[Mesa-dev] [PATCH] [RFC] i965: Rewrite the HiZ op (v2)

Kenneth Graunke kenneth at whitecape.org
Sat Feb 4 19:04:24 PST 2012


On 02/04/2012 10:10 AM, Chad Versace wrote:
> ==== RFC notes ====
>
> This patch needs to land in 8.0, so please share your comments. You can
> find this on my hiz-kill-meta-op-v12 branch.
>
> The patch is complete for gen6, and everything I test seems to work well.
> It introduces no Piglit delta; it fixes the remaining oglc failures in bug
> 43327; it fixes bug 44927. Nexuiz and Citybench like it.
>
> You may notice that /*TODO: gen7*/ is sprinkled about. And there's a few
> /*TODO: comment me*/'s too. I'm still working on that. But I wanted to
> get the patch out now, early, so that you can comment.
>
> v2: Incorporate Ken's comments. This largely meant removing the shaders
>      and removing some unneeded packets.
>
> What follows is the real commit message.
>
> ==== Summary ====
>
> This HiZ op was implemented as a meta-op. This patch reimplements it by
> constructing and emitting a special 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 called 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 gen6_resolve_slice with
>       gen6_hiz_exec. The new function does not call a meta-op, but instead
>       manually constructs and emits a batch to "draw" the HiZ op's
>       rectangle primitive. The new function alters no GL state.
>    2. Add fields to brw_context::hiz for the new HiZ op.
>    3. Rewrite gen6_hiz_init, and invoke it in the eglMakeCurrent codepath.
>    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)
>
> TODO: write gen7 variant for gen6_hiz_exec
> TODO: test egypt
> Note: This is a candidate for the 8.0 branch.
> CC: Eric Anholt<eric at anholt.net>
> CC: Kenneth Graunke<kenneth at whitecape.org>
> CC: Paul Berry<stereotype441 at gmail.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=43327
> Reported-by: xunx.fang at intel.com
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44927
> Reported-by: chao.a.chen at intel.com
> Signed-off-by: Chad Versace<chad.versace at linux.intel.com>
> ---
>   src/mesa/drivers/dri/i965/brw_context.c        |   55 --
>   src/mesa/drivers/dri/i965/brw_context.h        |   40 +-
>   src/mesa/drivers/dri/i965/brw_draw.c           |   47 +--
>   src/mesa/drivers/dri/i965/brw_state_upload.c   |    1 -
>   src/mesa/drivers/dri/i965/brw_vtbl.c           |    2 +
>   src/mesa/drivers/dri/i965/gen6_clip_state.c    |   20 +-
>   src/mesa/drivers/dri/i965/gen6_depthstencil.c  |    9 +-
>   src/mesa/drivers/dri/i965/gen6_hiz.c           |  883 ++++++++++++++++--------
>   src/mesa/drivers/dri/i965/gen6_sf_state.c      |   16 +-
>   src/mesa/drivers/dri/i965/gen6_vs_state.c      |   13 +
>   src/mesa/drivers/dri/i965/gen6_wm_state.c      |   20 +-
>   src/mesa/drivers/dri/i965/gen7_clip_state.c    |   20 +-
>   src/mesa/drivers/dri/i965/gen7_sf_state.c      |   19 +-
>   src/mesa/drivers/dri/i965/gen7_wm_state.c      |   18 -
>   src/mesa/drivers/dri/intel/intel_batchbuffer.c |   27 +
>   src/mesa/drivers/dri/intel/intel_batchbuffer.h |    1 +
>   16 files changed, 676 insertions(+), 515 deletions(-)
>   create mode 100644 src/mesa/drivers/dri/i965/junk
>
> diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
> index 1ab6310..65de260 100644
> --- a/src/mesa/drivers/dri/i965/brw_context.c
> +++ b/src/mesa/drivers/dri/i965/brw_context.c
> @@ -41,8 +41,6 @@
>   #include "brw_draw.h"
>   #include "brw_state.h"
>
> -#include "gen6_hiz.h"
> -
>   #include "intel_fbo.h"
>   #include "intel_mipmap_tree.h"
>   #include "intel_regions.h"
> @@ -57,58 +55,6 @@
>    * Mesa's Driver Functions
>    ***************************************/
>
> -/**
> - * \brief Prepare for entry into glBegin/glEnd block.
> - *
> - * Resolve buffers before entering a glBegin/glEnd block. This is
> - * necessary to prevent recursive calls to FLUSH_VERTICES.
> - *
> - * This resolves the depth buffer of each enabled depth texture and the HiZ
> - * buffer of the attached depth renderbuffer.
> - *
> - * Details
> - * -------
> - * When vertices are queued during a glBegin/glEnd block, those vertices must
> - * be drawn before any rendering state changes. To ensure this, Mesa calls
> - * FLUSH_VERTICES as a prehook to such state changes. Therefore,
> - * FLUSH_VERTICES itself cannot change rendering state without falling into a
> - * recursive trap.
> - *
> - * This precludes meta-ops, namely buffer resolves, from occurring while any
> - * vertices are queued. To prevent that situation, we resolve some buffers on
> - * entering a glBegin/glEnd
> - *
> - * \see brwCleanupExecEnd()
> - */
> -static void brwPrepareExecBegin(struct gl_context *ctx)
> -{
> -   struct brw_context *brw = brw_context(ctx);
> -   struct intel_context *intel =&brw->intel;
> -   struct intel_renderbuffer *draw_irb;
> -   struct intel_texture_object *tex_obj;
> -
> -   if (!intel->has_hiz) {
> -      /* The context uses no feature that requires buffer resolves. */
> -      return;
> -   }
> -
> -   /* Resolve each enabled texture. */
> -   for (int i = 0; i<  ctx->Const.MaxTextureImageUnits; i++) {
> -      if (!ctx->Texture.Unit[i]._ReallyEnabled)
> -	 continue;
> -      tex_obj = intel_texture_object(ctx->Texture.Unit[i]._Current);
> -      if (!tex_obj || !tex_obj->mt)
> -	 continue;
> -      intel_miptree_all_slices_resolve_depth(intel, tex_obj->mt);
> -   }
> -
> -   /* Resolve the attached depth buffer. */
> -   draw_irb = intel_get_renderbuffer(ctx->DrawBuffer, BUFFER_DEPTH);
> -   if (draw_irb) {
> -      intel_renderbuffer_resolve_hiz(intel, draw_irb);
> -   }
> -}
> -
>   static void brwInitDriverFunctions(struct intel_screen *screen,
>   				   struct dd_function_table *functions)
>   {
> @@ -117,7 +63,6 @@ static void brwInitDriverFunctions(struct intel_screen *screen,
>      brwInitFragProgFuncs( functions );
>      brw_init_queryobj_functions(functions);
>
> -   functions->PrepareExecBegin = brwPrepareExecBegin;
>      functions->BeginTransformFeedback = brw_begin_transform_feedback;
>
>      if (screen->gen>= 7)
> diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
> index c027bef..72e5059 100644
> --- a/src/mesa/drivers/dri/i965/brw_context.h
> +++ b/src/mesa/drivers/dri/i965/brw_context.h
> @@ -119,6 +119,10 @@
>   #define BRW_MAX_CURBE                    (32*16)
>
>   struct brw_context;
> +struct brw_instruction;
> +struct brw_vs_prog_key;
> +struct brw_wm_prog_key;
> +struct brw_wm_prog_data;
>
>   enum brw_state_id {
>      BRW_STATE_URB_FENCE,
> @@ -144,7 +148,6 @@ enum brw_state_id {
>      BRW_STATE_VS_CONSTBUF,
>      BRW_STATE_PROGRAM_CACHE,
>      BRW_STATE_STATE_BASE_ADDRESS,
> -   BRW_STATE_HIZ,
>      BRW_STATE_SOL_INDICES,
>   };
>
> @@ -174,7 +177,6 @@ enum brw_state_id {
>   #define BRW_NEW_VS_CONSTBUF            (1<<  BRW_STATE_VS_CONSTBUF)
>   #define BRW_NEW_PROGRAM_CACHE		(1<<  BRW_STATE_PROGRAM_CACHE)
>   #define BRW_NEW_STATE_BASE_ADDRESS	(1<<  BRW_STATE_STATE_BASE_ADDRESS)
> -#define BRW_NEW_HIZ			(1<<  BRW_STATE_HIZ)
>   #define BRW_NEW_SOL_INDICES		(1<<  BRW_STATE_SOL_INDICES)
>
>   struct brw_state_flags {
> @@ -950,38 +952,18 @@ struct brw_context
>      int state_batch_count;
>
>      /**
> -    * \brief State needed to execute HiZ meta-ops
> +    * \brief State needed to execute HiZ ops.
>       *
> -    * All fields except \c op are initialized by gen6_hiz_init().
> +    * \see gen6_hiz_init()
> +    * \see gen6_hiz_exec()
>       */
>      struct brw_hiz_state {
> -      /**
> -       * \brief Indicates which HiZ operation is in progress.
> +      /** \brief VBO for rectangle primitive.
>          *
> -       * See the following sections of the Sandy Bridge PRM, Volume 1, Part2:
> -       *   - 7.5.3.1 Depth Buffer Clear
> -       *   - 7.5.3.2 Depth Buffer Resolve
> -       *   - 7.5.3.3 Hierarchical Depth Buffer Resolve
> +       * Rather than using glGenBuffers(), we allocate the VBO directly
> +       * through drm.
>          */
> -      enum brw_hiz_op {
> -	 BRW_HIZ_OP_NONE = 0,
> -	 BRW_HIZ_OP_DEPTH_CLEAR,
> -	 BRW_HIZ_OP_DEPTH_RESOLVE,
> -	 BRW_HIZ_OP_HIZ_RESOLVE,
> -      } op;
> -
> -      /** \brief Shader state */
> -      struct {
> -	 GLuint program;
> -	 GLuint position_vbo;
> -	 GLint position_location;
> -      } shader;
> -
> -      /** \brief VAO for the rectangle primitive's vertices. */
> -      GLuint vao;
> -
> -      GLuint fbo;
> -      struct gl_renderbuffer *depth_rb;
> +      drm_intel_bo *vertex_bo;
>      } hiz;

Nice :) Down to one field!

