| /* |
| * Copyright © 2014 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. |
| */ |
| |
| #include "brw_fs.h" |
| #include "brw_cfg.h" |
| #include "brw_eu.h" |
| |
| /** @file brw_fs_cmod_propagation.cpp |
| * |
| * Implements a pass that propagates the conditional modifier from a CMP x 0.0 |
| * instruction into the instruction that generated x. For instance, in this |
| * sequence |
| * |
| * add(8) g70<1>F g69<8,8,1>F 4096F |
| * cmp.ge.f0(8) null g70<8,8,1>F 0F |
| * |
| * we can do the comparison as part of the ADD instruction directly: |
| * |
| * add.ge.f0(8) g70<1>F g69<8,8,1>F 4096F |
| * |
| * If there had been a use of the flag register and another CMP using g70 |
| * |
| * add.ge.f0(8) g70<1>F g69<8,8,1>F 4096F |
| * (+f0) sel(8) g71<F> g72<8,8,1>F g73<8,8,1>F |
| * cmp.ge.f0(8) null g70<8,8,1>F 0F |
| * |
| * we can recognize that the CMP is generating the flag value that already |
| * exists and therefore remove the instruction. |
| */ |
| |
| static bool |
| opt_cmod_propagation_local(const gen_device_info *devinfo, bblock_t *block) |
| { |
| bool progress = false; |
| int ip = block->end_ip + 1; |
| |
| foreach_inst_in_block_reverse_safe(fs_inst, inst, block) { |
| ip--; |
| |
| if ((inst->opcode != BRW_OPCODE_AND && |
| inst->opcode != BRW_OPCODE_CMP && |
| inst->opcode != BRW_OPCODE_MOV) || |
| inst->predicate != BRW_PREDICATE_NONE || |
| !inst->dst.is_null() || |
| inst->src[0].file != VGRF || |
| inst->src[0].abs) |
| continue; |
| |
| /* Only an AND.NZ can be propagated. Many AND.Z instructions are |
| * generated (for ir_unop_not in fs_visitor::emit_bool_to_cond_code). |
| * Propagating those would require inverting the condition on the CMP. |
| * This changes both the flag value and the register destination of the |
| * CMP. That result may be used elsewhere, so we can't change its value |
| * on a whim. |
| */ |
| if (inst->opcode == BRW_OPCODE_AND && |
| !(inst->src[1].is_one() && |
| inst->conditional_mod == BRW_CONDITIONAL_NZ && |
| !inst->src[0].negate)) |
| continue; |
| |
| if (inst->opcode == BRW_OPCODE_CMP && !inst->src[1].is_zero()) |
| continue; |
| |
| if (inst->opcode == BRW_OPCODE_MOV && |
| inst->conditional_mod != BRW_CONDITIONAL_NZ) |
| continue; |
| |
| bool read_flag = false; |
| foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst, inst) { |
| if (regions_overlap(scan_inst->dst, scan_inst->size_written, |
| inst->src[0], inst->size_read(0))) { |
| if (scan_inst->is_partial_write() || |
| scan_inst->dst.offset != inst->src[0].offset || |
| scan_inst->exec_size != inst->exec_size) |
| break; |
| |
| /* CMP's result is the same regardless of dest type. */ |
| if (inst->conditional_mod == BRW_CONDITIONAL_NZ && |
| scan_inst->opcode == BRW_OPCODE_CMP && |
| (inst->dst.type == BRW_REGISTER_TYPE_D || |
| inst->dst.type == BRW_REGISTER_TYPE_UD)) { |
| inst->remove(block); |
| progress = true; |
| break; |
| } |
| |
| /* If the AND wasn't handled by the previous case, it isn't safe |
| * to remove it. |
| */ |
| if (inst->opcode == BRW_OPCODE_AND) |
| break; |
| |
| /* Comparisons operate differently for ints and floats */ |
| if (scan_inst->dst.type != inst->dst.type && |
| (scan_inst->dst.type == BRW_REGISTER_TYPE_F || |
| inst->dst.type == BRW_REGISTER_TYPE_F)) |
| break; |
| |
| /* If the instruction generating inst's source also wrote the |
| * flag, and inst is doing a simple .nz comparison, then inst |
| * is redundant - the appropriate value is already in the flag |
| * register. Delete inst. |
| */ |
| if (inst->conditional_mod == BRW_CONDITIONAL_NZ && |
| !inst->src[0].negate && |
| scan_inst->flags_written()) { |
| inst->remove(block); |
| progress = true; |
| break; |
| } |
| |
| /* The conditional mod of the CMP/CMPN instructions behaves |
| * specially because the flag output is not calculated from the |
| * result of the instruction, but the other way around, which |
| * means that even if the condmod to propagate and the condmod |
| * from the CMP instruction are the same they will in general give |
| * different results because they are evaluated based on different |
| * inputs. |
| */ |
| if (scan_inst->opcode == BRW_OPCODE_CMP || |
| scan_inst->opcode == BRW_OPCODE_CMPN) |
| break; |
| |
| /* Otherwise, try propagating the conditional. */ |
| enum brw_conditional_mod cond = |
| inst->src[0].negate ? brw_swap_cmod(inst->conditional_mod) |
| : inst->conditional_mod; |
| |
| if (scan_inst->can_do_cmod() && |
| ((!read_flag && scan_inst->conditional_mod == BRW_CONDITIONAL_NONE) || |
| scan_inst->conditional_mod == cond)) { |
| scan_inst->conditional_mod = cond; |
| inst->remove(block); |
| progress = true; |
| } |
| break; |
| } |
| |
| if (scan_inst->flags_written()) |
| break; |
| |
| read_flag = read_flag || scan_inst->flags_read(devinfo); |
| } |
| } |
| |
| return progress; |
| } |
| |
| bool |
| fs_visitor::opt_cmod_propagation() |
| { |
| bool progress = false; |
| |
| foreach_block_reverse(block, cfg) { |
| progress = opt_cmod_propagation_local(devinfo, block) || progress; |
| } |
| |
| if (progress) |
| invalidate_live_intervals(); |
| |
| return progress; |
| } |
