diff options
Diffstat (limited to 'src/intel/compiler/brw_fs_live_variables.cpp')
| -rw-r--r-- | src/intel/compiler/brw_fs_live_variables.cpp | 334 |
1 files changed, 334 insertions, 0 deletions
diff --git a/src/intel/compiler/brw_fs_live_variables.cpp b/src/intel/compiler/brw_fs_live_variables.cpp new file mode 100644 index 00000000000..c449672a519 --- /dev/null +++ b/src/intel/compiler/brw_fs_live_variables.cpp @@ -0,0 +1,334 @@ +/* + * Copyright © 2012 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 <[email protected]> + * + */ + +#include "brw_cfg.h" +#include "brw_fs_live_variables.h" + +using namespace brw; + +#define MAX_INSTRUCTION (1 << 30) + +/** @file brw_fs_live_variables.cpp + * + * Support for calculating liveness information about virtual GRFs. + * + * This produces a live interval for each whole virtual GRF. We could + * choose to expose per-component live intervals for VGRFs of size > 1, + * but we currently do not. It is easier for the consumers of this + * information to work with whole VGRFs. + * + * However, we internally track use/def information at the per-GRF level for + * greater accuracy. Large VGRFs may be accessed piecemeal over many + * (possibly non-adjacent) instructions. In this case, examining a single + * instruction is insufficient to decide whether a whole VGRF is ultimately + * used or defined. Tracking individual components allows us to easily + * assemble this information. + * + * See Muchnick's Advanced Compiler Design and Implementation, section + * 14.1 (p444). + */ + +void +fs_live_variables::setup_one_read(struct block_data *bd, fs_inst *inst, + int ip, const fs_reg ®) +{ + int var = var_from_reg(reg); + assert(var < num_vars); + + start[var] = MIN2(start[var], ip); + end[var] = MAX2(end[var], ip); + + /* The use[] bitset marks when the block makes use of a variable (VGRF + * channel) without having completely defined that variable within the + * block. + */ + if (!BITSET_TEST(bd->def, var)) + BITSET_SET(bd->use, var); +} + +void +fs_live_variables::setup_one_write(struct block_data *bd, fs_inst *inst, + int ip, const fs_reg ®) +{ + int var = var_from_reg(reg); + assert(var < num_vars); + + start[var] = MIN2(start[var], ip); + end[var] = MAX2(end[var], ip); + + /* The def[] bitset marks when an initialization in a block completely + * screens off previous updates of that variable (VGRF channel). + */ + if (inst->dst.file == VGRF && !inst->is_partial_write()) { + if (!BITSET_TEST(bd->use, var)) + BITSET_SET(bd->def, var); + } +} + +/** + * Sets up the use[] and def[] bitsets. + * + * The basic-block-level live variable analysis needs to know which + * variables get used before they're completely defined, and which + * variables are completely defined before they're used. + * + * These are tracked at the per-component level, rather than whole VGRFs. + */ +void +fs_live_variables::setup_def_use() +{ + int ip = 0; + + foreach_block (block, cfg) { + assert(ip == block->start_ip); + if (block->num > 0) + assert(cfg->blocks[block->num - 1]->end_ip == ip - 1); + + struct block_data *bd = &block_data[block->num]; + + foreach_inst_in_block(fs_inst, inst, block) { + /* Set use[] for this instruction */ + for (unsigned int i = 0; i < inst->sources; i++) { + fs_reg reg = inst->src[i]; + + if (reg.file != VGRF) + continue; + + for (unsigned j = 0; j < regs_read(inst, i); j++) { + setup_one_read(bd, inst, ip, reg); + reg.offset += REG_SIZE; + } + } + + bd->flag_use[0] |= inst->flags_read(v->devinfo) & ~bd->flag_def[0]; + + /* Set def[] for this instruction */ + if (inst->dst.file == VGRF) { + fs_reg reg = inst->dst; + for (unsigned j = 0; j < regs_written(inst); j++) { + setup_one_write(bd, inst, ip, reg); + reg.offset += REG_SIZE; + } + } + + if (!inst->predicate && inst->exec_size >= 8) + bd->flag_def[0] |= inst->flags_written() & ~bd->flag_use[0]; + + ip++; + } + } +} + +/** + * The algorithm incrementally sets bits in liveout and livein, + * propagating it through control flow. It will eventually terminate + * because it only ever adds bits, and stops when no bits are added in + * a pass. + */ +void +fs_live_variables::compute_live_variables() +{ + bool cont = true; + + while (cont) { + cont = false; + + foreach_block_reverse (block, cfg) { + struct block_data *bd = &block_data[block->num]; + + /* Update liveout */ + foreach_list_typed(bblock_link, child_link, link, &block->children) { + struct