src/intel/compiler/brw_vue_map.c

   1 /*
   2  * Copyright © 2011 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 /**
  25  * @file brw_vue_map.c
  26  *
  27  * This file computes the "VUE map" for a (non-fragment) shader stage, which
  28  * describes the layout of its output varyings.  The VUE map is used to match
  29  * outputs from one stage with the inputs of the next.
  30  *
  31  * Largely, varyings can be placed however we like - producers/consumers simply
  32  * have to agree on the layout.  However, there is also a "VUE Header" that
  33  * prescribes a fixed-layout for items that interact with fixed function
  34  * hardware, such as the clipper and rasterizer.
  35  *
  36  * Authors:
  37  *   Paul Berry <stereotype441@gmail.com>
  38  *   Chris Forbes <chrisf@ijw.co.nz>
  39  *   Eric Anholt <eric@anholt.net>
  40  */
  41
  42
  43 #include "brw_compiler.h"
  44 #include "common/gen_debug.h"
  45
  46 static inline void
  47 assign_vue_slot(struct brw_vue_map *vue_map, int varying, int slot)
  48 {
  49    /* Make sure this varying hasn't been assigned a slot already */
  50    assert (vue_map->varying_to_slot[varying] == -1);
  51
  52    vue_map->varying_to_slot[varying] = slot;
  53    vue_map->slot_to_varying[slot] = varying;
  54 }
  55
  56 /**
  57  * Compute the VUE map for a shader stage.
  58  */
  59 void
  60 brw_compute_vue_map(const struct gen_device_info *devinfo,
  61                     struct brw_vue_map *vue_map,
  62                     uint64_t slots_valid,
  63                     bool separate)
  64 {
  65    /* Keep using the packed/contiguous layout on old hardware - we only need
  66     * the SSO layout when using geometry/tessellation shaders or 32 FS input
  67     * varyings, which only exist on Gen >= 6.  It's also a bit more efficient.
  68     */
  69    if (devinfo->gen < 6)
  70       separate = false;
  71
  72    if (separate) {
  73       /* In SSO mode, we don't know whether the adjacent stage will
  74        * read/write gl_ClipDistance, which has a fixed slot location.
  75        * We have to assume the worst and reserve a slot for it, or else
  76        * the rest of our varyings will be off by a slot.
  77        *
  78        * Note that we don't have to worry about COL/BFC, as those built-in
  79        * variables only exist in legacy GL, which only supports VS and FS.
  80        */
  81       slots_valid |= BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST0);
  82       slots_valid |= BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST1);
  83    }
  84
  85    vue_map->slots_valid = slots_valid;
  86    vue_map->separate = separate;
  87
  88    /* gl_Layer and gl_ViewportIndex don't get their own varying slots -- they
  89     * are stored in the first VUE slot (VARYING_SLOT_PSIZ).
  90     */
  91    slots_valid &= ~(VARYING_BIT_LAYER | VARYING_BIT_VIEWPORT);
  92
  93    /* Make sure that the values we store in vue_map->varying_to_slot and
  94     * vue_map->slot_to_varying won't overflow the signed chars that are used
  95     * to store them.  Note that since vue_map->slot_to_varying sometimes holds
  96     * values equal to BRW_VARYING_SLOT_COUNT, we need to ensure that
  97     * BRW_VARYING_SLOT_COUNT is <= 127, not 128.
  98     */
  99    STATIC_ASSERT(BRW_VARYING_SLOT_COUNT <= 127);
 100
 101    for (int i = 0; i < BRW_VARYING_SLOT_COUNT; ++i) {
 102       vue_map->varying_to_slot[i] = -1;
 103       vue_map->slot_to_varying[i] = BRW_VARYING_SLOT_PAD;
 104    }
 105
 106    int slot = 0;
 107
 108    /* VUE header: format depends on chip generation and whether clipping is
 109     * enabled.
 110     *
 111     * See the Sandybridge PRM, Volume 2 Part 1, section 1.5.1 (page 30),
 112     * "Vertex URB Entry (VUE) Formats" which describes the VUE header layout.
 113     */
 114    if (devinfo->gen < 6) {
 115       /* There are 8 dwords in VUE header pre-Ironlake:
 116        * dword 0-3 is indices, point width, clip flags.
 117        * dword 4-7 is ndc position
 118        * dword 8-11 is the first vertex data.
