/* * 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. */ /** @file brw_fs_copy_propagation.cpp * * Support for global copy propagation in two passes: A local pass that does * intra-block copy (and constant) propagation, and a global pass that uses * dataflow analysis on the copies available at the end of each block to re-do * local copy propagation with more copies available. * * See Muchnik's Advanced Compiler Design and Implementation, section * 12.5 (p356). */ #define ACP_HASH_SIZE 16 #include "main/bitset.h" #include "brw_fs.h" #include "brw_cfg.h" namespace { /* avoid conflict with opt_copy_propagation_elements */ struct acp_entry : public exec_node { fs_reg dst; fs_reg src; }; struct block_data { /** * Which entries in the fs_copy_prop_dataflow acp table are live at the * start of this block. This is the useful output of the analysis, since * it lets us plug those into the local copy propagation on the second * pass. */ BITSET_WORD *livein; /** * Which entries in the fs_copy_prop_dataflow acp table are live at the end * of this block. This is done in initial setup from the per-block acps * returned by the first local copy prop pass. */ BITSET_WORD *liveout; /** * Which entries in the fs_copy_prop_dataflow acp table are killed over the * course of this block. */ BITSET_WORD *kill; }; class fs_copy_prop_dataflow { public: fs_copy_prop_dataflow(void *mem_ctx, cfg_t *cfg, exec_list *out_acp[ACP_HASH_SIZE]); void setup_kills(); void run(); void *mem_ctx; cfg_t *cfg; acp_entry **acp; int num_acp; int bitset_words; struct block_data *bd; }; } /* anonymous namespace */ fs_copy_prop_dataflow::fs_copy_prop_dataflow(void *mem_ctx, cfg_t *cfg, exec_list *out_acp[ACP_HASH_SIZE]) : mem_ctx(mem_ctx), cfg(cfg) { bd = rzalloc_array(mem_ctx, struct block_data, cfg->num_blocks); num_acp = 0; for (int b = 0; b < cfg->num_blocks; b++) { for (int i = 0; i < ACP_HASH_SIZE; i++) { foreach_list(entry_node, &out_acp[b][i]) { num_acp++; } } } acp = rzalloc_array(mem_ctx, struct acp_entry *, num_acp); bitset_words = BITSET_WORDS(num_acp); int next_acp = 0; for (int b = 0; b < cfg->num_blocks; b++) { bd[b].livein = rzalloc_array(bd, BITSET_WORD, bitset_words); bd[b].liveout = rzalloc_array(bd, BITSET_WORD, bitset_words); bd[b].kill = rzalloc_array(bd, BITSET_WORD, bitset_words); for (int i = 0; i < ACP_HASH_SIZE; i++) { foreach_list(entry_node, &out_acp[b][i]) { acp_entry *entry = (acp_entry *)entry_node; acp[next_acp] = entry; BITSET_SET(bd[b].liveout, next_acp); next_acp++; } } } assert(next_acp == num_acp); setup_kills(); run(); } /** * Walk the set of instructions in the block, marking which entries in the acp * are killed by the block. */ void fs_copy_prop_dataflow::setup_kills() { for (int b = 0; b < cfg->num_blocks; b++) { bblock_t *block = cfg->blocks[b]; for (fs_inst *inst = (fs_inst *)block->start; inst != block->end->next; inst = (fs_inst *)inst->next) { if (inst->dst.file != GRF) continue; for (int i = 0; i < num_acp; i++) { if (inst->overwrites_reg(acp[i]->dst) || inst->overwrites_reg(acp[i]->src)) { BITSET_SET(bd[b].kill, i); } } } } } /** * Walk the set of instructions in the block, marking which entries in the acp * are killed by the block. */ void fs_copy_prop_dataflow::run() { bool progress; do { progress = false; for (int b = 0; b < cfg->num_blocks; b++) { for (int i = 0; i < bitset_words; i++) { BITSET_WORD new_liveout = (bd[b].livein[i] & ~bd[b].kill[i] & ~bd[b].liveout[i]); if (new_liveout) { bd[b].liveout[i] |= new_liveout; progress = true; } /* Update livein: if it's live