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intel/blorp: Increase the presision of coordinate transform calculations

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The result of this calculation goes into an fma() in the shader and we
would like it to be as precise as possible.  The division in particular
was a source of imprecision whenever dst1 - dst0 was not a power of two.
This prevents regressions in some of the new Vulkan CTS tests for blitting
using a filtering of NEAREST.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Jason Ekstrand 2016-09-03 09:49:24 -07:00
parent c70be1ead5
commit fa4627149d
1 changed files with 3 additions and 3 deletions
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6
src/intel/blorp/blorp_blit.c
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@ -1263,7 +1263,7 @@ brw_blorp_setup_coord_transform(struct brw_blorp_coord_transform *xform,
GLfloat dst0, GLfloat dst1,
bool mirror)
{
float scale = (src1 - src0) / (dst1 - dst0);
double scale = (double)(src1 - src0) / (double)(dst1 - dst0);
if (!mirror) {
/* When not mirroring a coordinate (say, X), we need:
* src_x - src_x0 = (dst_x - dst_x0 + 0.5) * scale
@ -1276,7 +1276,7 @@ brw_blorp_setup_coord_transform(struct brw_blorp_coord_transform *xform,
* so 0.5 provides the necessary correction.
*/
xform->multiplier = scale;
xform->offset = src0 + (-dst0 + 0.5f) * scale;
xform->offset = src0 + (-(double)dst0 + 0.5) * scale;
} else {
/* When mirroring X we need:
* src_x - src_x0 = dst_x1 - dst_x - 0.5
@ -1284,7 +1284,7 @@ brw_blorp_setup_coord_transform(struct brw_blorp_coord_transform *xform,
* src_x = src_x0 + (dst_x1 -dst_x - 0.5) * scale
*/
xform->multiplier = -scale;
xform->offset = src0 + (dst1 - 0.5f) * scale;
xform->offset = src0 + ((double)dst1 - 0.5) * scale;
}
}