 119        *
 120        * On Ironlake the VUE header is nominally 20 dwords, but the hardware
 121        * will accept the same header layout as Gen4 [and should be a bit faster]
 122        */
 123       assign_vue_slot(vue_map, VARYING_SLOT_PSIZ, slot++);
 124       assign_vue_slot(vue_map, BRW_VARYING_SLOT_NDC, slot++);
 125       assign_vue_slot(vue_map, VARYING_SLOT_POS, slot++);
 126    } else {
 127       /* There are 8 or 16 DWs (D0-D15) in VUE header on Sandybridge:
 128        * dword 0-3 of the header is indices, point width, clip flags.
 129        * dword 4-7 is the 4D space position
 130        * dword 8-15 of the vertex header is the user clip distance if
 131        * enabled.
 132        * dword 8-11 or 16-19 is the first vertex element data we fill.
 133        */
 134       assign_vue_slot(vue_map, VARYING_SLOT_PSIZ, slot++);
 135       assign_vue_slot(vue_map, VARYING_SLOT_POS, slot++);
 136       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST0))
 137          assign_vue_slot(vue_map, VARYING_SLOT_CLIP_DIST0, slot++);
 138       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST1))
 139          assign_vue_slot(vue_map, VARYING_SLOT_CLIP_DIST1, slot++);
 140
 141       /* front and back colors need to be consecutive so that we can use
 142        * ATTRIBUTE_SWIZZLE_INPUTATTR_FACING to swizzle them when doing
 143        * two-sided color.
 144        */
 145       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_COL0))
 146          assign_vue_slot(vue_map, VARYING_SLOT_COL0, slot++);
 147       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_BFC0))
 148          assign_vue_slot(vue_map, VARYING_SLOT_BFC0, slot++);
 149       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_COL1))
 150          assign_vue_slot(vue_map, VARYING_SLOT_COL1, slot++);
 151       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_BFC1))
 152          assign_vue_slot(vue_map, VARYING_SLOT_BFC1, slot++);
 153    }
 154
 155    /* The hardware doesn't care about the rest of the vertex outputs, so we
 156     * can assign them however we like.  For normal programs, we simply assign
 157     * them contiguously.
 158     *
 159     * For separate shader pipelines, we first assign built-in varyings
 160     * contiguous slots.  This works because ARB_separate_shader_objects
 161     * requires that all shaders have matching built-in varying interface
 162     * blocks.  Next, we assign generic varyings based on their location
 163     * (either explicit or linker assigned).  This guarantees a fixed layout.
 164     *
 165     * We generally don't need to assign a slot for VARYING_SLOT_CLIP_VERTEX,
 166     * since it's encoded as the clip distances by emit_clip_distances().
 167     * However, it may be output by transform feedback, and we'd rather not
 168     * recompute state when TF changes, so we just always include it.
 169     */
 170    uint64_t builtins = slots_valid & BITFIELD64_MASK(VARYING_SLOT_VAR0);
 171    while (builtins != 0) {
 172       const int varying = ffsll(builtins) - 1;
 173       if (vue_map->varying_to_slot[varying] == -1) {
 174          assign_vue_slot(vue_map, varying, slot++);
 175       }
 176       builtins &= ~BITFIELD64_BIT(varying);
 177    }
 178
 179    const int first_generic_slot = slot;
 180    uint64_t generics = slots_valid & ~BITFIELD64_MASK(VARYING_SLOT_VAR0);
 181    while (generics != 0) {
 182       const int varying = ffsll(generics) - 1;
 183       if (separate) {
 184          slot = first_generic_slot + varying - VARYING_SLOT_VAR0;
 185       }
 186       assign_vue_slot(vue_map, varying, slot++);
 187       generics &= ~BITFIELD64_BIT(varying);
 188    }
 189
 190    vue_map->num_slots = slot;
 191    vue_map->num_per_vertex_slots = 0;
 192    vue_map->num_per_patch_slots = 0;
 193 }
 194
 195 /**
 196  * Compute the VUE map for tessellation control shader outputs and
 197  * tessellation evaluation shader inputs.
 198  */
 199 void
 200 brw_compute_tess_vue_map(struct brw_vue_map *vue_map,
 201                          uint64_t vertex_slots,
 202                          uint32_t patch_slots)
 203 {
 204    /* I don't think anything actually uses this... */
 205    vue_map->slots_valid = vertex_slots;
 206
 207    /* separate isn't really meaningful, but make sure it's initialized */
 208    vue_map->separate = false;
 209
 210    vertex_slots &= ~(VARYING_BIT_TESS_LEVEL_OUTER |
 211                      VARYING_BIT_TESS_LEVEL_INNER);
 212
 213    /* Make sure that the values we store in vue_map->varying_to_slot and
 214     * vue_map->slot_to_varying won't overflow the signed chars that are used
 215     * to store them.  Note that since vue_map->slot_to_varying sometimes holds
 216     * values equal to VARYING_SLOT_TESS_MAX , we need to ensure that
 217     * VARYING_SLOT_TESS_MAX is <= 127, not 128.
