src/mesa/drivers/dri/i965/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 "main/compiler.h"
  44 #include "brw_context.h"
  45
  46 static inline void
  47 assign_vue_slot(struct brw_vue_map *vue_map, int varying)
  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] = vue_map->num_slots;
  53    vue_map->slot_to_varying[vue_map->num_slots++] = varying;
  54 }
  55
  56 /**
  57  * Compute the VUE map for a shader stage.
  58  */
  59 void
  60 brw_compute_vue_map(const struct brw_device_info *devinfo,
  61                     struct brw_vue_map *vue_map,
  62                     GLbitfield64 slots_valid)
  63 {
  64    vue_map->slots_valid = slots_valid;
  65    int i;
  66
  67    /* gl_Layer and gl_ViewportIndex don't get their own varying slots -- they
  68     * are stored in the first VUE slot (VARYING_SLOT_PSIZ).
  69     */
  70    slots_valid &= ~(VARYING_BIT_LAYER | VARYING_BIT_VIEWPORT);
  71
  72    /* Make sure that the values we store in vue_map->varying_to_slot and
  73     * vue_map->slot_to_varying won't overflow the signed chars that are used
  74     * to store them.  Note that since vue_map->slot_to_varying sometimes holds
  75     * values equal to BRW_VARYING_SLOT_COUNT, we need to ensure that
  76     * BRW_VARYING_SLOT_COUNT is <= 127, not 128.
  77     */
  78    STATIC_ASSERT(BRW_VARYING_SLOT_COUNT <= 127);
  79
  80    vue_map->num_slots = 0;
  81    for (i = 0; i < BRW_VARYING_SLOT_COUNT; ++i) {
  82       vue_map->varying_to_slot[i] = -1;
  83       vue_map->slot_to_varying[i] = BRW_VARYING_SLOT_COUNT;
  84    }
  85
  86    /* VUE header: format depends on chip generation and whether clipping is
  87     * enabled.
  88     *
  89     * See the Sandybridge PRM, Volume 2 Part 1, section 1.5.1 (page 30),
  90     * "Vertex URB Entry (VUE) Formats" which describes the VUE header layout.
  91     */
  92    if (devinfo->gen < 6) {
  93       /* There are 8 dwords in VUE header pre-Ironlake:
  94        * dword 0-3 is indices, point width, clip flags.
  95        * dword 4-7 is ndc position
  96        * dword 8-11 is the first vertex data.
  97        *
  98        * On Ironlake the VUE header is nominally 20 dwords, but the hardware
  99        * will accept the same header layout as Gen4 [and should be a bit faster]
 100        */
 101       assign_vue_slot(vue_map, VARYING_SLOT_PSIZ);
 102       assign_vue_slot(vue_map, BRW_VARYING_SLOT_NDC);
 103       assign_vue_slot(vue_map, VARYING_SLOT_POS);
 104    } else {
 105       /* There are 8 or 16 DWs (D0-D15) in VUE header on Sandybridge:
 106        * dword 0-3 of the header is indices, point width, clip flags.
 107        * dword 4-7 is the 4D space position
 108        * dword 8-15 of the vertex header is the user clip distance if
 109        * enabled.
 110        * dword 8-11 or 16-19 is the first vertex element data we fill.
 111        */
 112       assign_vue_slot(vue_map, VARYING_SLOT_PSIZ);
 113       assign_vue_slot(vue_map, VARYING_SLOT_POS);
 114       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST0))
 115          assign_vue_slot(vue_map, VARYING_SLOT_CLIP_DIST0);
 116       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST1))
 117          assign_vue_slot(vue_map, VARYING_SLOT_CLIP_DIST1);
 118
 119       /* front and back colors need to be consecutive so that we can use
 120        * ATTRIBUTE_SWIZZLE_INPUTATTR_FACING to swizzle them when doing
 121        * two-sided color.
 122        */
 123       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_COL0))
 124          assign_vue_slot(vue_map, VARYING_SLOT_COL0);
 125       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_BFC0))
 126          assign_vue_slot(vue_map, VARYING_SLOT_BFC0);
 127       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_COL1))
 128          assign_vue_slot(vue_map, VARYING_SLOT_COL1);
 129       if (slots_valid & BITFIELD64_BIT(VARYING_SLOT_BFC1))
 130          assign_vue_slot(vue_map, VARYING_SLOT_BFC1);
 131    }
 132
 133    /* The hardware doesn't care about the rest of the vertex outputs, so just
 134     * assign them contiguously.  Don't reassign outputs that already have a
 135     * slot.
 136     *
 137     * We generally don't need to assign a slot for VARYING_SLOT_CLIP_VERTEX,
 138     * since it's encoded as the clip distances by emit_clip_distances().
 139     * However, it may be output by transform feedback, and we'd rather not
 140     * recompute state when TF changes, so we just always include it.
 141     */
 142    for (int i = 0; i < VARYING_SLOT_MAX; ++i) {
 143       if ((slots_valid & BITFIELD64_BIT(i)) &&
 144           vue_map->varying_to_slot[i] == -1) {
 145          assign_vue_slot(vue_map, i);
 146       }
 147    }
 148 }