/* * Copyright © 2010 Intel Corporation * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS * IN THE SOFTWARE. * * Authors: * Eric Anholt * */ #include "brw_fs.h" #include "brw_vec4.h" #include "brw_cfg.h" #include "brw_shader.h" #include "glsl/glsl_types.h" #include "glsl/ir_optimization.h" using namespace brw; /** @file brw_fs_schedule_instructions.cpp * * List scheduling of FS instructions. * * The basic model of the list scheduler is to take a basic block, * compute a DAG of the dependencies (RAW ordering with latency, WAW * ordering with latency, WAR ordering), and make a list of the DAG heads. * Heuristically pick a DAG head, then put all the children that are * now DAG heads into the list of things to schedule. * * The heuristic is the important part. We're trying to be cheap, * since actually computing the optimal scheduling is NP complete. * What we do is track a "current clock". When we schedule a node, we * update the earliest-unblocked clock time of its children, and * increment the clock. Then, when trying to schedule, we just pick * the earliest-unblocked instruction to schedule. * * Note that often there will be many things which could execute * immediately, and there are a range of heuristic options to choose * from in picking among those. */ static bool debug = false; class instruction_scheduler; class schedule_node : public exec_node { public: schedule_node(backend_instruction *inst, instruction_scheduler *sched); void set_latency_gen4(); void set_latency_gen7(bool is_haswell); backend_instruction *inst; schedule_node **children; int *child_latency; int child_count; int parent_count; int child_array_size; int unblocked_time; int latency; /** * Which iteration of pushing groups of children onto the candidates list * this node was a part of. */ unsigned cand_generation; /** * This is the sum of the instruction's latency plus the maximum delay of * its children, or just the issue_time if it's a leaf node. */ int delay; }; void schedule_node::set_latency_gen4() { int chans = 8; int math_latency = 22; switch (inst->opcode) { case SHADER_OPCODE_RCP: this->latency = 1 * chans * math_latency; break; case SHADER_OPCODE_RSQ: this->latency = 2 * chans * math_latency; break; case SHADER_OPCODE_INT_QUOTIENT: case SHADER_OPCODE_SQRT: case SHADER_OPCODE_LOG2: /* full precision log. partial is 2. */ this->latency = 3 * chans * math_latency; break; case SHADER_OPCODE_INT_REMAINDER: case SHADER_OPCODE_EXP2: /* full precision. partial is 3, same throughput. */ this->latency = 4 * chans * math_latency; break; case SHADER_OPCODE_POW: this->latency = 8 * chans * math_latency; break; case SHADER_OPCODE_SIN: case SHADER_OPCODE_COS: /* minimum latency, max is 12 rounds. */ this->latency = 5 * chans * math_latency; break; default: this->latency = 2; break; } } void schedule_node::set_latency_gen7(bool is_haswell) { switch (inst->opcode) { case BRW_OPCODE_MAD: /* 2 cycles * (since the last two src operands are in different register banks): * mad(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g3.1<4,4,1>F.x { align16 WE_normal 1Q }; * * 3 cycles on IVB, 4 on HSW * (since the last two src operands are in the same register bank): * mad(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g2.1<4,4,1>F.x { align16 WE_normal 1Q }; * * 18 cycles on IVB, 16 on HSW * (since the last two src operands are in different register banks): * mad(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g3.1<4,4,1>F.x { align16 WE_normal 1Q }; * mov(8) null g4<4,5,1>F { align16 WE_normal 1Q }; * * 20 cycles on IVB, 18 on HSW * (since the last two src operands are in the same register bank): * mad(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g2.1<4,4,1>F.x { align16 WE_normal 1Q }; * mov(8) null g4<4,4,1>F { align16 WE_normal 1Q }; */ /* Our register allocator doesn't know about register banks, so use the * higher latency. */ latency = is_haswell ? 16 : 18; break; case BRW_OPCODE_LRP: /* 2 cycles * (since the last two src operands are in different register banks): * lrp(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g3.1<4,4,1>F.x { align16 WE_normal 1Q }; * * 3 cycles on IVB, 4 on HSW * (since the last two src operands are in the same register bank): * lrp(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g2.1<4,4,1>F.x { align16 WE_normal 1Q }; * * 16 cycles on IVB, 14 on HSW * (since the last two src operands are in different register banks): * lrp(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g3.1<4,4,1>F.x { align16 WE_normal 1Q }; * mov(8) null g4<4,4,1>F { align16 WE_normal 1Q }; * * 16 cycles * (since the last two src operands are in the same register bank): * lrp(8) g4<1>F g2.2<4,4,1>F.x g2<4,4,1>F.x g2.1<4,4,1>F.x { align16 WE_normal 1Q }; * mov(8) null g4<4,4,1>F { align16 WE_normal 1Q }; */ /* Our register allocator doesn't know about register banks, so use the * higher latency. */ latency = 14; break; case SHADER_OPCODE_RCP: case SHADER_OPCODE_RSQ: case SHADER_OPCODE_SQRT: case SHADER_OPCODE_LOG2: case SHADER_OPCODE_EXP2: case SHADER_OPCODE_SIN: case SHADER_OPCODE_COS: /* 2 cycles: * math inv(8) g4<1>F g2<0,1,0>F null { align1 WE_normal 1Q }; * * 18 cycles: * math inv(8) g4<1>F g2<0,1,0>F null { align1 WE_normal 1Q }; * mov(8) null g4<8,8,1>F { align1 WE_normal 1Q }; * * Same for exp2, log2, rsq, sqrt, sin, cos. */ latency = is_haswell ? 