i965: Rewrite the HiZ op

The HiZ op was implemented as a meta-op. This patch reimplements it by
emitting a special HiZ batch. This fixes several known bugs, and likely
a lot of undiscovered ones too.

==== Why the HiZ meta-op needed to die ====

The HiZ op was implemented as a meta-op, which caused lots of trouble. All
other meta-ops occur as a result of some GL call (for example, glClear and
glGenerateMipmap), but the HiZ meta-op was special. It was called in
places that Mesa (in particular, the vbo and swrast modules) did not
expect---and were not prepared for---state changes to occur (for example:
glDraw; glCallList; within glBegin/End blocks; and within
swrast_prepare_render as a result of intel_miptree_map).

In an attempt to work around these unexpected state changes, I added two
hooks in i965:
  - A hook for glDraw, located in brw_predraw_resolve_buffers (which is
    called in the glDraw path). This hook detected if a predraw resolve
    meta-op had occurred, and would hackishly repropagate some GL state
    if necessary. This ensured that the meta-op state changes would not
    intefere with the vbo module's subsequent execution of glDraw.
  - A hook for glBegin, implemented by brwPrepareExecBegin. This hook
    resolved all buffers before entering
    a glBegin/End block, thus preventing an infinitely recurring call to
    vbo_exec_FlushVertices. The vbo module calls vbo_exec_FlushVertices to
    flush its vertex queue in response to GL state changes.

Unfortunately, these hooks were not sufficient. The meta-op state changes
still interacted badly with glPopAttrib (as discovered in bug 44927) and
with swrast rendering (as discovered by debugging gen6's swrast fallback
for glBitmap). I expect there are more undiscovered bugs. Rather than play
whack-a-mole in a minefield, the sane approach is to replace the HiZ
meta-op with something safer.

==== How it was killed ====

This patch consists of several logical components:
  1. Rewrite the HiZ op by replacing function gen6_resolve_slice with
     gen6_hiz_exec and gen7_hiz_exec. The new functions do not call
     a meta-op, but instead manually construct and emit a batch to "draw"
     the HiZ op's rectangle primitive. The new functions alter no GL
     state.
  2. Add fields to brw_context::hiz for the new HiZ op.
  3. Emit a workaround flush when toggling 3DSTATE_VS.VsFunctionEnable.
  4. Kill all dead HiZ code:
     - the function gen6_resolve_slice
     - the dirty flag BRW_NEW_HIZ
     - the dead fields in brw_context::hiz
     - the state packet manipulation triggered by the now removed
       brw_context::hiz::op
     - the meta-op workaround in brw_predraw_resolve_buffers (discussed
       above)
     - the meta-op workaround brwPrepareExecBegin (discussed above)

Note: This is a candidate for the 8.0 branch.
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Paul Berry <stereotype441@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=43327
Reported-by: xunx.fang@intel.com
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44927
Reported-by: chao.a.chen@intel.com
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>

1 files changed, 1 insertions, 19 deletions

diff --git a/src/mesa/drivers/dri/i965/gen6_clip_state.c b/src/mesa/drivers/dri/i965/gen6_clip_state.c
index d2a5f75..b3bb8ae 100644
--- a/src/mesa/drivers/dri/i965/gen6_clip_state.c
+++ b/src/mesa/drivers/dri/i965/gen6_clip_state.c
@@ -67,23 +67,6 @@ upload_clip_state(struct brw_context *brw)
          GEN6_CLIP_NON_PERSPECTIVE_BARYCENTRIC_ENABLE;
    }
 
-   if (brw->hiz.op) {
-      /* HiZ operations emit a rectangle primitive, which requires clipping to
-       * be disabled. From page 10 of the Sandy Bridge PRM Volume 2 Part 1
-       * Section 1.3 3D Primitives Overview:
-       *    RECTLIST:
-       *    Either the CLIP unit should be DISABLED, or the CLIP unit's Clip
-       *    Mode should be set to a value other than CLIPMODE_NORMAL.
-       */
-      BEGIN_BATCH(4);
-      OUT_BATCH(_3DSTATE_CLIP << 16 | (4 - 2));
-      OUT_BATCH(0);
-      OUT_BATCH(0);
-      OUT_BATCH(0);
-      ADVANCE_BATCH();
-      return;
-   }
-
    if (!ctx->Transform.DepthClamp)
       depth_clamp = GEN6_CLIP_Z_TEST;
 
@@ -124,8 +107,7 @@ const struct brw_tracked_state gen6_clip_state = {
    .dirty = {
       .mesa  = _NEW_TRANSFORM | _NEW_LIGHT,
       .brw   = (BRW_NEW_CONTEXT |
-                BRW_NEW_FRAGMENT_PROGRAM |
-                BRW_NEW_HIZ),
+                BRW_NEW_FRAGMENT_PROGRAM),
       .cache = 0
    },
    .emit = upload_clip_state,