursery full
			}

			jsoff_t off = js->nursery_ptr;
			js->nursery_ptr += (jsoff_t)size;

			return off \| NURSERY_BIT; // tag as nursery pointer
			}

			// Forward a nursery pointer to old gen, return new offset
			static jsoff_t scavenge_copy_object(ant_t js, jsoff_t nursery_off, jsoff_t fwd_table, size_t fwd_cap) {
			jsoff_t raw_off = nursery_raw_off(nursery_off);

			// Check if already forwarded
			if (raw_off < fwd_cap && fwd_table[raw_off >> 3] != 0) {
			return fwd_table[raw_off >> 3];
			}

			// Get object header from nursery
			jsoff_t header;
			memcpy(&header, &js->nursery[raw_off], sizeof(header));

			// Calculate size based on type
			size_t size;
			uint8_t type = header & 3;

			if (type == T_STR) {
			if (header & ROPE_FLAG) {
			size = sizeof(rope_node_t);
			} else {
			size = esize(header);
			}
			} else {
			size = esize(header);
			}

			if (size == (size_t)~0 \|\| size == 0) {
			size = 24; // minimum object size
			}

			size = (size + 7) & ~(size_t)7;

			// Allocate in old gen
			jsoff_t available = js->size - js->brk;
			if (size > available) {
			return ~(jsoff_t)0; // OOM
			}

			jsoff_t new_off = js->brk;
			memcpy(&js->mem[new_off], &js->nursery[raw_off], size);
			js->brk += (jsoff_t)size;

			// Install forwarding pointer
			if (raw_off < fwd_cap) {
			fwd_table[raw_off >> 3] = new_off;
			}

			return new_off;
			}

			// Context for scavenge_op_val callback
			typedef struct {
			ant_t *js;
			jsoff_t *fwd_table;
			size_t fwd_cap;
			} scavenge_ctx_t;

			static jsval_t scavenge_update_val(ant_t js, jsval_t val, jsoff_t fwd_table, size_t fwd_cap);

			// Wrapper callbacks for js_gc_scavenge_roots during scavenge
			static void scavenge_op_val(void ctx, jsval_t val) {
			scavenge_ctx_t sctx = (scavenge_ctx_t )ctx;
			val = scavenge_update_val(sctx->js, val, sctx->fwd_table, sctx->fwd_cap);
			}

			static void scavenge_op_off(void ctx, jsoff_t off) {
			scavenge_ctx_t sctx = (scavenge_ctx_t )ctx;
			if (!is_nursery_off(*off)) return;
			jsoff_t new_off = scavenge_copy_object(sctx->js, *off, sctx->fwd_table, sctx->fwd_cap);
			if (new_off != ~(jsoff_t)0) *off = new_off;
			}

			// Recursively scan the scope chain and update parent pointers + properties
			static void scavenge_scan_scope_chain(ant_t js, jsoff_t scope_off, jsoff_t fwd_table, size_t fwd_cap, int depth);

			// Scan all properties of an old-gen object for nursery references
			static void scavenge_scan_object_props(ant_t js, jsoff_t obj_off, jsoff_t fwd_table, size_t fwd_cap) {
			if (obj_off >= js->brk \|\| is_nursery_off(obj_off)) return;

			jsoff_t header = gc_loadoff(js->mem, obj_off);
			jsoff_t first_prop = header & ~(3ULL \| FLAGMASK);

			// If first property is in nursery, copy it and update object header
			if (first_prop != 0 && is_nursery_off(first_prop)) {
			jsoff_t new_first = scavenge_copy_object(js, first_prop, fwd_table, fwd_cap);
			if (new_first != ~(jsoff_t)0) {
			jsoff_t new_header = (new_first & ~3ULL) \| (header & (3ULL \| FLAGMASK));
			gc_saveoff(js->mem, obj_off, new_header);
			first_prop = new_first;
			}
			}

			jsoff_t prop_off = first_prop;
			while (prop_off != 0 && prop_off < js->brk && !is_nursery_off(prop_off)) {
			jsoff_t prop_header = gc_loadoff(js->mem, prop_off);
			jsoff_t next_prop = prop_header & ~(3ULL \| FLAGMASK);

