Raymond Toy pushed to branch issue-243-weak-pointer-to-static-array at cmucl / cmucl

Commits: afb81c84 by Raymond Toy at 2024-02-23T14:41:27-08:00 Move phases of scanning static vectors into separate functions.

Make `scan_static_vectors` a bit easier to read by putting each phase into its own function.

- - - - -

1 changed file:

- src/lisp/gencgc.c

Changes:

===================================== src/lisp/gencgc.c ===================================== @@ -5439,85 +5439,84 @@ push(struct weak_pointer* wp, struct weak_pointer **list) *list = wp; }

+/* + * Phase 2: Find the weak pointers to static vectors that are in use + * and not in use. The vectors that are in use are added to + * inuse_list. Those that are not in use are added to freeable_list. + * Only unique vectors are added to freeable list; a duplicate has its + * weak pointer to it broken. + */ static void -scan_static_vectors(struct weak_pointer *static_vector_list) +scan_static_vectors_2(struct weak_pointer *static_vector_list, + struct weak_pointer **freeable_list, + struct weak_pointer **inuse_list) { - /* List of weak pointers to static vectors that can be freed. */ - struct weak_pointer *freeable_list = NULL; - - /* List of weak pointers to static vectors that are in in use. */ - struct weak_pointer *inuse_list = NULL; - struct weak_pointer *wp; - DPRINTF(debug_static_array_p, (stdout, "Phase 2: Find unused and unused static vectors\n"));

- /* - * static_vector_list points to all weak pointers to static - * vectors. If the static vector is in use, add it to the in-use - * list. If the static vector is not in use, and has not been - * visited, mark it as visited and add it to the freeable list. - * If it has been visited, just break the weak pointer. - */ while (static_vector_list) { - struct weak_pointer *this_wp; + struct weak_pointer *wp; lispobj *header;

/* Pop weak pointer from the list */ - this_wp = pop(&static_vector_list); - header = (lispobj *) PTR(this_wp->value); + wp = pop(&static_vector_list); + header = (lispobj *) PTR(wp->value);

DPRINTF(debug_static_array_p, (stdout, " wp %p value %p header 0x%08lx\n", - this_wp, (lispobj *) this_wp->value, *header)); + wp, (lispobj *) wp->value, *header));

- /* - * If the static vector is unused (mark bit clear) and if we - * haven't seen this vector before, set the visited flag. If - * we have visited this vector before, break the weak pointer. - */ if ((*header & STATIC_VECTOR_MARK_BIT) != 0) { /* * Static vector is in use. Add this to the in-use list. */ - printf(" In-use vector; add to in-use list\n"); - push(this_wp, &inuse_list); + DPRINTF(debug_static_array_p, + (stdout, " In-use vector; add to in-use list\n")); + + push(wp, inuse_list); } else { - /* Unused static vector */ + /* + * Static vector not in use. If we haven't seen this + * vector before, set the visited flag and add it to + * freeable_list. If we have visited this vector before, + * break the weak pointer. + */ if ((*header & STATIC_VECTOR_VISITED_BIT) == 0) { DPRINTF(debug_static_array_p, (stdout, " Visit unused vector, add to freeable list\n"));

*header |= STATIC_VECTOR_VISITED_BIT; - - /* - * Add this to the freeable list because it's a static - * vector that we can free. - */ - push(this_wp, &freeable_list); + push(wp, freeable_list); } else { DPRINTF(debug_static_array_p, (stdout, " Already visited unused vector; break weak pointer\n"));

- this_wp->value = NIL; - this_wp->broken = T; + wp->value = NIL; + wp->broken = T; } } } +} + +/* + * Free all the unused static vectors in freeable_list. + */ +static void +scan_static_vectors_3(struct weak_pointer *freeable_list) +{ + struct weak_pointer *wp;

DPRINTF(debug_static_array_p, (stdout, "Phase 3: Free static vectors\n"));

- /* - * freeable_list now contains weak pointers to unique static - * vectors that are not in use. Break the weak pointer and free - * the static vector. - */ for (wp = freeable_list; wp; wp = wp->next) { - /* Invariant: weak pointer must not be broken */ - gc_assert(wp->broken == NIL); - lispobj *header = (lispobj *) PTR(wp->value); + lispobj *static_array = (lispobj *) PTR(wp->value); + + /* + * Invariant: weak pointer must not be broken + */ + gc_assert(wp->broken == NIL);

DPRINTF(debug_static_array_p, (stdout, " wp %p value %p header 0x%08lx\n", @@ -5527,8 +5526,7 @@ scan_static_vectors(struct weak_pointer *static_vector_list) * Invariant: Mark bit must be clear */ gc_assert(((*header & STATIC_VECTOR_MARK_BIT) == 0)); - - lispobj *static_array = (lispobj *) PTR(wp->value); + DPRINTF(debug_static_array_p, (stdout, " Free static vector\n"));

@@ -5537,14 +5535,19 @@ scan_static_vectors(struct weak_pointer *static_vector_list)

free(static_array); } +} + +/* + * Unmark all the vectors in inuse_list + */ +static void +scan_static_vectors_4(struct weak_pointer *inuse_list) +{ + struct weak_pointer *wp;

DPRINTF(debug_static_array_p, (stdout, "Phase 4: unmark static vectors\n"));

- /* - * At this point, inuse_list is a list of weak pointers to static - * vectors that are still in use. Clear the mark bit. - */ for (wp = inuse_list; wp; wp = wp->next) { lispobj *header = (lispobj *) PTR(wp->value); /* @@ -5560,6 +5563,7 @@ scan_static_vectors(struct weak_pointer *static_vector_list) (stdout, " wp %p value %p broken %d header 0x%08lx\n", wp, (lispobj*) wp->value, wp->broken == T, *header));

+ /* Only clear if we haven't already */ if ((*header & STATIC_VECTOR_MARK_BIT) != 0) { DPRINTF(debug_static_array_p, (stdout, " Clearing mark bit\n")); @@ -5569,6 +5573,28 @@ scan_static_vectors(struct weak_pointer *static_vector_list) } }

+static void +scan_static_vectors(struct weak_pointer *static_vector_list) +{ + /* List of weak pointers to static vectors that can be freed. */ + struct weak_pointer *freeable_list = NULL; + + /* List of weak pointers to static vectors that are in in use. */ + struct weak_pointer *inuse_list = NULL; + + /* + * For each weak pointer, add it either the inuse list or the + * freeable list. + */ + scan_static_vectors_2(static_vector_list, &freeable_list, &inuse_list); + + /* Free the unused unique static vectors. */ + scan_static_vectors_3(freeable_list); + + /* Unmark all the static vectors that are still alive. */ + scan_static_vectors_4(inuse_list); +} + void scan_weak_pointers(void) {

View it on GitLab: https://gitlab.common-lisp.net/cmucl/cmucl/-/commit/afb81c84f83b2ca4b976b787...