>      struct brw_sol_state {
> diff --git a/src/mesa/drivers/dri/i965/brw_draw.c b/src/mesa/drivers/dri/i965/brw_draw.c
> index f50fffd..e919f3e 100644
> --- a/src/mesa/drivers/dri/i965/brw_draw.c
> +++ b/src/mesa/drivers/dri/i965/brw_draw.c
> @@ -126,12 +126,7 @@ static void gen6_set_prim(struct brw_context *brw,
>
>      DBG("PRIM: %s\n", _mesa_lookup_enum_by_nr(prim->mode));
>
> -   if (brw->hiz.op) {
> -      assert(prim->mode == GL_TRIANGLES);
> -      hw_prim = _3DPRIM_RECTLIST;
> -   } else {
> -      hw_prim = prim_to_hw_prim[prim->mode];
> -   }
> +   hw_prim = prim_to_hw_prim[prim->mode];
>
>      if (hw_prim != brw->primitive) {
>         brw->primitive = hw_prim;
> @@ -307,17 +302,11 @@ brw_predraw_resolve_buffers(struct brw_context *brw)
>      struct intel_context *intel =&brw->intel;
>      struct intel_renderbuffer *depth_irb;
>      struct intel_texture_object *tex_obj;
> -   bool did_resolve = false;
> -
> -   /* Avoid recursive HiZ op. */
> -   if (brw->hiz.op) {
> -      return;
> -   }
>
>      /* Resolve the depth buffer's HiZ buffer. */
>      depth_irb = intel_get_renderbuffer(ctx->DrawBuffer, BUFFER_DEPTH);
>      if (depth_irb&&  depth_irb->mt) {
> -      did_resolve |= intel_renderbuffer_resolve_hiz(intel, depth_irb);
> +      intel_renderbuffer_resolve_hiz(intel, depth_irb);
>      }
>
>      /* Resolve depth buffer of each enabled depth texture. */
> @@ -327,33 +316,7 @@ brw_predraw_resolve_buffers(struct brw_context *brw)
>         tex_obj = intel_texture_object(ctx->Texture.Unit[i]._Current);
>         if (!tex_obj || !tex_obj->mt)
>   	 continue;
> -      did_resolve |= intel_miptree_all_slices_resolve_depth(intel, tex_obj->mt);
> -   }
> -
> -   if (did_resolve) {
> -      /* Call vbo_bind_array() to synchronize the vbo module's vertex
> -       * attributes to the gl_context's.
> -       *
> -       * Details
> -       * -------
> -       * The vbo module tracks vertex attributes separately from the
> -       * gl_context.  Specifically, the vbo module maintins vertex attributes
> -       * in vbo_exec_context::array::inputs, which is synchronized with
> -       * gl_context::Array::ArrayObj::VertexAttrib by vbo_bind_array().
> -       * vbo_draw_arrays() calls vbo_bind_array() to perform the
> -       * synchronization before calling the real draw call,
> -       * vbo_context::draw_arrays.
> -       *
> -       * At this point (after performing a resolve meta-op but before calling
> -       * vbo_bind_array), the gl_context's vertex attributes have been
> -       * restored to their original state (that is, their state before the
> -       * meta-op began), but the vbo module's vertex attribute are those used
> -       * in the last meta-op. Therefore we must manually synchronize the two with
> -       * vbo_bind_array() before continuing with the original draw command.
> -       */
> -      _mesa_update_state(ctx);
> -      vbo_bind_arrays(ctx);
> -      _mesa_update_state(ctx);
> +      intel_miptree_all_slices_resolve_depth(intel, tex_obj->mt);
>      }
>   }
>
> @@ -372,9 +335,7 @@ static void brw_postdraw_set_buffers_need_resolve(struct brw_context *brw)
>      struct intel_renderbuffer *depth_irb =
>   	 intel_get_renderbuffer(fb, BUFFER_DEPTH);
>
> -   if (depth_irb&&
> -       ctx->Depth.Mask&&
> -       !brw->hiz.op) {
> +   if (depth_irb&&  ctx->Depth.Mask) {
>         intel_renderbuffer_set_needs_depth_resolve(depth_irb);
>      }
>   }
> diff --git a/src/mesa/drivers/dri/i965/brw_state_upload.c b/src/mesa/drivers/dri/i965/brw_state_upload.c
> index d071f87..f5e6fdc 100644
> --- a/src/mesa/drivers/dri/i965/brw_state_upload.c
> +++ b/src/mesa/drivers/dri/i965/brw_state_upload.c
> @@ -372,7 +372,6 @@ static struct dirty_bit_map brw_bits[] = {
>      DEFINE_BIT(BRW_NEW_GS_BINDING_TABLE),
>      DEFINE_BIT(BRW_NEW_PS_BINDING_TABLE),
>      DEFINE_BIT(BRW_NEW_STATE_BASE_ADDRESS),
> -   DEFINE_BIT(BRW_NEW_HIZ),
>      {0, 0, 0}
>   };
>
> diff --git a/src/mesa/drivers/dri/i965/brw_vtbl.c b/src/mesa/drivers/dri/i965/brw_vtbl.c
> index be975d1..a24b44d 100644
> --- a/src/mesa/drivers/dri/i965/brw_vtbl.c
> +++ b/src/mesa/drivers/dri/i965/brw_vtbl.c
> @@ -70,9 +70,11 @@ static void brw_destroy_context( struct intel_context *intel )
>
>      brw_destroy_state(brw);
>      brw_draw_destroy( brw );
> +
>      ralloc_free(brw->wm.compile_data);
>
>      dri_bo_release(&brw->curbe.curbe_bo);
> +   dri_bo_release(&brw->hiz.vertex_bo);
>      dri_bo_release(&brw->vs.const_bo);
>      dri_bo_release(&brw->wm.const_bo);
>
> 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,
> diff --git a/src/mesa/drivers/dri/i965/gen6_depthstencil.c b/src/mesa/drivers/dri/i965/gen6_depthstencil.c
> index d9f686a..4ea517f 100644
> --- a/src/mesa/drivers/dri/i965/gen6_depthstencil.c
> +++ b/src/mesa/drivers/dri/i965/gen6_depthstencil.c
> @@ -82,11 +82,7 @@ gen6_upload_depth_stencil_state(struct brw_context *brw)
>      }
>
>      /* _NEW_DEPTH */
> -   if ((ctx->Depth.Test || brw->hiz.op)&&  depth_irb) {
> -      assert(brw->hiz.op != BRW_HIZ_OP_DEPTH_RESOLVE || ctx->Depth.Test);
> -      assert(brw->hiz.op != BRW_HIZ_OP_HIZ_RESOLVE   || !ctx->Depth.Test);
> -      assert(brw->hiz.op != BRW_HIZ_OP_DEPTH_CLEAR   || !ctx->Depth.Test);
> -
> +   if (ctx->Depth.Test&&  depth_irb) {
>         ds->ds2.depth_test_enable = ctx->Depth.Test;
>         ds->ds2.depth_test_func = intel_translate_compare_func(ctx->Depth.Func);
>         ds->ds2.depth_write_enable = ctx->Depth.Mask;
> @@ -98,8 +94,7 @@ gen6_upload_depth_stencil_state(struct brw_context *brw)
>   const struct brw_tracked_state gen6_depth_stencil_state = {
>      .dirty = {
>         .mesa = _NEW_DEPTH | _NEW_STENCIL | _NEW_BUFFERS,
> -      .brw  = (BRW_NEW_BATCH |
> -	       BRW_NEW_HIZ),
> +      .brw  = BRW_NEW_BATCH,
>         .cache = 0,
>      },
