1 /* 2 * Copyright 2013 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 21 * DEALINGS IN THE SOFTWARE. 22 */ 23 24 /** 25 * \file brw_vec4_gs_visitor.cpp 26 * 27 * Geometry-shader-specific code derived from the vec4_visitor class. 28 */ 29 30 #include "brw_vec4_gs_visitor.h" 31 #include "gen6_gs_visitor.h" 32 #include "brw_fs.h" 33 #include "brw_nir.h" 34 35 namespace brw { 36 37 vec4_gs_visitor::vec4_gs_visitor(const struct brw_compiler *compiler, 38 void *log_data, 39 struct brw_gs_compile *c, 40 struct brw_gs_prog_data *prog_data, 41 const nir_shader *shader, 42 void *mem_ctx, 43 bool no_spills, 44 int shader_time_index) 45 : vec4_visitor(compiler, log_data, &c->key.tex, 46 &prog_data->base, shader, mem_ctx, 47 no_spills, shader_time_index), 48 c(c), 49 gs_prog_data(prog_data) 50 { 51 } 52 53 54 dst_reg * 55 vec4_gs_visitor::make_reg_for_system_value(int location) 56 { 57 dst_reg *reg = new(mem_ctx) dst_reg(this, glsl_type::int_type); 58 59 switch (location) { 60 case SYSTEM_VALUE_INVOCATION_ID: 61 this->current_annotation = "initialize gl_InvocationID"; 62 if (gs_prog_data->invocations > 1) 63 emit(GS_OPCODE_GET_INSTANCE_ID, *reg); 64 else 65 emit(MOV(*reg, brw_imm_ud(0))); 66 break; 67 default: 68 unreachable("not reached"); 69 } 70 71 return reg; 72 } 73 74 75 int 76 vec4_gs_visitor::setup_varying_inputs(int payload_reg, int *attribute_map, 77 int attributes_per_reg) 78 { 79 /* For geometry shaders there are N copies of the input attributes, where N 80 * is the number of input vertices. attribute_map[BRW_VARYING_SLOT_COUNT * 81 * i + j] represents attribute j for vertex i. 82 * 83 * Note that GS inputs are read from the VUE 256 bits (2 vec4's) at a time, 84 * so the total number of input slots that will be delivered to the GS (and 85 * thus the stride of the input arrays) is urb_read_length * 2. 86 */ 87 const unsigned num_input_vertices = nir->info->gs.vertices_in; 88 assert(num_input_vertices <= MAX_GS_INPUT_VERTICES); 89 unsigned input_array_stride = prog_data->urb_read_length * 2; 90 91 for (int slot = 0; slot < c->input_vue_map.num_slots; slot++) { 92 int varying = c->input_vue_map.slot_to_varying[slot]; 93 for (unsigned vertex = 0; vertex < num_input_vertices; vertex++) { 94 attribute_map[BRW_VARYING_SLOT_COUNT * vertex + varying] = 95 attributes_per_reg * payload_reg + input_array_stride * vertex + 96 slot; 97 } 98 } 99 100 int regs_used = ALIGN(input_array_stride * num_input_vertices, 101 attributes_per_reg) / attributes_per_reg; 102 return payload_reg + regs_used; 103 } 104 105 106 void 107 vec4_gs_visitor::setup_payload() 108 { 109 int attribute_map[BRW_VARYING_SLOT_COUNT * MAX_GS_INPUT_VERTICES]; 110 111 /* If we are in dual instanced or single mode, then attributes are going 112 * to be interleaved, so one register contains two attribute slots. 113 */ 114 int attributes_per_reg = 115 prog_data->dispatch_mode == DISPATCH_MODE_4X2_DUAL_OBJECT ? 1 : 2; 116 117 /* If a geometry shader tries to read from an input that wasn't written by 118 * the vertex shader, that produces undefined results, but it shouldn't 119 * crash anything. So initialize attribute_map to zeros--that ensures that 120 * these undefined results are read from r0. 121 */ 122 memset(attribute_map, 0, sizeof(attribute_map)); 123 124 int reg = 0; 125 126 /* The payload always contains important data in r0, which contains 127 * the URB handles that are passed on to the URB write at the end 128 * of the thread. 129 */ 130 reg++; 131 132 /* If the shader uses gl_PrimitiveIDIn, that goes in r1. */ 133 if (gs_prog_data->include_primitive_id) 134 attribute_map[VARYING_SLOT_PRIMITIVE_ID] = attributes_per_reg * reg++; 135 136 reg = setup_uniforms(reg); 137 138 reg = setup_varying_inputs(reg, attribute_map, attributes_per_reg); 139 140 lower_attributes_to_hw_regs(attribute_map, attributes_per_reg > 1); 141 142 this->first_non_payload_grf = reg; 143 } 144 145 146 void 147 vec4_gs_visitor::emit_prolog() 148 { 149 /* In vertex shaders, r0.2 is guaranteed to be initialized to zero. In 150 * geometry shaders, it isn't (it contains a bunch of information we don't 151 * need, like the input primitive type). We need r0.2 to be zero in order 152 * to build scratch read/write messages correctly (otherwise this value 153 * will be interpreted as a global offset, causing us to do our scratch 154 * reads/writes to garbage memory). So just set it to zero at the top of 155 * the shader. 