From: Eric Anholt Date: Wed, 19 Jan 2011 01:16:49 +0000 (-0800) Subject: i965/fs: Add an instruction scheduler. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=63879d90ace519749fed228ca0e21b5b56c7e1c0;p=mesa.git i965/fs: Add an instruction scheduler. Improves performance of my GLSL demo by 5.1% (+/- 1.4%, n=7). It also reschedules the giant multiply tree at the end of glsl-fs-convolution-1 so that we end up not spilling registers, producing the expected level of performance. --- diff --git a/src/mesa/drivers/dri/i965/Makefile b/src/mesa/drivers/dri/i965/Makefile index 7c3ac0c14ef..b05ba35d65f 100644 --- a/src/mesa/drivers/dri/i965/Makefile +++ b/src/mesa/drivers/dri/i965/Makefile @@ -108,6 +108,7 @@ CXX_SOURCES = \ brw_fs.cpp \ brw_fs_channel_expressions.cpp \ brw_fs_reg_allocate.cpp \ + brw_fs_schedule_instructions.cpp \ brw_fs_vector_splitting.cpp ASM_SOURCES = diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp index 5b595a3c0e7..c24060b8c6f 100644 --- a/src/mesa/drivers/dri/i965/brw_fs.cpp +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp @@ -3696,6 +3696,8 @@ brw_wm_fs_emit(struct brw_context *brw, struct brw_wm_compile *c) progress = v.dead_code_eliminate() || progress; } while (progress); + v.schedule_instructions(); + if (0) { /* Debug of register spilling: Go spill everything. */ int virtual_grf_count = v.virtual_grf_next; diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h index 65c8a1e020f..7c991f32658 100644 --- a/src/mesa/drivers/dri/i965/brw_fs.h +++ b/src/mesa/drivers/dri/i965/brw_fs.h @@ -436,6 +436,8 @@ public: bool dead_code_eliminate(); bool remove_duplicate_mrf_writes(); bool virtual_grf_interferes(int a, int b); + void schedule_instructions(); + void generate_code(); void generate_fb_write(fs_inst *inst); void generate_linterp(fs_inst *inst, struct brw_reg dst, diff --git a/src/mesa/drivers/dri/i965/brw_fs_schedule_instructions.cpp b/src/mesa/drivers/dri/i965/brw_fs_schedule_instructions.cpp new file mode 100644 index 00000000000..00aa99de7f1 --- /dev/null +++ b/src/mesa/drivers/dri/i965/brw_fs_schedule_instructions.cpp @@ -0,0 +1,474 @@ +/* + * 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 + * + */ + +extern "C" { + +#include + +#include "main/macros.h" +#include "main/shaderobj.h" +#include "main/uniforms.h" +#include "program/prog_optimize.h" +#include "program/register_allocate.h" +#include "program/sampler.h" +#include "program/hash_table.h" +#include "brw_context.h" +#include "brw_eu.h" +#include "brw_wm.h" +#include "talloc.h" +} +#include "brw_fs.h" +#include "../glsl/glsl_types.h" +#include "../glsl/ir_optimization.h" +#include "../glsl/ir_print_visitor.h" + +/** @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, 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. + */ + +class schedule_node : public exec_node +{ +public: + schedule_node(fs_inst *inst) + { + 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; + + int chans = 8; + int math_latency = 22; + + switch (inst->opcode) { + case FS_OPCODE_RCP: + this->latency = 1 * chans * math_latency; + break; + case FS_OPCODE_RSQ: + this->latency = 2 * chans * math_latency; + break; + case FS_OPCODE_SQRT: + case FS_OPCODE_LOG2: + /* full precision log. partial is 2. */ + this->latency = 3 * chans * math_latency; + break; + case FS_OPCODE_EXP2: + /* full precision. partial is 3, same throughput. */ + this->latency = 4 * chans * math_latency; + break; + case FS_OPCODE_POW: + this->latency = 8 * chans * math_latency; + break; + case FS_OPCODE_SIN: + case FS_OPCODE_COS: + /* minimum latency, max is 12 rounds. */ + this->latency = 5 * chans * math_latency; + break; + default: + this->latency = 2; + break; + } + } + + fs_inst *inst; + schedule_node **children; + int *child_latency; + int child_count; + int parent_count; + int child_array_size; + int unblocked_time; + int latency; +}; + +class instruction_scheduler { +public: + instruction_scheduler(fs_visitor *v, void *mem_ctx, int virtual_grf_count) + { + this->v = v; + this->mem_ctx = talloc_new(mem_ctx); + this->virtual_grf_count = virtual_grf_count; + this->instructions.make_empty(); + this->instructions_to_schedule = 0; + } + + ~instruction_scheduler() + { + talloc_free(this->mem_ctx); + } + void add_barrier_deps(schedule_node *n); + void add_dep(schedule_node *before, schedule_node *after, int latency); + + void add_inst(fs_inst *inst); + void calculate_deps(); + void schedule_instructions(fs_inst *next_block_header); + + void *mem_ctx; + + int instructions_to_schedule; + int virtual_grf_count; + exec_list instructions; + fs_visitor *v; +}; + +void +instruction_scheduler::add_inst(fs_inst *inst) +{ + schedule_node *n = new(mem_ctx) schedule_node(inst); + + assert(!inst->is_head_sentinel()); + assert(!inst->is_tail_sentinel()); + + this->instructions_to_schedule++; + + inst->remove(); + instructions.push_tail(n); +} + +/** + * 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 = talloc_realloc(mem_ctx, before->children, + schedule_node *, + before->child_array_size); + before->child_latency = talloc_realloc(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++; +} + +/** + * 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; + } + } +} + +void +instruction_scheduler::calculate_deps() +{ + schedule_node *last_grf_write[virtual_grf_count]; + schedule_node *last_mrf_write[BRW_MAX_MRF]; + schedule_node *last_conditional_mod = 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 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_iter(exec_list_iterator, iter, instructions) { + schedule_node *n = (schedule_node *)iter.get(); + fs_inst *inst = n->inst; + + /* read-after-write deps. */ + for (int i = 0; i < 3; i++) { + if (inst->src[i].file == GRF) { + if (last_grf_write[inst->src[i].reg]) { + add_dep(last_grf_write[inst->src[i].reg], n, + last_grf_write[inst->src[i].reg]->latency); + } + } else if (inst->src[i].file != BAD_FILE && + inst->src[i].file != IMM && + inst->src[i].file != UNIFORM) { + assert(inst->src[i].file != MRF); + 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. + */ + if (last_mrf_write[inst->base_mrf + i]) { + add_dep(last_mrf_write[inst->base_mrf + i], n, + last_mrf_write[inst->base_mrf + i]->latency); + } + } + + if (inst->predicated) { + assert(last_conditional_mod); + add_dep(last_conditional_mod, n, last_conditional_mod->latency); + } + + /* write-after-write deps. */ + if (inst->dst.file == GRF) { + if (last_grf_write[inst->dst.reg]) { + add_dep(last_grf_write[inst->dst.reg], n, + last_grf_write[inst->dst.reg]->latency); + } + last_grf_write[inst->dst.reg] = n; + } else if (inst->dst.file == MRF) { + if (last_mrf_write[inst->dst.hw_reg]) { + add_dep(last_mrf_write[inst->dst.hw_reg], n, + last_mrf_write[inst->dst.hw_reg]->latency); + } + last_mrf_write[inst->dst.hw_reg] = 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++) { + if (last_mrf_write[inst->base_mrf + i]) { + add_dep(last_mrf_write[inst->base_mrf + i], n, + last_mrf_write[inst->base_mrf + i]->latency); + } + last_mrf_write[inst->base_mrf + i] = n; + } + } + + if (inst->conditional_mod) { + add_dep(last_conditional_mod, n, 0); + last_conditional_mod = 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; + + 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 = n->inst; + + /* write-after-read deps. */ + for (int i = 0; i < 3; i++) { + if (inst->src[i].file == GRF) { + if (last_grf_write[inst->src[i].reg]) { + add_dep(n, last_grf_write[inst->src[i].reg], n->latency); + } + } else if (inst->src[i].file != BAD_FILE && + inst->src[i].file != IMM && + inst->src[i].file != UNIFORM) { + assert(inst->src[i].file != MRF); + 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->predicated) { + if (last_conditional_mod) { + add_dep(n, last_conditional_mod, n->latency); + } + } + + /* 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.hw_reg] = 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->conditional_mod) + last_conditional_mod = n; + } +} + +void +instruction_scheduler::schedule_instructions(fs_inst *next_block_header) +{ + int time = 0; + + /* Remove non-DAG heads from the list. */ + foreach_iter(exec_list_iterator, iter, instructions) { + schedule_node *n = (schedule_node *)iter.get(); + if (n->parent_count != 0) + n->remove(); + } + + while (!instructions.is_empty()) { + schedule_node *chosen = NULL; + int chosen_time = 0; + + foreach_iter(exec_list_iterator, iter, instructions) { + schedule_node *n = (schedule_node *)iter.get(); + + if (!chosen || n->unblocked_time < chosen_time) { + chosen = n; + chosen_time = n->unblocked_time; + } + } + + /* Schedule this instruction. */ + assert(chosen); + chosen->remove(); + next_block_header->insert_before(chosen->inst); + instructions_to_schedule--; + + /* Bump the clock. If we expected a delay for scheduling, then + * bump the clock to reflect that. + */ + time = MAX2(time + 1, chosen_time); + + /* 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 = 0; i < chosen->child_count; i++) { + schedule_node *child = chosen->children[i]; + + child->unblocked_time = MAX2(child->unblocked_time, + time + chosen->child_latency[i]); + + child->parent_count--; + if (child->parent_count == 0) { + instructions.push_tail(child); + } + } + } + + assert(instructions_to_schedule == 0); +} + +void +fs_visitor::schedule_instructions() +{ + fs_inst *next_block_header = (fs_inst *)instructions.head; + instruction_scheduler sched(this, mem_ctx, this->virtual_grf_next); + + while (!next_block_header->is_tail_sentinel()) { + /* Add things to be scheduled until we get to a new BB. */ + while (!next_block_header->is_tail_sentinel()) { + fs_inst *inst = next_block_header; + next_block_header = (fs_inst *)next_block_header->next; + + sched.add_inst(inst); + if (inst->opcode == BRW_OPCODE_IF || + inst->opcode == BRW_OPCODE_ELSE || + inst->opcode == BRW_OPCODE_ENDIF || + inst->opcode == BRW_OPCODE_DO || + inst->opcode == BRW_OPCODE_WHILE || + inst->opcode == BRW_OPCODE_BREAK || + inst->opcode == BRW_OPCODE_CONTINUE) { + break; + } + } + sched.calculate_deps(); + sched.schedule_instructions(next_block_header); + } + + this->live_intervals_valid = false; +}