			// If next property is in nursery, copy it and update current prop's header
			if (next_prop != 0 && is_nursery_off(next_prop)) {
			jsoff_t new_next = scavenge_copy_object(js, next_prop, fwd_table, fwd_cap);
			if (new_next != ~(jsoff_t)0) {
			jsoff_t new_prop_header = (new_next & ~3ULL) \| (prop_header & (3ULL \| FLAGMASK));
			gc_saveoff(js->mem, prop_off, new_prop_header);
			next_prop = new_next;
			}
			}

			// Update property key if it points to nursery
			jsoff_t key_off = gc_loadoff(js->mem, prop_off + sizeof(jsoff_t));
			if (is_nursery_off(key_off)) {
			jsoff_t new_key = scavenge_copy_object(js, key_off, fwd_table, fwd_cap);
			if (new_key != ~(jsoff_t)0) {
			gc_saveoff(js->mem, prop_off + sizeof(jsoff_t), new_key);
			}
			}

			// Update property value if it points to nursery
			jsval_t prop_val = gc_loadval(js->mem, prop_off + sizeof(jsoff_t) * 2);
			jsval_t new_val = scavenge_update_val(js, prop_val, fwd_table, fwd_cap);
			if (new_val != prop_val) {
			gc_saveval(js->mem, prop_off + sizeof(jsoff_t) * 2, new_val);
			}

			prop_off = next_prop;
			}
			}

			// Recursively scan the scope chain and update parent pointers + properties
			static void scavenge_scan_scope_chain(ant_t js, jsoff_t scope_off, jsoff_t fwd_table, size_t fwd_cap, int depth) {
			if (depth > 255) return; // prevent infinite recursion
			if (scope_off == 0 \|\| is_nursery_off(scope_off) \|\| scope_off >= js->brk) return;

			// Scan this scope's properties
			scavenge_scan_object_props(js, scope_off, fwd_table, fwd_cap);

			// Get parent scope offset (stored at scope_off + sizeof(jsoff_t))
			jsoff_t parent_off = gc_loadoff(js->mem, scope_off + sizeof(jsoff_t));

			// If parent is in nursery, copy it and update the pointer
			if (parent_off != 0 && is_nursery_off(parent_off)) {
			jsoff_t new_parent = scavenge_copy_object(js, parent_off, fwd_table, fwd_cap);
			if (new_parent != ~(jsoff_t)0) {
			gc_saveoff(js->mem, scope_off + sizeof(jsoff_t), new_parent);
			parent_off = new_parent;
			}
			}

			// Recurse into parent scope
			if (parent_off != 0 && !is_nursery_off(parent_off) && parent_off < js->brk) {
			scavenge_scan_scope_chain(js, parent_off, fwd_table, fwd_cap, depth + 1);
			}
			}

			// Update a jsval_t if it points to nursery
			static jsval_t scavenge_update_val(ant_t js, jsval_t val, jsoff_t fwd_table, size_t fwd_cap) {
			if ((val >> 53) != NANBOX_PREFIX_CHK) return val; // not a tagged value

			uint8_t type = (val >> NANBOX_TYPE_SHIFT) & NANBOX_TYPE_MASK;
			jsoff_t off = (jsoff_t)(val & NANBOX_DATA_MASK);

			if (!is_nursery_off(off)) return val; // not in nursery

			switch (type) {
			case T_OBJ:
			case T_FUNC:
			case T_ARR:
			case T_PROMISE:
			case T_GENERATOR:
			case T_STR:
			case T_PROP:
			case T_BIGINT: {
			jsoff_t new_off = scavenge_copy_object(js, off, fwd_table, fwd_cap);
			if (new_off != ~(jsoff_t)0) {
			return NANBOX_PREFIX \| ((jsval_t)(type & NANBOX_TYPE_MASK) << NANBOX_TYPE_SHIFT) \| (new_off & NANBOX_DATA_MASK);
			}
			break;
			}
			default:
			break;
			}

			return val;
			}

			// Scavenge nursery: copy live objects to old gen
			void nursery_scavenge(ant_t *js) {
			if (!js->nursery \|\| js->nursery_ptr == 0) {
			js->nursery_full = false;
			return;
			}

			mco_coro *running = mco_running();
			if (running != NULL && running->stack_base != NULL) {
			return;
			}

