i965: Add a driconf option to disable GL_ARB_blend_func_extended.

Unigine Heaven (at least) has a bug where it incorrectly uses the
GL_ARB_blend_func_extended extension.

Dual source blending allows two color outputs per render target;
individual shader outputs can be assigned to be either the first or
second blending input by setting the 'index' via one of two methods:

- An API call: glBindFragDataLocationIndexed()
- The GLSL 'layout' qualifier provided by GL_ARB_explicit_attrib_location

Both of these only work on user defined fragment shader outputs; it's an
error to use either on built-in outputs like gl_FragData.

Unigine uses gl_FragData and gl_FragColor exclusively, and doesn't even
attempt to use either method to set index == 1.  However, it does set
the blending function to SRC1 enums, which requires a fragment shader
output with index == 1 or else rendering is undefined.

In other words, enabling ARB_blend_func_extended causes Unigine to
render incorrectly, resulting in an apparent regression, even though our
driver code (as far as I can tell) is perfectly fine.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50291
Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Chad Versace <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

2 files changed, 14 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/common/drirc b/src/mesa/drivers/dri/common/drirc
index 2d92878520a..52d8dd7247c 100644
--- a/src/mesa/drivers/dri/common/drirc
+++ b/src/mesa/drivers/dri/common/drirc
@@ -2,15 +2,19 @@
     <device screen="0" driver="i965">
         <application name="Unigine Sanctuary" executable="Sanctuary">
             <option name="force_glsl_extensions_warn" value="true" />
+            <option name="disable_blend_func_extended" value="true" />
 	</application>
         <application name="Unigine Tropics" executable="Tropics">
             <option name="force_glsl_extensions_warn" value="true" />
+            <option name="disable_blend_func_extended" value="true" />
 	</application>
         <application name="Unigine Heaven (32-bit)" executable="heaven_x86">
             <option name="force_glsl_extensions_warn" value="true" />
+            <option name="disable_blend_func_extended" value="true" />
 	</application>
         <application name="Unigine Heaven (64-bit)" executable="heaven_x64">
             <option name="force_glsl_extensions_warn" value="true" />
+            <option name="disable_blend_func_extended" value="true" />
 	</application>
     </device>
 </driconf>
diff --git a/src/mesa/drivers/dri/common/xmlpool/options.h b/src/mesa/drivers/dri/common/xmlpool/options.h
index 75c887e5d06..a20e3d12dcf 100644
--- a/src/mesa/drivers/dri/common/xmlpool/options.h
+++ b/src/mesa/drivers/dri/common/xmlpool/options.h
@@ -636,3 +636,13 @@ DRI_CONF_OPT_BEGIN(force_glsl_extensions_warn,bool,def) \
         DRI_CONF_DESC(fr,"Force GLSL extension default behavior to 'warn'") \
         DRI_CONF_DESC(sv,"Force GLSL extension default behavior to 'warn'") \
 DRI_CONF_OPT_END
+
+#define DRI_CONF_DISABLE_BLEND_FUNC_EXTENDED(def) \
+DRI_CONF_OPT_BEGIN(disable_blend_func_extended,bool,def) \
+        DRI_CONF_DESC(en,"Disable dual source blending") \
+        DRI_CONF_DESC(de,"Disable dual source blending") \
+        DRI_CONF_DESC(es,"Disable dual source blending") \
+        DRI_CONF_DESC(nl,"Disable dual source blending") \
+        DRI_CONF_DESC(fr,"Disable dual source blending") \
+        DRI_CONF_DESC(sv,"Disable dual source blending") \
+DRI_CONF_OPT_END