 218     */
 219    STATIC_ASSERT(VARYING_SLOT_TESS_MAX <= 127);
 220
 221    for (int i = 0; i < VARYING_SLOT_TESS_MAX ; ++i) {
 222       vue_map->varying_to_slot[i] = -1;
 223       vue_map->slot_to_varying[i] = BRW_VARYING_SLOT_PAD;
 224    }
 225
 226    int slot = 0;
 227
 228    /* The first 8 DWords are reserved for the "Patch Header".
 229     *
 230     * VARYING_SLOT_TESS_LEVEL_OUTER / INNER live here, but the exact layout
 231     * depends on the domain type.  They might not be in slots 0 and 1 as
 232     * described here, but pretending they're separate allows us to uniquely
 233     * identify them by distinct slot locations.
 234     */
 235    assign_vue_slot(vue_map, VARYING_SLOT_TESS_LEVEL_INNER, slot++);
 236    assign_vue_slot(vue_map, VARYING_SLOT_TESS_LEVEL_OUTER, slot++);
 237
 238    /* first assign per-patch varyings */
 239    while (patch_slots != 0) {
 240       const int varying = ffsll(patch_slots) - 1;
 241       if (vue_map->varying_to_slot[varying + VARYING_SLOT_PATCH0] == -1) {
 242          assign_vue_slot(vue_map, varying + VARYING_SLOT_PATCH0, slot++);
 243       }
 244       patch_slots &= ~BITFIELD64_BIT(varying);
 245    }
 246
 247    /* apparently, including the patch header... */
 248    vue_map->num_per_patch_slots = slot;
 249
 250    /* then assign per-vertex varyings for each vertex in our patch */
 251    while (vertex_slots != 0) {
 252       const int varying = ffsll(vertex_slots) - 1;
 253       if (vue_map->varying_to_slot[varying] == -1) {
 254          assign_vue_slot(vue_map, varying, slot++);
 255       }
 256       vertex_slots &= ~BITFIELD64_BIT(varying);
 257    }
 258
 259    vue_map->num_per_vertex_slots = slot - vue_map->num_per_patch_slots;
 260    vue_map->num_slots = slot;
 261 }
 262
 263 static const char *
 264 varying_name(brw_varying_slot slot)
 265 {
 266    assume(slot < BRW_VARYING_SLOT_COUNT);
 267
 268    if (slot < VARYING_SLOT_MAX)
 269       return gl_varying_slot_name(slot);
 270
 271    static const char *brw_names[] = {
 272       [BRW_VARYING_SLOT_NDC - VARYING_SLOT_MAX] = "BRW_VARYING_SLOT_NDC",
 273       [BRW_VARYING_SLOT_PAD - VARYING_SLOT_MAX] = "BRW_VARYING_SLOT_PAD",
 274       [BRW_VARYING_SLOT_PNTC - VARYING_SLOT_MAX] = "BRW_VARYING_SLOT_PNTC",
 275    };
 276
 277    return brw_names[slot - VARYING_SLOT_MAX];
 278 }
 279
 280 void
 281 brw_print_vue_map(FILE *fp, const struct brw_vue_map *vue_map)
 282 {
 283    if (vue_map->num_per_vertex_slots > 0 || vue_map->num_per_patch_slots > 0) {
 284       fprintf(fp, "PUE map (%d slots, %d/patch, %d/vertex, %s)\n",
 285               vue_map->num_slots,
 286               vue_map->num_per_patch_slots,
 287               vue_map->num_per_vertex_slots,
 288               vue_map->separate ? "SSO" : "non-SSO");
 289       for (int i = 0; i < vue_map->num_slots; i++) {
 290          if (vue_map->slot_to_varying[i] >= VARYING_SLOT_PATCH0) {
 291             fprintf(fp, "  [%d] VARYING_SLOT_PATCH%d\n", i,
 292                     vue_map->slot_to_varying[i] - VARYING_SLOT_PATCH0);
 293          } else {
 294             fprintf(fp, "  [%d] %s\n", i,
 295                     varying_name(vue_map->slot_to_varying[i]));
 296          }
 297       }
 298    } else {
 299       fprintf(fp, "VUE map (%d slots, %s)\n",
 300               vue_map->num_slots, vue_map->separate ? "SSO" : "non-SSO");
 301       for (int i = 0; i < vue_map->num_slots; i++) {
 302          fprintf(fp, "  [%d] %s\n", i,
 303                  varying_name(vue_map->slot_to_varying[i]));
 304       }
 305    }
 306    fprintf(fp, "\n");
 307 }