			// Allocate forwarding table (indexed by nursery offset >> 3)
			size_t fwd_cap = js->nursery_ptr + 8;
			jsoff_t fwd_table = (jsoff_t )calloc(fwd_cap >> 3, sizeof(jsoff_t));
			if (!fwd_table) {
			js->nursery_ptr = 0;
			rs_clear(js);
			return;
			}

			jsoff_t scan_start = js->brk;

			// 1. Scan direct roots and copy nursery objects
			// Process remembered set (old gen objects pointing to nursery)
			for (size_t i = 0; i < js->rs_count; i++) {
			jsval_t old_obj = js->remembered_set[i];
			jsoff_t obj_off = (jsoff_t)(old_obj & NANBOX_DATA_MASK);

			if (is_nursery_off(obj_off)) continue; // skip nursery objects in rs
			if (obj_off >= js->brk) continue;

			// Scan object's properties for nursery references
			jsoff_t header = gc_loadoff(js->mem, obj_off);
			jsoff_t prop_off = header & ~(3ULL \| FLAGMASK);

			while (prop_off != 0 && prop_off < js->brk) {
			jsoff_t prop_header = gc_loadoff(js->mem, prop_off);

			// Update property value if it points to nursery
			jsval_t prop_val = gc_loadval(js->mem, prop_off + sizeof(jsoff_t) * 2);
			jsval_t new_val = scavenge_update_val(js, prop_val, fwd_table, fwd_cap);
			if (new_val != prop_val) {
			gc_saveval(js->mem, prop_off + sizeof(jsoff_t) * 2, new_val);
			}

			prop_off = prop_header & ~(3ULL \| FLAGMASK);
			}
			}

			// 2. Scan all runtime roots (scope stacks, for_let_stack, this_stack,
			// coroutines, promise registry, timers, modules, etc.)
			scavenge_ctx_t sctx = { .js = js, .fwd_table = fwd_table, .fwd_cap = fwd_cap };
			js_gc_scavenge_roots(js, scavenge_op_val, scavenge_op_off, &sctx);

			// Scan global object properties for nursery references
			jsoff_t global_off = (jsoff_t)(js->global & NANBOX_DATA_MASK);
			scavenge_scan_object_props(js, global_off, fwd_table, fwd_cap);

			// Scan the entire scope chain (current scope + all parents)
			jsoff_t scope_off = (jsoff_t)(js->scope & NANBOX_DATA_MASK);
			if (!is_nursery_off(scope_off)) {
			scavenge_scan_scope_chain(js, scope_off, fwd_table, fwd_cap, 0);
			}

			// 3. Cheney scan: process copied objects for more references
			jsoff_t scan = scan_start;
			int obj_count = 0;
			while (scan < js->brk) {
			jsoff_t header = gc_loadoff(js->mem, scan);
			uint8_t type = header & 3;
			size_t obj_size;

