[Mesa-dev] [PATCH v2] i965: Handle lum, intensity and missing components in the fast clear

[Neil Roberts]

It looks like the sampler hardware doesn't take into account the
surface format when sampling a cleared color after a fast clear has
been done. So for example if you clear a GL_RED surface to 1,1,1,1
then the sampling instructions will return 1,1,1,1 instead of 1,0,0,1.
This patch makes it override the color that is programmed in the
surface state in order to swizzle for luminance and intensity as well
as overriding the missing components.

v2: Handle luminance and intensity formats
---

I made a more extensive test case which tests all of the formats in
fbo_formats.h as well as using more than one test color here:

http://patchwork.freedesktop.org/patch/64578/

In the process I noticed that there is a similar problem with
luminance and intensity textures so here is a v2 to cope with that.

I've made another version of this patch which is rebased on top of
Ben's skl-fast-clear branch so we can take whichever version depending
on which lands first:

https://github.com/bpeel/mesa/commit/da7edcb6dfd93c7dd86b2e148c44dff7

 src/mesa/drivers/dri/i965/brw_meta_fast_clear.c | 38 +++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_meta_fast_clear.c b/src/mesa/drivers/dri/i965/brw_meta_fast_clear.c
index 69fe7b4..3071590 100644
--- a/src/mesa/drivers/dri/i965/brw_meta_fast_clear.c
+++ b/src/mesa/drivers/dri/i965/brw_meta_fast_clear.c
@@ -361,12 +361,43 @@ is_color_fast_clear_compatible(struct brw_context *brw,
  * SURFACE_STATE.
  */
 static uint32_t
-compute_fast_clear_color_bits(const union gl_color_union *color)
+compute_fast_clear_color_bits(mesa_format format,
+                              const union gl_color_union *color)
 {
+   union gl_color_union override_color = *color;
    uint32_t bits = 0;
+
+   /* The sampler doesn't look at the format of the surface when the fast
+    * clear color is used so we need to implement luminance, intensity and
+    * missing components manually.
+    */
+   switch (_mesa_get_format_base_format(format)) {
+   case GL_INTENSITY:
+      override_color.ui[3] = override_color.ui[0];
+      /* flow through */
+   case GL_LUMINANCE:
+   case GL_LUMINANCE_ALPHA:
+      override_color.ui[1] = override_color.ui[0];
+      override_color.ui[2] = override_color.ui[0];
+      break;
+   default:
+      for (int i = 0; i < 3; i++) {
+         if (!_mesa_format_has_color_component(format, i))
+            override_color.ui[i] = 0;
+      }
+      break;
+   }
+
+   if (!_mesa_format_has_color_component(format, 3)) {
+      if (_mesa_is_format_integer_color(format))
+         override_color.ui[3] = 1;
+      else
+         override_color.f[3] = 1.0f;
+   }
+
    for (int i = 0; i < 4; i++) {
       /* Testing for non-0 works for integer and float colors */
-      if (color->f[i] != 0.0f)
+      if (override_color.f[i] != 0.0f)
          bits |= 1 << (GEN7_SURFACE_CLEAR_COLOR_SHIFT + (3 - i));
    }
    return bits;
@@ -505,7 +536,8 @@ brw_meta_fast_clear(struct brw_context *brw, struct gl_framebuffer *fb,
       switch (clear_type) {
       case FAST_CLEAR:
          irb->mt->fast_clear_color_value =
-            compute_fast_clear_color_bits(&ctx->Color.ClearColor);
+            compute_fast_clear_color_bits(irb->mt->format,
+                                          &ctx->Color.ClearColor);
          irb->need_downsample = true;
 
          /* If the buffer is already in INTEL_FAST_CLEAR_STATE_CLEAR, the
-- 
1.9.3