ensure objects beyond bump allocated region are inserted into the obj…

…ect pool freelist

* addresses follow-up comments from #50137, particularly #50137 (comment)

src/gc.c

@@ -1238,7 +1238,10 @@ static NOINLINE jl_taggedvalue_t *gc_add_page(jl_gc_pool_t *p) JL_NOTSAFEPOINT
  // Do not pass in `ptls` as argument. This slows down the fast path
  // in pool_alloc significantly
  jl_ptls_t ptls = jl_current_task->ptls;
- jl_gc_pagemeta_t *pg = jl_gc_alloc_page();
+ jl_gc_pagemeta_t *pg = pop_page_metadata_back(&ptls->page_metadata_lazily_freed);
+ if (pg == NULL) {
+ pg = jl_gc_alloc_page();
+ }
  pg->osize = p->osize;
  pg->thread_n = ptls->tid;
  set_page_metadata(pg);
@@ -1295,20 +1298,8 @@ STATIC_INLINE jl_value_t *jl_gc_pool_alloc_inner(jl_ptls_t ptls, int pool_offset
  assert(pg->osize == p->osize);
  pg->nfree = 0;
  pg->has_young = 1;
- pg = pop_page_metadata_back(&ptls->page_metadata_lazily_freed);
- if (pg != NULL) {
- v = gc_reset_page(ptls, p, pg);
- pg->osize = p->osize;
- push_page_metadata_back(&ptls->page_metadata_allocd, pg);
- }
- else {
- v = NULL;
- }
- }
- // Not an else!!
- if (v == NULL) {
- v = gc_add_page(p);
  }
+ v = gc_add_page(p);
  next = (jl_taggedvalue_t*)((char*)v + osize);
  }
  p->newpages = next;
@@ -1353,15 +1344,19 @@ static jl_taggedvalue_t **gc_sweep_page(jl_gc_pool_t *p, jl_gc_pagemeta_t **allo
  char *data = pg->data;
  jl_taggedvalue_t *v = (jl_taggedvalue_t*)(data + GC_PAGE_OFFSET);
  char *lim = data + GC_PAGE_SZ - osize;
+ char *lim_newpages = data + GC_PAGE_SZ;
+ if (gc_page_data((char*)p->newpages - 1) == data) {
+ lim_newpages = (char*)p->newpages;
+ }
  size_t old_nfree = pg->nfree;
  size_t nfree;
 
- int reuse_page = 1;
+ int re_use_page = 1;
  int freed_lazily = 0;
  int freedall = 1;
  int pg_skpd = 1;
  if (!pg->has_marked) {
- reuse_page = 0;
+ re_use_page = 0;
  #ifdef _P64 // TODO: re-enable on `_P32`?
  // lazy version: (empty) if the whole page was already unused, free it (return it to the pool)
  // eager version: (freedall) free page as soon as possible
@@ -1402,7 +1397,8 @@ static jl_taggedvalue_t **gc_sweep_page(jl_gc_pool_t *p, jl_gc_pagemeta_t **allo
  jl_taggedvalue_t **pfl_begin = NULL;
  while ((char*)v <= lim) {
  int bits = v->bits.gc;
- if (!gc_marked(bits)) {
+ // if an object is past `lim_newpages` then we can guarantee it's garbage
+ if (!gc_marked(bits) || (char*)v >= lim_newpages) {
  *pfl = v;
  pfl = &v->next;
  pfl_begin = (pfl_begin != NULL) ? pfl_begin : pfl;
@@ -1439,7 +1435,7 @@ static jl_taggedvalue_t **gc_sweep_page(jl_gc_pool_t *p, jl_gc_pagemeta_t **allo
  nfree = pg->nfree;
 
 done:
- if (reuse_page) {
+ if (re_use_page) {
  push_page_metadata_back(allocd, pg);
  }
  else if (freed_lazily) {