156 */ 157 this->current_annotation = "clear r0.2"; 158 dst_reg r0(retype(brw_vec4_grf(0, 0), BRW_REGISTER_TYPE_UD)); 159 vec4_instruction *inst = emit(GS_OPCODE_SET_DWORD_2, r0, brw_imm_ud(0u)); 160 inst->force_writemask_all = true; 161 162 /* Create a virtual register to hold the vertex count */ 163 this->vertex_count = src_reg(this, glsl_type::uint_type); 164 165 /* Initialize the vertex_count register to 0 */ 166 this->current_annotation = "initialize vertex_count"; 167 inst = emit(MOV(dst_reg(this->vertex_count), brw_imm_ud(0u))); 168 inst->force_writemask_all = true; 169 170 if (c->control_data_header_size_bits > 0) { 171 /* Create a virtual register to hold the current set of control data 172 * bits. 173 */ 174 this->control_data_bits = src_reg(this, glsl_type::uint_type); 175 176 /* If we're outputting more than 32 control data bits, then EmitVertex() 177 * will set control_data_bits to 0 after emitting the first vertex. 178 * Otherwise, we need to initialize it to 0 here. 179 */ 180 if (c->control_data_header_size_bits <= 32) { 181 this->current_annotation = "initialize control data bits"; 182 inst = emit(MOV(dst_reg(this->control_data_bits), brw_imm_ud(0u))); 183 inst->force_writemask_all = true; 184 } 185 } 186 187 this->current_annotation = NULL; 188 } 189 190 void 191 vec4_gs_visitor::emit_thread_end() 192 { 193 if (c->control_data_header_size_bits > 0) { 194 /* During shader execution, we only ever call emit_control_data_bits() 195 * just prior to outputting a vertex. Therefore, the control data bits 196 * corresponding to the most recently output vertex still need to be 197 * emitted. 198 */ 199 current_annotation = "thread end: emit control data bits"; 200 emit_control_data_bits(); 201 } 202 203 /* MRF 0 is reserved for the debugger, so start with message header 204 * in MRF 1. 205 */ 206 int base_mrf = 1; 207 208 bool static_vertex_count = gs_prog_data->static_vertex_count != -1; 209 210 /* If the previous instruction was a URB write, we don't need to issue 211 * a second one - we can just set the EOT bit on the previous write. 212 * 213 * Skip this on Gen8+ unless there's a static vertex count, as we also 214 * need to write the vertex count out, and combining the two may not be 215 * possible (or at least not straightforward). 216 */ 217 vec4_instruction *last = (vec4_instruction *) instructions.get_tail(); 218 if (last && last->opcode == GS_OPCODE_URB_WRITE && 219 !(INTEL_DEBUG & DEBUG_SHADER_TIME) && 220 devinfo->gen >= 8 && static_vertex_count) { 221 last->urb_write_flags = BRW_URB_WRITE_EOT | last->urb_write_flags; 222 return; 223 } 224 225 current_annotation = "thread end"; 226 dst_reg mrf_reg(MRF, base_mrf); 227 src_reg r0(retype(brw_vec8_grf(0, 0), BRW_REGISTER_TYPE_UD)); 228 vec4_instruction *inst = emit(MOV(mrf_reg, r0)); 229 inst->force_writemask_all = true; 230 if (devinfo->gen < 8 || !static_vertex_count) 231 emit(GS_OPCODE_SET_VERTEX_COUNT, mrf_reg, this->vertex_count); 232 if (INTEL_DEBUG & DEBUG_SHADER_TIME) 233 emit_shader_time_end(); 234 inst = emit(GS_OPCODE_THREAD_END); 235 inst->base_mrf = base_mrf; 236 inst->mlen = devinfo->gen >= 8 && !static_vertex_count ? 2 : 1; 237 } 238 239 240 void 241 vec4_gs_visitor::emit_urb_write_header(int mrf) 242 { 243 /* The SEND instruction that writes the vertex data to the VUE will use 244 * per_slot_offset=true, which means that DWORDs 3 and 4 of the message 245 * header specify an offset (in multiples of 256 bits) into the URB entry 246 * at which the write should take place. 247 * 248 * So we have to prepare a message header with the appropriate offset 249 * values. 250 */ 251 dst_reg mrf_reg(MRF, mrf); 252 src_reg r0(retype(brw_vec8_grf(0, 0), BRW_REGISTER_TYPE_UD)); 253 this->current_annotation = "URB write header"; 254 vec4_instruction *inst = emit(MOV(mrf_reg, r0)); 255 inst->force_writemask_all = true; 256 emit(GS_OPCODE_SET_WRITE_OFFSET, mrf_reg, this->vertex_count, 257 brw_imm_ud(gs_prog_data->output_vertex_size_hwords)); 258 } 259 260 261 vec4_instruction * 262 vec4_gs_visitor::emit_urb_write_opcode(bool complete) 263 { 264 /* We don't care whether the vertex is complete, because in general 265 * geometry shaders output multiple vertices, and we don't terminate the 266 * thread until all vertices are complete. 267 */ 268 (void) complete; 269 270 vec4_instruction *inst = emit(GS_OPCODE_URB_WRITE); 271 inst->offset = gs_prog_data->control_data_header_size_hwords; 272 273 /* We need to increment Global Offset by 1 to make room for Broadwell's 274 * extra "Vertex Count" payload at the beginning of the URB entry. 