gallium/util: Really allow aliasing of dst for u_box_union_*

Gallium nine relies on aliasing to work with this function.
Without this patch, dirty region tracking was incorrect, which
could lead to incorrect textures or vertex buffers.
Fixes several game bugs with nine.
Fixes https://github.com/iXit/Mesa-3D/issues/234

Signed-off-by: Axel Davy <[email protected]>
Reviewed-by: Patrick Rudolph <[email protected]>
Reviewed-by: Nicolai Hähnle <[email protected]>
Reviewed-by: Roland Scheidegger <[email protected]>
Reviewed-by: Edward O'Callaghan <[email protected]>

Cc: "12.0" <[email protected]>

1 files changed, 20 insertions, 11 deletions

diff --git a/src/gallium/auxiliary/util/u_box.h b/src/gallium/auxiliary/util/u_box.h
index eb41f8aca36..b3f478e7bfc 100644
--- a/src/gallium/auxiliary/util/u_box.h
+++ b/src/gallium/auxiliary/util/u_box.h
@@ -124,11 +124,15 @@ static inline void
 u_box_union_2d(struct pipe_box *dst,
                const struct pipe_box *a, const struct pipe_box *b)
 {
-   dst->x = MIN2(a->x, b->x);
-   dst->y = MIN2(a->y, b->y);
+   int x, y;
 
-   dst->width = MAX2(a->x + a->width, b->x + b->width) - dst->x;
-   dst->height = MAX2(a->y + a->height, b->y + b->height) - dst->y;
+   x = MIN2(a->x, b->x);
+   y = MIN2(a->y, b->y);
+
+   dst->width = MAX2(a->x + a->width, b->x + b->width) - x;
+   dst->height = MAX2(a->y + a->height, b->y + b->height) - y;
+   dst->x = x;
+   dst->y = y;
 }
 
 /* Aliasing of @dst permitted. */
@@ -136,13 +140,18 @@ static inline void
 u_box_union_3d(struct pipe_box *dst,
                const struct pipe_box *a, const struct pipe_box *b)
 {
-   dst->x = MIN2(a->x, b->x);
-   dst->y = MIN2(a->y, b->y);
-   dst->z = MIN2(a->z, b->z);
-
-   dst->width = MAX2(a->x + a->width, b->x + b->width) - dst->x;
-   dst->height = MAX2(a->y + a->height, b->y + b->height) - dst->y;
-   dst->depth = MAX2(a->z + a->depth, b->z + b->depth) - dst->z;
+   int x, y, z;
+
+   x = MIN2(a->x, b->x);
+   y = MIN2(a->y, b->y);
+   z = MIN2(a->z, b->z);
+
+   dst->width = MAX2(a->x + a->width, b->x + b->width) - x;
+   dst->height = MAX2(a->y + a->height, b->y + b->height) - y;
+   dst->depth = MAX2(a->z + a->depth, b->z + b->depth) - z;
+   dst->x = x;
+   dst->y = y;
+   dst->z = z;
 }
 
 static inline boolean