| /* |
| * 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 |
| cmod_propagate_cmp_to_add(const gen_device_info *devinfo, bblock_t *block, |
| fs_inst *inst) |
| { |
| bool read_flag = false; |
| const unsigned flags_written = inst->flags_written(); |
| |
| foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst, inst) { |
| if (scan_inst->opcode == BRW_OPCODE_ADD && |
| !scan_inst->is_partial_write() && |
| scan_inst->exec_size == inst->exec_size) { |
| bool negate; |
| |
| /* A CMP is basically a subtraction. The result of the |
| * subtraction must be the same as the result of the addition. |
| * This means that one of the operands must be negated. So (a + |
| * b) vs (a == -b) or (a + -b) vs (a == b). |
| */ |
| if ((inst->src[0].equals(scan_inst->src[0]) && |
| inst->src[1].negative_equals(scan_inst->src[1])) || |
| (inst->src[0].equals(scan_inst->src[1]) && |
| inst->src[1].negative_equals(scan_inst->src[0]))) { |
| negate = false; |
| } else if ((inst->src[0].negative_equals(scan_inst->src[0]) && |
| inst->src[1].equals(scan_inst->src[1])) || |
| (inst->src[0].negative_equals(scan_inst->src[1]) && |
| inst->src[1].equals(scan_inst->src[0]))) { |
| negate = true; |
| } else { |
| goto not_match; |
| } |
| |
| /* If the scan instruction writes a different flag register than the |
| * instruction we're trying to propagate from, bail. |
| * |
| * FINISHME: The second part of the condition may be too strong. |
| * Perhaps (scan_inst->flags_written() & flags_written) != |
| * flags_written? |
| */ |
| if (scan_inst->flags_written() != 0 && |
| scan_inst->flags_written() != flags_written) |
| goto not_match; |
| |
| /* From the Sky Lake PRM Vol. 7 "Assigning Conditional Mods": |
| * |
| * * Note that the [post condition signal] bits generated at |
| * the output of a compute are before the .sat. |
| * |
| * So we don't have to bail if scan_inst has saturate. |
| */ |
| /* Otherwise, try propagating the conditional. */ |
| const enum brw_conditional_mod cond = |
| 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); |
| return true; |
| } |
| break; |
| } |
| |
| not_match: |
| if ((scan_inst->flags_written() & flags_written) != 0) |
| break; |
| |
| read_flag = read_flag || |
| (scan_inst->flags_read(devinfo) & flags_written) != 0; |
| } |
| |
| return false; |
| } |
| |
| /** |
| * Propagate conditional modifiers from NOT instructions |
| * |
| * Attempt to convert sequences like |
| * |
| * or(8) g78<8,8,1> g76<8,8,1>UD g77<8,8,1>UD |
| * ... |
| * not.nz.f0(8) null g78<8,8,1>UD |
| * |
| * into |
| * |
| * or.z.f0(8) g78<8,8,1> g76<8,8,1>UD g77<8,8,1>UD |
| */ |
| static bool |
| cmod_propagate_not(const gen_device_info *devinfo, bblock_t *block, |
| fs_inst *inst) |
| { |
| const enum brw_conditional_mod cond = brw_negate_cmod(inst->conditional_mod); |
| bool read_flag = false; |
| const unsigned flags_written = inst->flags_written(); |
| |
| if (cond != BRW_CONDITIONAL_Z && cond != BRW_CONDITIONAL_NZ) |
| return 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->opcode != BRW_OPCODE_OR && |
| scan_inst->opcode != BRW_OPCODE_AND) |
| break; |
| |
| if (scan_inst->is_partial_write() || |
| scan_inst->dst.offset != inst->src[0].offset || |
| scan_inst->exec_size != inst->exec_size) |
| break; |
| |
| /* If the scan instruction writes a different flag register than the |
| * instruction we're trying to propagate from, bail. |
| * |
| * FINISHME: The second part of the condition may be too strong. |
| * Perhaps (scan_inst->flags_written() & flags_written) != |
| * flags_written? |
| */ |
| if (scan_inst->flags_written() != 0 && |
| scan_inst->flags_written() != flags_written) |
| break; |
| |
| 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); |
| return true; |
| } |
| break; |
| } |
| |
| if ((scan_inst->flags_written() & flags_written) != 0) |
| break; |
| |
| read_flag = read_flag || |
| (scan_inst->flags_read(devinfo) & flags_written) != 0; |
| } |
| |
| return false; |
| } |
| |
| 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->opcode != BRW_OPCODE_NOT) || |
| inst->predicate != BRW_PREDICATE_NONE || |
| !inst->dst.is_null() || |
| (inst->src[0].file != VGRF && inst->src[0].file != ATTR && |
| inst->src[0].file != UNIFORM)) |
| continue; |
| |
| /* An ABS source modifier can only be handled when processing a compare |
| * with a value other than zero. |
| */ |
| if (inst->src[0].abs && |
| (inst->opcode != BRW_OPCODE_CMP || inst->src[1].is_zero())) |
| 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_MOV && |
| inst->conditional_mod != BRW_CONDITIONAL_NZ) |
| continue; |
| |
| /* A CMP with a second source of zero can match with anything. A CMP |
| * with a second source that is not zero can only match with an ADD |
| * instruction. |
| * |
| * Only apply this optimization to float-point sources. It can fail for |
| * integers. For inputs a = 0x80000000, b = 4, int(0x80000000) < 4, but |
| * int(0x80000000) - 4 overflows and results in 0x7ffffffc. that's not |
| * less than zero, so the flags get set differently than for (a < b). |
| */ |
