1 /* 2 * Copyright 2016 Red Hat 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining a 5 * copy of this software and associated documentation files (the "Software"), 6 * to deal in the Software without restriction, including without limitation 7 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 8 * and/or sell copies of the Software, and to permit persons to whom the 9 * Software is furnished to do so, subject to the following conditions: 10 * 11 * The above copyright notice and this permission notice (including the next 12 * paragraph) shall be included in all copies or substantial portions of the 13 * Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 21 * IN THE SOFTWARE. 22 */ 23 24 #include "nir.h" 25 #include "nir_builder.h" 26 27 /** @file nir_opt_conditional_discard.c 28 * 29 * Handles optimization of lowering if (cond) discard to discard_if(cond). 30 */ 31 32 static bool 33 nir_opt_conditional_discard_block(nir_builder *b, nir_block *block) 34 { 35 if (nir_cf_node_is_first(&block->cf_node)) 36 return false; 37 38 nir_cf_node *prev_node = nir_cf_node_prev(&block->cf_node); 39 if (prev_node->type != nir_cf_node_if) 40 return false; 41 42 nir_if *if_stmt = nir_cf_node_as_if(prev_node); 43 nir_block *then_block = nir_if_first_then_block(if_stmt); 44 nir_block *else_block = nir_if_first_else_block(if_stmt); 45 46 /* check there is only one else block and it is empty */ 47 if (nir_if_last_else_block(if_stmt) != else_block) 48 return false; 49 if (!exec_list_is_empty(&else_block->instr_list)) 50 return false; 51 52 /* check there is only one then block and it has only one instruction in it */ 53 if (nir_if_last_then_block(if_stmt) != then_block) 54 return false; 55 if (exec_list_is_empty(&then_block->instr_list)) 56 return false; 57 if (exec_list_length(&then_block->instr_list) > 1) 58 return false; 59 /* 60 * make sure no subsequent phi nodes point at this if. 61 */ 62 nir_block *after = nir_cf_node_as_block(nir_cf_node_next(&if_stmt->cf_node)); 63 nir_foreach_instr_safe(instr, after) { 64 if (instr->type != nir_instr_type_phi) 65 break; 66 nir_phi_instr *phi = nir_instr_as_phi(instr); 67 68 nir_foreach_phi_src(phi_src, phi) { 69 if (phi_src->pred == then_block || 70 phi_src->pred == else_block) 71 return false; 72 } 73 } 74 75 /* Get the first instruction in the then block and confirm it is 76 * a discard or a discard_if 77 */ 78 nir_instr *instr = nir_block_first_instr(then_block); 79 if (instr->type != nir_instr_type_intrinsic) 80 return false; 81 82 nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr); 83 if (intrin->intrinsic != nir_intrinsic_discard && 84 intrin->intrinsic != nir_intrinsic_discard_if) 85 return false; 86 87 nir_src cond; 88 89 b->cursor = nir_before_cf_node(prev_node); 90 if (intrin->intrinsic == nir_intrinsic_discard) 91 cond = if_stmt->condition; 92 else 93 cond = nir_src_for_ssa(nir_iand(b, 94 nir_ssa_for_src(b, if_stmt->condition, 1), 95 nir_ssa_for_src(b, intrin->src[0], 1))); 96 97 nir_intrinsic_instr *discard_if = 98 nir_intrinsic_instr_create(b->shader, nir_intrinsic_discard_if); 99 nir_src_copy(&discard_if->src[0], &cond, discard_if); 100 101 nir_instr_insert_before_cf(prev_node, &discard_if->instr); 102 nir_instr_remove(&intrin->instr); 103 nir_cf_node_remove(&if_stmt->cf_node); 104 105 return true; 106 } 107 108 bool 109 nir_opt_conditional_discard(nir_shader *shader) 110 { 111 bool progress = false; 112 113 nir_builder builder; 114 115 nir_foreach_function(function, shader) { 116 if (function->impl) { 117 nir_builder_init(&builder, function->impl); 118 nir_foreach_block_safe(block, function->impl) { 119 progress |= nir_opt_conditional_discard_block(&builder, block); 120 } 121 } 122 } 123 return progress; 124 } 125