src/compiler/nir/nir_passthrough_gs.c

   1 /*
   2  * Copyright © 2022 Collabora Ltc.
   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 FROM,
  20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  21  * SOFTWARE.
  22  */
  23
  24 #include "nir.h"
  25 #include "nir_xfb_info.h"
  26 #include "nir_builder.h"
  27 #include "util/u_memory.h"
  28
  29 static unsigned int
  30 gs_in_prim_for_topology(enum shader_prim prim)
  31 {
  32    switch (prim) {
  33    case SHADER_PRIM_QUADS:
  34       return SHADER_PRIM_LINES_ADJACENCY;
  35    default:
  36       return prim;
  37    }
  38 }
  39
  40 static enum shader_prim
  41 gs_out_prim_for_topology(enum shader_prim prim)
  42 {
  43    switch (prim) {
  44    case SHADER_PRIM_POINTS:
  45       return SHADER_PRIM_POINTS;
  46    case SHADER_PRIM_LINES:
  47    case SHADER_PRIM_LINE_LOOP:
  48    case SHADER_PRIM_LINES_ADJACENCY:
  49    case SHADER_PRIM_LINE_STRIP_ADJACENCY:
  50    case SHADER_PRIM_LINE_STRIP:
  51       return SHADER_PRIM_LINE_STRIP;
  52    case SHADER_PRIM_TRIANGLES:
  53    case SHADER_PRIM_TRIANGLE_STRIP:
  54    case SHADER_PRIM_TRIANGLE_FAN:
  55    case SHADER_PRIM_TRIANGLES_ADJACENCY:
  56    case SHADER_PRIM_TRIANGLE_STRIP_ADJACENCY:
  57    case SHADER_PRIM_POLYGON:
  58       return SHADER_PRIM_TRIANGLE_STRIP;
  59    case SHADER_PRIM_QUADS:
  60    case SHADER_PRIM_QUAD_STRIP:
  61    case SHADER_PRIM_PATCHES:
  62    default:
  63       return SHADER_PRIM_QUADS;
  64    }
  65 }
  66
  67 static unsigned int
  68 vertices_for_prim(enum shader_prim prim)
  69 {
  70    switch (prim) {
  71    case SHADER_PRIM_POINTS:
  72       return 1;
  73    case SHADER_PRIM_LINES:
  74    case SHADER_PRIM_LINE_LOOP:
  75    case SHADER_PRIM_LINES_ADJACENCY:
  76    case SHADER_PRIM_LINE_STRIP_ADJACENCY:
  77    case SHADER_PRIM_LINE_STRIP:
  78       return 2;
  79    case SHADER_PRIM_TRIANGLES:
  80    case SHADER_PRIM_TRIANGLE_STRIP:
  81    case SHADER_PRIM_TRIANGLE_FAN:
  82    case SHADER_PRIM_TRIANGLES_ADJACENCY:
  83    case SHADER_PRIM_TRIANGLE_STRIP_ADJACENCY:
  84    case SHADER_PRIM_POLYGON:
  85       return 3;
  86    case SHADER_PRIM_QUADS:
  87    case SHADER_PRIM_QUAD_STRIP:
  88       return 4;
  89    case SHADER_PRIM_PATCHES:
  90    default:
  91       unreachable("unsupported primitive for gs input");
  92    }
  93 }
  94
  95 static unsigned int
  96 array_size_for_prim(enum shader_prim prim)
  97 {
  98    switch (prim) {
  99    case SHADER_PRIM_POINTS:
 100       return 1;
 101    case SHADER_PRIM_LINES:
 102    case SHADER_PRIM_LINE_LOOP:
 103    case SHADER_PRIM_LINE_STRIP:
 104       return 2;
 105    case SHADER_PRIM_LINES_ADJACENCY:
 106    case SHADER_PRIM_LINE_STRIP_ADJACENCY:
 107       return 4;
 108    case SHADER_PRIM_TRIANGLES:
 109    case SHADER_PRIM_TRIANGLE_STRIP:
 110    case SHADER_PRIM_TRIANGLE_FAN:
 111    case SHADER_PRIM_POLYGON:
 112       return 3;
 113    case SHADER_PRIM_TRIANGLES_ADJACENCY:
 114    case SHADER_PRIM_TRIANGLE_STRIP_ADJACENCY:
 115       return 6;
 116    case SHADER_PRIM_QUADS:
 117    case SHADER_PRIM_QUAD_STRIP:
 118       return 4;
 119    case SHADER_PRIM_PATCHES:
 120    default:
 121       unreachable("unsupported primitive for gs input");
 122    }
 123 }
 124
 125 static void
 126 copy_vars(nir_builder *b, nir_deref_instr *dst, nir_deref_instr *src)
 127 {
 128    assert(glsl_get_bare_type(dst->type) == glsl_get_bare_type(src->type));
 129    if (glsl_type_is_struct(dst->type)) {
 130       for (unsigned i = 0; i < glsl_get_length(dst->type); ++i) {
 131          copy_vars(b, nir_build_deref_struct(b, dst, i), nir_build_deref_struct(b, src, i));
 132       }
 133    } else if (glsl_type_is_array_or_matrix(dst->type)) {
 134       unsigned count = glsl_type_is_array(dst->type) ? glsl_array_size(dst->type) : glsl_get_matrix_columns(dst->type);
 135       for (unsigned i = 0; i < count; i++) {
 136          copy_vars(b, nir_build_deref_array_imm(b, dst, i), nir_build_deref_array_imm(b, src, i));
 137       }
 138    } else {
 139       nir_ssa_def *load = nir_load_deref(b, src);
 140       nir_store_deref(b, dst, load, BITFIELD_MASK(load->num_components));
 141    }
 142 }
 143
 144 /*
 145  * A helper to create a passthrough GS shader for drivers that needs to lower
 146  * some rendering tasks to the GS.