>      .emit = gen6_upload_depth_stencil_state,
> diff --git a/src/mesa/drivers/dri/i965/gen6_hiz.c b/src/mesa/drivers/dri/i965/gen6_hiz.c
> index d7698ed..3638000 100644
> --- a/src/mesa/drivers/dri/i965/gen6_hiz.c
> +++ b/src/mesa/drivers/dri/i965/gen6_hiz.c
> @@ -25,324 +25,653 @@
>
>   #include<assert.h>
>
> -#include "mesa/drivers/common/meta.h"
> -
> -#include "mesa/main/arrayobj.h"
> -#include "mesa/main/bufferobj.h"
> -#include "mesa/main/depth.h"
> -#include "mesa/main/enable.h"
> -#include "mesa/main/fbobject.h"
> -#include "mesa/main/framebuffer.h"
> -#include "mesa/main/get.h"
> -#include "mesa/main/renderbuffer.h"
> +#include "glsl/ralloc.h"
> +
>   #include "mesa/main/shaderapi.h"
> -#include "mesa/main/varray.h"
> +#include "mesa/main/shaderobj.h"
>
> +#include "intel_batchbuffer.h"
>   #include "intel_fbo.h"
>   #include "intel_mipmap_tree.h"
> -#include "intel_regions.h"
> -#include "intel_tex.h"
>
>   #include "brw_context.h"
>   #include "brw_defines.h"
> +#include "brw_state.h"
> +#include "brw_vs.h"
> +#include "brw_wm.h"
>
> -static const uint32_t gen6_hiz_meta_save =
> -
> -      /* Disable alpha, depth, and stencil test.
> -       *
> -       * See the following sections of the Sandy Bridge PRM, Volume 1, Part2:
> -       *   - 7.5.3.1 Depth Buffer Clear
> -       *   - 7.5.3.2 Depth Buffer Resolve
> -       *   - 7.5.3.3 Hierarchical Depth Buffer Resolve
> -       */
> -      MESA_META_ALPHA_TEST |
> -      MESA_META_DEPTH_TEST |
> -      MESA_META_STENCIL_TEST |
> -
> -      /* Disable viewport mapping.
> -       *
> -       * From page 11 of the Sandy Bridge PRM, Volume 2, Part 1, Section 1.3
> -       * 3D Primitives Overview:
> -       *    RECTLIST:
> -       *    Viewport Mapping must be DISABLED (as is typical with the use of
> -       *    screen- space coordinates).
> -       *
> -       * We must also manually disable 3DSTATE_SF.Viewport_Transform_Enable.
> -       */
> -      MESA_META_VIEWPORT |
> -
> -      /* Disable clipping.
> -       *
> -       * From page 11 of the Sandy Bridge PRM, Volume 2, Part 1, Section 1.3
> -       * 3D Primitives Overview:
> -       *     Either the CLIP unit should be DISABLED, or the CLIP unit’s Clip
> -       *     Mode should be set to a value other than CLIPMODE_NORMAL.
> -       */
> -      MESA_META_CLIP |
> -
> -      /* Render a solid rectangle (set 3DSTATE_SF.FrontFace_Fill_Mode).
> -       *
> -       * From page 249 of the Sandy Bridge PRM, Volume 2, Part 1, Section
> -       * 6.4.1.1 3DSTATE_SF, FrontFace_Fill_Mode:
> -       *     SOLID: Any triangle or rectangle object found to be front-facing
> -       *     is rendered as a solid object. This setting is required when
> -       *     (rendering rectangle (RECTLIST) objects.
> -       * Also see field BackFace_Fill_Mode.
> -       *
> -       * Note: MESA_META_RASTERIZAION also disables culling, but that is
> -       * irrelevant. See 3DSTATE_SF.Cull_Mode.
> -       */
> -      MESA_META_RASTERIZATION |
> -
> -      /* Each HiZ operation uses a vertex shader and VAO. */
> -      MESA_META_SHADER |
> -      MESA_META_VERTEX |
> -
> -      /* Disable scissoring.
> -       *
> -       * Scissoring is disabled for resolves because a resolve operation
> -       * should resolve the entire buffer. Scissoring is disabled for depth
> -       * clears because, if we are performing a partial depth clear, then we
> -       * specify the clear region with the RECTLIST vertices.
> -       */
> -      MESA_META_SCISSOR |
> -
> -      MESA_META_SELECT_FEEDBACK;
> +/**
> + * For an overview of the HiZ operations, see the following sections of the
> + * Sandy Bridge PRM, Volume 1, Part2:
> + *   - 7.5.3.1 Depth Buffer Clear
> + *   - 7.5.3.2 Depth Buffer Resolve
> + *   - 7.5.3.3 Hierarchical Depth Buffer Resolve
> + */
> +enum gen6_hiz_op {
> +   GEN6_HIZ_OP_DEPTH_CLEAR,
> +   GEN6_HIZ_OP_DEPTH_RESOLVE,
> +   GEN6_HIZ_OP_HIZ_RESOLVE,
> +};
>
> -static void
> -gen6_hiz_get_framebuffer_enum(struct gl_context *ctx,
> -                              GLenum *bind_enum,
> -                              GLenum *get_enum)
> -{
> -   if (ctx->Extensions.EXT_framebuffer_blit&&  ctx->API == API_OPENGL) {
> -      /* Different buffers may be bound to GL_DRAW_FRAMEBUFFER and
> -       * GL_READ_FRAMEBUFFER. Take care to not disrupt the read buffer.
> -       */
> -      *bind_enum = GL_DRAW_FRAMEBUFFER;
> -      *get_enum = GL_DRAW_FRAMEBUFFER_BINDING;
> -   } else {
> -      /* The enums GL_DRAW_FRAMEBUFFER and GL_READ_FRAMEBUFFER do not exist.
> -       * The bound framebuffer is both the read and draw buffer.
> -       */
> -      *bind_enum = GL_FRAMEBUFFER;
> -      *get_enum = GL_FRAMEBUFFER_BINDING;
> -   }
> -}
> +/**
> + * \name Constants for HiZ VBO
> + * \{
> + *
> + * \see brw_context::hiz::vertex_bo
> + */
> +#define GEN6_HIZ_NUM_VERTICES 3
> +#define GEN6_HIZ_NUM_VERTEX_COMPONENTS 4
> +#define GEN6_HIZ_VBO_SIZE (GEN6_HIZ_NUM_VERTICES \
> +                           * GEN6_HIZ_NUM_VERTEX_COMPONENTS \
> +                           * sizeof(float))
> +/** \} */
>
>   /**
> - * Initialize static data needed for HiZ operations.
> + * \brief Initialize data needed for the HiZ op.
> + *
> + * This called when executing the first HiZ op.
> + * \see brw_context::hiz
>    */
>   static void
>   gen6_hiz_init(struct brw_context *brw)
>   {
>      struct gl_context *ctx =&brw->intel.ctx;
> +   struct intel_context *intel =&brw->intel;
>      struct brw_hiz_state *hiz =&brw->hiz;
> -   GLenum fb_bind_enum, fb_get_enum;
>
> -   if (hiz->fbo != 0)
> -      return;
> -
> -   gen6_hiz_get_framebuffer_enum(ctx,&fb_bind_enum,&fb_get_enum);
> +   hiz->vertex_bo = drm_intel_bo_alloc(intel->bufmgr, "bufferobj",
> +                                       GEN6_HIZ_VBO_SIZE, /* size */
> +                                       64); /* alignment */