275 */ 276 if (devinfo->gen >= 8 && gs_prog_data->static_vertex_count == -1) 277 inst->offset++; 278 279 inst->urb_write_flags = BRW_URB_WRITE_PER_SLOT_OFFSET; 280 return inst; 281 } 282 283 284 /** 285 * Write out a batch of 32 control data bits from the control_data_bits 286 * register to the URB. 287 * 288 * The current value of the vertex_count register determines which DWORD in 289 * the URB receives the control data bits. The control_data_bits register is 290 * assumed to contain the correct data for the vertex that was most recently 291 * output, and all previous vertices that share the same DWORD. 292 * 293 * This function takes care of ensuring that if no vertices have been output 294 * yet, no control bits are emitted. 295 */ 296 void 297 vec4_gs_visitor::emit_control_data_bits() 298 { 299 assert(c->control_data_bits_per_vertex != 0); 300 301 /* Since the URB_WRITE_OWORD message operates with 128-bit (vec4 sized) 302 * granularity, we need to use two tricks to ensure that the batch of 32 303 * control data bits is written to the appropriate DWORD in the URB. To 304 * select which vec4 we are writing to, we use the "slot {0,1} offset" 305 * fields of the message header. To select which DWORD in the vec4 we are 306 * writing to, we use the channel mask fields of the message header. To 307 * avoid penalizing geometry shaders that emit a small number of vertices 308 * with extra bookkeeping, we only do each of these tricks when 309 * c->prog_data.control_data_header_size_bits is large enough to make it 310 * necessary. 311 * 312 * Note: this means that if we're outputting just a single DWORD of control 313 * data bits, we'll actually replicate it four times since we won't do any 314 * channel masking. But that's not a problem since in this case the 315 * hardware only pays attention to the first DWORD. 316 */ 317 enum brw_urb_write_flags urb_write_flags = BRW_URB_WRITE_OWORD; 318 if (c->control_data_header_size_bits > 32) 319 urb_write_flags = urb_write_flags | BRW_URB_WRITE_USE_CHANNEL_MASKS; 320 if (c->control_data_header_size_bits > 128) 321 urb_write_flags = urb_write_flags | BRW_URB_WRITE_PER_SLOT_OFFSET; 322 323 /* If we are using either channel masks or a per-slot offset, then we 324 * need to figure out which DWORD we are trying to write to, using the 325 * formula: 326 * 327 * dword_index = (vertex_count - 1) * bits_per_vertex / 32 328 * 329 * Since bits_per_vertex is a power of two, and is known at compile 330 * time, this can be optimized to: 331 * 332 * dword_index = (vertex_count - 1) >> (6 - log2(bits_per_vertex)) 333 */ 334 src_reg dword_index(this, glsl_type::uint_type); 335 if (urb_write_flags) { 336 src_reg prev_count(this, glsl_type::uint_type); 337 emit(ADD(dst_reg(prev_count), this->vertex_count, 338 brw_imm_ud(0xffffffffu))); 339 unsigned log2_bits_per_vertex = 340 util_last_bit(c->control_data_bits_per_vertex); 341 emit(SHR(dst_reg(dword_index), prev_count, 342 brw_imm_ud(6 - log2_bits_per_vertex))); 343 } 344 345 /* Start building the URB write message. The first MRF gets a copy of 346 * R0. 347 */ 348 int base_mrf = 1; 349 dst_reg mrf_reg(MRF, base_mrf); 350 src_reg r0(retype(brw_vec8_grf(0, 0), BRW_REGISTER_TYPE_UD)); 351 vec4_instruction *inst = emit(MOV(mrf_reg, r0)); 352 inst->force_writemask_all = true; 353 354 if (urb_write_flags & BRW_URB_WRITE_PER_SLOT_OFFSET) { 355 /* Set the per-slot offset to dword_index / 4, to that we'll write to 356 * the appropriate OWORD within the control data header. 357 */ 358 src_reg per_slot_offset(this, glsl_type::uint_type); 359 emit(SHR(dst_reg(per_slot_offset), dword_index, brw_imm_ud(2u))); 360 emit(GS_OPCODE_SET_WRITE_OFFSET, mrf_reg, per_slot_offset, 361 brw_imm_ud(1u)); 362 } 363 364 if (urb_write_flags & BRW_URB_WRITE_USE_CHANNEL_MASKS) { 365 /* Set the channel masks to 1 << (dword_index % 4), so that we'll 366 * write to the appropriate DWORD within the OWORD. We need to do 367 * this computation with force_writemask_all, otherwise garbage data 368 * from invocation 0 might clobber the mask for invocation 1 when 369 * GS_OPCODE_PREPARE_CHANNEL_MASKS tries to OR the two masks 370 * together. 