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 "dev/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                     uint32_t pos_slots)
  65 {
  66    /* Keep using the packed/contiguous layout on old hardware - we only need
  67     * the SSO layout when using geometry/tessellation shaders or 32 FS input
  68     * varyings, which only exist on Gen >= 6.  It's also a bit more efficient.
  69     */
  70    if (devinfo->gen < 6)
  71       separate = false;
  72
  73    if (separate) {
  74       /* In SSO mode, we don't know whether the adjacent stage will
  75        * read/write gl_ClipDistance, which has a fixed slot location.
  76        * We have to assume the worst and reserve a slot for it, or else
  77        * the rest of our varyings will be off by a slot.
  78        *
  79        * Note that we don't have to worry about COL/BFC, as those built-in
  80        * variables only exist in legacy GL, which only supports VS and FS.
  81        */
  82       slots_valid |= BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST0);
  83       slots_valid |= BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST1);
  84    }
  85
  86    vue_map->slots_valid = slots_valid;
  87    vue_map->separate = separate;
  88
  89    /* gl_Layer and gl_ViewportIndex don't get their own varying slots -- they
  90     * are stored in the first VUE slot (VARYING_SLOT_PSIZ).
  91     */
  92    slots_valid &= ~(VARYING_BIT_LAYER | VARYING_BIT_VIEWPORT);
  93
  94    /* Make sure that the values we store in vue_map->varying_to_slot and
  95     * vue_map->slot_to_varying won't overflow the signed chars that are used
  96     * to store them.  Note that since vue_map->slot_to_varying sometimes holds
  97     * values equal to BRW_VARYING_SLOT_COUNT, we need to ensure that
  98     * BRW_VARYING_SLOT_COUNT is <= 127, not 128.
  99     */
 100    STATIC_ASSERT(BRW_VARYING_SLOT_COUNT <= 127);
 101
 102    for (int i = 0; i < BRW_VARYING_SLOT_COUNT; ++i) {
 103       vue_map->varying_to_slot[i] = -1;
 104       vue_map->slot_to_varying[i] = BRW_VARYING_SLOT_PAD;
 105    }
 106
 107    int slot = 0;
 108
 109    /* VUE header: format depends on chip generation and whether clipping is
 110     * enabled.
 111     *
 112     * See the Sandybridge PRM, Volume 2 Part 1, section 1.5.1 (page 30),
 113     * "Vertex URB Entry (VUE) Formats" which describes the VUE header layout.
 114     */
 115    if (devinfo->gen < 6) {
 116       /* There are 8 dwords in VUE header pre-Ironlake:
 117        * dword 0-3 is indices, point width, clip flags.
 118        * dword 4-7 is ndc position
 119        * dword 8-11 is the first vertex data.
 120        *
 121        * On Ironlake the VUE header is nominally 20 dwords, but the hardware
 122        * will accept the same header layout as Gen4 [and should be a bit faster]
 123        */
 124       assign_vue_slot(vue_map, VARYING_SLOT_PSIZ, slot++);
 125       assign_vue_slot(vue_map, BRW_VARYING_SLOT_NDC, slot++);
 126       assign_vue_slot(vue_map, VARYING_SLOT_POS, slot++);
 127    } else {
 128       /* There are 8 or 16 DWs (D0-D15) in VUE header on Sandybridge:
 129        * dword 0-3 of the header is indices, point width, clip flags.
 130        * dword 4-7 is the 4D space position
 131        * dword 8-15 of the vertex header is the user clip distance if
 132        * enabled.
 133        * dword 8-11 or 16-19 is the first vertex element data we fill.
 134        */
 135       assign_vue_slot(vue_map, VARYING_SLOT_PSIZ, slot++);
 136       assign_vue_slot(vue_map, VARYING_SLOT_POS, slot++);
 137
 138       /* When using Primitive Replication, multiple slots are used for storing
 139        * positions for each view.
 140        */
 141       assert(pos_slots >= 1);
 142       if (pos_slots > 1) {
 143          for (int i = 1; i < pos_slots; i++) {
 144             vue_map->slot_to_varying[slot++] = VARYING_SLOT_POS;
 145          }
 146       }
 147
 148       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST0))
 149          assign_vue_slot(vue_map, VARYING_SLOT_CLIP_DIST0, slot++);
 150       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST1))
 151          assign_vue_slot(vue_map, VARYING_SLOT_CLIP_DIST1, slot++);
 152
 153       /* Vertex URB Formats table says: "Vertex Header shall be padded at the
 154        * end so that the header ends on a 32-byte boundary".
