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/* Copyright (c) 1993-2008 by Richard Kelsey and Jonathan Rees.
See file COPYING. */
/* Implements area_roots.h */
#include <stdlib.h>
#include "scheme48.h"
#include "area_roots.h"
#include "areas.h"
#include "memory.h"
#include "memory_map.h"
#include "utils.h"
#include "data.h"
#include "measure.h"
#include "generation_gc.h"
#include "gc_config.h"
#if (S48_USE_REMEMBERED_SETS)
#include "remset.h"
#endif
/* initializes the dirty vector of AREA */
void s48_init_dirty_vector(Area* area) {
Dirty_vector* dv = &area->dirty_vector;
unsigned long area_size = area->end - area->start;
/* The number of logical cards is the division of area_size through
the logical card_size (number of 32-bit-addresses). Bitwise Division:
shift right */
unsigned long number_of_cards = area_size >> S48_LOG_CARD_SIZE ;
dv->length = number_of_cards;
/* Space allocation and initialisation */
#if S48_DIRTY_VECTOR_METHOD==S48_OFFSET_DIRTY_VECTORS
/* A vector of bytes (offset is max 2^9 - 1 = 511 => max logical card size = 9) */
dv->items = (char*)calloc(sizeof(char), number_of_cards);
#endif
#if S48_DIRTY_VECTOR_METHOD==S48_ADDRESS_DIRTY_VECTORS
/* A vector of double words */
dv->items = (s48_address*)calloc(sizeof(s48_address), number_of_cards);
#endif
#if S48_DIRTY_VECTOR_METHOD==S48_CROSSINGMAP_DIRTY_VECTORS
/* This method uses two bits per card. One bit marks a card as
beeing dirty, the second marks a card as beeing tracable, which
means that the card does not begin within a B-vector (A string
for example). We use a full char to store the bit. */
dv->dirty_bits = (char*)calloc(sizeof(char), number_of_cards);
dv->traceable_bits = (char*)calloc(sizeof(char), number_of_cards);
dv->last_frontier = area->frontier;
#endif
#if (S48_USE_CARD_GENERATION_INDEXING)
dv->minimum_index = (unsigned char*)malloc(sizeof(char) * number_of_cards);
for (i = 0; i < number_of_cards; i++)
dv->minimum_index[i] = 255;
#endif
}
/* deinitializes the dirty vector of AREA. (should free the memory
allocated in init_dirty_vector */
void s48_deinit_dirty_vector(Area* area) {
Dirty_vector* dv = &area->dirty_vector;
#if S48_DIRTY_VECTOR_METHOD==S48_OFFSET_DIRTY_VECTORS
free(dv->items);
#endif
#if S48_DIRTY_VECTOR_METHOD==S48_ADDRESS_DIRTY_VECTORS
free(dv->items);
#endif
#if S48_DIRTY_VECTOR_METHOD==S48_CROSSINGMAP_DIRTY_VECTORS
free(dv->dirty_bits);
free(dv->traceable_bits);
#endif
}
#if (MEASURE_GC)
static unsigned long areas_visited = 0;
static unsigned long areas_passed = 0;
#endif
/* FPage 9 */
/* passes all dirty regions in all areas in the linked list starting
with AREAS, to trace_locationsB */
void s48_trace_areas_roots(Area* areas, int generations_count) {
while(areas != NULL) {
Dirty_vector* dirty_vector = &areas->dirty_vector;
s48_address frontier = areas->frontier;
s48_address card_start_address = areas->start;
s48_address start_address, end_address;
int i;
#if S48_DIRTY_VECTOR_METHOD==S48_CROSSINGMAP_DIRTY_VECTORS
/* This method uses two bits per card. One bit marks a card as
beeing dirty, the second marks a card as beeing tracable, which
means that the card does not begin within a B-vector (A string
for example). We use a full char to store the bit. */
char* dirty_bits = dirty_vector->dirty_bits;
char* traceable_bits = dirty_vector->traceable_bits;
/* if new objects were allocated since the last trace, then scan
the new part of the area to find out which of the new cards are