I might name this "HiZ VBO" or something more descriptive than 
"bufferobj"...but not a big deal either way.

> -   /* Create depthbuffer.
> -    *
> -    * Until glRenderbufferStorage is called, the renderbuffer hash table
> -    * maps the renderbuffer name to a dummy renderbuffer. We need the
> -    * renderbuffer to be registered in the hash table so that framebuffer
> -    * validation succeeds, so we hackishly allocate storage then immediately
> -    * discard it.
> -    */
> -   GLuint depth_rb_name;
> -   _mesa_GenRenderbuffersEXT(1,&depth_rb_name);
> -   _mesa_BindRenderbufferEXT(GL_RENDERBUFFER, depth_rb_name);
> -   _mesa_RenderbufferStorageEXT(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, 32, 32);
> -   _mesa_reference_renderbuffer(&hiz->depth_rb,
> -                                _mesa_lookup_renderbuffer(ctx, depth_rb_name));
> -   intel_miptree_release(&((struct intel_renderbuffer*) hiz->depth_rb)->mt);
> -
> -   /* Setup FBO. */
> -   _mesa_GenFramebuffersEXT(1,&hiz->fbo);
> -   _mesa_BindFramebufferEXT(fb_bind_enum, hiz->fbo);
> -   _mesa_FramebufferRenderbufferEXT(fb_bind_enum,
> -                                    GL_DEPTH_ATTACHMENT,
> -                                    GL_RENDERBUFFER,
> -                                    hiz->depth_rb->Name);
> -
> -   /* Compile vertex shader. */
> -   const char *vs_source =
> -      "attribute vec4 position;\n"
> -      "void main()\n"
> -      "{\n"
> -      "   gl_Position = position;\n"
> -      "}\n";
> -   GLuint vs = _mesa_CreateShaderObjectARB(GL_VERTEX_SHADER);
> -   _mesa_ShaderSourceARB(vs, 1,&vs_source, NULL);
> -   _mesa_CompileShaderARB(vs);
> -
> -   /* Compile fragment shader. */
> -   const char *fs_source = "void main() {}";
> -   GLuint fs = _mesa_CreateShaderObjectARB(GL_FRAGMENT_SHADER);
> -   _mesa_ShaderSourceARB(fs, 1,&fs_source, NULL);
> -   _mesa_CompileShaderARB(fs);
> -
> -   /* Link and use program. */
> -   hiz->shader.program = _mesa_CreateProgramObjectARB();
> -   _mesa_AttachShader(hiz->shader.program, vs);
> -   _mesa_AttachShader(hiz->shader.program, fs);
> -   _mesa_LinkProgramARB(hiz->shader.program);
> -   _mesa_UseProgramObjectARB(hiz->shader.program);
> -
> -   /* Create and bind VAO. */
> -   _mesa_GenVertexArrays(1,&hiz->vao);
> -   _mesa_BindVertexArray(hiz->vao);
> -
> -   /* Setup VBO for 'position'. */
> -   hiz->shader.position_location =
> -      _mesa_GetAttribLocationARB(hiz->shader.program, "position");
> -   _mesa_GenBuffersARB(1,&hiz->shader.position_vbo);
> -   _mesa_BindBufferARB(GL_ARRAY_BUFFER_ARB, hiz->shader.position_vbo);
> -   _mesa_VertexAttribPointerARB(hiz->shader.position_location,
> -				2, /*components*/
> -				GL_FLOAT,
> -				GL_FALSE, /*normalized?*/
> -				0, /*stride*/
> -				NULL);
> -   _mesa_EnableVertexAttribArrayARB(hiz->shader.position_location);
> -
> -   /* Cleanup. */
> -   _mesa_DeleteShader(vs);
> -   _mesa_DeleteShader(fs);
> +   if (!hiz->vertex_bo)
> +      _mesa_error(ctx, GL_OUT_OF_MEMORY, "failed to allocate internal VBO");
>   }
>
>   /**
> - * Wrap \c brw->hiz.depth_rb around a miptree.
> + * \brief Execute a HiZ op on a miptree slice.
>    *
> - * \see gen6_hiz_teardown_depth_buffer()
> - */
> -static void
> -gen6_hiz_setup_depth_buffer(struct brw_context *brw,
> -			    struct intel_mipmap_tree *mt,
> -			    unsigned int level,
> -			    unsigned int layer)
> -{
> -   struct gl_renderbuffer *rb = brw->hiz.depth_rb;
> -   struct intel_renderbuffer *irb = intel_renderbuffer(rb);
> -
> -   rb->Format = mt->format;
> -   rb->_BaseFormat = _mesa_get_format_base_format(rb->Format);
> -   rb->InternalFormat = rb->_BaseFormat;
> -   rb->Width = mt->level[level].width;
> -   rb->Height = mt->level[level].height;
> -
> -   irb->mt_level = level;
> -   irb->mt_layer = layer;
> -
> -   intel_miptree_reference(&irb->mt, mt);
> -   intel_renderbuffer_set_draw_offset(irb);
> -}
> -
> -/**
> - * Release the region from \c brw->hiz.depth_rb.
> + * To execute the HiZ op, this function manually constructs and emits a batch
> + * to "draw" the HiZ op's rectangle primitive. The batchbuffer is flushed
> + * before constructing and after emitting the batch.
>    *
> - * \see gen6_hiz_setup_depth_buffer()
> + * This function alters no GL state.
> + *
> + * For an overview of HiZ ops, see the following sections of the Sandy Bridge
> + * PRM, Volume 1, Part2:
> + *   - 7.5.3.1 Depth Buffer Clear
> + *   - 7.5.3.2 Depth Buffer Resolve
> + *   - 7.5.3.3 Hierarchical Depth Buffer Resolve
>    */
>   static void
> -gen6_hiz_teardown_depth_buffer(struct gl_renderbuffer *rb)
> -{
> -   struct intel_renderbuffer *irb = intel_renderbuffer(rb);
> -   intel_miptree_release(&irb->mt);
> -}
> -
> -static void
> -gen6_resolve_slice(struct intel_context *intel,
> -	         struct intel_mipmap_tree *mt,
> -		 unsigned int level,
> -		 unsigned int layer,
> -                 enum brw_hiz_op op)
> +gen6_hiz_exec(struct intel_context *intel,
> +              struct intel_mipmap_tree *mt,
> +              unsigned int level,
> +              unsigned int layer,
> +              enum gen6_hiz_op op)
>   {
>      struct gl_context *ctx =&intel->ctx;
>      struct brw_context *brw = brw_context(ctx);
>      struct brw_hiz_state *hiz =&brw->hiz;
> -   GLenum fb_bind_enum, fb_get_enum;
> -
> -   /* Do not recurse. */
> -   assert(!brw->hiz.op);
>
> +   assert(op != GEN6_HIZ_OP_DEPTH_CLEAR); /* Not implemented yet. */
>      assert(mt->hiz_mt != NULL);
> -   assert(level>= mt->first_level);
> -   assert(level<= mt->last_level);
> -   assert(layer<  mt->level[level].depth);
> -
> -   gen6_hiz_get_framebuffer_enum(ctx,&fb_bind_enum,&fb_get_enum);
> -
> -   /* Save state. */
> -   GLint save_drawbuffer;
> -   GLint save_renderbuffer;
> -   _mesa_meta_begin(ctx, gen6_hiz_meta_save);
> -   _mesa_GetIntegerv(fb_get_enum,&save_drawbuffer);
> -   _mesa_GetIntegerv(GL_RENDERBUFFER_BINDING,&save_renderbuffer);
> -
> -   /* Initialize context data for HiZ operations. */
> -   gen6_hiz_init(brw);
> -
> -   /* Set depth state. */
> -   if (!ctx->Depth.Mask) {
> -      /* This sets 3DSTATE_WM.Depth_Buffer_Write_Enable. */
> -      _mesa_DepthMask(GL_TRUE);
> -   }
> -   if (op == BRW_HIZ_OP_DEPTH_RESOLVE) {
> -      _mesa_set_enable(ctx, GL_DEPTH_TEST, GL_TRUE);
> -      _mesa_DepthFunc(GL_NEVER);
> -   }
> +   intel_miptree_check_level_layer(mt, level, layer);
>
> -   /* Setup FBO. */
> -   gen6_hiz_setup_depth_buffer(brw, mt, level, layer);
> -   _mesa_BindFramebufferEXT(fb_bind_enum, hiz->fbo);
> +   if (hiz->vertex_bo == NULL)
> +      gen6_hiz_init(brw);
>
> +   if (hiz->vertex_bo == NULL) {
> +      /* Ouch. Give up. */
> +      return;
> +   }
>
> -   /* A rectangle primitive (3DPRIM_RECTLIST) consists of only three vertices.
> -    * The vertices reside in screen space with DirectX coordinates (this is,
> -    * (0, 0) is the upper left corner).
> +   /* Setup VBO for the rectangle primitive..
> +    *
> +    * A rectangle primitive (3DPRIM_RECTLIST) consists of only three
> +    * vertices. The vertices reside in screen space with DirectX coordinates
> +    * (that is, (0, 0) is the upper left corner).
>       *
>       *   v2 ------ implied
>       *    |        |
>       *    |        |
>       *   v0 ----- v1
> +    *
> +    * Since the VS is disabled, the clipper loads each vertex directly from
> +    * the VBO.  As the clipper loads each vertex, perspective division occurs.
> +    * This requires that we explicity provide the vertex's w component. (This
> +    * requirement was discovered by observing the simulator).
> +    */
> +   {
> +      const int width = mt->level[level].width;
> +      const int height = mt->level[level].height;
> +      const float vertices[GEN6_HIZ_VBO_SIZE] = {
> +             0, height, 0, 1, /* v0 */
> +         width, height, 0, 1, /* v1 */
> +             0,      0, 0, 1, /* v2 */
> +      };
> +
> +      drm_intel_bo_subdata(hiz->vertex_bo, 0, GEN6_HIZ_VBO_SIZE, vertices);
> +   }

If it helps...3DSTATE_CLIP DW2 bit 9 is "Perspective Divide Disable". 
That said, I'm not sure using it would save a lot of complexity.

