[Mesa-dev] [PATCH] blorp: Use normalized coordinates on Gen6

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

Apparently, the sampler has some sort of precision issues for
non-normalized texture coordinates with linear filtering.  This caused
some small precision issues in scaled blits.  Work around this by using
normalized coordinates.  There is some extra work necessary because Gen6
uses TEX (instead of TXF) for some multisample resolve blits.

Fixes piglit.spec.arb_framebuffer_object.fbo-blit-stretch on SNB.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=68365
Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
---
 src/intel/blorp/blorp_blit.c      | 11 +++++++----
 src/intel/blorp/blorp_genX_exec.h |  2 +-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/intel/blorp/blorp_blit.c b/src/intel/blorp/blorp_blit.c
index f552302..0850473 100644
--- a/src/intel/blorp/blorp_blit.c
+++ b/src/intel/blorp/blorp_blit.c
@@ -1195,9 +1195,10 @@ brw_blorp_build_nir_shader(struct blorp_context *blorp, void *mem_ctx,
           * representing the four samples that maxe up a pixel.  So we need
           * to multiply our X and Y coordinates each by 2 and then add 1.
           */
-         src_pos = nir_ishl(&b, src_pos, nir_imm_int(&b, 1));
-         src_pos = nir_iadd(&b, src_pos, nir_imm_int(&b, 1));
-         src_pos = nir_i2f32(&b, src_pos);
+         assert(key->src_coords_normalized);
+         src_pos = nir_fadd(&b,
+                            nir_i2f32(&b, src_pos),
+                            nir_imm_float(&b, 0.5f));
          color = blorp_nir_tex(&b, &v, key, src_pos);
       } else {
          /* Gen7+ hardware doesn't automaticaly blend. */
@@ -1825,7 +1826,9 @@ try_blorp_blit(struct blorp_batch *batch,
 
    params->num_samples = params->dst.surf.samples;
 
-   if (wm_prog_key->bilinear_filter && batch->blorp->isl_dev->info->gen < 6) {
+   if ((wm_prog_key->bilinear_filter ||
+        (wm_prog_key->blend && !wm_prog_key->blit_scaled)) &&
+       batch->blorp->isl_dev->info->gen <= 6) {
       /* Gen4-5 don't support non-normalized texture coordinates */
       wm_prog_key->src_coords_normalized = true;
       params->wm_inputs.src_inv_size[0] =
diff --git a/src/intel/blorp/blorp_genX_exec.h b/src/intel/blorp/blorp_genX_exec.h
index 1d77877..91c0756 100644
--- a/src/intel/blorp/blorp_genX_exec.h
+++ b/src/intel/blorp/blorp_genX_exec.h
@@ -535,7 +535,7 @@ blorp_emit_sampler_state(struct blorp_batch *batch,
       sampler.VAddressMagFilterRoundingEnable = true;
       sampler.UAddressMinFilterRoundingEnable = true;
       sampler.UAddressMagFilterRoundingEnable = true;
-#if GEN_GEN >= 6
+#if GEN_GEN > 6
       sampler.NonnormalizedCoordinateEnable = true;
 #endif
    }
-- 
2.9.4