i965: handle gl_PointCoord for Gen4 and Gen5 platforms

This patch add the support of gl_PointCoord gl builtin variable for
platform gen4 and gen5(ILK).

Unlike gen6+, we don't have a hardware support of gl_PointCoord, means
hardware will not calculate the interpolation coefficient for you.
Instead, you should handle it yourself in sf shader stage.

But badly, gl_PointCoord is a FS instead of VS builtin variable, thus
it's not included in c.vue_map generated in VS stage. Thus the current
code doesn't aware of this attribute. And to handle it correctly, we
need add it to c.vue_map manually to let SF shader generate the needed
interpolation coefficient for FS shader. SF stage has it's own copy of
vue_map, thus I think it's safe to do it manually.

Since handling gl_PointCoord for gen4 and gen5 platforms is somehow a
little special, I added a lot of comments and hope I didn't overdo it ;)

v2: add a /* _NEW_BUFFERS */ comment to note the state flag dependency
    and also add the _NEW_BUFFERS dirty mask (Eric).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=45975
Piglit: glsl-fs-pointcoord and fbo-gl_pointcoord

NOTE: This is a candidate for stable release branches.

Signed-off-by: Yuanhan Liu <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

5 files changed, 45 insertions, 5 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index a16145b9baa..0c50b6bc513 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -296,6 +296,12 @@ typedef enum
    BRW_VERT_RESULT_NDC = VERT_RESULT_MAX,
    BRW_VERT_RESULT_HPOS_DUPLICATE,
    BRW_VERT_RESULT_PAD,
+   /*
+    * It's actually not a vert_result but just a _mark_ to let sf aware that
+    * he need do something special to handle gl_PointCoord builtin variable
+    * correctly. see compile_sf_prog() for more info.
+    */
+   BRW_VERT_RESULT_PNTC,
    BRW_VERT_RESULT_MAX
 } brw_vert_result;
 
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index bf59da3a4d6..5f3d79d1d09 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -710,6 +710,15 @@ fs_visitor::calculate_urb_setup()
 	       urb_setup[fp_index] = urb_next++;
 	 }
       }
+
+      /*
+       * It's a FS only attribute, and we did interpolation for this attribute
+       * in SF thread. So, count it here, too.
+       *
+       * See compile_sf_prog() for more info.
+       */
+      if (brw->fragment_program->Base.InputsRead & BITFIELD64_BIT(FRAG_ATTRIB_PNTC))
+         urb_setup[FRAG_ATTRIB_PNTC] = urb_next++;
    }
 
    /* Each attribute is 4 setup channels, each of which is half a reg. */
diff --git a/src/mesa/drivers/dri/i965/brw_sf.c b/src/mesa/drivers/dri/i965/brw_sf.c
index 6e63583e546..37d1ee502d8 100644
--- a/src/mesa/drivers/dri/i965/brw_sf.c
+++ b/src/mesa/drivers/dri/i965/brw_sf.c
@@ -64,6 +64,16 @@ static void compile_sf_prog( struct brw_context *brw,
 
    c.key = *key;
    c.vue_map = brw->vs.prog_data->vue_map;
+   if (c.key.do_point_coord) {
+      /*
+       * gl_PointCoord is a FS instead of VS builtin variable, thus it's
+       * not included in c.vue_map generated in VS stage. Here we add
+       * it manually to let SF shader generate the needed interpolation
+       * coefficient for FS shader.
+       */
+      c.vue_map.vert_result_to_slot[BRW_VERT_RESULT_PNTC] = c.vue_map.num_slots;
+      c.vue_map.slot_to_vert_result[c.vue_map.num_slots++] = BRW_VERT_RESULT_PNTC;
+   }
    c.urb_entry_read_offset = brw_sf_compute_urb_entry_read_offset(intel);
    c.nr_attr_regs = (c.vue_map.num_slots + 1)/2 - c.urb_entry_read_offset;
    c.nr_setup_regs = c.nr_attr_regs;
@@ -125,6 +135,8 @@ brw_upload_sf_prog(struct brw_context *brw)
 {
    struct gl_context *ctx = &brw->intel.ctx;
    struct brw_sf_prog_key key;
+   /* _NEW_BUFFERS */
+   bool render_to_fbo = ctx->DrawBuffer->Name != 0;
 
    memset(&key, 0, sizeof(key));
 
