[Mesa-dev] [PATCH] intel: Emit assertion failure ASAP when DRI2 separate stencil handshake fails

[Chad Versace]

When intel_verify_dri2_has_hiz() discovers that DRI2 (that is, the DDX
driver) cannot provide a separate stencil buffer, but
intel_context::hw_must_use_separate_stencil is set, then emit an
informative assertion failure as soon as possible.

Currently, we do emit an assertion failure, but the its location is
sufficiently unrelated to the DRI2 HiZ handshake as to be uninformative.
In experimenting with HiZ, Anholt encountered this assertion failure and
was unable to understand its cause.

CC: Eric Anholt <eric at anholt.net>
Signed-off-by: Chad Versace <chad at chad-versace.us>
---
 src/mesa/drivers/dri/intel/intel_context.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/src/mesa/drivers/dri/intel/intel_context.c b/src/mesa/drivers/dri/intel/intel_context.c
index fe8be08..b9d2579 100644
--- a/src/mesa/drivers/dri/intel/intel_context.c
+++ b/src/mesa/drivers/dri/intel/intel_context.c
@@ -1454,6 +1454,10 @@ intel_verify_dri2_has_hiz(struct intel_context *intel,
 	  * a combined depth/stencil buffer. Discard the hiz buffer too.
 	  */
 	 intel->intelScreen->dri2_has_hiz = INTEL_DRI2_HAS_HIZ_FALSE;
+	 if (intel->must_use_separate_stencil) {
+	    assert(!"intel_context requires separate stencil, but the "
+		    "DRIscreen does not support it");
+	 }
 
 	 /* 1. Discard depth and stencil renderbuffers. */
 	 _mesa_remove_renderbuffer(fb, BUFFER_DEPTH);
-- 
1.7.6