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Switch is_pointer_to_heap to use library bsearch

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This commit switches from a custom implemented bsearch algorithm to
use the one provided by the C standard library.

Because `is_pointer_to_heap` will only return true if the pointer
being searched for is a valid slot starting address within the heap
page body, we've extracted the bsearch call site into a more general
function so we can use it elsewhere.

The new function `heap_page_for_ptr` returns the heap page for any heap
page pointer, regardless of whether that is at the start of a slot or
in the middle of one.

We then use this function as the basis of `is_pointer_to_heap`.
This commit is contained in:
Matt Valentine-House 2021-11-15 21:28:20 +00:00 • committed by Peter Zhu
parent 615e9b2865
commit ad007bc6ea
Notes: git 2022-01-05 00:28:13 +09:00
1 changed files with 50 additions and 23 deletions
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73
gc.c
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@ -2797,13 +2797,49 @@ rb_objspace_data_type_name(VALUE obj)
}
}
static int
ptr_in_page_body_p(const void *ptr, const void *memb)
{
struct heap_page *page = *(struct heap_page **)memb;
uintptr_t p_body = (uintptr_t)GET_PAGE_BODY(page->start);
if ((uintptr_t)ptr >= p_body) {
return (uintptr_t)ptr < (p_body + HEAP_PAGE_SIZE) ? 0 : 1;
}
else {
return -1;
}
}
PUREFUNC(static inline struct heap_page * heap_page_for_ptr(rb_objspace_t *objspace, uintptr_t ptr);)
static inline struct heap_page *
heap_page_for_ptr(rb_objspace_t *objspace, uintptr_t ptr)
{
struct heap_page **res;
if (ptr < (uintptr_t)heap_pages_lomem ||
ptr > (uintptr_t)heap_pages_himem) {
return NULL;
}
res = bsearch((void *)ptr, heap_pages_sorted,
(size_t)heap_allocated_pages, sizeof(struct heap_page *),
ptr_in_page_body_p);
if (res) {
return *res;
}
else {
return NULL;
}
}
PUREFUNC(static inline int is_pointer_to_heap(rb_objspace_t *objspace, void *ptr);)
static inline int
is_pointer_to_heap(rb_objspace_t *objspace, void *ptr)
{
register RVALUE *p = RANY(ptr);
register struct heap_page *page;
register size_t hi, lo, mid;
RB_DEBUG_COUNTER_INC(gc_isptr_trial);
@ -2813,30 +2849,21 @@ is_pointer_to_heap(rb_objspace_t *objspace, void *ptr)
if ((VALUE)p % sizeof(RVALUE) != 0) return FALSE;
RB_DEBUG_COUNTER_INC(gc_isptr_align);
/* check if p looks like a pointer using bsearch*/
lo = 0;
hi = heap_allocated_pages;
while (lo < hi) {
mid = (lo + hi) / 2;
page = heap_pages_sorted[mid];
if (page->start <= p) {
if ((uintptr_t)p < ((uintptr_t)page->start + (page->total_slots * page->slot_size))) {
RB_DEBUG_COUNTER_INC(gc_isptr_maybe);
page = heap_page_for_ptr(objspace, (uintptr_t)ptr);
if (page) {
GC_ASSERT(page == GET_HEAP_PAGE(ptr));
if (page->flags.in_tomb) {
return FALSE;
}
else {
if ((NUM_IN_PAGE(p) * sizeof(RVALUE)) % page->slot_size != 0) return FALSE;
RB_DEBUG_COUNTER_INC(gc_isptr_maybe);
if (page->flags.in_tomb) {
return FALSE;
}
else {
if ((uintptr_t)p < ((uintptr_t)page->start)) return FALSE;
if ((uintptr_t)p >= ((uintptr_t)page->start + (page->total_slots * page->slot_size))) return FALSE;
if ((NUM_IN_PAGE(p) * sizeof(RVALUE)) % page->slot_size != 0) return FALSE;
return TRUE;
}
}
lo = mid + 1;
}
else {
hi = mid;
}
return TRUE;
}
}
return FALSE;
}