> +   /* To ensure that the batch contains only the resolve, flush the batch
> +    * before beginning and after finishing emitting the resolve packets.
> +    *
> +    * Ideally, we would not need to flush for the resolve op. But, I suspect
> +    * that it's unsafe for CMD_PIPELINE_SELECT to occur multiple times in
> +    * a single batch, and there is no safe way to ensure that other than by
> +    * fencing the resolve with flushes. Ideally, we would just detect if
> +    * a batch is in progress and do the right thing, but that would require
> +    * the ability to safely manipulate brw_context::state::dirty::brw outside
> +    * of brw_state_init().
> +    */
> +   intel_flush(ctx);
> +
> +   /* Emit the following packets:
> +    *     CMD_PIPELINE_SELECT
> +    *     3DSTATE_MULTISAMPLE
> +    *     3DSTATE_SAMPLE_MASK
> +    *     3DSTATE_GS_SVB_INDEX
> +    *     CMD_STATE_SIP
> +    *     CMD_VF_STATISTICS
> +    */
> +   brw_invariant_state.emit(brw);
> +
> +   /* CMD_STATE_BASE_ADDRESS
> +    *
> +    * From the Sandy Bridge PRM, Volume 1, Part 1, Table STATE_BASE_ADDRESS:
> +    *
> +    *     The following commands must be reissued following any change to the
> +    *     base addresses:
> +    *         3DSTATE_CC_POINTERS
> +    *         3DSTATE_BINDING_TABLE_POINTERS
> +    *         3DSTATE_SAMPLER_STATE_POINTERS
> +    *         3DSTATE_VIEWPORT_STATE_POINTERS
> +    *         MEDIA_STATE_POINTERS
> +    */
> +   {
> +      BEGIN_BATCH(10);
> +      OUT_BATCH(CMD_STATE_BASE_ADDRESS<<  16 | (10 - 2));
> +      OUT_BATCH(1); /* GeneralStateBaseAddressModifyEnable */
> +      /* SurfaceStateBaseAddress */
> +      OUT_RELOC(intel->batch.bo, I915_GEM_DOMAIN_SAMPLER, 0, 1);
> +      /* DynamicStateBaseAddress */
> +      OUT_RELOC(intel->batch.bo, (I915_GEM_DOMAIN_RENDER |
> +                                  I915_GEM_DOMAIN_INSTRUCTION), 0, 1);
> +      OUT_BATCH(1); /* IndirectObjectBaseAddress */
> +      OUT_BATCH(1); /* InstructionBaseAddress */
> +      OUT_BATCH(1); /* GeneralStateUpperBound */
> +      OUT_BATCH(1); /* DynamicStateUpperBound */
> +      OUT_BATCH(1); /* IndirectObjectUpperBound*/
> +      OUT_BATCH(1); /* InstructionAccessUpperBound */
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_VIEWPORT_STATE_POINTERS
> +    *
> +    * Viewport mapping is disabled for the HiZ op, so it's safe to
> +    * set all viewport state pointers to null.
> +    *
> +    * From page 11 of the Sandy Bridge PRM, Volume 2, Part 1, Section 1.3
> +    * 3D Primitives Overview:
> +    *    RECTLIST:
> +    *    Viewport Mapping must be DISABLED (as is typical with the use of
> +    *    screen- space coordinates).
> +    */
> +   {
> +      BEGIN_BATCH(4);
> +      OUT_BATCH(_3DSTATE_VIEWPORT_STATE_POINTERS<<  16 | (4 - 2) |
> +                GEN6_CC_VIEWPORT_MODIFY |
> +                GEN6_SF_VIEWPORT_MODIFY |
> +                GEN6_CLIP_VIEWPORT_MODIFY);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_URB
> +    *
> +    * Assign the entire URB to the VS.
> +    *
> +    * A warning appears in the Sandybridge PRM Volume 2 Part 1 Section 1.4.7
> +    * 3DSTATE_URB, but here we can safely ignore it:
> +    *     Because of URB corruption caused by allocating a previous GS unit
> +    *     URB entry to the VS unit, software is required to send a “GS NULL
> +    *     Fence” (Send URB fence with VS URB size == 1 and GS URB size == 0)
> +    *     plus a dummy DRAW call before any case where VS will be taking over
> +    *     GS URB space.
> +    * We can ignore it because this batch contains only one draw call.
> +    *
> +    * TODO: Explain why max vs entries must be set. Quote spec.
> +    */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      BEGIN_BATCH(3);
> +      OUT_BATCH(_3DSTATE_URB<<  16 | (3 - 2));
> +      OUT_BATCH(brw->urb.max_vs_entries<<  GEN6_URB_VS_ENTRIES_SHIFT);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* DEPTH_STENCIL_STATE
> +    *
> +    * The offset is relative CMD_STATE_BASE_ADDRESS.DynamicStateBaseAddress.
> +    */
> +   uint32_t depthstencil_offset;
> +   {
> +      assert(intel->gen == 6);
> +
> +      struct gen6_depth_stencil_state *state;
> +      state = brw_state_batch(brw, AUB_TRACE_DEPTH_STENCIL_STATE,
> +                                 sizeof(*state), 64,
> +&depthstencil_offset);
> +      memset(state, 0, sizeof(*state));
> +
> +      /* See the following sections of the Sandy Bridge PRM, Volume 1, Part2:
> +       *   - 7.5.3.1 Depth Buffer Clear
> +       *   - 7.5.3.2 Depth Buffer Resolve
> +       *   - 7.5.3.3 Hierarchical Depth Buffer Resolve
> +       */
> +      state->ds2.depth_write_enable = 1;
> +      if (op == GEN6_HIZ_OP_DEPTH_RESOLVE) {
> +         state->ds2.depth_test_enable = 1;
> +         state->ds2.depth_test_func = COMPAREFUNC_NEVER;
> +      }
> +   }
> +
> +   /* 3DSTATE_CC_STATE_POINTERS
> +    *
> +    * The HiZ op doesn't use BLEND_STATE or COLOR_CALC_STATE.
> +    */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +      BEGIN_BATCH(4);
> +      OUT_BATCH(_3DSTATE_CC_STATE_POINTERS<<  16 | (4 - 2));
> +      OUT_BATCH(1); /* BLEND_STATE offset */
> +      OUT_BATCH(depthstencil_offset | 1); /* DEPTH_STENCIL_STATE offset */
> +      OUT_BATCH(1); /* COLOR_CALC_STATE offset */
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_VS
> +    *
> +    * Disable vertex shader.
> +    */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      intel_emit_vs_enable_flush(intel);
> +
> +      BEGIN_BATCH(6);
> +      OUT_BATCH(_3DSTATE_VS<<  16 | (6 - 2));
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_GS
> +    *
> +    * Disable the geometry shader.
> +    */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      BEGIN_BATCH(7);
> +      OUT_BATCH(_3DSTATE_GS<<  16 | (7 - 2));
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_CLIP
> +    *
> +    * Disable the clipper.
> +    *
> +    * The HiZ op emits 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.
> +    */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      BEGIN_BATCH(4);
> +      OUT_BATCH(_3DSTATE_CLIP<<  16 | (4 - 2));
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_SF
> +    *
> +    * Disable ViewportTransformEnable (dw2.1)
> +    *
> +    * From the SandyBridge PRM, Volume 2, Part 1, Section 1.3, "3D
> +    * Primitives Overview":
> +    *     RECTLIST: Viewport Mapping must be DISABLED (as is typical with the
> +    *     use of screen- space coordinates).
> +    *
> +    * A solid rectangle must be rendered, so set FrontFaceFillMode (dw2.4:3)
> +    * and BackFaceFillMode (dw2.5:6) to SOLID(0).
> +    *
> +    * From the Sandy Bridge PRM, Volume 2, Part 1, Section
> +    * 6.4.1.1 3DSTATE_SF, Field FrontFaceFillMode:
> +    *     SOLID: Any triangle or rectangle object found to be front-facing
> +    *     is rendered as a solid object. This setting is required when
> +    *     (rendering rectangle (RECTLIST) objects.
>       */
> -   const int width = hiz->depth_rb->Width;
> -   const int height = hiz->depth_rb->Height;
> -   const GLfloat positions[] = {
> -          0, height,
> -      width, height,
> -          0,      0,
> -   };
> -
> -   /* Setup program and vertex attributes. */
> -   _mesa_UseProgramObjectARB(hiz->shader.program);
> -   _mesa_BindVertexArray(hiz->vao);
> -   _mesa_BindBufferARB(GL_ARRAY_BUFFER, hiz->shader.position_vbo);
> -   _mesa_BufferDataARB(GL_ARRAY_BUFFER_ARB, sizeof(positions), positions,
> -		       GL_DYNAMIC_DRAW_ARB);
> -
> -   /* Execute the HiZ operation. */
> -   brw->hiz.op = op;
> -   brw->state.dirty.brw |= BRW_NEW_HIZ;
> -   _mesa_DrawArrays(GL_TRIANGLES, 0, 3);
> -   brw->state.dirty.brw |= BRW_NEW_HIZ;
> -   brw->hiz.op = BRW_HIZ_OP_NONE;
> -
> -   /* Restore state.
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      BEGIN_BATCH(20);
> +      OUT_BATCH(_3DSTATE_SF<<  16 | (20 - 2));
> +      OUT_BATCH((1 - 1)<<  GEN6_SF_NUM_OUTPUTS_SHIFT | /* only position */
> +                1<<  GEN6_SF_URB_ENTRY_READ_LENGTH_SHIFT |
> +                1<<  GEN6_SF_URB_ENTRY_READ_OFFSET_SHIFT);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_CONSTANT_PS
>       *
> -    * The order in which state is restored is significant. The draw buffer
> -    * used for the HiZ op has no stencil buffer, and glStencilFunc() clamps
> -    * the stencil reference value to the range allowed by the draw buffer's
> -    * number of stencil bits. So, the draw buffer binding must be restored
> -    * before the stencil state, or else the stencil ref will be clamped to 0.
> +    * Disable the push constant buffer.
>       */
> -   gen6_hiz_teardown_depth_buffer(hiz->depth_rb);
> -   _mesa_BindRenderbufferEXT(GL_RENDERBUFFER, save_renderbuffer);
> -   _mesa_BindFramebufferEXT(fb_bind_enum, save_drawbuffer);
> -   _mesa_meta_end(ctx);
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      BEGIN_BATCH(5);
> +      OUT_BATCH(_3DSTATE_CONSTANT_PS<<  16 | (5 - 2));
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }

I think you can drop this constant buffer, no?

