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 <yuanhan.liu@linux.intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_sf_emit.c b/src/mesa/drivers/dri/i965/brw_sf_emit.c
index 1ee0098..ff6383b 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;
 }