14 : 16; break; case SHADER_OPCODE_POW: /* 2 cycles: * math pow(8) g4<1>F g2<0,1,0>F g2.1<0,1,0>F { align1 WE_normal 1Q }; * * 26 cycles: * math pow(8) g4<1>F g2<0,1,0>F g2.1<0,1,0>F { align1 WE_normal 1Q }; * mov(8) null g4<8,8,1>F { align1 WE_normal 1Q }; */ latency = is_haswell ? 22 : 24; break; case SHADER_OPCODE_TEX: case SHADER_OPCODE_TXD: case SHADER_OPCODE_TXF: case SHADER_OPCODE_TXL: /* 18 cycles: * mov(8) g115<1>F 0F { align1 WE_normal 1Q }; * mov(8) g114<1>F 0F { align1 WE_normal 1Q }; * send(8) g4<1>UW g114<8,8,1>F * sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q }; * * 697 +/-49 cycles (min 610, n=26): * mov(8) g115<1>F 0F { align1 WE_normal 1Q }; * mov(8) g114<1>F 0F { align1 WE_normal 1Q }; * send(8) g4<1>UW g114<8,8,1>F * sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q }; * mov(8) null g4<8,8,1>F { align1 WE_normal 1Q }; * * So the latency on our first texture load of the batchbuffer takes * ~700 cycles, since the caches are cold at that point. * * 840 +/- 92 cycles (min 720, n=25): * mov(8) g115<1>F 0F { align1 WE_normal 1Q }; * mov(8) g114<1>F 0F { align1 WE_normal 1Q }; * send(8) g4<1>UW g114<8,8,1>F * sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q }; * mov(8) null g4<8,8,1>F { align1 WE_normal 1Q }; * send(8) g4<1>UW g114<8,8,1>F * sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q }; * mov(8) null g4<8,8,1>F { align1 WE_normal 1Q }; * * On the second load, it takes just an extra ~140 cycles, and after * accounting for the 14 cycles of the MOV's latency, that makes ~130. * * 683 +/- 49 cycles (min = 602, n=47): * mov(8) g115<1>F 0F { align1 WE_normal 1Q }; * mov(8) g114<1>F 0F { align1 WE_normal 1Q }; * send(8) g4<1>UW g114<8,8,1>F * sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q }; * send(8) g50<1>UW g114<8,8,1>F * sampler (10, 0, 0, 1) mlen 2 rlen 4 { align1 WE_normal 1Q }; * mov(8) null g4<8,8,1>F { align1 WE_normal 1Q }; * * The unit appears to be pipelined, since this matches up with the * cache-cold case, despite there being two loads here. If you replace * the g4 in the MOV to null with g50, it's still 693 +/- 52 (n=39). * * So, take some number between the cache-hot 140 cycles and the * cache-cold 700 cycles. No particular tuning was done on this. * * I haven't done significant testing of the non-TEX opcodes. TXL at * least looked about the same as TEX. */ latency = 200; break; case SHADER_OPCODE_TXS: /* Testing textureSize(sampler2D, 0), one load was 420 +/- 41 * cycles (n=15): * mov(8) g114<1>UD 0D { align1 WE_normal 1Q }; * send(8) g6<1>UW g114<8,8,1>F * sampler (10, 0, 10, 1) mlen 1 rlen 4 { align1 WE_normal 1Q }; * mov(16) g6<1>F g6<8,8,1>D { align1 WE_normal 1Q }; * * * Two loads was 535 +/- 30 cycles (n=19): * mov(16) g114<1>UD 0D { align1 WE_normal 1H }; * send(16) g6<1>UW g114<8,8,1>F * sampler (10, 0, 10, 2) mlen 2 rlen 8 { align1 WE_normal 1H }; * mov(16) g114<1>UD 0D { align1 WE_normal 1H }; * mov(16) g6<1>F g6<8,8,1>D { align1 WE_normal 1H }; * send(16) g8<1>UW g114<8,8,1>F * sampler (10, 0, 10, 2) mlen 2 rlen 8 { align1 WE_normal 1H }; * mov(16) g8<1>F g8<8,8,1>D { align1 WE_normal 1H }; * add(16) g6<1>F g6<8,8,1>F g8<8,8,1>F { align1 WE_normal 1H }; * * Since the only caches that should matter are just the * instruction/state cache containing the surface state, assume that we * always have hot caches. */ latency = 100; break; case FS_OPCODE_VARYING_PULL_CONSTANT_LOAD: case FS_OPCODE_UNIFORM_PULL_CONSTANT_LOAD: case VS_OPCODE_PULL_CONSTANT_LOAD: /* testing using varying-index pull constants: * * 16 cycles: * mov(8) g4<1>D g2.1<0,1,0>F { align1 WE_normal 1Q }; * send(8) g4<1>F g4<8,8,1>D * data (9, 2, 3) mlen 1 rlen 1 { align1 WE_normal 1Q }; * * ~480 cycles: * mov(8) g4<1>D g2.1<0,1,0>F { align1 WE_normal 1Q }; * send(8) g4<1>F g4<8,8,1>D * data (9, 2, 3) mlen 1 rlen 1 { align1 WE_normal 1Q }; * mov(8) null g4<8,8,1>F { align1 WE_normal 1Q }; * * ~620 cycles: * mov(8) g4<1>D g2.1<0,1,0>F { align1 WE_normal 1Q }; * send(8) g4<1>F g4<8,8,1>D * data (9, 2, 3) mlen 1 rlen 1 { align1 WE_normal 1Q }; * mov(8) null g4<8,8,1>F { align1 WE_normal 1Q }; * send(8) g4<1>F g4<8,8,1>D * data (9, 2, 3) mlen 1 rlen 1 { align1 WE_normal 1Q }; * mov(8) null g4<8,8,1>F { align1 WE_normal 1Q }; * * So, if it's cache-hot, it's about 140. If it's cache cold, it's * about 460. We expect to mostly be cache hot, so pick something more * in that direction. */ latency = 200; break; case SHADER_OPCODE_GEN7_SCRATCH_READ: /* Testing a load from offset 0, that had been previously written: * * send(8) g114<1>UW g0<8,8,1>F data (0, 0, 0) mlen 1 rlen 1 { align1 WE_normal 1Q }; * mov(8) null g114<8,8,1>F { align1 WE_normal 1Q }; * * The cycles spent seemed to be grouped around 40-50 (as low as 38), * then around 140. Presumably this is cache hit vs miss. */ latency = 50; break; case SHADER_OPCODE_UNTYPED_ATOMIC: /* Test code: * mov(8) g112<1>ud 0x00000000ud { align1 WE_all 1Q }; * mov(1) g112.7<1>ud g1.7<0,1,0>ud { align1 WE_all }; * mov(8) g113<1>ud 