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[spans] Add a sentinel cell to the cell_list.

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By terminating the list with a cell for INT_MAX, we remove a few
conditionals from the hot-paths.
This commit is contained in:
Chris Wilson 2008-12-11 01:45:31 +00:00
parent 3b2bb95249
commit 30cef3116e
1 changed files with 15 additions and 10 deletions
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25
src/cairo-tor-scan-converter.c
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@ -457,6 +457,8 @@ struct cell {
struct cell_list {
/* Points to the left-most cell in the scan line. */
struct cell *head;
/* Sentinel node */
struct cell tail;
/* Cursor state for iterating through the cell list. Points to
* a pointer to the current cell: either &cell_list->head or the next
@ -680,7 +682,7 @@ inline static void
cell_list_maybe_rewind(struct cell_list *cells, int x)
{
struct cell *tail = *cells->cursor;
if (tail && tail->x > x) {
if (tail->x > x) {
cell_list_rewind(cells);
}
}
@ -691,7 +693,9 @@ cell_list_init(struct cell_list *cells)
pool_init(cells->cell_pool.base,
256*sizeof(struct cell),
sizeof(cells->cell_pool.embedded));
cells->head = NULL;
cells->tail.next = NULL;
cells->tail.x = INT_MAX;
cells->head = &cells->tail;
cell_list_rewind(cells);
}
@ -708,7 +712,7 @@ inline static void
cell_list_reset(struct cell_list *cells)
{
cell_list_rewind(cells);
cells->head = NULL;
cells->head = &cells->tail;
pool_reset(cells->cell_pool.base);
}
@ -726,14 +730,15 @@ cell_list_find(struct cell_list *cells, int x)
while (1) {
UNROLL3({
tail = *cursor;
if (NULL == tail || tail->x >= x) {
if (tail->x >= x) {
break;
}
cursor = &tail->next;
});
}
cells->cursor = cursor;
if (tail && tail->x == x) {
if (tail->x == x) {
return tail;
} else {
struct cell *cell = pool_alloc(
@ -758,7 +763,7 @@ cell_list_find(struct cell_list *cells, int x)
*
* except with less function call overhead. */
inline static struct cell_pair
cell_list_find2(struct cell_list *cells, int x1, int x2)
cell_list_find_pair(struct cell_list *cells, int x1, int x2)
{
struct cell_pair pair;
struct cell **cursor = cells->cursor;
@ -770,7 +775,7 @@ cell_list_find2(struct cell_list *cells, int x1, int x2)
while (1) {
UNROLL3({
cell1 = *cursor;
if (NULL == cell1 || cell1->x > x1)
if (cell1->x > x1)
break;
if (cell1->x == x1)
goto found_first;
@ -796,7 +801,7 @@ cell_list_find2(struct cell_list *cells, int x1, int x2)
while (1) {
UNROLL3({
cell2 = *cursor;
if (NULL == cell2 || cell2->x > x2)
if (cell2->x > x2)
break;
if (cell2->x == x2)
goto found_second;
@ -860,7 +865,7 @@ cell_list_add_subspan(
if (ix1 != ix2) {
struct cell_pair p;
p = cell_list_find2(cells, ix1, ix2);
p = cell_list_find_pair(cells, ix1, ix2);
if (p.cell1 && p.cell2) {
p.cell1->uncovered_area += 2*fx1;
++p.cell1->covered_height;
@ -974,7 +979,7 @@ cell_list_render_edge(
* this function that the active list order won't change. */
cell_list_maybe_rewind(cells, ix1);
pair = cell_list_find2(cells, ix1, ix1+1);
pair = cell_list_find_pair(cells, ix1, ix1+1);
if (!pair.cell1 || !pair.cell2)
return GLITTER_STATUS_NO_MEMORY;