[Mesa-dev] [PATCH 7/8] i965/msaa: Add CMS support to blorp.

[Paul Berry]

This patch updates the blorp engine to properly handle the case where
the surface being textured from uses Gen7's CMS MSAA layout.  The
following changes were necessary:

- Before reading color values from the surface, we need to read from
  the MCS buffer using the ld_mcs sampler message.  This is done by
  the mcs_fetch() function, and the result is stored in the mcs_data
  register.  This only needs to be done once per pixel, since the MCS
  value is shared between all samples belonging to a pixel.

- When reading color values from the surface, we need to use the
  ld2dms sampler message instead of the ld2dss message, and we need to
  provide the value read from the MCS buffer as an argument.
---
 src/mesa/drivers/dri/i965/brw_blorp_blit.cpp |   45 ++++++++++++++++++++++++-
 1 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
index ea98a66..6954733 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
@@ -273,6 +273,7 @@ enum sampler_message_arg
    SAMPLER_MESSAGE_ARG_U_INT,
    SAMPLER_MESSAGE_ARG_V_INT,
    SAMPLER_MESSAGE_ARG_SI_INT,
+   SAMPLER_MESSAGE_ARG_MCS_INT,
    SAMPLER_MESSAGE_ARG_ZERO_INT,
 };
 
@@ -427,6 +428,7 @@ private:
    void manual_blend();
    void sample(struct brw_reg dst);
    void texel_fetch(struct brw_reg dst);
+   void mcs_fetch();
    void expand_to_32_bits(struct brw_reg src, struct brw_reg dst);
    void texture_lookup(struct brw_reg dst, GLuint msg_type,
                        const sampler_message_arg *args, int num_args);
@@ -461,6 +463,13 @@ private:
     */
    struct brw_reg texture_data;
 
+   /* Auxiliary storage for the contents of the MCS surface.
+    *
+    * Since the sampler always returns 8 registers worth of data, this is 8
+    * registers wide, even though we only use the first 2 registers of it.
+    */
+   struct brw_reg mcs_data;
+
    /* X coordinates.  We have two of them so that we can perform coordinate
     * transformations easily.
     */
@@ -645,6 +654,8 @@ brw_blorp_blit_program::compile(struct brw_context *brw,
        * the texturing unit, will cause data to be read from the correct
        * memory location.  So we can fetch the texel now.
        */
+      if (key->tex_layout == INTEL_MSAA_LAYOUT_CMS)
+         mcs_fetch();
       texel_fetch(result);
    }
 
@@ -686,6 +697,8 @@ brw_blorp_blit_program::alloc_regs()
    reg += BRW_BLORP_NUM_PUSH_CONST_REGS;
    this->result = vec16(brw_vec8_grf(reg, 0)); reg += 8;
    this->texture_data = vec16(brw_vec8_grf(reg, 0)); reg += 8;
+   this->mcs_data =
+      retype(brw_vec8_grf(reg, 0), BRW_REGISTER_TYPE_UD); reg += 8;
    for (int i = 0; i < 2; ++i) {
       this->x_coords[i]
          = vec16(retype(brw_vec8_grf(reg++, 0), BRW_REGISTER_TYPE_UW));
@@ -1054,6 +1067,9 @@ brw_blorp_blit_program::manual_blend()
    /* TODO: support num_samples != 4 */
    const int num_samples = 4;
 
+   if (key->tex_layout == INTEL_MSAA_LAYOUT_CMS)
+      mcs_fetch();
+
    /* Gather sample 0 data first */
    s_is_zero = true;
    texel_fetch(result);
@@ -1118,6 +1134,12 @@ brw_blorp_blit_program::texel_fetch(struct brw_reg dst)
       SAMPLER_MESSAGE_ARG_U_INT,
       SAMPLER_MESSAGE_ARG_V_INT
    };
+   static const sampler_message_arg gen7_ld2dms_args[4] = {
+      SAMPLER_MESSAGE_ARG_SI_INT,
+      SAMPLER_MESSAGE_ARG_MCS_INT,
+      SAMPLER_MESSAGE_ARG_U_INT,
+      SAMPLER_MESSAGE_ARG_V_INT
+   };
 
    switch (brw->intel.gen) {
    case 6:
@@ -1126,8 +1148,13 @@ brw_blorp_blit_program::texel_fetch(struct brw_reg dst)
       break;
    case 7:
       if (key->tex_samples > 0) {
-         texture_lookup(dst, GEN7_SAMPLER_MESSAGE_SAMPLE_LD2DSS,
-                        gen7_ld2dss_args, ARRAY_SIZE(gen7_ld2dss_args));
+         if (key->tex_layout == INTEL_MSAA_LAYOUT_CMS) {
+            texture_lookup(dst, GEN7_SAMPLER_MESSAGE_SAMPLE_LD2DMS,
+                           gen7_ld2dms_args, ARRAY_SIZE(gen7_ld2dms_args));
+         } else {
+            texture_lookup(dst, GEN7_SAMPLER_MESSAGE_SAMPLE_LD2DSS,
+                           gen7_ld2dss_args, ARRAY_SIZE(gen7_ld2dss_args));
+         }
       } else {
          assert(s_is_zero);
          texture_lookup(dst, GEN5_SAMPLER_MESSAGE_SAMPLE_LD, gen7_ld_args,
@@ -1141,6 +1168,17 @@ brw_blorp_blit_program::texel_fetch(struct brw_reg dst)
 }
 
 void
+brw_blorp_blit_program::mcs_fetch()
+{
+   static const sampler_message_arg gen7_ld_mcs_args[2] = {
+      SAMPLER_MESSAGE_ARG_U_INT,
+      SAMPLER_MESSAGE_ARG_V_INT
+   };
+   texture_lookup(vec16(mcs_data), GEN7_SAMPLER_MESSAGE_SAMPLE_LD_MCS,
+                  gen7_ld_mcs_args, ARRAY_SIZE(gen7_ld_mcs_args));
+}
+
+void
 brw_blorp_blit_program::expand_to_32_bits(struct brw_reg src,
                                           struct brw_reg dst)
 {
@@ -1183,6 +1221,9 @@ brw_blorp_blit_program::texture_lookup(struct brw_reg dst,
          else
             expand_to_32_bits(S, mrf);
          break;
+      case SAMPLER_MESSAGE_ARG_MCS_INT:
+         brw_MOV(&func, mrf, mcs_data);
+         break;
       case SAMPLER_MESSAGE_ARG_ZERO_INT:
          brw_MOV(&func, mrf, brw_imm_ud(0));
          break;
-- 
1.7.7.6