traceable */
s48_address start = areas->start;
s48_address addr = dirty_vector->last_frontier;
while (addr < frontier) {
s48_value v = *((s48_value*)addr);
unsigned long offset = addr - start;
if ((offset % S48_CARD_SIZE) == 0) {
traceable_bits[offset >> S48_LOG_CARD_SIZE] = TRUE;
}
else {
traceable_bits[offset >> S48_LOG_CARD_SIZE] = FALSE;
}
if (S48_B_VECTOR_HEADER_P(v))
addr = addr + S48_STOB_OVERHEAD_IN_A_UNITS +
S48_HEADER_LENGTH_IN_A_UNITS(v);
else
addr = S48_ADDRESS_INC(addr);
}
/* remember that we have looked at this part of the area */
dirty_vector->last_frontier = frontier;
#endif
#if (MEASURE_GC)
areas_visited += areas->frontier - areas->start;
#endif
/* MAIN SCANNING OF THE DIRTY VECTOR */
/* Search through the whole dirty_vector */
for (i = 0; i < dirty_vector->length;
i++, card_start_address += S48_CARD_SIZE) {
#if (S48_USE_CARD_GENERATION_INDEXING)
/* we can skip this card, if it doesn't contain pointers to a
generation that we're collected right now. */
if (dirty_vector->minimum_index[i] >= generations_count)
continue;
#endif
#if S48_DIRTY_VECTOR_METHOD==S48_OFFSET_DIRTY_VECTORS
dirty_byte = dirty_vector->items[i];
if (dirty_byte != 0) {
/* Get the relative offset in addressable units to the start
address of the i-th card */
unsigned char card_offset = dirty_byte >> 1;
/* Get the absolute start_address and end_address of the i-th
card */
start_address = card_start_address + S48_CELLS_TO_BYTES(card_offset);
end_address = card_start_address + S48_CARD_SIZE;
/* reset to 0. internal_write_barrier will be called to mark
the still dirty cards. */
dirty_vector->items[i] = 0;
#endif
#if S48_DIRTY_VECTOR_METHOD==S48_ADDRESS_DIRTY_VECTORS
start_address = dirty_vector->items[i];
if (start_address != NULL) {
end_address = card_start_address + S48_CARD_SIZE;
dirty_vector->items[i] = NULL;
#endif
#if S48_DIRTY_VECTOR_METHOD==S48_CROSSINGMAP_DIRTY_VECTORS
if (dirty_bits[i]) {
int j = i;
/* search backwards for a traceable card (the first one must
be a traceable one). */
start_address = card_start_address;
end_address = card_start_address + S48_CARD_SIZE;
while ((j > 0) && (!traceable_bits[j])) {
j--;
start_address = start_address - S48_CARD_SIZE;
}
dirty_bits[i] = FALSE;
/* a possible optimization would be to avoid tracing a card
twice completely, e.g. by tracing backwards from the end to
beginning, or to search forward for more consecutive dirty
cards. */
#endif
#if (S48_USE_CARD_GENERATION_INDEXING)
/* clear the minimum_index too */
dirty_vector->minimum_index[i] = 255;
#endif
/* adjust/control addresses */
if (end_address > frontier) end_address = frontier;
if (start_address > frontier)
/* i'm not sure if this just has to be ignored... */
s48_gc_error("s48_trace_areas_roots: dirty bit set behind frontier.");
#if (MEASURE_GC)
areas_passed += (end_address - start_address);
#endif
s48_internal_trace_locationsB(areas, start_address, end_address, "s48_trace_areas_roots");
}
}
areas = areas->next;
}
#if (MEASURE_GC)
measure_areas_roots(areas_visited, areas_passed);
areas_visited = 0;
areas_passed = 0;
#endif
}
void s48_set_dirty_vector(Area* area, s48_address addr, long stob,
Area* maybe_to_area) {
s48_set_dirty_vector_inline(area, addr, stob, maybe_to_area);
}
void s48_write_barrier(long stob, s48_address address, long value) {
s48_write_barrier_inline(stob, address, value);
}
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