 155        */
 156       slot += slot % 2;
 157
 158       /* front and back colors need to be consecutive so that we can use
 159        * ATTRIBUTE_SWIZZLE_INPUTATTR_FACING to swizzle them when doing
 160        * two-sided color.
 161        */
 162       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_COL0))
 163          assign_vue_slot(vue_map, VARYING_SLOT_COL0, slot++);
 164       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_BFC0))
 165          assign_vue_slot(vue_map, VARYING_SLOT_BFC0, slot++);
 166       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_COL1))
 167          assign_vue_slot(vue_map, VARYING_SLOT_COL1, slot++);
 168       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_BFC1))
 169          assign_vue_slot(vue_map, VARYING_SLOT_BFC1, slot++);
 170    }
 171
 172    /* The hardware doesn't care about the rest of the vertex outputs, so we
 173     * can assign them however we like.  For normal programs, we simply assign
 174     * them contiguously.
 175     *
 176     * For separate shader pipelines, we first assign built-in varyings
 177     * contiguous slots.  This works because ARB_separate_shader_objects
 178     * requires that all shaders have matching built-in varying interface
 179     * blocks.  Next, we assign generic varyings based on their location
 180     * (either explicit or linker assigned).  This guarantees a fixed layout.
 181     *
 182     * We generally don't need to assign a slot for VARYING_SLOT_CLIP_VERTEX,
 183     * since it's encoded as the clip distances by emit_clip_distances().
 184     * However, it may be output by transform feedback, and we'd rather not
 185     * recompute state when TF changes, so we just always include it.
 186     */
 187    uint64_t builtins = slots_valid & BITFIELD64_MASK(VARYING_SLOT_VAR0);
 188    while (builtins != 0) {
 189       const int varying = ffsll(builtins) - 1;
 190       if (vue_map->varying_to_slot[varying] == -1) {
 191          assign_vue_slot(vue_map, varying, slot++);
 192       }
 193       builtins &= ~BITFIELD64_BIT(varying);
 194    }
 195
 196    const int first_generic_slot = slot;
 197    uint64_t generics = slots_valid & ~BITFIELD64_MASK(VARYING_SLOT_VAR0);
 198    while (generics != 0) {
 199       const int varying = ffsll(generics) - 1;
 200       if (separate) {
 201          slot = first_generic_slot + varying - VARYING_SLOT_VAR0;
 202       }
 203       assign_vue_slot(vue_map, varying, slot++);
 204       generics &= ~BITFIELD64_BIT(varying);
 205    }
 206
 207    vue_map->num_slots = slot;
 208    vue_map->num_per_vertex_slots = 0;
 209    vue_map->num_per_patch_slots = 0;
 210 }
 211
 212 /**
 213  * Compute the VUE map for tessellation control shader outputs and
 214  * tessellation evaluation shader inputs.
 215  */
 216 void
 217 brw_compute_tess_vue_map(struct brw_vue_map *vue_map,
 218                          uint64_t vertex_slots,
 219                          uint32_t patch_slots)
 220 {
 221    /* I don't think anything actually uses this... */
 222    vue_map->slots_valid = vertex_slots;
 223
 224    /* separate isn't really meaningful, but make sure it's initialized */
 225    vue_map->separate = false;
 226
 227    vertex_slots &= ~(VARYING_BIT_TESS_LEVEL_OUTER |
 228                      VARYING_BIT_TESS_LEVEL_INNER);
 229
 230    /* Make sure that the values we store in vue_map->varying_to_slot and
 231     * vue_map->slot_to_varying won't overflow the signed chars that are used
 232     * to store them.  Note that since vue_map->slot_to_varying sometimes holds
 233     * values equal to VARYING_SLOT_TESS_MAX , we need to ensure that
 234     * VARYING_SLOT_TESS_MAX is <= 127, not 128.
 235     */
 236    STATIC_ASSERT(VARYING_SLOT_TESS_MAX <= 127);
 237
 238    for (int i = 0; i < VARYING_SLOT_TESS_MAX ; ++i) {
 239       vue_map->varying_to_slot[i] = -1;
 240       vue_map->slot_to_varying[i] = BRW_VARYING_SLOT_PAD;
 241    }
 242
 243    int slot = 0;
 244
 245    /* The first 8 DWords are reserved for the "Patch Header".
