i915: Drop broken front_buffer_reading/drawing optimization

Bring the following commit over to i915:
 commit ec542d74578bbef6b55125dd6aba1dc7f5079e65
 Author: Eric Anholt <[email protected]>
 Date:   Mon Mar 3 10:43:10 2014 -0800

    i965: Drop broken front_buffer_reading/drawing optimization.

Not sure if it might fix anything, but since the i965 and i915 used to
share a bunch of that code, it would seem reasonable the same problems
could be present in the i915 code still, and the i965 approach is well
tested by now so bringing it over seems fairly safe.

No piglit regressions on 855.

v2: Rebase on _mesa_is_front_buffer_* refactor.

Signed-off-by: Ville Syrjälä <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>

3 files changed, 15 insertions, 41 deletions

diff --git a/src/mesa/drivers/dri/i915/intel_buffers.c b/src/mesa/drivers/dri/i915/intel_buffers.c
index 51eaea43a50..386e032443a 100644
--- a/src/mesa/drivers/dri/i915/intel_buffers.c
+++ b/src/mesa/drivers/dri/i915/intel_buffers.c
@@ -55,20 +55,14 @@ intel_check_front_buffer_rendering(struct intel_context *intel)
 static void
 intelDrawBuffer(struct gl_context * ctx, GLenum mode)
 {
-   if (ctx->DrawBuffer && _mesa_is_winsys_fbo(ctx->DrawBuffer)) {
+   if (_mesa_is_front_buffer_drawing(ctx->DrawBuffer)) {
       struct intel_context *const intel = intel_context(ctx);
-      const bool was_front_buffer_rendering =
-	intel->is_front_buffer_rendering;
 
-      intel->is_front_buffer_rendering = (mode == GL_FRONT_LEFT)
-	|| (mode == GL_FRONT) || (mode == GL_FRONT_AND_BACK);
-
-      /* If we weren't front-buffer rendering before but we are now,
-       * invalidate our DRI drawable so we'll ask for new buffers
+      /* If we might be front-buffer rendering on this buffer for the first
+       * time, invalidate our DRI drawable so we'll ask for new buffers
        * (including the fake front) before we start rendering again.
        */
-      if (!was_front_buffer_rendering && intel->is_front_buffer_rendering)
-	 dri2InvalidateDrawable(intel->driContext->driDrawablePriv);
+      dri2InvalidateDrawable(intel->driContext->driDrawablePriv);
    }
 
    intel_draw_buffer(ctx);
@@ -78,20 +72,14 @@ intelDrawBuffer(struct gl_context * ctx, GLenum mode)
 static void
 intelReadBuffer(struct gl_context * ctx, GLenum mode)
 {
-   if (ctx->ReadBuffer && _mesa_is_winsys_fbo(ctx->ReadBuffer)) {
+   if (_mesa_is_front_buffer_reading(ctx->ReadBuffer)) {
       struct intel_context *const intel = intel_context(ctx);
-      const bool was_front_buffer_reading =
-	intel->is_front_buffer_reading;
-
-      intel->is_front_buffer_reading = (mode == GL_FRONT_LEFT)
-	|| (mode == GL_FRONT);
 
-      /* If we weren't front-buffer reading before but we are now,
-       * invalidate our DRI drawable so we'll ask for new buffers
+      /* If we might be front-buffer reading on this buffer for the first
+       * time, invalidate our DRI drawable so we'll ask for new buffers
        * (including the fake front) before we start reading again.
        */
-      if (!was_front_buffer_reading && intel->is_front_buffer_reading)
-	 dri2InvalidateDrawable(intel->driContext->driReadablePriv);
+      dri2InvalidateDrawable(intel->driContext->driReadablePriv);
    }
 }
 
diff --git a/src/mesa/drivers/dri/i915/intel_context.c b/src/mesa/drivers/dri/i915/intel_context.c
index 6c737ea6877..644bede9d47 100644
--- a/src/mesa/drivers/dri/i915/intel_context.c
+++ b/src/mesa/drivers/dri/i915/intel_context.c
@@ -243,7 +243,7 @@ intel_prepare_render(struct intel_context *intel)
     * that will happen next will probably dirty the front buffer.  So
     * mark it as dirty here.
     */
-   if (intel->is_front_buffer_rendering)
+   if (_mesa_is_front_buffer_drawing(intel->ctx.DrawBuffer))
       intel->front_buffer_dirty = true;
 
    /* Wait for the swapbuffers before the one we just emitted, so we
@@ -356,7 +356,7 @@ intel_glFlush(struct gl_context *ctx)
 
    intel_flush(ctx);
    intel_flush_front(ctx);
-   if (intel->is_front_buffer_rendering)
+   if (_mesa_is_front_buffer_drawing(ctx->DrawBuffer))
       intel->need_throttle = true;
 }
 
@@ -700,8 +700,8 @@ intel_query_dri2_buffers(struct intel_context *intel,
    back_rb = intel_get_renderbuffer(fb, BUFFER_BACK_LEFT);
 
    memset(attachments, 0, sizeof(attachments));
-   if ((intel->is_front_buffer_rendering ||
-	intel->is_front_buffer_reading ||
+   if ((_mesa_is_front_buffer_drawing(fb) ||
+        _mesa_is_front_buffer_reading(fb) ||
 	!back_rb) && front_rb) {
       /* If a fake front buffer is in use, then querying for
        * __DRI_BUFFER_FRONT_LEFT will cause the server to copy the image from
@@ -866,8 +866,10 @@ intel_update_image_buffers(struct intel_context *intel, __DRIdrawable *drawable)
    else
       return;
 
-   if ((intel->is_front_buffer_rendering || intel->is_front_buffer_reading || !back_rb) && front_rb)
+   if (front_rb && (_mesa_is_front_buffer_drawing(fb) ||
+                    _mesa_is_front_buffer_reading(fb) || !back_rb)) {
       buffer_mask |= __DRI_IMAGE_BUFFER_FRONT;
+   }
 
    if (back_rb)
       buffer_mask |= __DRI_IMAGE_BUFFER_BACK;
diff --git a/src/mesa/drivers/dri/i915/intel_context.h b/src/mesa/drivers/dri/i915/intel_context.h
index 4ec4015d453..aecd7c23f45 100644
--- a/src/mesa/drivers/dri/i915/intel_context.h
+++ b/src/mesa/drivers/dri/i915/intel_context.h
@@ -255,22 +255,6 @@ struct intel_context
     */
    bool front_buffer_dirty;
 
-   /**
-    * Track whether front-buffer rendering is currently enabled
-    *
-    * A separate flag is used to track this in order to support MRT more
-    * easily.
-    */
-   bool is_front_buffer_rendering;
-   /**
-    * Track whether front-buffer is the current read target.
-    *
-    * This is closely associated with is_front_buffer_rendering, but may
-    * be set separately.  The DRI2 fake front buffer must be referenced
-    * either way.
-    */
-   bool is_front_buffer_reading;
-
    bool use_early_z;
 
    __DRIcontext *driContext;