371 */ 372 src_reg channel(this, glsl_type::uint_type); 373 inst = emit(AND(dst_reg(channel), dword_index, brw_imm_ud(3u))); 374 inst->force_writemask_all = true; 375 src_reg one(this, glsl_type::uint_type); 376 inst = emit(MOV(dst_reg(one), brw_imm_ud(1u))); 377 inst->force_writemask_all = true; 378 src_reg channel_mask(this, glsl_type::uint_type); 379 inst = emit(SHL(dst_reg(channel_mask), one, channel)); 380 inst->force_writemask_all = true; 381 emit(GS_OPCODE_PREPARE_CHANNEL_MASKS, dst_reg(channel_mask), 382 channel_mask); 383 emit(GS_OPCODE_SET_CHANNEL_MASKS, mrf_reg, channel_mask); 384 } 385 386 /* Store the control data bits in the message payload and send it. */ 387 dst_reg mrf_reg2(MRF, base_mrf + 1); 388 inst = emit(MOV(mrf_reg2, this->control_data_bits)); 389 inst->force_writemask_all = true; 390 inst = emit(GS_OPCODE_URB_WRITE); 391 inst->urb_write_flags = urb_write_flags; 392 /* We need to increment Global Offset by 256-bits to make room for 393 * Broadwell's extra "Vertex Count" payload at the beginning of the 394 * URB entry. Since this is an OWord message, Global Offset is counted 395 * in 128-bit units, so we must set it to 2. 396 */ 397 if (devinfo->gen >= 8 && gs_prog_data->static_vertex_count == -1) 398 inst->offset = 2; 399 inst->base_mrf = base_mrf; 400 inst->mlen = 2; 401 } 402 403 void 404 vec4_gs_visitor::set_stream_control_data_bits(unsigned stream_id) 405 { 406 /* control_data_bits |= stream_id << ((2 * (vertex_count - 1)) % 32) */ 407 408 /* Note: we are calling this *before* increasing vertex_count, so 409 * this->vertex_count == vertex_count - 1 in the formula above. 410 */ 411 412 /* Stream mode uses 2 bits per vertex */ 413 assert(c->control_data_bits_per_vertex == 2); 414 415 /* Must be a valid stream */ 416 assert(stream_id >= 0 && stream_id < MAX_VERTEX_STREAMS); 417 418 /* Control data bits are initialized to 0 so we don't have to set any 419 * bits when sending vertices to stream 0. 420 */ 421 if (stream_id == 0) 422 return; 423 424 /* reg::sid = stream_id */ 425 src_reg sid(this, glsl_type::uint_type); 426 emit(MOV(dst_reg(sid), brw_imm_ud(stream_id))); 427 428 /* reg:shift_count = 2 * (vertex_count - 1) */ 429 src_reg shift_count(this, glsl_type::uint_type); 430 emit(SHL(dst_reg(shift_count), this->vertex_count, brw_imm_ud(1u))); 431 432 /* Note: we're relying on the fact that the GEN SHL instruction only pays 433 * attention to the lower 5 bits of its second source argument, so on this 434 * architecture, stream_id << 2 * (vertex_count - 1) is equivalent to 435 * stream_id << ((2 * (vertex_count - 1)) % 32). 436 */ 437 src_reg mask(this, glsl_type::uint_type); 438 emit(SHL(dst_reg(mask), sid, shift_count)); 439 emit(OR(dst_reg(this->control_data_bits), this->control_data_bits, mask)); 440 } 441 442 void 443 vec4_gs_visitor::gs_emit_vertex(int stream_id) 444 { 445 this->current_annotation = "emit vertex: safety check"; 446 447 /* Haswell and later hardware ignores the "Render Stream Select" bits 448 * from the 3DSTATE_STREAMOUT packet when the SOL stage is disabled, 449 * and instead sends all primitives down the pipeline for rasterization. 450 * If the SOL stage is enabled, "Render Stream Select" is honored and 451 * primitives bound to non-zero streams are discarded after stream output. 452 * 453 * Since the only purpose of primives sent to non-zero streams is to 454 * be recorded by transform feedback, we can simply discard all geometry 455 * bound to these streams when transform feedback is disabled. 456 */ 457 if (stream_id > 0 && !nir->info->has_transform_feedback_varyings) 458 return; 459 460 /* If we're outputting 32 control data bits or less, then we can wait 461 * until the shader is over to output them all. Otherwise we need to 462 * output them as we go. Now is the time to do it, since we're about to 463 * output the vertex_count'th vertex, so it's guaranteed that the 464 * control data bits associated with the (vertex_count - 1)th vertex are 465 * correct. 