[Mesa-dev] [PATCH] i965/msaa: Set KILL_ENABLE when GL_ALPHA_TO_COVERAGE enabled.

[Paul Berry]

i965 hardware needs to be informed of situations in which it's
possible for pixels (or samples) to be discarded for reasons other
than depth/stencil testing (e.g. due to an explicit "discard" in the
fragment shader).  One of these situations is when
GL_ALPHA_TO_COVERAGE is enabled, since that can cause samples to be
discarded by the color calculator when the pixel's alpha value is less
than 1.0.

Without this patch, GL_ALPHA_TO_COVERAGE does not take effect on depth
buffers.
---
 src/mesa/drivers/dri/i965/gen6_wm_state.c |    5 +++--
 src/mesa/drivers/dri/i965/gen7_wm_state.c |    5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/gen6_wm_state.c b/src/mesa/drivers/dri/i965/gen6_wm_state.c
index 662435e..fa83ece 100644
--- a/src/mesa/drivers/dri/i965/gen6_wm_state.c
+++ b/src/mesa/drivers/dri/i965/gen6_wm_state.c
@@ -186,8 +186,9 @@ upload_wm_state(struct brw_context *brw)
    dw6 |= brw->wm.prog_data->barycentric_interp_modes <<
       GEN6_WM_BARYCENTRIC_INTERPOLATION_MODE_SHIFT;
 
-   /* _NEW_COLOR */
-   if (fp->program.UsesKill || ctx->Color.AlphaEnabled)
+   /* _NEW_COLOR, _NEW_MULTISAMPLE */
+   if (fp->program.UsesKill || ctx->Color.AlphaEnabled ||
+       ctx->Multisample.SampleAlphaToCoverage)
       dw5 |= GEN6_WM_KILL_ENABLE;
 
    if (brw_color_buffer_write_enabled(brw) ||
diff --git a/src/mesa/drivers/dri/i965/gen7_wm_state.c b/src/mesa/drivers/dri/i965/gen7_wm_state.c
index 45c8e46..8e4417e 100644
--- a/src/mesa/drivers/dri/i965/gen7_wm_state.c
+++ b/src/mesa/drivers/dri/i965/gen7_wm_state.c
@@ -70,8 +70,9 @@ upload_wm_state(struct brw_context *brw)
    dw1 |= brw->wm.prog_data->barycentric_interp_modes <<
       GEN7_WM_BARYCENTRIC_INTERPOLATION_MODE_SHIFT;
 
-   /* _NEW_COLOR */
-   if (fp->program.UsesKill || ctx->Color.AlphaEnabled)
+   /* _NEW_COLOR, _NEW_MULTISAMPLE */
+   if (fp->program.UsesKill || ctx->Color.AlphaEnabled ||
+       ctx->Multisample.SampleAlphaToCoverage)
       dw1 |= GEN7_WM_KILL_ENABLE;
 
    /* _NEW_BUFFERS */
-- 
1.7.7.6