[Mesa-dev] [PATCH 11/12] meta: Support 16x MSAA in the multisample scaled blit shader

[Neil Roberts]

I'm not too sure about the expression used to index into sample_map in
the shader. It looks like if fract(coord.x) and fract(coord.y) are
close to 1.0 then it would index outside of the array. However the
code for 4 and 8 has the same problem and the results seems to look
reasonable. It might make more sense to change it to something like
this:

 sample_map[int(4 * fract(coord.x)) + 4 * int(fract(coord.y) * 4)]
---
 src/mesa/drivers/common/meta.h                     |  2 ++
 src/mesa/drivers/common/meta_blit.c                |  8 ++++++--
 src/mesa/drivers/dri/i965/gen6_multisample_state.c | 14 ++++++++++++++
 src/mesa/main/mtypes.h                             | 15 ++++++++++++++-
 4 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/common/meta.h b/src/mesa/drivers/common/meta.h
index fe43915..e42ddc8 100644
--- a/src/mesa/drivers/common/meta.h
+++ b/src/mesa/drivers/common/meta.h
@@ -285,9 +285,11 @@ enum blit_msaa_shader {
    BLIT_2X_MSAA_SHADER_2D_MULTISAMPLE_SCALED_RESOLVE,
    BLIT_4X_MSAA_SHADER_2D_MULTISAMPLE_SCALED_RESOLVE,
    BLIT_8X_MSAA_SHADER_2D_MULTISAMPLE_SCALED_RESOLVE,
+   BLIT_16X_MSAA_SHADER_2D_MULTISAMPLE_SCALED_RESOLVE,
    BLIT_2X_MSAA_SHADER_2D_MULTISAMPLE_ARRAY_SCALED_RESOLVE,
    BLIT_4X_MSAA_SHADER_2D_MULTISAMPLE_ARRAY_SCALED_RESOLVE,
    BLIT_8X_MSAA_SHADER_2D_MULTISAMPLE_ARRAY_SCALED_RESOLVE,
+   BLIT_16X_MSAA_SHADER_2D_MULTISAMPLE_ARRAY_SCALED_RESOLVE,
    BLIT_MSAA_SHADER_COUNT,
 };
 
diff --git a/src/mesa/drivers/common/meta_blit.c b/src/mesa/drivers/common/meta_blit.c
index a41fe42..b545c37 100644
--- a/src/mesa/drivers/common/meta_blit.c
+++ b/src/mesa/drivers/common/meta_blit.c
@@ -86,8 +86,8 @@ setup_glsl_msaa_blit_scaled_shader(struct gl_context *ctx,
    while (samples >> (shader_offset + 1)) {
       shader_offset++;
    }
-   /* Update the assert if we plan to support more than 8X MSAA. */
-   assert(shader_offset > 0 && shader_offset < 4);
+   /* Update the assert if we plan to support more than 16X MSAA. */
+   assert(shader_offset > 0 && shader_offset <= 4);
 
    assert(target == GL_TEXTURE_2D_MULTISAMPLE ||
           target == GL_TEXTURE_2D_MULTISAMPLE_ARRAY);
@@ -132,6 +132,10 @@ setup_glsl_msaa_blit_scaled_shader(struct gl_context *ctx,
       sample_number =  "sample_map[int(2 * fract(coord.x) + 8 * fract(coord.y))]";
       sample_map = ctx->Const.SampleMap8x;
       break;
+   case 16:
+      sample_number =  "sample_map[int(4 * fract(coord.x) + 16 * fract(coord.y))]";
+      sample_map = ctx->Const.SampleMap16x;
+      break;
    default:
       sample_number = NULL;
       sample_map = NULL;
diff --git a/src/mesa/drivers/dri/i965/gen6_multisample_state.c b/src/mesa/drivers/dri/i965/gen6_multisample_state.c
index 49c6eba..8eb620d 100644
--- a/src/mesa/drivers/dri/i965/gen6_multisample_state.c
+++ b/src/mesa/drivers/dri/i965/gen6_multisample_state.c
@@ -91,6 +91,17 @@ gen6_get_sample_position(struct gl_context *ctx,
  *           | 6 | 7 |                      | 7 | 1 |
  *           ---------                      ---------
  *
+ * 16X MSAA sample index layout  16x MSAA sample number layout
+ *         -----------------            -----------------
+ *         | 0 | 1 | 2 | 3 |            |15 |10 | 9 | 7 |
+ *         -----------------            -----------------
+ *         | 4 | 5 | 6 | 7 |            | 4 | 1 | 3 |13 |
+ *         -----------------            -----------------
+ *         | 8 | 9 |10 |11 |            |12 | 2 | 0 | 6 |
+ *         -----------------            -----------------
+ *         |12 |13 |14 |15 |            |11 | 8 | 5 |14 |
+ *         -----------------            -----------------
+ *
  * A sample map is used to map sample indices to sample numbers.
  */
 void
@@ -99,10 +110,13 @@ gen6_set_sample_maps(struct gl_context *ctx)
    uint8_t map_2x[2] = {0, 1};
    uint8_t map_4x[4] = {0, 1, 2, 3};
    uint8_t map_8x[8] = {5, 2, 4, 6, 0, 3, 7, 1};
+   uint8_t map_16x[16] = { 15, 10, 9, 7, 4, 1, 3, 13,
+                           12, 2, 0, 6, 11, 8, 5, 14 };
 
    memcpy(ctx->Const.SampleMap2x, map_2x, sizeof(map_2x));
    memcpy(ctx->Const.SampleMap4x, map_4x, sizeof(map_4x));
    memcpy(ctx->Const.SampleMap8x, map_8x, sizeof(map_8x));
+   memcpy(ctx->Const.SampleMap16x, map_16x, sizeof(map_16x));
 }
 
 /**
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index fac45aa..e0a06f4 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -3550,11 +3550,24 @@ struct gl_constants
     * below:
     *    SampleMap8x = {a, b, c, d, e, f, g, h};
     *
-    * Follow the logic for other sample counts.
+    * Follow the logic for sample counts 2-8.
+    *
+    * For 16x the sample indices layout as a 4x4 grid as follows:
+    *
+    *            -----------------
+    *            | 0 | 1 | 2 | 3 |
+    *            -----------------
+    *            | 4 | 5 | 6 | 7 |
+    *            -----------------
+    *            | 8 | 9 |10 |11 |
+    *            -----------------
+    *            |12 |13 |14 |15 |
+    *            -----------------
     */
    uint8_t SampleMap2x[2];
    uint8_t SampleMap4x[4];
    uint8_t SampleMap8x[8];
+   uint8_t SampleMap16x[16];
 
    /** GL_ARB_shader_atomic_counters */
    GLuint MaxAtomicBufferBindings;
-- 
1.9.3