			// Handle rope nodes specially (strings with ROPE_FLAG set)
			if (type == T_STR && (header & ROPE_FLAG)) {
			obj_size = sizeof(rope_node_t);
			} else {
			obj_size = esize(header);
			}

			if (obj_size == (size_t)~0) obj_size = 24;
			obj_size = (obj_size + 7) & ~(size_t)7;
			obj_count++;

			if (type == T_OBJ \|\| type == T_PROP) {
			// Update first prop/next prop
			jsoff_t prop_ref = header & ~(3ULL \| FLAGMASK);
			if (is_nursery_off(prop_ref)) {
			jsoff_t new_ref = scavenge_copy_object(js, prop_ref, fwd_table, fwd_cap);
			if (new_ref != ~(jsoff_t)0) {

			header = (new_ref & ~3ULL) \| (header & (3ULL \| FLAGMASK));
			gc_saveoff(js->mem, scan, header);
			}
			}

			if (type == T_OBJ) {
			// Update parent
			jsoff_t parent = gc_loadoff(js->mem, scan + sizeof(jsoff_t));
			if (is_nursery_off(parent)) {
			jsoff_t new_parent = scavenge_copy_object(js, parent, fwd_table, fwd_cap);
			if (new_parent != ~(jsoff_t)0) {
			gc_saveoff(js->mem, scan + sizeof(jsoff_t), new_parent);
			}
			}

			// Update tail
			jsoff_t tail = gc_loadoff(js->mem, scan + sizeof(jsoff_t) * 2);
			if (is_nursery_off(tail)) {
			jsoff_t new_tail = scavenge_copy_object(js, tail, fwd_table, fwd_cap);
			if (new_tail != ~(jsoff_t)0) {
			gc_saveoff(js->mem, scan + sizeof(jsoff_t) * 2, new_tail);
			}
			}
			} else if (type == T_PROP) {
			// Update property key (string offset stored at scan + sizeof(jsoff_t))
			jsoff_t key_off = gc_loadoff(js->mem, scan + sizeof(jsoff_t));
			if (is_nursery_off(key_off)) {
			jsoff_t new_key = scavenge_copy_object(js, key_off, fwd_table, fwd_cap);
			if (new_key != ~(jsoff_t)0) {
			gc_saveoff(js->mem, scan + sizeof(jsoff_t), new_key);
			}
			}
			// Update property value
			jsval_t prop_val = gc_loadval(js->mem, scan + sizeof(jsoff_t) * 2);
			jsval_t new_val = scavenge_update_val(js, prop_val, fwd_table, fwd_cap);
			if (new_val != prop_val) {
			gc_saveval(js->mem, scan + sizeof(jsoff_t) * 2, new_val);
			}
			}
			} else if (type == T_STR && (header & ROPE_FLAG)) {
			// Rope node - update left/right/cached
			jsval_t left = gc_loadval(js->mem, scan + offsetof(rope_node_t, left));
			jsval_t right = gc_loadval(js->mem, scan + offsetof(rope_node_t, right));
			jsval_t cached = gc_loadval(js->mem, scan + offsetof(rope_node_t, cached));

			jsval_t new_left = scavenge_update_val(js, left, fwd_table, fwd_cap);
			jsval_t new_right = scavenge_update_val(js, right, fwd_table, fwd_cap);
			jsval_t new_cached = scavenge_update_val(js, cached, fwd_table, fwd_cap);

			if (new_left != left) gc_saveval(js->mem, scan + offsetof(rope_node_t, left), new_left);
			if (new_right != right) gc_saveval(js->mem, scan + offsetof(rope_node_t, right), new_right);
			if (new_cached != cached) gc_saveval(js->mem, scan + offsetof(rope_node_t, cached), new_cached);
			}

			scan += obj_size;
			}



			// 4. Reset nursery
			js->nursery_ptr = 0;
			js->nursery_full = false;
			rs_clear(js);

