| /* |
| * Copyright © 2013 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" |
| |
| /** @file brw_fs_sel_peephole.cpp |
| * |
| * This file contains the opt_peephole_sel() optimization pass that replaces |
| * MOV instructions to the same destination in the "then" and "else" bodies of |
| * an if statement with SEL instructions. |
| */ |
| |
| /* Four MOVs seems to be pretty typical, so I picked the next power of two in |
| * the hopes that it would handle almost anything possible in a single |
| * pass. |
| */ |
| #define MAX_MOVS 8 /**< The maximum number of MOVs to attempt to match. */ |
| |
| using namespace brw; |
| |
| /** |
| * Scans forwards from an IF counting consecutive MOV instructions in the |
| * "then" and "else" blocks of the if statement. |
| * |
| * A pointer to the bblock_t following the IF is passed as the <then_block> |
| * argument. The function stores pointers to the MOV instructions in the |
| * <then_mov> and <else_mov> arrays. |
| * |
| * \return the minimum number of MOVs found in the two branches or zero if |
| * an error occurred. |
| * |
| * E.g.: |
| * IF ... |
| * then_mov[0] = MOV g4, ... |
| * then_mov[1] = MOV g5, ... |
| * then_mov[2] = MOV g6, ... |
| * ELSE ... |
| * else_mov[0] = MOV g4, ... |
| * else_mov[1] = MOV g5, ... |
| * else_mov[2] = MOV g7, ... |
| * ENDIF |
| * returns 3. |
| */ |
| static int |
| count_movs_from_if(fs_inst *then_mov[MAX_MOVS], fs_inst *else_mov[MAX_MOVS], |
| bblock_t *then_block, bblock_t *else_block) |
| { |
| int then_movs = 0; |
| foreach_inst_in_block(fs_inst, inst, then_block) { |
| if (then_movs == MAX_MOVS || inst->opcode != BRW_OPCODE_MOV) |
| break; |
| |
| then_mov[then_movs] = inst; |
| then_movs++; |
| } |
| |
| int else_movs = 0; |
| foreach_inst_in_block(fs_inst, inst, else_block) { |
| if (else_movs == MAX_MOVS || inst->opcode != BRW_OPCODE_MOV) |
| break; |
| |
| else_mov[else_movs] = inst; |
| else_movs++; |
| } |
| |
| return MIN2(then_movs, else_movs); |
| } |
| |
| /** |
| * Try to replace IF/MOV+/ELSE/MOV+/ENDIF with SEL. |
| * |
| * Many GLSL shaders contain the following pattern: |
| * |
| * x = condition ? foo : bar |
| * |
| * or |
| * |
| * if (...) a.xyzw = foo.xyzw; |
| * else a.xyzw = bar.xyzw; |
| * |
| * The compiler emits an ir_if tree for this, since each subexpression might be |
| * a complex tree that could have side-effects or short-circuit logic. |
| * |
| * However, the common case is to simply select one of two constants or |
| * variable values---which is exactly what SEL is for. In this case, the |
| * assembly looks like: |
| * |
| * (+f0) IF |
| * MOV dst src0 |
| * ... |
| * ELSE |
| * MOV dst src1 |
| * ... |
| * ENDIF |
| * |
| * where each pair of MOVs to a common destination and can be easily translated |
| * into |
| * |
| * (+f0) SEL dst src0 src1 |
| * |
| * If src0 is an immediate value, we promote it to a temporary GRF. |
| */ |
| bool |
| fs_visitor::opt_peephole_sel() |
| { |
| bool progress = false; |
| |
| foreach_block (block, cfg) { |
| /* IF instructions, by definition, can only be found at the ends of |
| * basic blocks. |
| */ |
| fs_inst *if_inst = (fs_inst *)block->end(); |
| if (if_inst->opcode != BRW_OPCODE_IF) |
| continue; |
| |
| fs_inst *else_mov[MAX_MOVS] = { NULL }; |
| fs_inst *then_mov[MAX_MOVS] = { NULL }; |
| |
| bblock_t *then_block = block->next(); |
| bblock_t *else_block = NULL; |
| foreach_list_typed(bblock_link, child, link, &block->children) { |
| if (child->block != then_block) { |
| if (child->block->prev()->end()->opcode == BRW_OPCODE_ELSE) { |
| else_block = child->block; |
| } |
| break; |
| } |
| } |
| if (else_block == NULL) |
| continue; |
| |
| int movs = count_movs_from_if(then_mov, else_mov, then_block, else_block); |
| |
| if (movs == 0) |
| continue; |
| |
| /* Generate SEL instructions for pairs of MOVs to a common destination. */ |
| for (int i = 0; i < movs; i++) { |
| if (!then_mov[i] || !else_mov[i]) |
| break; |
| |
| /* Check that the MOVs are the right form. */ |
| if (!then_mov[i]->dst.equals(else_mov[i]->dst) || |
| then_mov[i]->exec_size != else_mov[i]->exec_size || |
| then_mov[i]->group != else_mov[i]->group || |
| then_mov[i]->force_writemask_all != else_mov[i]->force_writemask_all || |
| then_mov[i]->is_partial_write() || |
| else_mov[i]->is_partial_write() || |
| then_mov[i]->conditional_mod != BRW_CONDITIONAL_NONE || |
| else_mov[i]->conditional_mod != BRW_CONDITIONAL_NONE) { |
| movs = i; |
| break; |
| } |
| |
| /* Check that source types for mov operations match. */ |
| if (then_mov[i]->src[0].type != else_mov[i]->src[0].type) { |
| movs = i; |
| break; |
| } |
| } |
| |
| if (movs == 0) |
| continue; |
| |
| for (int i = 0; i < movs; i++) { |
| const fs_builder ibld = fs_builder(this, then_block, then_mov[i]) |
| .at(block, if_inst); |
| |
| if (then_mov[i]->src[0].equals(else_mov[i]->src[0])) { |
| ibld.MOV(then_mov[i]->dst, then_mov[i]->src[0]); |
| } else { |
| /* Only the last source register can be a constant, so if the MOV |
| * in the "then" clause uses a constant, we need to put it in a |
| * temporary. |
| */ |
| fs_reg src0(then_mov[i]->src[0]); |
| if (src0.file == IMM) { |
| src0 = vgrf(glsl_type::float_type); |
| src0.type = then_mov[i]->src[0].type; |
| ibld.MOV(src0, then_mov[i]->src[0]); |
| } |
| |
| set_predicate_inv(if_inst->predicate, if_inst->predicate_inverse, |
| ibld.SEL(then_mov[i]->dst, src0, |
| else_mov[i]->src[0])); |
| } |
| |
| then_mov[i]->remove(then_block); |
| else_mov[i]->remove(else_block); |
| } |
| |
| progress = true; |
| } |
| |
| if (progress) |
| invalidate_live_intervals(); |
| |
| return progress; |
| } |