> +   /* 3DSTATE_WM
> +    *
> +    * Disable thread dispatch (dw5.19) and enable the HiZ op.
> +    */
> +   {
> +      uint32_t dw4 = 0;
> +
> +      switch (op) {
> +      case GEN6_HIZ_OP_DEPTH_CLEAR:
> +         assert(!"not implemented");
> +         dw4 |= GEN6_WM_DEPTH_CLEAR;
> +         break;
> +      case GEN6_HIZ_OP_DEPTH_RESOLVE:
> +         dw4 |= GEN6_WM_DEPTH_RESOLVE;
> +         break;
> +      case GEN6_HIZ_OP_HIZ_RESOLVE:
> +         dw4 |= GEN6_WM_HIERARCHICAL_DEPTH_RESOLVE;
> +         break;
> +      default:
> +         assert(0);
> +         break;
> +      }
> +
> +      /* Even though thread dispatch disabled, max threads (dw5.25) must be
> +       * nonzero to prevent the GPU from hanging.
> +       */
> +      uint32_t dw5 = (brw->max_wm_threads - 1)<<  GEN6_WM_MAX_THREADS_SHIFT;

Weird.  But okay.

> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      BEGIN_BATCH(9);
> +      OUT_BATCH(_3DSTATE_WM<<  16 | (9 - 2));
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      OUT_BATCH(dw4);
> +      OUT_BATCH(dw5);
> +      OUT_BATCH((1 - 1)<<  GEN6_WM_NUM_SF_OUTPUTS_SHIFT); /* only position */
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_SCISSOR_STATE_POINTERS
> +    *
> +    * The HiZ op does not use scissoring, so set the state pointer to null.
> +    */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      BEGIN_BATCH(2);
> +      OUT_BATCH(_3DSTATE_SCISSOR_STATE_POINTERS<<  16 | (2 - 2));
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_BINDING_TABLE_POINTERS */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      gen6_binding_table_pointers.emit(brw);
> +   }

Hm.  I think it would be safe to leave the binding table alone, since 
you're not using any buffers.  I'd think you could drop this.  Maybe I'm 
wrong though.

> +   /* 3DSTATE_DEPTH_BUFFER */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      uint32_t width = mt->level[level].width;
> +      uint32_t height = mt->level[level].height;
> +
> +      uint32_t tile_x;
> +      uint32_t tile_y;
> +      uint32_t offset;
> +      {
> +         /* Construct a dummy renderbuffer just to extract tile offsets. */
> +         struct intel_renderbuffer rb;
> +         rb.mt = mt;
> +         rb.mt_level = level;
> +         rb.mt_layer = layer;
> +         intel_renderbuffer_set_draw_offset(&rb);
> +         offset = intel_renderbuffer_tile_offsets(&rb,&tile_x,&tile_y);
> +      }
> +
> +      uint32_t format;
> +      switch (mt->format) {
> +      case MESA_FORMAT_Z16:       format = BRW_DEPTHFORMAT_D16_UNORM; break;
> +      case MESA_FORMAT_Z32_FLOAT: format = BRW_DEPTHFORMAT_D32_FLOAT; break;
> +      case MESA_FORMAT_X8_Z24:    format = BRW_DEPTHFORMAT_D24_UNORM_X8_UINT; break;
> +      default:                    assert(0); break;
> +      }
> +
> +      intel_emit_post_sync_nonzero_flush(intel);
> +      intel_emit_depth_stall_flushes(intel);
> +
> +      BEGIN_BATCH(7);
> +      OUT_BATCH(_3DSTATE_DEPTH_BUFFER<<  16 | (7 - 2));
> +      OUT_BATCH(((mt->region->pitch * mt->region->cpp) - 1) |
> +                format<<  18 |
> +                1<<  21 | /* separate stencil enable */
> +                1<<  22 | /* hiz enable */
> +                BRW_TILEWALK_YMAJOR<<  26 |
> +                1<<  27 | /* y-tiled */
> +                BRW_SURFACE_2D<<  29);
> +      OUT_RELOC(mt->region->bo,
> +                I915_GEM_DOMAIN_RENDER, I915_GEM_DOMAIN_RENDER,
> +                offset);
> +      OUT_BATCH(BRW_SURFACE_MIPMAPLAYOUT_BELOW<<  1 |
> +                (width + tile_x - 1)<<  6 |
> +                (height + tile_y - 1)<<  19);
> +      OUT_BATCH(0);
> +      OUT_BATCH(tile_x |
> +                tile_y<<  16);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_HIER_DEPTH_BUFFER */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      struct intel_region *hiz_region = mt->hiz_mt->region;
> +
> +      BEGIN_BATCH(3);
> +      OUT_BATCH((_3DSTATE_HIER_DEPTH_BUFFER<<  16) | (3 - 2));
> +      OUT_BATCH(hiz_region->pitch * hiz_region->cpp - 1);
> +      OUT_RELOC(hiz_region->bo,
> +                I915_GEM_DOMAIN_RENDER, I915_GEM_DOMAIN_RENDER,
> +                0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_STENCIL_BUFFER */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      BEGIN_BATCH(3);
> +      OUT_BATCH((_3DSTATE_STENCIL_BUFFER<<  16) | (3 - 2));
> +      OUT_BATCH(0);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_CLEAR_PARAMS
> +    *
> +    * From the Sandybridge PRM, Volume 2, Part 1, Section 3DSTATE_CLEAR_PARAMS:
> +    *   3DSTATE_CLEAR_PARAMS packet must follow the DEPTH_BUFFER_STATE packet
> +    *   when HiZ is enabled and the DEPTH_BUFFER_STATE changes.
> +    */
> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +      intel_emit_post_sync_nonzero_flush(intel);

I don't think need the W/A PIPE_CONTROL here.  You already had one just 
before emitting 3DSTATE_DEPTH_BUFFER, and IIRC you're supposed to do the 
flushes, then program everything.

> +      BEGIN_BATCH(2);
> +      OUT_BATCH(_3DSTATE_CLEAR_PARAMS<<  16 | (2 - 2));
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_DRAWING_RECTANGLE */
> +   {
> +      BEGIN_BATCH(4);
> +      OUT_BATCH(_3DSTATE_DRAWING_RECTANGLE<<  16 | (4 - 2));
> +      OUT_BATCH(0);
> +      OUT_BATCH(((mt->level[level].width - 1)&  0xffff) |
> +                ((mt->level[level].height - 1)<<  16));
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_VERTEX_BUFFERS */
> +   {
> +      const int num_buffers = 1;
> +      const int batch_length = 1 + 4 * num_buffers;
> +
> +      uint32_t dw0 = GEN6_VB0_ACCESS_VERTEXDATA |
> +                     (GEN6_HIZ_NUM_VERTEX_COMPONENTS * sizeof(float))<<  BRW_VB0_PITCH_SHIFT;
> +      if (intel->gen>= 7)
> +         dw0 |= GEN7_VB0_ADDRESS_MODIFYENABLE;
> +
> +      BEGIN_BATCH(batch_length);
> +      OUT_BATCH((_3DSTATE_VERTEX_BUFFERS<<  16) | (batch_length - 2));
> +      OUT_BATCH(dw0);
> +      OUT_RELOC(hiz->vertex_bo, I915_GEM_DOMAIN_VERTEX, 0, 0);
> +      OUT_RELOC(hiz->vertex_bo, I915_GEM_DOMAIN_VERTEX, 0, hiz->vertex_bo->size - 1);
> +      OUT_BATCH(0);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* 3DSTATE_VERTEX_ELEMENTS
> +    *
> +    * TODO: Explain WTF is happening here.
> +    */
> +   {
> +      const int num_elements = 2;
> +      const int batch_length = 1 + 2 * num_elements;
> +
> +      BEGIN_BATCH(batch_length);
> +      OUT_BATCH((_3DSTATE_VERTEX_ELEMENTS<<  16) | (batch_length - 2));
> +      OUT_BATCH(0<<  GEN6_VE0_INDEX_SHIFT |
> +                GEN6_VE0_VALID |
> +                BRW_SURFACEFORMAT_R32G32B32A32_FLOAT<<  BRW_VE0_FORMAT_SHIFT |
> +                0<<  BRW_VE0_SRC_OFFSET_SHIFT |
> +                0<<  BRW_VE1_DST_OFFSET_SHIFT);
> +      OUT_BATCH(BRW_VE1_COMPONENT_STORE_0<<  BRW_VE1_COMPONENT_0_SHIFT |
> +                BRW_VE1_COMPONENT_STORE_0<<  BRW_VE1_COMPONENT_1_SHIFT |
> +                BRW_VE1_COMPONENT_STORE_0<<  BRW_VE1_COMPONENT_2_SHIFT |
> +                BRW_VE1_COMPONENT_STORE_0<<  BRW_VE1_COMPONENT_3_SHIFT);
> +      OUT_BATCH(0<<  GEN6_VE0_INDEX_SHIFT |
> +                GEN6_VE0_VALID |
> +                BRW_SURFACEFORMAT_R32G32B32A32_FLOAT<<  BRW_VE0_FORMAT_SHIFT |
> +                0<<  BRW_VE0_SRC_OFFSET_SHIFT |
> +                0<<  BRW_VE1_DST_OFFSET_SHIFT);
> +      OUT_BATCH(BRW_VE1_COMPONENT_STORE_SRC<<  BRW_VE1_COMPONENT_0_SHIFT |
> +                BRW_VE1_COMPONENT_STORE_SRC<<  BRW_VE1_COMPONENT_1_SHIFT |
> +                BRW_VE1_COMPONENT_STORE_0<<  BRW_VE1_COMPONENT_2_SHIFT |
> +                BRW_VE1_COMPONENT_STORE_1_FLT<<  BRW_VE1_COMPONENT_3_SHIFT);
> +      ADVANCE_BATCH();
> +   }
> +
> +   /* CMD_3D_PRIM */

