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sna/trapezoids: Sacrifice precision to avoid 64bit overflow 

References: https://bugs.freedesktop.org/show_bug.cgi?id=70461#c71
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
This commit is contained in:
Chris Wilson 2014-10-10 11:42:09 +01:00
parent 069f7878dc
commit 70a1710e18
2 changed files with 19 additions and 2 deletions
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11
src/sna/sna_trapezoids_imprecise.c
View File

@ -502,6 +502,7 @@ polygon_add_edge(struct polygon *polygon,
Ex = (int64_t)(edge->p2.x - edge->p1.x) * FAST_SAMPLES_X;
Ey = (int64_t)(edge->p2.y - edge->p1.y) * FAST_SAMPLES_Y * (2 << 16);
assert(Ey > 0);
e->dxdy.quo = Ex * (2 << 16) / Ey;
e->dxdy.rem = Ex * (2 << 16) % Ey;
@ -514,7 +515,14 @@ polygon_add_edge(struct polygon *polygon,
tmp = (int64_t)edge->p1.x * FAST_SAMPLES_X;
e->x.quo += tmp / (1 << 16) + dx;
e->x.rem += ((tmp & ((1 << 16) - 1)) * Ey) / (1 << 16);
tmp &= (1 << 16) - 1;
if (tmp) {
if (Ey < INT64_MAX >> 16)
tmp = (tmp * Ey) / (1 << 16);
else /* Handle overflow by losing precision */
tmp = tmp * (Ey / (1 << 16));
e->x.rem += tmp;
}
if (e->x.rem < 0) {
--e->x.quo;
@ -523,6 +531,7 @@ polygon_add_edge(struct polygon *polygon,
++e->x.quo;
e->x.rem -= Ey;
}
assert(e->x.rem >= 0 && e->x.rem < Ey);
e->cell = e->x.quo + (e->x.rem >= Ey/2);
e->dy = Ey;

10
src/sna/sna_trapezoids_precise.c
View File

@ -555,6 +555,7 @@ polygon_add_edge(struct polygon *polygon,
Ex = (int64_t)(edge->p2.x - edge->p1.x) * SAMPLES_X;
Ey = (int64_t)(edge->p2.y - edge->p1.y) * SAMPLES_Y * (2 << 16);
assert(Ey > 0);
e->dxdy.quo = Ex * (2 << 16) / Ey;
e->dxdy.rem = Ex * (2 << 16) % Ey;
@ -566,7 +567,14 @@ polygon_add_edge(struct polygon *polygon,
tmp = (int64_t)edge->p1.x * SAMPLES_X;
e->x.quo += (tmp >> 16) + dx;
e->x.rem += ((tmp & ((1 << 16) - 1)) * Ey) / (1 << 16);
tmp &= (1 << 16) - 1;
if (tmp) {
if (Ey < INT64_MAX >> 16)
tmp = (tmp * Ey) / (1 << 16);
else /* Handle overflow by losing precision */
tmp = tmp * (Ey / (1 << 16));
e->x.rem += tmp;
}
if (e->x.rem < 0) {
e->x.quo--;