0x00000000ud { align1 WE_normal 1Q }; * send(8) g4<1>ud g112<8,8,1>ud * data (38, 5, 6) mlen 2 rlen 1 { align1 WE_normal 1Q }; * * Running it 100 times as fragment shader on a 128x128 quad * gives an average latency of 13867 cycles per atomic op, * standard deviation 3%. Note that this is a rather * pessimistic estimate, the actual latency in cases with few * collisions between threads and favorable pipelining has been * seen to be reduced by a factor of 100. */ latency = 14000; break; case SHADER_OPCODE_UNTYPED_SURFACE_READ: /* Test code: * mov(8) g112<1>UD 0x00000000UD { align1 WE_all 1Q }; * mov(1) g112.7<1>UD g1.7<0,1,0>UD { align1 WE_all }; * mov(8) g113<1>UD 0x00000000UD { align1 WE_normal 1Q }; * send(8) g4<1>UD g112<8,8,1>UD * data (38, 6, 5) mlen 2 rlen 1 { align1 WE_normal 1Q }; * . * . [repeats 8 times] * . * mov(8) g112<1>UD 0x00000000UD { align1 WE_all 1Q }; * mov(1) g112.7<1>UD g1.7<0,1,0>UD { align1 WE_all }; * mov(8) g113<1>UD 0x00000000UD { align1 WE_normal 1Q }; * send(8) g4<1>UD g112<8,8,1>UD * data (38, 6, 5) mlen 2 rlen 1 { align1 WE_normal 1Q }; * * Running it 100 times as fragment shader on a 128x128 quad * gives an average latency of 583 cycles per surface read, * standard deviation 0.9%. */ latency = is_haswell ? 300 : 600; break; default: /* 2 cycles: * mul(8) g4<1>F g2<0,1,0>F 0.5F { align1 WE_normal 1Q }; * * 16 cycles: * mul(8) g4<1>F g2<0,1,0>F 0.5F { align1 WE_normal 1Q }; * mov(8) null g4<8,8,1>F { align1 WE_normal 1Q }; */ latency = 14; break; } } class instruction_scheduler { public: instruction_scheduler(backend_visitor *v, int grf_count, instruction_scheduler_mode mode) { this->bv = v; this->mem_ctx = ralloc_context(NULL); this->grf_count = grf_count; this->instructions.make_empty(); this->instructions_to_schedule = 0; this->post_reg_alloc = (mode == SCHEDULE_POST); this->mode = mode; this->time = 0; if (!post_reg_alloc) { this->remaining_grf_uses = rzalloc_array(mem_ctx, int, grf_count); this->grf_active = rzalloc_array(mem_ctx, bool, grf_count); } else { this->remaining_grf_uses = NULL; this->grf_active = NULL; } } ~instruction_scheduler() { ralloc_free(this->mem_ctx); } void add_barrier_deps(schedule_node *n); void add_dep(schedule_node *before, schedule_node *after, int latency); void add_dep(schedule_node *before, schedule_node *after); void run(cfg_t *cfg); void add_insts_from_block(bblock_t *block); void compute_delay(schedule_node *node); virtual void calculate_deps() = 0; virtual schedule_node *choose_instruction_to_schedule() = 0; /** * Returns how many cycles it takes the instruction to issue. * * Instructions in gen hardware are handled one simd4 vector at a time, * with 1 cycle per vector dispatched. Thus SIMD8 pixel shaders take 2 * cycles to dispatch and SIMD16 (compressed) instructions take 4. */ virtual int issue_time(backend_instruction *inst) = 0; virtual void count_remaining_grf_uses(backend_instruction *inst) = 0; virtual void update_register_pressure(backend_instruction *inst) = 0; virtual int get_register_pressure_benefit(backend_instruction *inst) = 0; void schedule_instructions(bblock_t *block); void *mem_ctx; bool post_reg_alloc; int instructions_to_schedule; int grf_count; int time; exec_list instructions; backend_visitor *bv; instruction_scheduler_mode mode; /** * Number of instructions left to schedule that reference each vgrf. * * Used so that we can prefer scheduling instructions that will end the * live intervals of multiple variables, to reduce register pressure. */ int *remaining_grf_uses; /** * Tracks whether each VGRF has had an instruction scheduled that uses it. * * This is used to estimate whether scheduling a new instruction will * increase register pressure. */ bool *grf_active; }; class fs_instruction_scheduler : public instruction_scheduler { public: fs_instruction_scheduler(fs_visitor *v, int grf_count, instruction_scheduler_mode mode); void calculate_deps(); bool is_compressed(fs_inst *inst); schedule_node *choose_instruction_to_schedule(); int issue_time(backend_instruction *inst); fs_visitor *v; void count_remaining_grf_uses(backend_instruction *inst); void update_register_pressure(backend_instruction *inst); int get_register_pressure_benefit(backend_instruction *inst); }; fs_instruction_scheduler::fs_instruction_scheduler(fs_visitor *v, int grf_count, instruction_scheduler_mode mode) : instruction_scheduler(v, grf_count, mode), v(v) { } void fs_instruction_scheduler::count_remaining_grf_uses(backend_instruction *be) { fs_inst *inst = (fs_inst *)be; if (!remaining_grf_uses) return; if (inst->dst.file == GRF) remaining_grf_uses[inst->dst.reg]++; for (int i = 0; i < inst->sources; i++) { if (inst->src[i].file != GRF) continue; remaining_grf_uses[inst->src[i].reg]++; } } void fs_instruction_scheduler::update_register_pressure(backend_instruction *be) { fs_inst *inst = (fs_inst *)be; if (!remaining_grf_uses) return; if (inst->dst.file == GRF) { remaining_grf_uses[inst->dst.reg]--; grf_active[inst->dst.reg] = true; } for (int i = 0; i < inst->sources; i++) { if (inst->src[i].file == GRF) { remaining_grf_uses[inst->src[i].reg]--; grf_active[inst->src[i].reg] = true; } } } int