| if (inst->opcode == BRW_OPCODE_CMP && !inst->src[1].is_zero()) { |
| if (brw_reg_type_is_floating_point(inst->src[0].type) && |
| cmod_propagate_cmp_to_add(devinfo, block, inst)) |
| progress = true; |
| |
| continue; |
| } |
| |
| if (inst->opcode == BRW_OPCODE_NOT) { |
| progress = cmod_propagate_not(devinfo, block, inst) || progress; |
| continue; |
| } |
| |
| bool read_flag = false; |
| const unsigned flags_written = inst->flags_written(); |
| 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 the scan instruction writes a different flag register than |
| * the instruction we're trying to propagate from, bail. |
| * |
| * FINISHME: The second part of the condition may be too strong. |
| * Perhaps (scan_inst->flags_written() & flags_written) != |
| * flags_written? |
| */ |
| if (scan_inst->flags_written() != 0 && |
| scan_inst->flags_written() != flags_written) |
| break; |
| |
| 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 && |
| brw_reg_type_is_integer(inst->dst.type)) { |
| 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; |
| |
| /* Not safe to use inequality operators if the types are different |
| */ |
| if (scan_inst->dst.type != inst->src[0].type && |
| inst->conditional_mod != BRW_CONDITIONAL_Z && |
| inst->conditional_mod != BRW_CONDITIONAL_NZ) |
| break; |
| |
| /* Comparisons operate differently for ints and floats */ |
| if (scan_inst->dst.type != inst->dst.type) { |
| /* Comparison result may be altered if the bit-size changes |
| * since that affects range, denorms, etc |
| */ |
| if (type_sz(scan_inst->dst.type) != type_sz(inst->dst.type)) |
| break; |
| |
| /* We should propagate from a MOV to another instruction in a |
| * sequence like: |
| * |
| * and(16) g31<1>UD g20<8,8,1>UD g22<8,8,1>UD |
| * mov.nz.f0(16) null<1>F g31<8,8,1>D |
| */ |
| if (inst->opcode == BRW_OPCODE_MOV) { |
| if ((inst->src[0].type != BRW_REGISTER_TYPE_D && |
| inst->src[0].type != BRW_REGISTER_TYPE_UD) || |
| (scan_inst->dst.type != BRW_REGISTER_TYPE_D && |
| scan_inst->dst.type != BRW_REGISTER_TYPE_UD)) { |
| break; |
| } |
| } else if (brw_reg_type_is_floating_point(scan_inst->dst.type) != |
| brw_reg_type_is_floating_point(inst->dst.type)) { |
| 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; |
| |
| /* From the Sky Lake PRM, Vol 2a, "Multiply": |
| * |
| * "When multiplying integer data types, if one of the sources |
| * is a DW, the resulting full precision data is stored in |
| * the accumulator. However, if the destination data type is |
| * either W or DW, the low bits of the result are written to |
| * the destination register and the remaining high bits are |
| * discarded. This results in undefined Overflow and Sign |
| * flags. Therefore, conditional modifiers and saturation |
| * (.sat) cannot be used in this case." |
| * |
| * We just disallow cmod propagation on all integer multiplies. |
| */ |
| if (!brw_reg_type_is_floating_point(scan_inst->dst.type) && |
| scan_inst->opcode == BRW_OPCODE_MUL) |
| break; |
| |
| enum brw_conditional_mod cond = |
| inst->src[0].negate ? brw_swap_cmod(inst->conditional_mod) |
| : inst->conditional_mod; |
| |
| /* From the Sky Lake PRM Vol. 7 "Assigning Conditional Mods": |
| * |
| * * Note that the [post condition signal] bits generated at |
| * the output of a compute are before the .sat. |
| * |
| * This limits the cases where we can propagate the conditional |
| * modifier. If scan_inst has a saturate modifier, then we can |
| * only propagate from inst if inst is 'scan_inst <= 0', |
| * 'scan_inst == 0', 'scan_inst != 0', or 'scan_inst > 0'. If |
| * inst is 'scan_inst == 0', the conditional modifier must be |
| * replace with LE. Likewise, if inst is 'scan_inst != 0', the |
| * conditional modifier must be replace with G. |
| * |
| * The only other cases are 'scan_inst < 0' (which is a |
| * contradiction) and 'scan_inst >= 0' (which is a tautology). |
| */ |
| if (scan_inst->saturate) { |
| if (scan_inst->dst.type != BRW_REGISTER_TYPE_F) |
| break; |
| |
| if (cond != BRW_CONDITIONAL_Z && |
| cond != BRW_CONDITIONAL_NZ && |
| cond != BRW_CONDITIONAL_LE && |
| cond != BRW_CONDITIONAL_G) |
| break; |
| |
| if (inst->opcode != BRW_OPCODE_MOV && |
| inst->opcode != BRW_OPCODE_CMP) |
| break; |
| |
| /* inst->src[1].is_zero() was tested before, but be safe |
| * against possible future changes in this code. |
| */ |
| assert(inst->opcode != BRW_OPCODE_CMP || inst->src[1].is_zero()); |
| |
| if (cond == BRW_CONDITIONAL_Z) |
| cond = BRW_CONDITIONAL_LE; |
| else if (cond == BRW_CONDITIONAL_NZ) |
| cond = BRW_CONDITIONAL_G; |
| } |
| |
| /* Otherwise, try propagating the conditional. */ |
| 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; |
| scan_inst->flag_subreg = inst->flag_subreg; |
| inst->remove(block); |
| progress = true; |
| } |
| break; |
| } |
| |
| if ((scan_inst->flags_written() & flags_written) != 0) |
| break; |
| |
| read_flag = read_flag || |
| (scan_inst->flags_read(devinfo) & flags_written) != 0; |
| } |
| } |
| |
| 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; |
| } |