intel: Add hiz_region to intel_renderbuffer

A hiz surface must be supplied to the hardware when rendering to a depth
buffer with hiz. There are three potential places to store that surface:
    1. Allocate a larger intel_region for the depthbuffer, and let the
       region's tail be the hiz surface.
    2. Allocate a separate intel_region for hiz, and store it as
       brw_context state.
    3. Allocate a separate intel_region for hiz, and store it in
       intel_renderbuffer.

We choose method 3.

Method 1 has not been chosen due to future complications it might cause
when requesting a DRI drawable's depth buffer attachment from X.

Method 2 has not been chosen because storing the hiz region apart from
the depth region makes lazy hiz/depth resolves difficult to implement.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Chad Versace <chad@chad-versace.us>

src/mesa/drivers/dri/intel/intel_fbo.c

@@ -79,6 +79,9 @@ intel_delete_renderbuffer(struct gl_renderbuffer *rb)
    if (intel && irb->region) {
       intel_region_release(&irb->region);
    }
+   if (intel && irb->hiz_region) {
+      intel_region_release(&irb->hiz_region);
+   }
 
    free(irb);
 }
@@ -148,6 +151,9 @@ intel_alloc_renderbuffer_storage(struct gl_context * ctx, struct gl_renderbuffer
    if (irb->region) {
       intel_region_release(&irb->region);
    }
+   if (irb->hiz_region) {
+      intel_region_release(&irb->hiz_region);
+   }
 
    /* allocate new memory region/renderbuffer */
 
@@ -194,6 +200,19 @@ intel_alloc_renderbuffer_storage(struct gl_context * ctx, struct gl_renderbuffer
 
    ASSERT(irb->region->buffer);
 
+   if (intel->vtbl.is_hiz_depth_format(intel, rb->Format)) {
+      irb->hiz_region = intel_region_alloc(intel->intelScreen,
+                                           I915_TILING_Y,
+                                           irb->region->cpp,
+                                           irb->region->width,
+                                           irb->region->height,
+                                           GL_TRUE);
+      if (!irb->hiz_region) {
+         intel_region_release(&irb->region);
+         return GL_FALSE;
+      }
+   }
+
    rb->Width = width;
    rb->Height = height;