/* 3DPRIMITIVE */

> +   {
> +      /* TODO(chad): gen7 */
> +      assert(intel->gen == 6);
> +
> +     BEGIN_BATCH(6);
> +     OUT_BATCH(CMD_3D_PRIM<<  16 | (6 - 2) |
> +               _3DPRIM_RECTLIST<<  GEN4_3DPRIM_TOPOLOGY_TYPE_SHIFT |
> +               GEN4_3DPRIM_VERTEXBUFFER_ACCESS_SEQUENTIAL);
> +     OUT_BATCH(GEN6_HIZ_NUM_VERTICES); /* vertex count per instance */
> +     OUT_BATCH(0);
> +     OUT_BATCH(1); /* instance count */
> +     OUT_BATCH(0);
> +     OUT_BATCH(0);
> +     ADVANCE_BATCH();
> +   }
> +
> +   /* See comments above at first invocation of intel_flush(). */
> +   intel_flush(ctx);
> +
> +   /* Be safe. */
> +   brw->state.dirty.brw = ~0;
> +   brw->state.dirty.cache = ~0;
>   }
>
>   void
> @@ -351,7 +680,7 @@ gen6_resolve_hiz_slice(struct intel_context *intel,
>                          uint32_t level,
>                          uint32_t layer)
>   {
> -   gen6_resolve_slice(intel, mt, level, layer, BRW_HIZ_OP_HIZ_RESOLVE);
> +   gen6_hiz_exec(intel, mt, level, layer, GEN6_HIZ_OP_HIZ_RESOLVE);
>   }
>
>
> @@ -361,5 +690,5 @@ gen6_resolve_depth_slice(struct intel_context *intel,
>                            uint32_t level,
>                            uint32_t layer)
>   {
> -   gen6_resolve_slice(intel, mt, level, layer, BRW_HIZ_OP_DEPTH_RESOLVE);
> +   gen6_hiz_exec(intel, mt, level, layer, GEN6_HIZ_OP_DEPTH_RESOLVE);
>   }
> diff --git a/src/mesa/drivers/dri/i965/gen6_sf_state.c b/src/mesa/drivers/dri/i965/gen6_sf_state.c
> index 163b54c..07b8e6d 100644
> --- a/src/mesa/drivers/dri/i965/gen6_sf_state.c
> +++ b/src/mesa/drivers/dri/i965/gen6_sf_state.c
> @@ -149,17 +149,8 @@ upload_sf_state(struct brw_context *brw)
>         urb_entry_read_length<<  GEN6_SF_URB_ENTRY_READ_LENGTH_SHIFT |
>         urb_entry_read_offset<<  GEN6_SF_URB_ENTRY_READ_OFFSET_SHIFT;
>
> -   dw2 = GEN6_SF_STATISTICS_ENABLE;
> -
> -   /* Enable viewport transform only if no HiZ operation is progress
> -    *
> -    * From page 11 of the SandyBridge PRM, Volume 2, Part 1, Section 1.3, "3D
> -    * Primitives Overview":
> -    *     RECTLIST: Viewport Mapping must be DISABLED (as is typical with the
> -    *     use of screen- space coordinates).
> -    */
> -   if (!brw->hiz.op)
> -      dw2 |= GEN6_SF_VIEWPORT_TRANSFORM_ENABLE;
> +   dw2 = GEN6_SF_STATISTICS_ENABLE |
> +         GEN6_SF_VIEWPORT_TRANSFORM_ENABLE;
>
>      dw3 = 0;
>      dw4 = 0;
> @@ -354,8 +345,7 @@ const struct brw_tracked_state gen6_sf_state = {
>   		_NEW_POINT |
>   		_NEW_TRANSFORM),
>         .brw   = (BRW_NEW_CONTEXT |
> -		BRW_NEW_FRAGMENT_PROGRAM |
> -		BRW_NEW_HIZ),
> +		BRW_NEW_FRAGMENT_PROGRAM),
>         .cache = CACHE_NEW_VS_PROG
>      },
>      .emit = upload_sf_state,
> diff --git a/src/mesa/drivers/dri/i965/gen6_vs_state.c b/src/mesa/drivers/dri/i965/gen6_vs_state.c
> index 63efaa4..c481ac6 100644
> --- a/src/mesa/drivers/dri/i965/gen6_vs_state.c
> +++ b/src/mesa/drivers/dri/i965/gen6_vs_state.c
> @@ -164,6 +164,19 @@ upload_vs_state(struct brw_context *brw)
>      if (intel->ctx.Shader.CurrentVertexProgram == NULL)
>         floating_point_mode = GEN6_VS_FLOATING_POINT_MODE_ALT;
>
> +   if (intel->gen == 6) {
> +      BEGIN_BATCH(4);
> +      OUT_BATCH(_3DSTATE_PIPE_CONTROL);
> +      OUT_BATCH(PIPE_CONTROL_CS_STALL |
> +                PIPE_CONTROL_WRITE_IMMEDIATE);
> +      OUT_RELOC(intel->batch.workaround_bo,
> +                I915_GEM_DOMAIN_INSTRUCTION, I915_GEM_DOMAIN_INSTRUCTION, 0);
> +      OUT_BATCH(0); /* write data */
> +      ADVANCE_BATCH();
> +   }
> +
> +   intel_emit_vs_enable_flush(intel);
> +
>      BEGIN_BATCH(6);
>      OUT_BATCH(_3DSTATE_VS<<  16 | (6 - 2));
>      OUT_BATCH(brw->vs.prog_offset);
> diff --git a/src/mesa/drivers/dri/i965/gen6_wm_state.c b/src/mesa/drivers/dri/i965/gen6_wm_state.c
> index 3669811..205e648 100644
> --- a/src/mesa/drivers/dri/i965/gen6_wm_state.c
> +++ b/src/mesa/drivers/dri/i965/gen6_wm_state.c
> @@ -149,23 +149,6 @@ upload_wm_state(struct brw_context *brw)
>      dw4 |= (brw->wm.prog_data->first_curbe_grf_16<<
>   	GEN6_WM_DISPATCH_START_GRF_SHIFT_2);
>
> -   switch (brw->hiz.op) {
> -   case BRW_HIZ_OP_NONE:
> -      break;
> -   case BRW_HIZ_OP_DEPTH_CLEAR:
> -      dw4 |= GEN6_WM_DEPTH_CLEAR;
> -      break;
> -   case BRW_HIZ_OP_DEPTH_RESOLVE:
> -      dw4 |= GEN6_WM_DEPTH_RESOLVE;
> -      break;
> -   case BRW_HIZ_OP_HIZ_RESOLVE:
> -      dw4 |= GEN6_WM_HIERARCHICAL_DEPTH_RESOLVE;
> -      break;
> -   default:
> -      assert(0);
> -      break;
> -   }
> -
>      dw5 |= (brw->max_wm_threads - 1)<<  GEN6_WM_MAX_THREADS_SHIFT;
>
>      /* CACHE_NEW_WM_PROG */
> @@ -233,8 +216,7 @@ const struct brw_tracked_state gen6_wm_state = {
>   		_NEW_PROGRAM_CONSTANTS |
>   		_NEW_POLYGON),
>         .brw   = (BRW_NEW_FRAGMENT_PROGRAM |
> -		BRW_NEW_BATCH |
> -		BRW_NEW_HIZ),
> +		BRW_NEW_BATCH),
>         .cache = (CACHE_NEW_SAMPLER |
>   		CACHE_NEW_WM_PROG)
>      },
> diff --git a/src/mesa/drivers/dri/i965/gen7_clip_state.c b/src/mesa/drivers/dri/i965/gen7_clip_state.c
> index 9be3ce9..c32cd98 100644
> --- a/src/mesa/drivers/dri/i965/gen7_clip_state.c
> +++ b/src/mesa/drivers/dri/i965/gen7_clip_state.c
> @@ -39,23 +39,6 @@ upload_clip_state(struct brw_context *brw)
>      /* BRW_NEW_FRAGMENT_PROGRAM */
>      const struct gl_fragment_program *fprog = brw->fragment_program;
>
> -   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;
> -   }
> -
>      /* _NEW_BUFFERS */
>      bool render_to_fbo = brw->intel.ctx.DrawBuffer->Name != 0;
>
> @@ -133,8 +116,7 @@ const struct brw_tracked_state gen7_clip_state = {
>                   _NEW_LIGHT |