 246     *
 247     * VARYING_SLOT_TESS_LEVEL_OUTER / INNER live here, but the exact layout
 248     * depends on the domain type.  They might not be in slots 0 and 1 as
 249     * described here, but pretending they're separate allows us to uniquely
 250     * identify them by distinct slot locations.
 251     */
 252    assign_vue_slot(vue_map, VARYING_SLOT_TESS_LEVEL_INNER, slot++);
 253    assign_vue_slot(vue_map, VARYING_SLOT_TESS_LEVEL_OUTER, slot++);
 254
 255    /* first assign per-patch varyings */
 256    while (patch_slots != 0) {
 257       const int varying = ffsll(patch_slots) - 1;
 258       if (vue_map->varying_to_slot[varying + VARYING_SLOT_PATCH0] == -1) {
 259          assign_vue_slot(vue_map, varying + VARYING_SLOT_PATCH0, slot++);
 260       }
 261       patch_slots &= ~BITFIELD64_BIT(varying);
 262    }
 263
 264    /* apparently, including the patch header... */
 265    vue_map->num_per_patch_slots = slot;
 266
 267    /* then assign per-vertex varyings for each vertex in our patch */
 268    while (vertex_slots != 0) {
 269       const int varying = ffsll(vertex_slots) - 1;
 270       if (vue_map->varying_to_slot[varying] == -1) {
 271          assign_vue_slot(vue_map, varying, slot++);
 272       }
 273       vertex_slots &= ~BITFIELD64_BIT(varying);
 274    }
 275
 276    vue_map->num_per_vertex_slots = slot - vue_map->num_per_patch_slots;
 277    vue_map->num_slots = slot;
 278 }
 279
 280 static const char *
 281 varying_name(brw_varying_slot slot)
 282 {
 283    assume(slot < BRW_VARYING_SLOT_COUNT);
 284
 285    if (slot < VARYING_SLOT_MAX)
 286       return gl_varying_slot_name((gl_varying_slot)slot);
 287
 288    static const char *brw_names[] = {
 289       [BRW_VARYING_SLOT_NDC - VARYING_SLOT_MAX] = "BRW_VARYING_SLOT_NDC",
 290       [BRW_VARYING_SLOT_PAD - VARYING_SLOT_MAX] = "BRW_VARYING_SLOT_PAD",
 291       [BRW_VARYING_SLOT_PNTC - VARYING_SLOT_MAX] = "BRW_VARYING_SLOT_PNTC",
 292    };
 293
 294    return brw_names[slot - VARYING_SLOT_MAX];
 295 }
 296
 297 void
 298 brw_print_vue_map(FILE *fp, const struct brw_vue_map *vue_map)
 299 {
 300    if (vue_map->num_per_vertex_slots > 0 || vue_map->num_per_patch_slots > 0) {
 301       fprintf(fp, "PUE map (%d slots, %d/patch, %d/vertex, %s)\n",
 302               vue_map->num_slots,
 303               vue_map->num_per_patch_slots,
 304               vue_map->num_per_vertex_slots,
 305               vue_map->separate ? "SSO" : "non-SSO");
 306       for (int i = 0; i < vue_map->num_slots; i++) {
 307          if (vue_map->slot_to_varying[i] >= VARYING_SLOT_PATCH0) {
 308             fprintf(fp, "  [%d] VARYING_SLOT_PATCH%d\n", i,
 309                     vue_map->slot_to_varying[i] - VARYING_SLOT_PATCH0);
 310          } else {
 311             fprintf(fp, "  [%d] %s\n", i,
 312                     varying_name(vue_map->slot_to_varying[i]));
 313          }
 314       }
 315    } else {
 316       fprintf(fp, "VUE map (%d slots, %s)\n",
 317               vue_map->num_slots, vue_map->separate ? "SSO" : "non-SSO");
 318       for (int i = 0; i < vue_map->num_slots; i++) {
 319          fprintf(fp, "  [%d] %s\n", i,
 320                  varying_name(vue_map->slot_to_varying[i]));
 321       }
 322    }
 323    fprintf(fp, "\n");
 324 }