block_data *child_bd = &block_data[child_link->block->num]; + + for (int i = 0; i < bitset_words; i++) { + BITSET_WORD new_liveout = (child_bd->livein[i] & + ~bd->liveout[i]); + if (new_liveout) { + bd->liveout[i] |= new_liveout; + cont = true; + } + } + BITSET_WORD new_liveout = (child_bd->flag_livein[0] & + ~bd->flag_liveout[0]); + if (new_liveout) { + bd->flag_liveout[0] |= new_liveout; + cont = true; + } + } + + /* Update livein */ + for (int i = 0; i < bitset_words; i++) { + BITSET_WORD new_livein = (bd->use[i] | + (bd->liveout[i] & + ~bd->def[i])); + if (new_livein & ~bd->livein[i]) { + bd->livein[i] |= new_livein; + cont = true; + } + } + BITSET_WORD new_livein = (bd->flag_use[0] | + (bd->flag_liveout[0] & + ~bd->flag_def[0])); + if (new_livein & ~bd->flag_livein[0]) { + bd->flag_livein[0] |= new_livein; + cont = true; + } + } + } +} + +/** + * Extend the start/end ranges for each variable to account for the + * new information calculated from control flow. + */ +void +fs_live_variables::compute_start_end() +{ + foreach_block (block, cfg) { + struct block_data *bd = &block_data[block->num]; + + for (int i = 0; i < num_vars; i++) { + if (BITSET_TEST(bd->livein, i)) { + start[i] = MIN2(start[i], block->start_ip); + end[i] = MAX2(end[i], block->start_ip); + } + + if (BITSET_TEST(bd->liveout, i)) { + start[i] = MIN2(start[i], block->end_ip); + end[i] = MAX2(end[i], block->end_ip); + } + } + } +} + +fs_live_variables::fs_live_variables(fs_visitor *v, const cfg_t *cfg) + : v(v), cfg(cfg) +{ + mem_ctx = ralloc_context(NULL); + + num_vgrfs = v->alloc.count; + num_vars = 0; + var_from_vgrf = rzalloc_array(mem_ctx, int, num_vgrfs); + for (int i = 0; i < num_vgrfs; i++) { + var_from_vgrf[i] = num_vars; + num_vars += v->alloc.sizes[i]; + } + + vgrf_from_var = rzalloc_array(mem_ctx, int, num_vars); + for (int i = 0; i < num_vgrfs; i++) { + for (unsigned j = 0; j < v->alloc.sizes[i]; j++) { + vgrf_from_var[var_from_vgrf[i] + j] = i; + } + } + + start = ralloc_array(mem_ctx, int, num_vars); + end = rzalloc_array(mem_ctx, int, num_vars); + for (int i = 0; i < num_vars; i++) { + start[i] = MAX_INSTRUCTION; + end[i] = -1; + } + + block_data= rzalloc_array(mem_ctx, struct block_data, cfg->num_blocks); + + bitset_words = BITSET_WORDS(num_vars); + for (int i = 0; i < cfg->num_blocks; i++) { + block_data[i].def = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words); + block_data[i].use = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words); + block_data[i].livein = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words); + block_data[i].liveout = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words); + + block_data[i].flag_def[0] = 0; + block_data[i].flag_use[0] = 0; + block_data[i].flag_livein[0] = 0; + block_data[i].flag_liveout[0] = 0; + } + + setup_def_use(); + compute_live_variables(); + compute_start_end(); +} + +fs_live_variables::~fs_live_variables() +{ + ralloc_free(mem_ctx); +} + +void +fs_visitor::invalidate_live_intervals() +{ + ralloc_free(live_intervals); + live_intervals = NULL; +} + +/** + * Compute the live intervals for each virtual GRF. + * + * This uses the per-component use/def data, but combines it to produce + * information about whole VGRFs. + */ +void +fs_visitor::calculate_live_intervals() +{ + if (this->live_intervals) + return; + + int num_vgrfs = this->alloc.count; + ralloc_free(this->virtual_grf_start); + ralloc_free(this->virtual_grf_end); + virtual_grf_start = ralloc_array(mem_ctx, int, num_vgrfs); + virtual_grf_end = ralloc_array(mem_ctx, int, num_vgrfs); + + for (int i = 0; i < num_vgrfs; i++) { + virtual_grf_start[i] = MAX_INSTRUCTION; + virtual_grf_end[i] = -1; + } + + this->live_intervals = new(mem_ctx) fs_live_variables(this, cfg); + + /* Merge the per-component live ranges to whole VGRF live ranges. */ + for (int i = 0; i < live_intervals->num_vars; i++) { + int vgrf = live_intervals->vgrf_from_var[i]; + virtual_grf_start[vgrf] = MIN2(virtual_grf_start[vgrf], + live_intervals->start[i]); + virtual_grf_end[vgrf] = MAX2(virtual_grf_end[vgrf], + live_intervals->end[i]); + } +} + +bool +fs_live_variables::vars_interfere(int a, int b) +{ + return !(end[b] <= start[a] || + end[a] <= start[b]); +} + +bool +fs_visitor::virtual_grf_interferes(int a, int b) +{ + return !(virtual_grf_end[a] <= virtual_grf_start[b] || + virtual_grf_end[b] <= virtual_grf_start[a]); +} |