i965: Initialize the SampleMap{2,4,8}x variables

with values specific to Intel hardware.

V2: Define and use gen6_get_sample_map() function to initialize
    the variables.

V3: Change the function name to gen6_set_sample_maps() and use
    memcpy() to fill in the data.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

3 files changed, 55 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
index ca389f80d7b..8b3f45b68d8 100644
--- a/src/mesa/drivers/dri/i965/brw_context.c
+++ b/src/mesa/drivers/dri/i965/brw_context.c
@@ -406,6 +406,14 @@ brw_initialize_context_constants(struct brw_context *brw)
    ctx->Const.MaxDepthTextureSamples = max_samples;
    ctx->Const.MaxIntegerSamples = max_samples;
 
+   /* gen6_set_sample_maps() sets SampleMap{2,4,8}x variables which are used
+    * to map indices of rectangular grid to sample numbers within a pixel.
+    * These variables are used by GL_EXT_framebuffer_multisample_blit_scaled
+    * extension implementation. For more details see the comment above
+    * gen6_set_sample_maps() definition.
+    */
+   gen6_set_sample_maps(ctx);
+
    if (brw->gen >= 7)
       ctx->Const.MaxProgramTextureGatherComponents = 4;
    else if (brw->gen == 6)
diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index 317724fa2e7..884e28bf8b4 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -1693,6 +1693,8 @@ gen6_get_sample_position(struct gl_context *ctx,
                          struct gl_framebuffer *fb,
                          GLuint index,
                          GLfloat *result);
+void
+gen6_set_sample_maps(struct gl_context *ctx);
 
 /* gen8_multisample_state.c */
 void gen8_emit_3dstate_multisample(struct brw_context *brw, unsigned num_samp);
diff --git a/src/mesa/drivers/dri/i965/gen6_multisample_state.c b/src/mesa/drivers/dri/i965/gen6_multisample_state.c
index 429a590a2b5..ee20c0806de 100644
--- a/src/mesa/drivers/dri/i965/gen6_multisample_state.c
+++ b/src/mesa/drivers/dri/i965/gen6_multisample_state.c
@@ -57,6 +57,51 @@ gen6_get_sample_position(struct gl_context *ctx,
 }
 
 /**
+ * Sample index layout shows the numbering of slots in a rectangular
+ * grid of samples with in a pixel. Sample number layout shows the
+ * rectangular grid of samples roughly corresponding to the real sample
+ * locations with in a pixel. Sample number layout matches the sample
+ * index layout in case of 2X and 4x MSAA, but they are different in
+ * case of 8X MSAA.
+ *
+ * 2X MSAA sample index / number layout
+ *           ---------
+ *           | 0 | 1 |
+ *           ---------
+ *
+ * 4X MSAA sample index / number layout
+ *           ---------
+ *           | 0 | 1 |
+ *           ---------
+ *           | 2 | 3 |
+ *           ---------
+ *
+ * 8X MSAA sample index layout    8x MSAA sample number layout
+ *           ---------                      ---------
+ *           | 0 | 1 |                      | 5 | 2 |
+ *           ---------                      ---------
+ *           | 2 | 3 |                      | 4 | 6 |
+ *           ---------                      ---------
+ *           | 4 | 5 |                      | 0 | 3 |
+ *           ---------                      ---------
+ *           | 6 | 7 |                      | 7 | 1 |
+ *           ---------                      ---------
+ *
+ * A sample map is used to map sample indices to sample numbers.
+ */
+void
+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};
+
+   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));
+}
+
+/**
  * 3DSTATE_MULTISAMPLE
  */
 void