 147  */
 148
 149 nir_shader *
 150 nir_create_passthrough_gs(const nir_shader_compiler_options *options,
 151                           const nir_shader *prev_stage,
 152                           enum shader_prim primitive_type,
 153                           bool emulate_edgeflags,
 154                           bool force_line_strip_out)
 155 {
 156    unsigned int vertices_out = vertices_for_prim(primitive_type);
 157    emulate_edgeflags = emulate_edgeflags && (prev_stage->info.outputs_written & VARYING_BIT_EDGE);
 158    bool needs_closing = (force_line_strip_out || emulate_edgeflags) && vertices_out >= 3;
 159    enum shader_prim original_our_prim = gs_out_prim_for_topology(primitive_type);
 160    nir_builder b = nir_builder_init_simple_shader(MESA_SHADER_GEOMETRY,
 161                                                   options,
 162                                                   "gs passthrough");
 163
 164    nir_shader *nir = b.shader;
 165    nir->info.gs.input_primitive = gs_in_prim_for_topology(primitive_type);
 166    nir->info.gs.output_primitive = (force_line_strip_out || emulate_edgeflags) ?
 167       SHADER_PRIM_LINE_STRIP : original_our_prim;
 168    nir->info.gs.vertices_in = vertices_out;
 169    nir->info.gs.vertices_out = needs_closing ? vertices_out + 1 : vertices_out;
 170    nir->info.gs.invocations = 1;
 171    nir->info.gs.active_stream_mask = 1;
 172
 173    nir->info.has_transform_feedback_varyings = prev_stage->info.has_transform_feedback_varyings;
 174    memcpy(nir->info.xfb_stride, prev_stage->info.xfb_stride, sizeof(prev_stage->info.xfb_stride));
 175    if (prev_stage->xfb_info) {
 176       nir->xfb_info = mem_dup(prev_stage->xfb_info, sizeof(nir_xfb_info));
 177    }
 178
 179    bool handle_flat = nir->info.gs.output_primitive == SHADER_PRIM_LINE_STRIP &&
 180                       nir->info.gs.output_primitive != original_our_prim;
 181    nir_variable *in_vars[VARYING_SLOT_MAX];
 182    nir_variable *out_vars[VARYING_SLOT_MAX];
 183    unsigned num_inputs = 0, num_outputs = 0;
 184
 185    /* Create input/output variables. */
 186    nir_foreach_shader_out_variable(var, prev_stage) {
 187       assert(!var->data.patch);
 188
 189       char name[100];
 190       if (var->name)
 191          snprintf(name, sizeof(name), "in_%s", var->name);
 192       else
 193          snprintf(name, sizeof(name), "in_%d", var->data.driver_location);
 194
 195       nir_variable *in = nir_variable_create(nir, nir_var_shader_in,
 196                                              glsl_array_type(var->type,
 197                                                              array_size_for_prim(primitive_type),
 198                                                              false),
 199                                              name);
 200       in->data.location = var->data.location;
 201       in->data.location_frac = var->data.location_frac;
 202       in->data.driver_location = var->data.driver_location;
 203       in->data.interpolation = var->data.interpolation;
 204       in->data.compact = var->data.compact;
 205
 206       in_vars[num_inputs++] = in;
 207
 208       nir->num_inputs++;
 209       if (in->data.location == VARYING_SLOT_EDGE)
 210          continue;
 211
 212       if (var->data.location != VARYING_SLOT_POS)
 213          nir->num_outputs++;
 214
 215       if (var->name)
 216          snprintf(name, sizeof(name), "out_%s", var->name);
 217       else
 218          snprintf(name, sizeof(name), "out_%d", var->data.driver_location);
 219