>                   _NEW_TRANSFORM),
>         .brw   = (BRW_NEW_CONTEXT |
> -                BRW_NEW_FRAGMENT_PROGRAM |
> -                BRW_NEW_HIZ),
> +                BRW_NEW_FRAGMENT_PROGRAM),
>         .cache = 0
>      },
>      .emit = upload_clip_state,
> diff --git a/src/mesa/drivers/dri/i965/gen7_sf_state.c b/src/mesa/drivers/dri/i965/gen7_sf_state.c
> index da7ef81..b215af2 100644
> --- a/src/mesa/drivers/dri/i965/gen7_sf_state.c
> +++ b/src/mesa/drivers/dri/i965/gen7_sf_state.c
> @@ -149,8 +149,7 @@ const struct brw_tracked_state gen7_sbe_state = {
>   		_NEW_PROGRAM |
>   		_NEW_TRANSFORM),
>         .brw   = (BRW_NEW_CONTEXT |
> -		BRW_NEW_FRAGMENT_PROGRAM |
> -		BRW_NEW_HIZ),
> +		BRW_NEW_FRAGMENT_PROGRAM),
>         .cache = CACHE_NEW_VS_PROG
>      },
>      .emit = upload_sbe_state,
> @@ -166,17 +165,8 @@ upload_sf_state(struct brw_context *brw)
>      /* _NEW_BUFFERS */
>      bool render_to_fbo = brw->intel.ctx.DrawBuffer->Name != 0;
>
> -   dw1 = GEN6_SF_STATISTICS_ENABLE;
> -
> -   /* Enable viewport transform only if no HiZ operation is progress
> -    *
> -    * From page 11 of the SandyBridge PRM, Volume 2, Part 1, Section 1.3, "3D
> -    * Primitives Overview":
> -    *     RECTLIST: Viewport Mapping must be DISABLED (as is typical with the
> -    *     use of screen- space coordinates).
> -    */
> -   if (!brw->hiz.op)
> -      dw1 |= GEN6_SF_VIEWPORT_TRANSFORM_ENABLE;
> +   dw1 = GEN6_SF_STATISTICS_ENABLE |
> +         GEN6_SF_VIEWPORT_TRANSFORM_ENABLE;
>
>      /* _NEW_BUFFERS */
>      dw1 |= (brw_depthbuffer_format(brw)<<  GEN7_SF_DEPTH_BUFFER_SURFACE_FORMAT_SHIFT);
> @@ -310,8 +300,7 @@ const struct brw_tracked_state gen7_sf_state = {
>   		_NEW_SCISSOR |
>   		_NEW_BUFFERS |
>   		_NEW_POINT),
> -      .brw   = (BRW_NEW_CONTEXT |
> -		BRW_NEW_HIZ),
> +      .brw   = BRW_NEW_CONTEXT,
>         .cache = CACHE_NEW_VS_PROG
>      },
>      .emit = upload_sf_state,
> diff --git a/src/mesa/drivers/dri/i965/gen7_wm_state.c b/src/mesa/drivers/dri/i965/gen7_wm_state.c
> index 32222f9..870590f 100644
> --- a/src/mesa/drivers/dri/i965/gen7_wm_state.c
> +++ b/src/mesa/drivers/dri/i965/gen7_wm_state.c
> @@ -49,23 +49,6 @@ upload_wm_state(struct brw_context *brw)
>      dw1 |= GEN7_WM_LINE_AA_WIDTH_1_0;
>      dw1 |= GEN7_WM_LINE_END_CAP_AA_WIDTH_0_5;
>
> -   switch (brw->hiz.op) {
> -   case BRW_HIZ_OP_NONE:
> -      break;
> -   case BRW_HIZ_OP_DEPTH_CLEAR:
> -      dw1 |= GEN7_WM_DEPTH_CLEAR;
> -      break;
> -   case BRW_HIZ_OP_DEPTH_RESOLVE:
> -      dw1 |= GEN7_WM_DEPTH_RESOLVE;
> -      break;
> -   case BRW_HIZ_OP_HIZ_RESOLVE:
> -      dw1 |= GEN7_WM_HIERARCHICAL_DEPTH_RESOLVE;
> -      break;
> -   default:
> -      assert(0);
> -      break;
> -   }
> -
>      /* _NEW_LINE */
>      if (ctx->Line.StippleFlag)
>         dw1 |= GEN7_WM_LINE_STIPPLE_ENABLE;
> @@ -106,7 +89,6 @@ const struct brw_tracked_state gen7_wm_state = {
>         .mesa  = (_NEW_LINE | _NEW_LIGHT | _NEW_POLYGON |
>   	        _NEW_COLOR | _NEW_BUFFERS),
>         .brw   = (BRW_NEW_FRAGMENT_PROGRAM |
> -                BRW_NEW_HIZ |
>   		BRW_NEW_BATCH),
>         .cache = 0,
>      },
> diff --git a/src/mesa/drivers/dri/i965/junk b/src/mesa/drivers/dri/i965/junk
> new file mode 100644
> index 0000000..e69de29
> diff --git a/src/mesa/drivers/dri/intel/intel_batchbuffer.c b/src/mesa/drivers/dri/intel/intel_batchbuffer.c
> index f4bc6b2..e0c3879 100644
> --- a/src/mesa/drivers/dri/intel/intel_batchbuffer.c
> +++ b/src/mesa/drivers/dri/intel/intel_batchbuffer.c
> @@ -361,6 +361,33 @@ emit:
>      item->header = intel->batch.emit;
>   }
>
> +
> +/**
> + * \brief This flush must occur before toggling 3DSTATE_VS.VsFunctionEnable.
> + *
> + * From the BSpec, Volume 2a, Part 3 "Vertex Shader", Section
> + * 3DSTATE_VS, Field "VS Function Enable":
> + *   A pipeline flush must be programmed prior to a 3DSTATE_VS command
> + *   that causes the VS Function Enable to toggle. Pipeline flush can
> + *   be executed by sending a PIPE_CONTROL command with CS stall bit
> + *   set and a post sync operation.
> + */
> +void
> +intel_emit_vs_enable_flush(struct intel_context *intel)
> +{
> +   if (intel->gen != 6)
> +      return;
> +
> +   BEGIN_BATCH(4);
> +   OUT_BATCH(_3DSTATE_PIPE_CONTROL);
> +   OUT_BATCH(PIPE_CONTROL_CS_STALL |
> +             PIPE_CONTROL_WRITE_IMMEDIATE);
> +   OUT_RELOC(intel->batch.workaround_bo,
> +             I915_GEM_DOMAIN_INSTRUCTION, I915_GEM_DOMAIN_INSTRUCTION, 0);
> +   OUT_BATCH(0); /* write data */
> +   ADVANCE_BATCH();
> +}
> +

Ugh.  Sorry, I had no idea you needed a workaround flush for this. :(

>   /**
>    * Restriction [DevSNB, DevIVB]:
>    *
> diff --git a/src/mesa/drivers/dri/intel/intel_batchbuffer.h b/src/mesa/drivers/dri/intel/intel_batchbuffer.h
> index e5e5bd4..f010cc4 100644
> --- a/src/mesa/drivers/dri/intel/intel_batchbuffer.h
> +++ b/src/mesa/drivers/dri/intel/intel_batchbuffer.h
> @@ -40,6 +40,7 @@ bool intel_batchbuffer_emit_reloc_fenced(struct intel_context *intel,
>   					      uint32_t read_domains,
>   					      uint32_t write_domain,
>   					      uint32_t offset);
> +void intel_emit_vs_enable_flush(struct intel_context *intel);
>   void intel_batchbuffer_emit_mi_flush(struct intel_context *intel);
>   void intel_emit_post_sync_nonzero_flush(struct intel_context *intel);
>   void intel_emit_depth_stall_flushes(struct intel_context *intel);

This looks good, though I still don't think you need/want the invariant 
state.  My main concern now is Gen7.  I assume it just dies in a fire ATM.


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