466 */ 467 if (c->control_data_header_size_bits > 32) { 468 this->current_annotation = "emit vertex: emit control data bits"; 469 /* Only emit control data bits if we've finished accumulating a batch 470 * of 32 bits. This is the case when: 471 * 472 * (vertex_count * bits_per_vertex) % 32 == 0 473 * 474 * (in other words, when the last 5 bits of vertex_count * 475 * bits_per_vertex are 0). Assuming bits_per_vertex == 2^n for some 476 * integer n (which is always the case, since bits_per_vertex is 477 * always 1 or 2), this is equivalent to requiring that the last 5-n 478 * bits of vertex_count are 0: 479 * 480 * vertex_count & (2^(5-n) - 1) == 0 481 * 482 * 2^(5-n) == 2^5 / 2^n == 32 / bits_per_vertex, so this is 483 * equivalent to: 484 * 485 * vertex_count & (32 / bits_per_vertex - 1) == 0 486 */ 487 vec4_instruction *inst = 488 emit(AND(dst_null_ud(), this->vertex_count, 489 brw_imm_ud(32 / c->control_data_bits_per_vertex - 1))); 490 inst->conditional_mod = BRW_CONDITIONAL_Z; 491 492 emit(IF(BRW_PREDICATE_NORMAL)); 493 { 494 /* If vertex_count is 0, then no control data bits have been 495 * accumulated yet, so we skip emitting them. 496 */ 497 emit(CMP(dst_null_ud(), this->vertex_count, brw_imm_ud(0u), 498 BRW_CONDITIONAL_NEQ)); 499 emit(IF(BRW_PREDICATE_NORMAL)); 500 emit_control_data_bits(); 501 emit(BRW_OPCODE_ENDIF); 502 503 /* Reset control_data_bits to 0 so we can start accumulating a new 504 * batch. 505 * 506 * Note: in the case where vertex_count == 0, this neutralizes the 507 * effect of any call to EndPrimitive() that the shader may have 508 * made before outputting its first vertex. 509 */ 510 inst = emit(MOV(dst_reg(this->control_data_bits), brw_imm_ud(0u))); 511 inst->force_writemask_all = true; 512 } 513 emit(BRW_OPCODE_ENDIF); 514 } 515 516 this->current_annotation = "emit vertex: vertex data"; 517 emit_vertex(); 518 519 /* In stream mode we have to set control data bits for all vertices 520 * unless we have disabled control data bits completely (which we do 521 * do for GL_POINTS outputs that don't use streams). 522 */ 523 if (c->control_data_header_size_bits > 0 && 524 gs_prog_data->control_data_format == 525 GEN7_GS_CONTROL_DATA_FORMAT_GSCTL_SID) { 526 this->current_annotation = "emit vertex: Stream control data bits"; 527 set_stream_control_data_bits(stream_id); 528 } 529 530 this->current_annotation = NULL; 531 } 532 533 void 534 vec4_gs_visitor::gs_end_primitive() 535 { 536 /* We can only do EndPrimitive() functionality when the control data 537 * consists of cut bits. Fortunately, the only time it isn't is when the 538 * output type is points, in which case EndPrimitive() is a no-op. 539 */ 540 if (gs_prog_data->control_data_format != 541 GEN7_GS_CONTROL_DATA_FORMAT_GSCTL_CUT) { 542 return; 543 } 544 545 if (c->control_data_header_size_bits == 0) 546 return; 547 548 /* Cut bits use one bit per vertex. */ 549 assert(c->control_data_bits_per_vertex == 1); 550 551 /* Cut bit n should be set to 1 if EndPrimitive() was called after emitting 552 * vertex n, 0 otherwise. So all we need to do here is mark bit 553 * (vertex_count - 1) % 32 in the cut_bits register to indicate that 554 * EndPrimitive() was called after emitting vertex (vertex_count - 1); 555 * vec4_gs_visitor::emit_control_data_bits() will take care of the rest. 556 * 557 * Note that if EndPrimitve() is called before emitting any vertices, this 558 * will cause us to set bit 31 of the control_data_bits register to 1. 559 * That's fine because: 560 * 561 * - If max_vertices < 32, then vertex number 31 (zero-based) will never be 562 * output, so the hardware will ignore cut bit 31. 563 * 564 * - If max_vertices == 32, then vertex number 31 is guaranteed to be the 565 * last vertex, so setting cut bit 31 has no effect (since the primitive 566 * is automatically ended when the GS terminates). 567 * 568 * - If max_vertices > 32, then the ir_emit_vertex visitor will reset the 569 * control_data_bits register to 0 when the first vertex is emitted. 570 */ 571 572 /* control_data_bits |= 1 << ((vertex_count - 1) % 32) */ 573 src_reg one(this, glsl_type::uint_type); 574 emit(MOV(dst_reg(one), brw_imm_ud(1u))); 575 src_reg prev_count(this, glsl_type::uint_type); 576 emit(ADD(dst_reg(prev_count), this->vertex_count, brw_imm_ud(0xffffffffu))); 577 src_reg mask(this, glsl_type::uint_type); 578 /* Note: we're relying on the fact that the GEN SHL instruction only pays 579 * attention to the lower 5 bits of its second source argument, so on this 580 * architecture, 1 << (vertex_count - 1) is equivalent to 1 << 581 * ((vertex_count - 1) % 32). 