i965: Add stencil miptree copy for sampling

For gen < 8, we can't sample from the stencil buffer. We'll make a
copy of the stencil data into a new texture that we can sample using
the R8_UINT surface type.

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>

2 files changed, 14 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
index 0836b92f983..7246aa89a97 100644
--- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
+++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
@@ -532,6 +532,7 @@ intel_miptree_create_layout(struct brw_context *brw,
 	 intel_miptree_release(&mt);
 	 return NULL;
       }
+      mt->stencil_mt->stencil_tex_needs_update = true;
 
       /* Fix up the Z miptree format for how we're splitting out separate
        * stencil.  Gen7 expects there to be no stencil bits in its depth buffer.
@@ -995,6 +996,7 @@ intel_miptree_release(struct intel_mipmap_tree **mt)
 
       drm_intel_bo_unreference((*mt)->bo);
       intel_miptree_release(&(*mt)->stencil_mt);
+      intel_miptree_release(&(*mt)->stencil_tex_mt);
       if ((*mt)->hiz_buf) {
          if ((*mt)->hiz_buf->mt)
             intel_miptree_release(&(*mt)->hiz_buf->mt);
diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.h b/src/mesa/drivers/dri/i965/intel_mipmap_tree.h
index c28fb3364f6..4d93f952aae 100644
--- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.h
+++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.h
@@ -615,6 +615,18 @@ struct intel_mipmap_tree
    struct intel_mipmap_tree *stencil_mt;
 
    /**
+    * \brief Stencil texturing miptree for sampling from a stencil texture
+    *
+    * Some hardware doesn't support sampling from the stencil texture as
+    * required by the GL_ARB_stencil_texturing extenion. To overcome this we
+    * blit the texture into a new texture that can be sampled.
+    *
+    * \see intel_miptree_stencil_texturing()
+    */
+   struct intel_mipmap_tree *stencil_tex_mt;
+   bool stencil_tex_needs_update;
+
+   /**
     * \brief MCS miptree.
     *
     * This miptree contains the "multisample control surface", which stores