			// Debug: check scope chain depth and global_scope_stack
			{
			jsoff_t dbg_off = (jsoff_t)(js->scope & NANBOX_DATA_MASK);
			int chain_depth = 0;
			while (dbg_off != 0 && chain_depth < 50) {
			if (is_nursery_off(dbg_off) \|\| dbg_off >= js->brk) break;
			dbg_off = gc_loadoff(js->mem, dbg_off + sizeof(jsoff_t));
			chain_depth++;
			}
			int stack_len = global_scope_stack ? (int)utarray_len(global_scope_stack) : 0;
			fprintf(stderr, "SCAVENGE: scope chain depth=%d, stack_len=%d, scope=0x%llx, global=0x%llx\n",
			chain_depth, stack_len,
			(unsigned long long)(js->scope & NANBOX_DATA_MASK),
			(unsigned long long)(js->global & NANBOX_DATA_MASK));
			if (stack_len > 0) {
			jsoff_t first = (jsoff_t )utarray_eltptr(global_scope_stack, 0);
			fprintf(stderr, "SCAVENGE: scope_stack[0]=0x%llx\n", (unsigned long long)*first);
			}
			}
			// Debug: verify no nursery refs remain in scope chain after scavenge
			{
			jsoff_t dbg_off = (jsoff_t)(js->scope & NANBOX_DATA_MASK);
			int dbg_depth = 0;
			while (dbg_off != 0 && dbg_depth < 50) {
			if (is_nursery_off(dbg_off)) {
			fprintf(stderr, "POST-SCAVENGE BUG: scope chain[%d] is nursery 0x%llx\n", dbg_depth, (unsigned long long)dbg_off);
			break;
			}
			if (dbg_off >= js->brk) {
			fprintf(stderr, "POST-SCAVENGE BUG: scope chain[%d] OOB 0x%llx (brk=0x%llx)\n", dbg_depth, (unsigned long long)dbg_off, (unsigned long long)js->brk);
			break;
			}
			jsoff_t hdr = gc_loadoff(js->mem, dbg_off);
			jsoff_t fp = hdr & ~(3ULL \| FLAGMASK);
			if (fp != 0 && is_nursery_off(fp)) {
			fprintf(stderr, "POST-SCAVENGE BUG: scope[%d] first_prop nursery 0x%llx\n", dbg_depth, (unsigned long long)fp);
			}
			jsoff_t pp = fp;
			int pi = 0;
			while (pp != 0 && !is_nursery_off(pp) && pp < js->brk && pi < 500) {
			jsoff_t ph = gc_loadoff(js->mem, pp);
			jsoff_t np = ph & ~(3ULL \| FLAGMASK);
			if (np != 0 && is_nursery_off(np))
			fprintf(stderr, "POST-SCAVENGE BUG: scope[%d].prop[%d] next nursery 0x%llx\n", dbg_depth, pi, (unsigned long long)np);
			jsoff_t koff = gc_loadoff(js->mem, pp + sizeof(jsoff_t));
			if (is_nursery_off(koff))
			fprintf(stderr, "POST-SCAVENGE BUG: scope[%d].prop[%d] key nursery 0x%llx\n", dbg_depth, pi, (unsigned long long)koff);
			jsval_t pv = gc_loadval(js->mem, pp + sizeof(jsoff_t) * 2);
			jsoff_t pv_off = (jsoff_t)(pv & NANBOX_DATA_MASK);
			if ((pv >> 53) == NANBOX_PREFIX_CHK && is_nursery_off(pv_off))
			fprintf(stderr, "POST-SCAVENGE BUG: scope[%d].prop[%d] val nursery 0x%llx\n", dbg_depth, pi, (unsigned long long)pv_off);
			pp = np;
			pi++;
			}
			dbg_off = gc_loadoff(js->mem, dbg_off + sizeof(jsoff_t));
			dbg_depth++;
			}
			// Also check global_scope_stack entries
			if (global_scope_stack) {
			jsoff_t *sp = NULL;
			int si = 0;
			while ((sp = (jsoff_t *)utarray_next(global_scope_stack, sp)) != NULL) {
			if (is_nursery_off(*sp))
			fprintf(stderr, "POST-SCAVENGE BUG: scope_stack[%d] nursery 0x%llx\n", si, (unsigned long long)*sp);
			si++;
			}
			}
			}

			free(fwd_table);
			}

Owner Packages

No Owners

ant/src/gc.cddfe6237cab5feature/nursery

gc.cView Options

Owner Packages

ant/src/gc.c
ddfe6237cab5feature/nursery

gc.c
View Options