582 */ 583 emit(SHL(dst_reg(mask), one, prev_count)); 584 emit(OR(dst_reg(this->control_data_bits), this->control_data_bits, mask)); 585 } 586 587 extern "C" const unsigned * 588 brw_compile_gs(const struct brw_compiler *compiler, void *log_data, 589 void *mem_ctx, 590 const struct brw_gs_prog_key *key, 591 struct brw_gs_prog_data *prog_data, 592 const nir_shader *src_shader, 593 struct gl_program *prog, 594 int shader_time_index, 595 unsigned *final_assembly_size, 596 char **error_str) 597 { 598 struct brw_gs_compile c; 599 memset(&c, 0, sizeof(c)); 600 c.key = *key; 601 602 const bool is_scalar = compiler->scalar_stage[MESA_SHADER_GEOMETRY]; 603 nir_shader *shader = nir_shader_clone(mem_ctx, src_shader); 604 605 /* The GLSL linker will have already matched up GS inputs and the outputs 606 * of prior stages. The driver does extend VS outputs in some cases, but 607 * only for legacy OpenGL or Gen4-5 hardware, neither of which offer 608 * geometry shader support. So we can safely ignore that. 609 * 610 * For SSO pipelines, we use a fixed VUE map layout based on variable 611 * locations, so we can rely on rendezvous-by-location making this work. 612 */ 613 GLbitfield64 inputs_read = shader->info->inputs_read; 614 brw_compute_vue_map(compiler->devinfo, 615 &c.input_vue_map, inputs_read, 616 shader->info->separate_shader); 617 618 shader = brw_nir_apply_sampler_key(shader, compiler, &key->tex, is_scalar); 619 brw_nir_lower_vue_inputs(shader, is_scalar, &c.input_vue_map); 620 brw_nir_lower_vue_outputs(shader, is_scalar); 621 shader = brw_postprocess_nir(shader, compiler, is_scalar); 622 623 prog_data->base.clip_distance_mask = 624 ((1 << shader->info->clip_distance_array_size) - 1); 625 prog_data->base.cull_distance_mask = 626 ((1 << shader->info->cull_distance_array_size) - 1) << 627 shader->info->clip_distance_array_size; 628 629 prog_data->include_primitive_id = 630 (shader->info->system_values_read & (1 << SYSTEM_VALUE_PRIMITIVE_ID)) != 0; 631 632 prog_data->invocations = shader->info->gs.invocations; 633 634 if (compiler->devinfo->gen >= 8) 635 prog_data->static_vertex_count = nir_gs_count_vertices(shader); 636 637 if (compiler->devinfo->gen >= 7) { 638 if (shader->info->gs.output_primitive == GL_POINTS) { 639 /* When the output type is points, the geometry shader may output data 640 * to multiple streams, and EndPrimitive() has no effect. So we 641 * configure the hardware to interpret the control data as stream ID. 642 */ 643 prog_data->control_data_format = GEN7_GS_CONTROL_DATA_FORMAT_GSCTL_SID; 644 645 /* We only have to emit control bits if we are using streams */ 646 if (prog && prog->info.gs.uses_streams) 647 c.control_data_bits_per_vertex = 2; 648 else 649 c.control_data_bits_per_vertex = 0; 650 } else { 651 /* When the output type is triangle_strip or line_strip, EndPrimitive() 652 * may be used to terminate the current strip and start a new one 653 * (similar to primitive restart), and outputting data to multiple 654 * streams is not supported. So we configure the hardware to interpret 655 * the control data as EndPrimitive information (a.k.a. "cut bits"). 656 */ 657 prog_data->control_data_format = GEN7_GS_CONTROL_DATA_FORMAT_GSCTL_CUT; 658 659 /* We only need to output control data if the shader actually calls 660 * EndPrimitive(). 661 */ 662 c.control_data_bits_per_vertex = 663 shader->info->gs.uses_end_primitive ? 1 : 0; 664 } 665 } else { 666 /* There are no control data bits in gen6. */ 667 c.control_data_bits_per_vertex = 0; 668 } 669 c.control_data_header_size_bits = 670 shader->info->gs.vertices_out * c.control_data_bits_per_vertex; 671 672 /* 1 HWORD = 32 bytes = 256 bits */ 673 prog_data->control_data_header_size_hwords = 674 ALIGN(c.control_data_header_size_bits, 256) / 256; 675 676 /* Compute the output vertex size. 677 * 678 * From the Ivy Bridge PRM, Vol2 Part1 7.2.1.1 STATE_GS - Output Vertex 679 * Size (p168): 680 * 681 * [0,62] indicating [1,63] 16B units 682 * 683 * Specifies the size of each vertex stored in the GS output entry 684 * (following any Control Header data) as a number of 128-bit units 685 * (minus one). 686 * 687 * Programming Restrictions: The vertex size must be programmed as a 688 * multiple of 32B units with the following exception: Rendering is 689 * disabled (as per SOL stage state) and the vertex size output by the 690 * GS thread is 16B. 691 * 692 * If rendering is enabled (as per SOL state) the vertex size must be 693 * programmed as a multiple of 32B units. In other words, the only time 694 * software can program a vertex size with an odd number of 16B units 695 * is when rendering is disabled. 696 * 697 * Note: B=bytes in the above text. 698 * 699 * It doesn't seem worth the extra trouble to optimize the case where the 700 * vertex size is 16B (especially since this would require special-casing 701 * the GEN assembly that writes to the URB). So we just set the vertex 702 * size to a multiple of 32B (2 vec4's) in all cases. 