meta: Allow meta operations to pause/resume an active occlusion query

This allows for avoiding the occlusion query erroneously accumulating results
during the meta operation. This functionality is made conditional on a new
MESA_META_OCCLUSION_QUERY bit so that meta-operations which should generate
fragments can continue to get the current behavior.

The implementation of glClear is specifically augmented to request the flag
since glClear is specified to not generate fragments.

This fixes the following es3conform tests:

	occlusion_query_draw_occluded.test
 	occlusion_query_clear
	occlusion_query_custom_framebuffer
	occlusion_query_stencil_test
	occlusion_query_discarded_fragments

As well as the following piglit test:

	occlusion_query_meta_no_fragments

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

2 files changed, 28 insertions, 1 deletions

diff --git a/src/mesa/drivers/common/meta.c b/src/mesa/drivers/common/meta.c
index d211fda9de4..12a4d98c223 100644
--- a/src/mesa/drivers/common/meta.c
+++ b/src/mesa/drivers/common/meta.c
@@ -54,6 +54,7 @@
 #include "main/pixel.h"
 #include "main/pbo.h"
 #include "main/polygon.h"
+#include "main/queryobj.h"
 #include "main/readpix.h"
 #include "main/scissor.h"
 #include "main/shaderapi.h"
@@ -89,6 +90,9 @@ struct save_state
 {
    GLbitfield SavedState;  /**< bitmask of MESA_META_* flags */
 
+   /** MESA_META_CLEAR (and others?) */
+   struct gl_query_object *CurrentOcclusionObject;
+
    /** MESA_META_ALPHA_TEST */
    GLboolean AlphaEnabled;
    GLenum AlphaFunc;
@@ -478,6 +482,15 @@ _mesa_meta_begin(struct gl_context *ctx, GLbitfield state)
    if (save->TransformFeedbackNeedsResume)
       _mesa_PauseTransformFeedback();
 
+   /* After saving the current occlusion object, call EndQuery so that no
+    * occlusion querying will be active during the meta-operation.
+    */
+   if (state & MESA_META_OCCLUSION_QUERY) {
+      save->CurrentOcclusionObject = ctx->Query.CurrentOcclusionObject;
+      if (save->CurrentOcclusionObject)
+         _mesa_EndQuery(save->CurrentOcclusionObject->Target);
+   }
+
    if (state & MESA_META_ALPHA_TEST) {
       save->AlphaEnabled = ctx->Color.AlphaEnabled;
       save->AlphaFunc = ctx->Color.AlphaFunc;
@@ -806,6 +819,18 @@ _mesa_meta_end(struct gl_context *ctx)
    struct save_state *save = &ctx->Meta->Save[ctx->Meta->SaveStackDepth - 1];
    const GLbitfield state = save->SavedState;
 
+   /* After starting a new occlusion query, initialize the results to the
+    * values saved previously. The driver will then continue to increment
+    * these values.
+    */
+   if (state & MESA_META_OCCLUSION_QUERY) {
+      if (save->CurrentOcclusionObject) {
+         _mesa_BeginQuery(save->CurrentOcclusionObject->Target,
+                          save->CurrentOcclusionObject->Id);
+         ctx->Query.CurrentOcclusionObject->Result = save->CurrentOcclusionObject->Result;
+      }
+   }
+
    if (state & MESA_META_ALPHA_TEST) {
       if (ctx->Color.AlphaEnabled != save->AlphaEnabled)
          _mesa_set_enable(ctx, GL_ALPHA_TEST, save->AlphaEnabled);
@@ -1987,7 +2012,8 @@ _mesa_meta_glsl_Clear(struct gl_context *ctx, GLbitfield buffers)
 	       MESA_META_VIEWPORT |
 	       MESA_META_CLIP |
 	       MESA_META_CLAMP_FRAGMENT_COLOR |
-               MESA_META_MULTISAMPLE);
+               MESA_META_MULTISAMPLE |
+               MESA_META_OCCLUSION_QUERY);
 
    if (!(buffers & BUFFER_BITS_COLOR)) {
       /* We'll use colormask to disable color writes.  Otherwise,
diff --git a/src/mesa/drivers/common/meta.h b/src/mesa/drivers/common/meta.h
index 6ffc5b56a1f..a6bdd39473f 100644
--- a/src/mesa/drivers/common/meta.h
+++ b/src/mesa/drivers/common/meta.h
@@ -57,6 +57,7 @@
 #define MESA_META_SELECT_FEEDBACK       0x80000
 #define MESA_META_MULTISAMPLE          0x100000
 #define MESA_META_FRAMEBUFFER_SRGB     0x200000
+#define MESA_META_OCCLUSION_QUERY      0x400000
 /**\}*/
 
 extern void