src/gallium/drivers/r300/r300_hyperz.c

   1 /*
   2  * Copyright 2008 Corbin Simpson <MostAwesomeDude@gmail.com>
   3  * Copyright 2009 Marek Olšák <maraeo@gmail.com>
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a
   6  * copy of this software and associated documentation files (the "Software"),
   7  * to deal in the Software without restriction, including without limitation
   8  * on the rights to use, copy, modify, merge, publish, distribute, sub
   9  * license, and/or sell copies of the Software, and to permit persons to whom
  10  * the Software is furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice (including the next
  13  * paragraph) shall be included in all copies or substantial portions of the
  14  * Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
  20  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  21  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  22  * USE OR OTHER DEALINGS IN THE SOFTWARE. */
  23
  24
  25 #include "r300_hyperz.h"
  26 #include "r300_context.h"
  27 #include "r300_reg.h"
  28 #include "r300_fs.h"
  29
  30 /*****************************************************************************/
  31 /* The ZTOP state                                                            */
  32 /*****************************************************************************/
  33
  34 static boolean r300_dsa_writes_stencil(
  35         struct pipe_stencil_state *s)
  36 {
  37     return s->enabled && s->writemask &&
  38            (s->fail_op  != PIPE_STENCIL_OP_KEEP ||
  39             s->zfail_op != PIPE_STENCIL_OP_KEEP ||
  40             s->zpass_op != PIPE_STENCIL_OP_KEEP);
  41 }
  42
  43 static boolean r300_dsa_writes_depth_stencil(
  44         struct pipe_depth_stencil_alpha_state *dsa)
  45 {
  46     /* We are interested only in the cases when a depth or stencil value
  47      * can be changed. */
  48
  49     if (dsa->depth.enabled && dsa->depth.writemask &&
  50         dsa->depth.func != PIPE_FUNC_NEVER)
  51         return TRUE;
  52
  53     if (r300_dsa_writes_stencil(&dsa->stencil[0]) ||
  54         r300_dsa_writes_stencil(&dsa->stencil[1]))
  55         return TRUE;
  56
  57     return FALSE;
  58 }
  59
  60 static boolean r300_dsa_alpha_test_enabled(
  61         struct pipe_depth_stencil_alpha_state *dsa)
  62 {
  63     /* We are interested only in the cases when alpha testing can kill
  64      * a fragment. */
  65
  66     return dsa->alpha.enabled && dsa->alpha.func != PIPE_FUNC_ALWAYS;
  67 }
  68
  69 static void r300_update_ztop(struct r300_context* r300)
  70 {
  71     struct r300_ztop_state* ztop_state =
  72         (struct r300_ztop_state*)r300->ztop_state.state;
  73     uint32_t old_ztop = ztop_state->z_buffer_top;
  74
  75     /* This is important enough that I felt it warranted a comment.
  76      *
  77      * According to the docs, these are the conditions where ZTOP must be
  78      * disabled:
  79      * 1) Alpha testing enabled
  80      * 2) Texture kill instructions in fragment shader
  81      * 3) Chroma key culling enabled
  82      * 4) W-buffering enabled
  83      *
  84      * The docs claim that for the first three cases, if no ZS writes happen,
  85      * then ZTOP can be used.
  86      *
  87      * (3) will never apply since we do not support chroma-keyed operations.
  88      * (4) will need to be re-examined (and this comment updated) if/when
  89      * Hyper-Z becomes supported.
  90      *
  91      * Additionally, the following conditions require disabled ZTOP:
  92      * 5) Depth writes in fragment shader
  93      * 6) Outstanding occlusion queries
  94      *
  95      * This register causes stalls all the way from SC to CB when changed,
  96      * but it is buffered on-chip so it does not hurt to write it if it has
  97      * not changed.
  98      *
  99      * ~C.
 100      */
 101
 102     /* ZS writes */
 103     if (r300_dsa_writes_depth_stencil(r300->dsa_state.state) &&
 104            (r300_dsa_alpha_test_enabled(r300->dsa_state.state) ||  /* (1) */
 105             r300_fs(r300)->shader->info.uses_kill)) {              /* (2) */
 106         ztop_state->z_buffer_top = R300_ZTOP_DISABLE;
 107     } else if (r300_fragment_shader_writes_depth(r300_fs(r300))) { /* (5) */
 108         ztop_state->z_buffer_top = R300_ZTOP_DISABLE;
 109     } else if (r300->query_current) {                              /* (6) */
 110         ztop_state->z_buffer_top = R300_ZTOP_DISABLE;
 111     } else {
 112         ztop_state->z_buffer_top = R300_ZTOP_ENABLE;
 113     }
 114
 115     if (ztop_state->z_buffer_top != old_ztop)
 116         r300->ztop_state.dirty = TRUE;
 117 }
 118
 119 void r300_update_hyperz_state(struct r300_context* r300)
 120 {
 121     r300_update_ztop(r300);
 122 }