703 * 704 * The maximum output vertex size is 62*16 = 992 bytes (31 hwords). We 705 * budget that as follows: 706 * 707 * 512 bytes for varyings (a varying component is 4 bytes and 708 * gl_MaxGeometryOutputComponents = 128) 709 * 16 bytes overhead for VARYING_SLOT_PSIZ (each varying slot is 16 710 * bytes) 711 * 16 bytes overhead for gl_Position (we allocate it a slot in the VUE 712 * even if it's not used) 713 * 32 bytes overhead for gl_ClipDistance (we allocate it 2 VUE slots 714 * whenever clip planes are enabled, even if the shader doesn't 715 * write to gl_ClipDistance) 716 * 16 bytes overhead since the VUE size must be a multiple of 32 bytes 717 * (see below)--this causes up to 1 VUE slot to be wasted 718 * 400 bytes available for varying packing overhead 719 * 720 * Worst-case varying packing overhead is 3/4 of a varying slot (12 bytes) 721 * per interpolation type, so this is plenty. 722 * 723 */ 724 unsigned output_vertex_size_bytes = prog_data->base.vue_map.num_slots * 16; 725 assert(compiler->devinfo->gen == 6 || 726 output_vertex_size_bytes <= GEN7_MAX_GS_OUTPUT_VERTEX_SIZE_BYTES); 727 prog_data->output_vertex_size_hwords = 728 ALIGN(output_vertex_size_bytes, 32) / 32; 729 730 /* Compute URB entry size. The maximum allowed URB entry size is 32k. 731 * That divides up as follows: 732 * 733 * 64 bytes for the control data header (cut indices or StreamID bits) 734 * 4096 bytes for varyings (a varying component is 4 bytes and 735 * gl_MaxGeometryTotalOutputComponents = 1024) 736 * 4096 bytes overhead for VARYING_SLOT_PSIZ (each varying slot is 16 737 * bytes/vertex and gl_MaxGeometryOutputVertices is 256) 738 * 4096 bytes overhead for gl_Position (we allocate it a slot in the VUE 739 * even if it's not used) 740 * 8192 bytes overhead for gl_ClipDistance (we allocate it 2 VUE slots 741 * whenever clip planes are enabled, even if the shader doesn't 742 * write to gl_ClipDistance) 743 * 4096 bytes overhead since the VUE size must be a multiple of 32 744 * bytes (see above)--this causes up to 1 VUE slot to be wasted 745 * 8128 bytes available for varying packing overhead 746 * 747 * Worst-case varying packing overhead is 3/4 of a varying slot per 748 * interpolation type, which works out to 3072 bytes, so this would allow 749 * us to accommodate 2 interpolation types without any danger of running 750 * out of URB space. 751 * 752 * In practice, the risk of running out of URB space is very small, since 753 * the above figures are all worst-case, and most of them scale with the 754 * number of output vertices. So we'll just calculate the amount of space 755 * we need, and if it's too large, fail to compile. 756 * 757 * The above is for gen7+ where we have a single URB entry that will hold 758 * all the output. In gen6, we will have to allocate URB entries for every 759 * vertex we emit, so our URB entries only need to be large enough to hold 760 * a single vertex. Also, gen6 does not have a control data header. 761 */ 762 unsigned output_size_bytes; 763 if (compiler->devinfo->gen >= 7) { 764 output_size_bytes = 765 prog_data->output_vertex_size_hwords * 32 * shader->info->gs.vertices_out; 766 output_size_bytes += 32 * prog_data->control_data_header_size_hwords; 767 } else { 768 output_size_bytes = prog_data->output_vertex_size_hwords * 32; 769 } 770 771 /* Broadwell stores "Vertex Count" as a full 8 DWord (32 byte) URB output, 772 * which comes before the control header. 773 */ 774 if (compiler->devinfo->gen >= 8) 775 output_size_bytes += 32; 776 777 /* Shaders can technically set max_vertices = 0, at which point we 778 * may have a URB size of 0 bytes. Nothing good can come from that, 779 * so enforce a minimum size. 780 */ 781 if (output_size_bytes == 0) 782 output_size_bytes = 1; 783 784 unsigned max_output_size_bytes = GEN7_MAX_GS_URB_ENTRY_SIZE_BYTES; 785 if (compiler->devinfo->gen == 6) 786 max_output_size_bytes = GEN6_MAX_GS_URB_ENTRY_SIZE_BYTES; 787 if (output_size_bytes > max_output_size_bytes) 788 return NULL; 789 790 791 /* URB entry sizes are stored as a multiple of 64 bytes in gen7+ and 792 * a multiple of 128 bytes in gen6. 