at the end of all parents, it's * live at our start. */ BITSET_WORD new_livein = ~bd[b].livein[i]; foreach_list(block_node, &cfg->blocks[b]->parents) { bblock_link *link = (bblock_link *)block_node; bblock_t *block = link->block; new_livein &= bd[block->block_num].liveout[i]; if (!new_livein) break; } if (new_livein) { bd[b].livein[i] |= new_livein; progress = true; } } } } while (progress); } bool fs_visitor::try_copy_propagate(fs_inst *inst, int arg, acp_entry *entry) { if (entry->src.file == IMM) return false; if (inst->src[arg].file != entry->dst.file || inst->src[arg].reg != entry->dst.reg || inst->src[arg].reg_offset != entry->dst.reg_offset) { return false; } /* See resolve_ud_negate() and comment in brw_fs_emit.cpp. */ if (inst->conditional_mod && inst->src[arg].type == BRW_REGISTER_TYPE_UD && entry->src.negate) return false; bool has_source_modifiers = entry->src.abs || entry->src.negate; if ((has_source_modifiers || entry->src.file == UNIFORM || entry->src.smear != -1) && !can_do_source_mods(inst)) return false; if (has_source_modifiers && entry->dst.type != inst->src[arg].type) return false; inst->src[arg].file = entry->src.file; inst->src[arg].reg = entry->src.reg; inst->src[arg].reg_offset = entry->src.reg_offset; if (entry->src.smear != -1) inst->src[arg].smear = entry->src.smear; if (!inst->src[arg].abs) { inst->src[arg].abs = entry->src.abs; inst->src[arg].negate ^= entry->src.negate; } return true; } bool fs_visitor::try_constant_propagate(fs_inst *inst, acp_entry *entry) { bool progress = false; if (entry->src.file != IMM) return false; for (int i = 2; i >= 0; i--) { if (inst->src[i].file != entry->dst.file || inst->src[i].reg != entry->dst.reg || inst->src[i].reg_offset != entry->dst.reg_offset) continue; /* Don't bother with cases that should have been taken care of by the * GLSL compiler's constant folding pass. */ if (inst->src[i].negate || inst->src[i].abs) continue; switch (inst->opcode) { case BRW_OPCODE_MOV: inst->src[i] = entry->src; progress = true; break; case BRW_OPCODE_MACH: case BRW_OPCODE_MUL: case BRW_OPCODE_ADD: if (i == 1) { inst->src[i] = entry->src; progress = true; } else if (i == 0 && inst->src[1].file != IMM) { /* Fit this constant in by commuting the operands. * Exception: we can't do this for 32-bit integer MUL/MACH * because it's asymmetric. */ if ((inst->opcode == BRW_OPCODE_MUL || inst->opcode == BRW_OPCODE_MACH) && (inst->src[1].type == BRW_REGISTER_TYPE_D || inst->src[1].type == BRW_REGISTER_TYPE_UD)) break; inst->src[0] = inst->src[1]; inst->src[1] = entry->src; progress = true; } break; case BRW_OPCODE_CMP: case BRW_OPCODE_IF: if (i == 1) { inst->src[i] = entry->src; progress = true; } else if (i == 0 && inst->src[1].file != IMM) { uint32_t new_cmod; new_cmod = brw_swap_cmod(inst->conditional_mod); if (new_cmod != ~0u) { /* Fit this constant in by swapping the operands and * flipping the test */ inst->src[0] = inst->src[1]; inst->src[1] = entry->src; inst->conditional_mod = new_cmod; progress = true; } } break; case BRW_OPCODE_SEL: if (i == 1) { inst->src[i] = entry->src; progress = true; } else if (i == 0 && inst->src[1].file != IMM) { inst->src[0] = inst->src[1]; inst->src[1] = entry->src; /* If this was predicated, flipping operands means * we also need to flip the predicate. */ if (inst->conditional_mod == BRW_CONDITIONAL_NONE) { inst->predicate_inverse = !inst->predicate_inverse; } progress = true; } break; case SHADER_OPCODE_RCP: /* The hardware doesn't do math on immediate values * (because why are you doing that, seriously?), but * the correct answer is to just constant fold it * anyway. */ assert(i == 0); if (inst->src[0].imm.f != 0.0f) { inst->opcode = BRW_OPCODE_MOV; inst->src[0] = entry->src; inst->src[0].imm.f = 1.0f / inst->src[0].imm.f; progress = true; } break; case FS_OPCODE_UNIFORM_PULL_CONSTANT_LOAD: inst->src[i] = entry->src; progress = true; break; default: break; } } return progress; } /* Walks a basic block and does copy propagation on it using the acp * list. */ bool fs_visitor::opt_copy_propagate_local(void *mem_ctx, bblock_t *block, exec_list *acp) { bool progress = false; for (fs_inst *inst = (fs_inst *)block->start; inst != block->end->next; inst = (fs_inst *)inst->next) { /* Try propagating into this instruction. */ for (int i = 0; i < 3; i++) { if (inst->src[i].file != GRF) continue; foreach_list(entry_node, &acp[inst->src[i].reg % ACP_HASH_SIZE]) { acp_entry *entry = (acp_entry *)entry_node; if (try_constant_propagate(inst, entry)) progress = true; if (try_copy_propagate(inst, i, entry)) progress = true; } } /* kill the destination from the ACP */ if (inst->dst.file == GRF) { foreach_list_safe(entry_node, &acp[inst->dst.reg % ACP_HASH_SIZE]) { acp_entry *entry = (acp_entry *)entry_node; if (inst->overwrites_reg(entry->dst)) { entry->remove(); } } /* Oops, we only have the chaining hash based on the destination, not * the source, so walk across the entire table. */ for (int i = 0; i < ACP_HASH_SIZE; i++) { foreach_list_safe(entry_node, &acp[i]) { acp_entry *entry = (acp_entry *)entry_node; if (inst->overwrites_reg(entry->src)) entry->remove(); } } } /* If this instruction's source could potentially be folded into the * operand of another instruction, add it to the ACP. */ if (inst->opcode == BRW_OPCODE_MOV && inst->dst.file == GRF && ((inst->src[0].file == GRF && (inst->src[0].reg != inst->dst.reg || inst->src[0].reg_offset != inst->dst.reg_offset)) || inst->src[0].file == UNIFORM || inst->src[0].file == IMM) && inst->src[0].type == inst->dst.type && !inst->saturate && !inst->is_partial_write()) { acp_entry *entry = ralloc(mem_ctx, acp_entry); entry->dst = inst->dst; entry->src = inst->src[0]; acp[entry->dst.reg % ACP_HASH_SIZE].push_tail(entry); } } return progress; } bool fs_visitor::opt_copy_propagate() { bool progress = false; void *mem_ctx = ralloc_context(this->mem_ctx); cfg_t cfg(this); exec_list *out_acp[cfg.num_blocks]; for (int i = 0; i < cfg.num_blocks; i++) out_acp[i] = new exec_list [ACP_HASH_SIZE]; /* First, walk through each block doing local copy propagation and getting * the set of copies available at the end of the block. */ for (int b = 0; b < cfg.num_blocks; b++) { bblock_t *block = cfg.blocks[b]; progress = opt_copy_propagate_local(mem_ctx, block, out_acp[b]) || progress; } #if 0 /* Do dataflow analysis for those available copies. */ fs_copy_prop_dataflow dataflow(mem_ctx, &cfg, out_acp); /* Next, re-run local copy propagation, this time with the set of copies * provided by the dataflow analysis available at the start of a block. */ for (int b = 0; b < cfg.num_blocks; b++) { bblock_t *block = cfg.blocks[b]; exec_list in_acp[ACP_HASH_SIZE]; for (int i = 0; i < dataflow.num_acp; i++) { if (BITSET_TEST(dataflow.bd[b].livein, i)) { struct acp_entry *entry = dataflow.acp[i]; in_acp[entry->dst.reg % ACP_HASH_SIZE].push_tail(entry); } } progress = opt_copy_propagate_local(mem_ctx, block, in_acp) || progress; } #endif for (int i = 0; i < cfg.num_blocks; i++) delete [] out_acp[i]; ralloc_free(mem_ctx); if (progress) live_intervals_valid = false; return progress; }