fs_instruction_scheduler::get_register_pressure_benefit(backend_instruction *be) { fs_inst *inst = (fs_inst *)be; int benefit = 0; if (inst->dst.file == GRF) { if (remaining_grf_uses[inst->dst.reg] == 1) benefit += v->virtual_grf_sizes[inst->dst.reg]; if (!grf_active[inst->dst.reg]) benefit -= v->virtual_grf_sizes[inst->dst.reg]; } for (int i = 0; i < inst->sources; i++) { if (inst->src[i].file != GRF) continue; if (remaining_grf_uses[inst->src[i].reg] == 1) benefit += v->virtual_grf_sizes[inst->src[i].reg]; if (!grf_active[inst->src[i].reg]) benefit -= v->virtual_grf_sizes[inst->src[i].reg]; } return benefit; } class vec4_instruction_scheduler : public instruction_scheduler { public: vec4_instruction_scheduler(vec4_visitor *v, int grf_count); void calculate_deps(); schedule_node *choose_instruction_to_schedule(); int issue_time(backend_instruction *inst); vec4_visitor *v; void count_remaining_grf_uses(backend_instruction *inst); void update_register_pressure(backend_instruction *inst); int get_register_pressure_benefit(backend_instruction *inst); }; vec4_instruction_scheduler::vec4_instruction_scheduler(vec4_visitor *v, int grf_count) : instruction_scheduler(v, grf_count, SCHEDULE_POST), v(v) { } void vec4_instruction_scheduler::count_remaining_grf_uses(backend_instruction *be) { } void vec4_instruction_scheduler::update_register_pressure(backend_instruction *be) { } int vec4_instruction_scheduler::get_register_pressure_benefit(backend_instruction *be) { return 0; } schedule_node::schedule_node(backend_instruction *inst, instruction_scheduler *sched) { struct brw_context *brw = sched->bv->brw; this->inst = inst; this->child_array_size = 0; this->children = NULL; this->child_latency = NULL; this->child_count = 0; this->parent_count = 0; this->unblocked_time = 0; this->cand_generation = 0; this->delay = 0; /* We can't measure Gen6 timings directly but expect them to be much * closer to Gen7 than Gen4. */ if (!sched->post_reg_alloc) this->latency = 1; else if (brw->gen >= 6) set_latency_gen7(brw->is_haswell); else set_latency_gen4(); } void instruction_scheduler::add_insts_from_block(bblock_t *block) { /* Removing the last instruction from a basic block removes the block as * well, so put a NOP at the end to keep it alive. */ if (!block->end()->is_control_flow()) { backend_instruction *nop = new(mem_ctx) backend_instruction(); nop->opcode = BRW_OPCODE_NOP; block->end()->insert_after(block, nop); } foreach_inst_in_block_safe(backend_instruction, inst, block) { if (inst->opcode == BRW_OPCODE_NOP || inst->is_control_flow()) continue; schedule_node *n = new(mem_ctx) schedule_node(inst, this); this->instructions_to_schedule++; inst->remove(block); instructions.push_tail(n); } } /** Recursive computation of the delay member of a node. */ void instruction_scheduler::compute_delay(schedule_node *n) { if (!n->child_count) { n->delay = issue_time(n->inst); } else { for (int i = 0; i < n->child_count; i++) { if (!n->children[i]->delay) compute_delay(n->children[i]); n->delay = MAX2(n->delay, n->latency + n->children[i]->delay); } } } /** * Add a dependency between two instruction nodes. * * The @after node will be scheduled after @before. We will try to * schedule it @latency cycles after @before, but no guarantees there. */ void instruction_scheduler::add_dep(schedule_node *before, schedule_node *after, int latency) { if (!before || !after) return; assert(before != after); for (int i = 0; i < before->child_count; i++) { if (before->children[i] == after) { before->child_latency[i] = MAX2(before->child_latency[i], latency); return; } } if (before->child_array_size <= before->child_count) { if (before->child_array_size < 16) before->child_array_size = 16; else before->child_array_size *= 2; before->children = reralloc(mem_ctx, before->children, schedule_node *, before->child_array_size); before->child_latency = reralloc(mem_ctx, before->child_latency, int, before->child_array_size); } before->children[before->child_count] = after; before->child_latency[before->child_count] = latency; before->child_count++; after->parent_count++; } void instruction_scheduler::add_dep(schedule_node *before, schedule_node *after) { if (!before) return; add_dep(before, after, before->latency); } /** * Sometimes we really want this node to execute after everything that * was before it and before everything that followed it. This adds * the deps to do so. */ void instruction_scheduler::add_barrier_deps(schedule_node *n) { schedule_node *prev = (schedule_node *)n->prev; schedule_node *next = (schedule_node *)n->next; if (prev) { while (!prev->is_head_sentinel()) { add_dep(prev, n, 0); prev = (schedule_node *)prev->prev; } } if (next) { while (!next->is_tail_sentinel()) { add_dep(n, next, 0); next = (schedule_node *)next->next; } } } /* instruction scheduling needs to be aware of when an MRF write * actually writes 2 MRFs. */ bool fs_instruction_scheduler::is_compressed(fs_inst *inst) { return inst->exec_size == 16; } void fs_instruction_scheduler::calculate_deps() { /* Pre-register-allocation, this tracks the last write per VGRF offset. * After register allocation, reg_offsets are gone and we track individual * GRF registers. */ schedule_node *last_grf_write[grf_count * 16]; schedule_node *last_mrf_write[BRW_MAX_MRF]; schedule_node *last_conditional_mod[2] = { NULL, NULL }; schedule_node *last_accumulator_write = NULL; /* Fixed HW registers are assumed to be separate from the virtual * GRFs, so they can be tracked separately. We don't really write * to fixed GRFs much, so don't bother tracking them on a more * granular level. */ schedule_node *last_fixed_grf_write = NULL; int reg_width = v->dispatch_width / 8; /* The last instruction always needs to still be the last * instruction. Either it's flow control (IF, ELSE, ENDIF, DO, * WHILE) and scheduling other things after it would disturb the * basic block, or it's FB_WRITE and we should do a better job at * dead code elimination anyway. */ schedule_node *last = (schedule_node *)instructions.get_tail(); add_barrier_deps(last); memset(last_grf_write, 0, sizeof(last_grf_write)); memset(last_mrf_write, 0, sizeof(last_mrf_write)); /* top-to-bottom dependencies: RAW and WAW. */ foreach_in_list(schedule_node, n, &instructions) { fs_inst *inst = (fs_inst *)n->inst; if (inst->opcode == FS_OPCODE_PLACEHOLDER_HALT || inst->has_side_effects()) add_barrier_deps(n); /* read-after-write deps. */ for (int i = 0; i < inst->sources; i++) { if (inst->src[i].file == GRF) { if (post_reg_alloc) { for (int r = 0; r < inst->regs_read(v, i); r++) add_dep(last_grf_write[inst->src[i].reg + r], n); } else { for (int r = 0; r < inst->regs_read(v, i); r++) { add_dep(last_grf_write[inst->src[i].reg * 16 + inst->src[i].reg_offset + r], n); } } } else if (inst->src[i].file == HW_REG && (inst->src[i].fixed_hw_reg.file == BRW_GENERAL_REGISTER_FILE)) { if (post_reg_alloc) { int size = reg_width; if (inst->src[i].fixed_hw_reg.vstride == BRW_VERTICAL_STRIDE_0) size = 1; for (int r = 0; r < size; r++) add_dep(last_grf_write[inst->src[i].fixed_hw_reg.nr + r], n); } else { add_dep(last_fixed_grf_write, n); } } else if (inst->src[i].is_accumulator()) { add_dep(last_accumulator_write, n); } else if (inst->src[i].file != BAD_FILE && inst->src[i].file != IMM && inst->src[i].file != UNIFORM && (inst->src[i].file != HW_REG || inst->src[i].fixed_hw_reg.file != IMM)) { assert(inst->src[i].file != MRF); add_barrier_deps(n); } } if (inst->base_mrf != -1) { for (int i = 0; i < inst->mlen; i++) { /* It looks like the MRF regs are released in the send * instruction once it's sent, not when the result comes * back. */ add_dep(last_mrf_write[inst->base_mrf + i], n); } } if (inst->reads_flag()) { add_dep(last_conditional_mod[inst->flag_subreg], n); } if (inst->reads_accumulator_implicitly()) { add_dep(last_accumulator_write, n); } /* write-after-write deps. */ if (inst->dst.file == GRF) { if (post_reg_alloc) { for (int r = 0; r < inst->regs_written; r++) { add_dep(last_grf_write[inst->dst.reg + r], n); last_grf_write[inst->dst.reg + r] = n; } } else { for (int r = 0; r < inst->regs_written; r++) { add_dep(last_grf_write[inst->dst.reg * 16 + inst->dst.reg_offset + r], n); last_grf_write[inst->dst.reg * 16 + inst->dst.reg_offset + r] = n; } } } else if (inst->dst.file == MRF) { int reg = inst->dst.reg & ~BRW_MRF_COMPR4; add_dep(last_mrf_write[reg], n); last_mrf_write[reg] = n; if (is_compressed(inst)) { if (inst->dst.reg & BRW_MRF_COMPR4) reg += 4; else reg++; add_dep(last_mrf_write[reg], n); last_mrf_write[reg] = n; } } else if (inst->dst.file == HW_REG && inst->dst.fixed_hw_reg.file == BRW_GENERAL_REGISTER_FILE) { if (post_reg_alloc) { for (int r = 0; r < reg_width; r++) last_grf_write[inst->dst.fixed_hw_reg.nr + r] = n; } else { last_fixed_grf_write = n; } } else if (inst->dst.is_accumulator()) { add_dep(last_accumulator_write, n); last_accumulator_write = n; } else if (inst->dst.file != BAD_FILE) { add_barrier_deps(n); } if (inst->mlen > 0 && inst->base_mrf != -1) { for (int i = 0; i < v->implied_mrf_writes(inst); i++) { add_dep(last_mrf_write[inst->base_mrf + i], n); last_mrf_write[inst->base_mrf + i] = n; } } if (inst->writes_flag()) { add_dep(last_conditional_mod[inst->flag_subreg], n, 0); last_conditional_mod[inst->flag_subreg] = n; } if (inst->writes_accumulator_implicitly(v->brw) && !inst->dst.is_accumulator()) { add_dep(last_accumulator_write, n); last_accumulator_write = n; } } /* bottom-to-top dependencies: WAR */ memset(last_grf_write, 0, sizeof(last_grf_write)); memset(last_mrf_write, 0, sizeof(last_mrf_write)); memset(last_conditional_mod, 0, sizeof(last_conditional_mod)); last_accumulator_write = NULL; last_fixed_grf_write = NULL; exec_node *node; exec_node *prev; for (node = instructions.get_tail(), prev = node->prev; !node->is_head_sentinel(); node = prev, prev = node->prev) { schedule_node *n = (schedule_node *)node; fs_inst *inst = (fs_inst *)n->inst; /* write-after-read deps. */ for (int i = 0; i < inst->sources; i++) { if (inst->src[i].file == GRF) { if (post_reg_alloc) { for (int r = 0; r < inst->regs_read(v, i); r++) add_dep(n, last_grf_write[inst->src[i].reg + r]); } else { for (int r = 0; r < inst->regs_read(v, i); r++) { add_dep(n, last_grf_write[inst->src[i].reg * 16 + inst->src[i].reg_offset + r]); } } } else if (inst->src[i].file == HW_REG && (inst->src[i].fixed_hw_reg.file == BRW_GENERAL_REGISTER_FILE)) { if (post_reg_alloc) { int size = reg_width; if (inst->src[i].fixed_hw_reg.vstride == BRW_VERTICAL_STRIDE_0) size = 1; for (int r = 0; r < size; r++) add_dep(n, last_grf_write[inst->src[i].fixed_hw_reg.nr + r]); } else { add_dep(n, last_fixed_grf_write); } } else if (inst->src[i].is_accumulator()) { add_dep(n, last_accumulator_write); } else if (inst->src[i].file != BAD_FILE && inst->src[i].file != IMM && inst->src[i].file != UNIFORM && (inst->src[i].file != HW_REG || inst->src[i].fixed_hw_reg.file != IMM)) { assert(inst->src[i].file != MRF); add_barrier_deps(n); } } if (inst->base_mrf != -1) { for (int i = 0; i < inst->mlen; i++) { /* It looks like the MRF regs are released in the send * instruction once it's sent, not when the result comes * back. */ add_dep(n, last_mrf_write[inst->base_mrf + i], 2); } } if (inst->reads_flag()) { add_dep(n, last_conditional_mod[inst->flag_subreg]); } if (inst->reads_accumulator_implicitly()) { add_dep(n, last_accumulator_write); } /* Update the things this instruction wrote, so earlier reads * can mark this as WAR dependency. */ if (inst->dst.file == GRF) { if (post_reg_alloc) { for (int r = 0; r < inst->regs_written; r++) last_grf_write[inst->dst.reg + r] = n; } else { for (int r = 0; r < inst->regs_written; r++) { last_grf_write[inst->dst.reg * 16 + inst->dst.reg_offset + r] = n; } } } else if (inst->dst.file == MRF) { int reg = inst->dst.reg & ~BRW_MRF_COMPR4; last_mrf_write[reg] = n; if (is_compressed(inst)) { if (inst->dst.reg & BRW_MRF_COMPR4) reg += 4; else reg++; last_mrf_write[reg] = n; } } else if (inst->dst.file == HW_REG && inst->dst.fixed_hw_reg.file == BRW_GENERAL_REGISTER_FILE) { if (post_reg_alloc) { for (int r = 0; r < reg_width; r++) last_grf_write[inst->dst.fixed_hw_reg.nr + r] = n; } else { last_fixed_grf_write = n; } } else if (inst->dst.is_accumulator()) { last_accumulator_write = n; } else if (inst->dst.file != BAD_FILE) { add_barrier_deps(n); } if (inst->mlen > 0 && inst->base_mrf != -1) { for (int i = 0; i < v->implied_mrf_writes(inst); i++) { last_mrf_write[inst->base_mrf + i] = n; } } if (inst->writes_flag()) { last_conditional_mod[inst->flag_subreg] = n; } if (inst->writes_accumulator_implicitly(v->brw)) { last_accumulator_write = n; } } } void vec4_instruction_scheduler::calculate_deps() { schedule_node *last_grf_write[grf_count]; schedule_node *last_mrf_write[BRW_MAX_MRF]; schedule_node *last_conditional_mod = NULL; schedule_node *last_accumulator_write = NULL; /* Fixed HW registers are assumed to be separate from the virtual * GRFs, so they can be tracked separately. We don't really write * to fixed GRFs much, so don't bother tracking them on a more * granular level. */ schedule_node *last_fixed_grf_write = NULL; /* The last instruction always needs to still be the last instruction. * Either it's flow control (IF, ELSE, ENDIF, DO, WHILE) and scheduling * other things after it would disturb the basic block, or it's the EOT * URB_WRITE and we should do a better job at dead code eliminating * anything that could have been scheduled after it. */ schedule_node *last = (schedule_node *)instructions.get_tail(); add_barrier_deps(last); memset(last_grf_write, 0, sizeof(last_grf_write)); memset(last_mrf_write, 0, sizeof(last_mrf_write)); /* top-to-bottom dependencies: RAW and WAW. */ foreach_in_list(schedule_node, n, &instructions) { vec4_instruction *inst = (vec4_instruction *)n->inst; if (inst->has_side_effects()) add_barrier_deps(n); /* read-after-write deps. */ for (int i = 0; i < 3; i++) { if (inst->src[i].file == GRF) { add_dep(last_grf_write[inst->src[i].reg], n); } else if (inst->src[i].file == HW_REG && (inst->src[i].fixed_hw_reg.file == BRW_GENERAL_REGISTER_FILE)) { add_dep(last_fixed_grf_write, n); } else if (inst->src[i].is_accumulator()) { assert(last_accumulator_write); add_dep(last_accumulator_write, n); } else if (inst->src[i].file != BAD_FILE && inst->src[i].file != IMM && inst->src[i].file != UNIFORM && (inst->src[i].file != HW_REG || inst->src[i].fixed_hw_reg.file != IMM)) { /* No reads from MRF, and ATTR is already translated away */ assert(inst->src[i].file != MRF && inst->src[i].file != ATTR); add_barrier_deps(n); } } for (int i = 0; i < inst->mlen; i++) { /* It looks like the MRF regs are released in the send * instruction once it's sent, not when the result comes * back. */ add_dep(last_mrf_write[inst->base_mrf + i], n); } if (inst->reads_flag()) { assert(last_conditional_mod); add_dep(last_conditional_mod, n); } if (inst->reads_accumulator_implicitly()) { assert(last_accumulator_write); add_dep(last_accumulator_write, n); } /* write-after-write deps. */ if (inst->dst.file == GRF) { add_dep(last_grf_write[inst->dst.reg], n); last_grf_write[inst->dst.reg] = n; } else if (inst->dst.file == MRF) { add_dep(last_mrf_write[inst->dst.reg], n); last_mrf_write[inst->dst.reg] = n; } else if (inst->dst.file == HW_REG && inst->dst.fixed_hw_reg.file == BRW_GENERAL_REGISTER_FILE) { last_fixed_grf_write = n; } else if (inst->dst.is_accumulator()) { add_dep(last_accumulator_write, n); last_accumulator_write = n; } else if (inst->dst.file != BAD_FILE) { add_barrier_deps(n); } if (inst->mlen > 0) { for (int i = 0; i < v->implied_mrf_writes(inst); i++) { add_dep(last_mrf_write[inst->base_mrf + i], n); last_mrf_write[inst->base_mrf + i] = n; } } if (inst->writes_flag()) { add_dep(last_conditional_mod, n, 0); last_conditional_mod = n; } if (inst->writes_accumulator_implicitly(v->brw) && !inst->dst.is_accumulator()) { add_dep(last_accumulator_write, n); last_accumulator_write = n; } } /* bottom-to-top dependencies: WAR */ memset(last_grf_write, 0, sizeof(last_grf_write)); memset(last_mrf_write, 0, sizeof(last_mrf_write)); last_conditional_mod = NULL; last_accumulator_write = NULL; last_fixed_grf_write = NULL; exec_node *node; exec_node *prev; for (node = instructions.get_tail(), prev = node->prev; !node->is_head_sentinel(); node = prev, prev = node->prev) { schedule_node *n = (schedule_node *)node; vec4_instruction *inst = (vec4_instruction *)n->inst; /* write-after-read deps. */ for (int i = 0; i < 3; i++) { if (inst->src[i].file == GRF) { add_dep(n, last_grf_write[inst->src[i].reg]); } else if (inst->src[i].file == HW_REG && (inst->src[i].fixed_hw_reg.file == BRW_GENERAL_REGISTER_FILE)) { add_dep(n, last_fixed_grf_write); } else if (inst->src[i].is_accumulator()) { add_dep(n, last_accumulator_write); } else if (inst->src[i].file != BAD_FILE && inst->src[i].file != IMM && inst->src[i].file != UNIFORM && (inst->src[i].file != HW_REG || inst->src[i].fixed_hw_reg.file != IMM)) { assert(inst->src[i].file != MRF && inst->src[i].file != ATTR); add_barrier_deps(n); } } for (int i = 0; i < inst->mlen; i++) { /* It looks like the MRF regs are released in the send * instruction once it's sent, not when the result comes * back. */ add_dep(n, last_mrf_write[inst->base_mrf + i], 2); } if (inst->reads_flag()) { add_dep(n, last_conditional_mod); } if (inst->reads_accumulator_implicitly()) { add_dep(n, last_accumulator_write); } /* Update the things this instruction wrote, so earlier reads * can mark this as WAR dependency. */ if (inst->dst.file == GRF) { last_grf_write[inst->dst.reg] = n; } else if (inst->dst.file == MRF) { last_mrf_write[inst->dst.reg] = n; } else if (inst->dst.file == HW_REG && inst->dst.fixed_hw_reg.file == BRW_GENERAL_REGISTER_FILE) { last_fixed_grf_write = n; } else if (inst->dst.is_accumulator()) { last_accumulator_write = n; } else if (inst->dst.file != BAD_FILE) { add_barrier_deps(n); } if (inst->mlen > 0) { for (int i = 0; i < v->implied_mrf_writes(inst); i++) { last_mrf_write[inst->base_mrf + i] = n; } } if (inst->writes_flag()) { last_conditional_mod = n; } if (inst->writes_accumulator_implicitly(v->brw)) { last_accumulator_write = n; } } } schedule_node * fs_instruction_scheduler::choose_instruction_to_schedule() { struct brw_context *brw = v->brw; schedule_node *chosen = NULL; if (mode == SCHEDULE_PRE || mode == SCHEDULE_POST) { int chosen_time = 0; /* Of the instructions ready to execute or the closest to * being ready, choose the oldest one. */ foreach_in_list(schedule_node, n, &instructions) { if (!chosen || n->unblocked_time < chosen_time) { chosen = n; chosen_time = n->unblocked_time; } } } else { /* Before register allocation, we don't care about the latencies of * instructions. All we care about is reducing live intervals of * variables so that we can avoid register spilling, or get SIMD16 * shaders which naturally do a better job of hiding instruction * latency. */ foreach_in_list(schedule_node, n, &instructions) { fs_inst *inst = (fs_inst *)n->inst; if (!chosen) { chosen = n; continue; } /* Most important: If we can definitely reduce register pressure, do * so immediately. */ int register_pressure_benefit = get_register_pressure_benefit(n->inst); int chosen_register_pressure_benefit = get_register_pressure_benefit(chosen->inst); if (register_pressure_benefit > 0 && register_pressure_benefit > chosen_register_pressure_benefit) { chosen = n; continue; } else if (chosen_register_pressure_benefit > 0 && (register_pressure_benefit < chosen_register_pressure_benefit)) { continue; } if (mode == SCHEDULE_PRE_LIFO) { /* Prefer instructions that recently became available for * scheduling. These are the things that are most likely to * (eventually) make a variable dead and reduce register pressure. * Typical register pressure estimates don't work for us because * most of our pressure comes from texturing, where no single * instruction to schedule will make a vec4 value dead. */ if (n->cand_generation > chosen->cand_generation) { chosen = n; continue; } else if (n->cand_generation < chosen->cand_generation) { continue; } /* On MRF-using chips, prefer non-SEND instructions. If we don't * do this, then because we prefer instructions that just became * candidates, we'll end up in a pattern of scheduling a SEND, * then the MRFs for the next SEND, then the next SEND, then the * MRFs, etc., without ever consuming the results of a send. */ if (brw->gen < 7) { fs_inst *chosen_inst = (fs_inst *)chosen->inst; /* We use regs_written > 1 as our test for the kind of send * instruction to avoid -- only sends generate many regs, and a * single-result send is probably actually reducing register * pressure. */ if (inst->regs_written <= inst->dst.width / 8 && chosen_inst->regs_written > chosen_inst->dst.width / 8) { chosen = n; continue; } else if (inst->regs_written > chosen_inst->regs_written) { continue; } } } /* For instructions pushed on the cands list at the same time, prefer * the one with the highest delay to the end of the program. This is * most likely to have its values able to be consumed first (such as * for a large tree of lowered ubo loads, which appear reversed in * the instruction stream with respect to when they can be consumed). */ if (n->delay > chosen->delay) { chosen = n; continue; } else if (n->delay < chosen->delay) { continue; } /* If all other metrics are equal, we prefer the first instruction in * the list (program execution). */ } } return chosen; } schedule_node * vec4_instruction_scheduler::choose_instruction_to_schedule() { schedule_node *chosen = NULL; int chosen_time = 0; /* Of the instructions ready to execute or the closest to being ready, * choose the oldest one. */ foreach_in_list(schedule_node, n, &instructions) { if (!chosen || n->unblocked_time < chosen_time) { chosen = n; chosen_time = n->unblocked_time; } } return chosen; } int fs_instruction_scheduler::issue_time(backend_instruction *inst) { if (is_compressed((fs_inst *)inst)) return 4; else return 2; } int vec4_instruction_scheduler::issue_time(backend_instruction *inst) { /* We always execute as two vec4s in parallel. */ return 2; } void instruction_scheduler::schedule_instructions(bblock_t *block) { struct brw_context *brw = bv->brw; backend_instruction *inst = block->end(); time = 0; /* Remove non-DAG heads from the list. */ foreach_in_list_safe(schedule_node, n, &instructions) { if (n->parent_count != 0) n->remove(); } unsigned cand_generation = 1; while (!instructions.is_empty()) { schedule_node *chosen = choose_instruction_to_schedule(); /* Schedule this instruction. */ assert(chosen); chosen->remove(); inst->insert_before(block, chosen->inst); instructions_to_schedule--; update_register_pressure(chosen->inst); /* Update the clock for how soon an instruction could start after the * chosen one. */ time += issue_time(chosen->inst); /* If we expected a delay for scheduling, then bump the clock to reflect * that as well. In reality, the hardware will switch to another * hyperthread and may not return to dispatching our thread for a while * even after we're unblocked. */ time = MAX2(time, chosen->unblocked_time); if (debug) { fprintf(stderr, "clock %4d, scheduled: ", time); bv->dump_instruction(chosen->inst); } /* Now that we've scheduled a new instruction, some of its * children can be promoted to the list of instructions ready to * be scheduled. Update the children's unblocked time for this * DAG edge as we do so. */ for (int i = chosen->child_count - 1; i >= 0; i--) { schedule_node *child = chosen->children[i]; child->unblocked_time = MAX2(child->unblocked_time, time + chosen->child_latency[i]); if (debug) { fprintf(stderr, "\tchild %d, %d parents: ", i, child->parent_count); bv->dump_instruction(child->inst); } child->cand_generation = cand_generation; child->parent_count--; if (child->parent_count == 0) { if (debug) { fprintf(stderr, "\t\tnow available\n"); } instructions.push_head(child); } } cand_generation++; /* Shared resource: the mathbox. There's one mathbox per EU on Gen6+ * but it's more limited pre-gen6, so if we send something off to it then * the next math instruction isn't going to make progress until the first * is done. */ if (brw->gen < 6 && chosen->inst->is_math()) { foreach_in_list(schedule_node, n, &instructions) { if (n->inst->is_math()) n->unblocked_time = MAX2(n->unblocked_time, time + chosen->latency); } } } if (block->end()->opcode == BRW_OPCODE_NOP) block->end()->remove(block); assert(instructions_to_schedule == 0); } void instruction_scheduler::run(cfg_t *cfg) { if (debug) { fprintf(stderr, "\nInstructions before scheduling (reg_alloc %d)\n", post_reg_alloc); bv->dump_instructions(); } /* Populate the remaining GRF uses array to improve the pre-regalloc * scheduling. */ if (remaining_grf_uses) { foreach_block_and_inst(block, backend_instruction, inst, cfg) { count_remaining_grf_uses(inst); } } foreach_block(block, cfg) { if (block->end_ip - block->start_ip <= 1) continue; add_insts_from_block(block); calculate_deps(); foreach_in_list(schedule_node, n, &instructions) { compute_delay(n); } schedule_instructions(block); } if (debug) { fprintf(stderr, "\nInstructions after scheduling (reg_alloc %d)\n", post_reg_alloc); bv->dump_instructions(); } } void fs_visitor::schedule_instructions(instruction_scheduler_mode mode) { int grf_count; if (mode == SCHEDULE_POST) grf_count = grf_used; else grf_count = virtual_grf_count; fs_instruction_scheduler sched(this, grf_count, mode); sched.run(cfg); if (unlikely(INTEL_DEBUG & DEBUG_WM) && mode == SCHEDULE_POST) { fprintf(stderr, "fs%d estimated execution time: %d cycles\n", dispatch_width, sched.time); } invalidate_live_intervals(); } void vec4_visitor::opt_schedule_instructions() { vec4_instruction_scheduler sched(this, prog_data->total_grf); sched.run(cfg); if (unlikely(debug_flag)) { fprintf(stderr, "vec4 estimated execution time: %d cycles\n", sched.time); } invalidate_live_intervals(); }