793 */ 794 if (compiler->devinfo->gen >= 7) 795 prog_data->base.urb_entry_size = ALIGN(output_size_bytes, 64) / 64; 796 else 797 prog_data->base.urb_entry_size = ALIGN(output_size_bytes, 128) / 128; 798 799 prog_data->output_topology = 800 get_hw_prim_for_gl_prim(shader->info->gs.output_primitive); 801 802 prog_data->vertices_in = shader->info->gs.vertices_in; 803 804 /* GS inputs are read from the VUE 256 bits (2 vec4's) at a time, so we 805 * need to program a URB read length of ceiling(num_slots / 2). 806 */ 807 prog_data->base.urb_read_length = (c.input_vue_map.num_slots + 1) / 2; 808 809 /* Now that prog_data setup is done, we are ready to actually compile the 810 * program. 811 */ 812 if (unlikely(INTEL_DEBUG & DEBUG_GS)) { 813 fprintf(stderr, "GS Input "); 814 brw_print_vue_map(stderr, &c.input_vue_map); 815 fprintf(stderr, "GS Output "); 816 brw_print_vue_map(stderr, &prog_data->base.vue_map); 817 } 818 819 if (is_scalar) { 820 fs_visitor v(compiler, log_data, mem_ctx, &c, prog_data, shader, 821 shader_time_index); 822 if (v.run_gs()) { 823 prog_data->base.dispatch_mode = DISPATCH_MODE_SIMD8; 824 prog_data->base.base.dispatch_grf_start_reg = v.payload.num_regs; 825 826 fs_generator g(compiler, log_data, mem_ctx, &c.key, 827 &prog_data->base.base, v.promoted_constants, 828 false, MESA_SHADER_GEOMETRY); 829 if (unlikely(INTEL_DEBUG & DEBUG_GS)) { 830 const char *label = 831 shader->info->label ? shader->info->label : "unnamed"; 832 char *name = ralloc_asprintf(mem_ctx, "%s geometry shader %s", 833 label, shader->info->name); 834 g.enable_debug(name); 835 } 836 g.generate_code(v.cfg, 8); 837 return g.get_assembly(final_assembly_size); 838 } 839 } 840 841 if (compiler->devinfo->gen >= 7) { 842 /* Compile the geometry shader in DUAL_OBJECT dispatch mode, if we can do 843 * so without spilling. If the GS invocations count > 1, then we can't use 844 * dual object mode. 845 */ 846 if (prog_data->invocations <= 1 && 847 likely(!(INTEL_DEBUG & DEBUG_NO_DUAL_OBJECT_GS))) { 848 prog_data->base.dispatch_mode = DISPATCH_MODE_4X2_DUAL_OBJECT; 849 850 vec4_gs_visitor v(compiler, log_data, &c, prog_data, shader, 851 mem_ctx, true /* no_spills */, shader_time_index); 852 if (v.run()) { 853 return brw_vec4_generate_assembly(compiler, log_data, mem_ctx, 854 shader, &prog_data->base, v.cfg, 855 final_assembly_size); 856 } 857 } 858 } 859 860 /* Either we failed to compile in DUAL_OBJECT mode (probably because it 861 * would have required spilling) or DUAL_OBJECT mode is disabled. So fall 862 * back to DUAL_INSTANCED or SINGLE mode, which consumes fewer registers. 863 * 864 * FIXME: Single dispatch mode requires that the driver can handle 865 * interleaving of input registers, but this is already supported (dual 866 * instance mode has the same requirement). However, to take full advantage 867 * of single dispatch mode to reduce register pressure we would also need to 868 * do interleaved outputs, but currently, the vec4 visitor and generator 869 * classes do not support this, so at the moment register pressure in 870 * single and dual instance modes is the same. 871 * 872 * From the Ivy Bridge PRM, Vol2 Part1 7.2.1.1 "3DSTATE_GS" 873 * "If InstanceCount>1, DUAL_OBJECT mode is invalid. Software will likely 874 * want to use DUAL_INSTANCE mode for higher performance, but SINGLE mode 875 * is also supported. When InstanceCount=1 (one instance per object) software 876 * can decide which dispatch mode to use. DUAL_OBJECT mode would likely be 877 * the best choice for performance, followed by SINGLE mode." 878 * 879 * So SINGLE mode is more performant when invocations == 1 and DUAL_INSTANCE 880 * mode is more performant when invocations > 1. Gen6 only supports 881 * SINGLE mode. 882 */ 883 if (prog_data->invocations <= 1 || compiler->devinfo->gen < 7) 884 prog_data->base.dispatch_mode = DISPATCH_MODE_4X1_SINGLE; 885 else 886 prog_data->base.dispatch_mode = DISPATCH_MODE_4X2_DUAL_INSTANCE; 887 888 vec4_gs_visitor *gs = NULL; 889 const unsigned *ret = NULL; 890 891 if (compiler->devinfo->gen >= 7) 892 gs = new vec4_gs_visitor(compiler, log_data, &c, prog_data, 893 shader, mem_ctx, false /* no_spills */, 894 shader_time_index); 895 else 896 gs = new gen6_gs_visitor(compiler, log_data, &c, prog_data, prog, 897 shader, mem_ctx, false /* no_spills */, 898 shader_time_index); 899 900 if (!gs->run()) { 901 if (error_str) 902 *error_str = ralloc_strdup(mem_ctx, gs->fail_msg); 903 } else { 904 ret = brw_vec4_generate_assembly(compiler, log_data, mem_ctx, shader, 905 &prog_data->base, gs->cfg, 906 final_assembly_size); 907 } 908 909 delete gs; 910 return ret; 911 } 912 913 914 } /* namespace brw */ 915