@@ -167,7 +179,15 @@ brw_upload_sf_prog(struct brw_context *brw)
 	    key.point_sprite_coord_replace |= (1 << i);
       }
    }
-   key.sprite_origin_lower_left = (ctx->Point.SpriteOrigin == GL_LOWER_LEFT);
+   if (brw->fragment_program->Base.InputsRead & BITFIELD64_BIT(FRAG_ATTRIB_PNTC))
+      key.do_point_coord = 1;
+   /*
+    * Window coordinates in a FBO are inverted, which means point
+    * sprite origin must be inverted, too.
+    */
+   if ((ctx->Point.SpriteOrigin == GL_LOWER_LEFT) != render_to_fbo)
+      key.sprite_origin_lower_left = true;
+
    /* _NEW_LIGHT */
    key.do_flat_shading = (ctx->Light.ShadeModel == GL_FLAT);
    key.do_twoside_color = (ctx->Light.Enabled && ctx->Light.Model.TwoSide);
@@ -176,10 +196,9 @@ brw_upload_sf_prog(struct brw_context *brw)
    if (key.do_twoside_color) {
       /* If we're rendering to a FBO, we have to invert the polygon
        * face orientation, just as we invert the viewport in
-       * sf_unit_create_from_key().  ctx->DrawBuffer->Name will be
-       * nonzero if we're rendering to such an FBO.
+       * sf_unit_create_from_key().
        */
-      key.frontface_ccw = (ctx->Polygon.FrontFace == GL_CCW) ^ (ctx->DrawBuffer->Name != 0);
+      key.frontface_ccw = (ctx->Polygon.FrontFace == GL_CCW) != render_to_fbo;
    }
 
    if (!brw_search_cache(&brw->cache, BRW_SF_PROG,
@@ -192,7 +211,8 @@ brw_upload_sf_prog(struct brw_context *brw)
 
 const struct brw_tracked_state brw_sf_prog = {
    .dirty = {
-      .mesa  = (_NEW_HINT | _NEW_LIGHT | _NEW_POLYGON | _NEW_POINT | _NEW_TRANSFORM),
+      .mesa  = (_NEW_HINT | _NEW_LIGHT | _NEW_POLYGON | _NEW_POINT |
+                _NEW_TRANSFORM | _NEW_BUFFERS),
       .brw   = (BRW_NEW_REDUCED_PRIMITIVE),
       .cache = CACHE_NEW_VS_PROG
    },
diff --git a/src/mesa/drivers/dri/i965/brw_sf.h b/src/mesa/drivers/dri/i965/brw_sf.h
index 4ef024043ec..f908fc0667b 100644
--- a/src/mesa/drivers/dri/i965/brw_sf.h
+++ b/src/mesa/drivers/dri/i965/brw_sf.h
@@ -52,6 +52,7 @@ struct brw_sf_prog_key {
    GLuint do_flat_shading:1;
    GLuint frontface_ccw:1;
    GLuint do_point_sprite:1;
+   GLuint do_point_coord:1;
    GLuint sprite_origin_lower_left:1;
    GLuint userclip_active:1;
 };
diff --git a/src/mesa/drivers/dri/i965/brw_sf_emit.c b/src/mesa/drivers/dri/i965/brw_sf_emit.c
index 1ee0098d982..ff6383bb188 100644
--- a/src/mesa/drivers/dri/i965/brw_sf_emit.c
+++ b/src/mesa/drivers/dri/i965/brw_sf_emit.c
@@ -386,6 +386,8 @@ calculate_point_sprite_mask(struct brw_sf_compile *c, GLuint reg)
       if (c->key.point_sprite_coord_replace & (1 << (vert_result1 - VERT_RESULT_TEX0)))
 	 pc |= 0x0f;
    }
+   if (vert_result1 == BRW_VERT_RESULT_PNTC)
+      pc |= 0x0f;
 
    vert_result2 = vert_reg_to_vert_result(c, reg, 1);
    if (vert_result2 >= VERT_RESULT_TEX0 && vert_result2 <= VERT_RESULT_TEX7) {
@@ -393,6 +395,8 @@ calculate_point_sprite_mask(struct brw_sf_compile *c, GLuint reg)
                                                      VERT_RESULT_TEX0)))
          pc |= 0xf0;
    }
+   if (vert_result2 == BRW_VERT_RESULT_PNTC)
+      pc |= 0xf0;
 
    return pc;
 }