 220       nir_variable *out = nir_variable_create(nir, nir_var_shader_out,
 221                                               var->type, name);
 222       out->data.location = var->data.location;
 223       out->data.location_frac = var->data.location_frac;
 224       out->data.driver_location = var->data.driver_location;
 225       out->data.interpolation = var->data.interpolation;
 226       out->data.compact = var->data.compact;
 227       out->data.is_xfb = var->data.is_xfb;
 228       out->data.is_xfb_only = var->data.is_xfb_only;
 229       out->data.explicit_xfb_buffer = var->data.explicit_xfb_buffer;
 230       out->data.explicit_xfb_stride = var->data.explicit_xfb_stride;
 231       out->data.xfb = var->data.xfb;
 232       out->data.offset = var->data.offset;
 233
 234       out_vars[num_outputs++] = out;
 235    }
 236
 237    unsigned int start_vert = 0;
 238    unsigned int end_vert = vertices_out;
 239    unsigned int vert_step = 1;
 240    switch (primitive_type) {
 241    case PIPE_PRIM_LINES_ADJACENCY:
 242    case PIPE_PRIM_LINE_STRIP_ADJACENCY:
 243       start_vert = 1;
 244       end_vert += 1;
 245       break;
 246    case PIPE_PRIM_TRIANGLES_ADJACENCY:
 247    case PIPE_PRIM_TRIANGLE_STRIP_ADJACENCY:
 248       end_vert = 5;
 249       vert_step = 2;
 250       break;
 251    default:
 252       break;
 253    }
 254
 255    nir_variable *edge_var = nir_find_variable_with_location(nir, nir_var_shader_in, VARYING_SLOT_EDGE);
 256    nir_ssa_def *flat_interp_mask_def = nir_load_flat_mask(&b);
 257    nir_ssa_def *last_pv_vert_def = nir_load_provoking_last(&b);
 258    last_pv_vert_def = nir_ine_imm(&b, last_pv_vert_def, 0);
 259    nir_ssa_def *start_vert_index = nir_imm_int(&b, start_vert);
 260    nir_ssa_def *end_vert_index = nir_imm_int(&b, end_vert - 1);
 261    nir_ssa_def *pv_vert_index = nir_bcsel(&b, last_pv_vert_def, end_vert_index, start_vert_index);
 262    for (unsigned i = start_vert; i < end_vert || needs_closing; i += vert_step) {
 263       int idx = i < end_vert ? i : start_vert;
 264       /* Copy inputs to outputs. */
 265       for (unsigned j = 0, oj = 0, of = 0; j < num_inputs; ++j) {
 266          if (in_vars[j]->data.location == VARYING_SLOT_EDGE) {
 267             continue;
 268          }
 269          /* no need to use copy_var to save a lower pass */
 270          nir_ssa_def *index;
 271          if (in_vars[j]->data.location == VARYING_SLOT_POS || !handle_flat)
 272             index = nir_imm_int(&b, idx);
 273          else {
 274             unsigned mask = 1u << (of++);
 275             index = nir_bcsel(&b, nir_ieq_imm(&b, nir_iand_imm(&b, flat_interp_mask_def, mask), 0), nir_imm_int(&b, idx), pv_vert_index);
 276          }
 277          nir_deref_instr *value = nir_build_deref_array(&b, nir_build_deref_var(&b, in_vars[j]), index);
 278          copy_vars(&b, nir_build_deref_var(&b, out_vars[oj]), value);
 279          ++oj;
 280       }
 281       nir_emit_vertex(&b, 0);
 282       if (emulate_edgeflags) {
 283          nir_ssa_def *edge_value = nir_channel(&b, nir_load_array_var_imm(&b, edge_var, idx), 0);
 284          nir_if *edge_if = nir_push_if(&b, nir_fneu(&b, edge_value, nir_imm_float(&b, 1.0)));
 285          nir_end_primitive(&b, 0);
 286          nir_pop_if(&b, edge_if);
 287       }
 288       if (i >= end_vert)
 289          break;
 290    }
 291
 292    nir_end_primitive(&b, 0);
 293    nir_shader_gather_info(nir, nir_shader_get_entrypoint(nir));
 294    nir_validate_shader(nir, "in nir_create_passthrough_gs");
 295
 296    return nir;
 297 }