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| 5564 | serge | 1 | /* |
| 2 | * Copyright © 2010 Intel Corporation |
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| 3 | * |
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| 4 | * Permission is hereby granted, free of charge, to any person obtaining a |
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| 5 | * copy of this software and associated documentation files (the "Software"), |
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| 6 | * to deal in the Software without restriction, including without limitation |
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| 7 | * the rights to use, copy, modify, merge, publish, distribute, sublicense, |
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| 8 | * and/or sell copies of the Software, and to permit persons to whom the |
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| 9 | * Software is furnished to do so, subject to the following conditions: |
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| 10 | * |
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| 11 | * The above copyright notice and this permission notice (including the next |
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| 12 | * paragraph) shall be included in all copies or substantial portions of the |
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| 13 | * Software. |
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| 14 | * |
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| 15 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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| 16 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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| 17 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
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| 18 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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| 19 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
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| 20 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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| 21 | * DEALINGS IN THE SOFTWARE. |
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| 22 | */ |
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| 23 | |||
| 24 | /** |
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| 25 | * \file lower_discard.cpp |
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| 26 | * |
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| 27 | * This pass moves discards out of if-statements. |
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| 28 | * |
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| 29 | * Case 1: The "then" branch contains a conditional discard: |
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| 30 | * --------------------------------------------------------- |
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| 31 | * |
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| 32 | * if (cond1) { |
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| 33 | * s1; |
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| 34 | * discard cond2; |
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| 35 | * s2; |
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| 36 | * } else { |
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| 37 | * s3; |
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| 38 | * } |
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| 39 | * |
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| 40 | * becomes: |
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| 41 | * |
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| 42 | * temp = false; |
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| 43 | * if (cond1) { |
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| 44 | * s1; |
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| 45 | * temp = cond2; |
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| 46 | * s2; |
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| 47 | * } else { |
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| 48 | * s3; |
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| 49 | * } |
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| 50 | * discard temp; |
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| 51 | * |
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| 52 | * Case 2: The "else" branch contains a conditional discard: |
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| 53 | * --------------------------------------------------------- |
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| 54 | * |
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| 55 | * if (cond1) { |
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| 56 | * s1; |
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| 57 | * } else { |
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| 58 | * s2; |
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| 59 | * discard cond2; |
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| 60 | * s3; |
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| 61 | * } |
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| 62 | * |
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| 63 | * becomes: |
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| 64 | * |
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| 65 | * temp = false; |
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| 66 | * if (cond1) { |
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| 67 | * s1; |
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| 68 | * } else { |
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| 69 | * s2; |
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| 70 | * temp = cond2; |
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| 71 | * s3; |
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| 72 | * } |
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| 73 | * discard temp; |
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| 74 | * |
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| 75 | * Case 3: Both branches contain a conditional discard: |
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| 76 | * ---------------------------------------------------- |
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| 77 | * |
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| 78 | * if (cond1) { |
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| 79 | * s1; |
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| 80 | * discard cond2; |
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| 81 | * s2; |
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| 82 | * } else { |
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| 83 | * s3; |
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| 84 | * discard cond3; |
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| 85 | * s4; |
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| 86 | * } |
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| 87 | * |
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| 88 | * becomes: |
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| 89 | * |
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| 90 | * temp = false; |
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| 91 | * if (cond1) { |
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| 92 | * s1; |
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| 93 | * temp = cond2; |
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| 94 | * s2; |
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| 95 | * } else { |
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| 96 | * s3; |
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| 97 | * temp = cond3; |
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| 98 | * s4; |
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| 99 | * } |
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| 100 | * discard temp; |
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| 101 | * |
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| 102 | * If there are multiple conditional discards, we need only deal with one of |
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| 103 | * them. Repeatedly applying this pass will take care of the others. |
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| 104 | * |
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| 105 | * Unconditional discards are treated as having a condition of "true". |
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| 106 | */ |
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| 107 | |||
| 108 | #include "glsl_types.h" |
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| 109 | #include "ir.h" |
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| 110 | |||
| 111 | namespace { |
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| 112 | |||
| 113 | class lower_discard_visitor : public ir_hierarchical_visitor { |
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| 114 | public: |
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| 115 | lower_discard_visitor() |
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| 116 | { |
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| 117 | this->progress = false; |
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| 118 | } |
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| 119 | |||
| 120 | ir_visitor_status visit_leave(ir_if *); |
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| 121 | |||
| 122 | bool progress; |
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| 123 | }; |
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| 124 | |||
| 125 | } /* anonymous namespace */ |
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| 126 | |||
| 127 | bool |
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| 128 | lower_discard(exec_list *instructions) |
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| 129 | { |
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| 130 | lower_discard_visitor v; |
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| 131 | |||
| 132 | visit_list_elements(&v, instructions); |
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| 133 | |||
| 134 | return v.progress; |
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| 135 | } |
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| 136 | |||
| 137 | |||
| 138 | static ir_discard * |
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| 139 | find_discard(exec_list &instructions) |
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| 140 | { |
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| 141 | foreach_in_list(ir_instruction, node, &instructions) { |
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| 142 | ir_discard *ir = node->as_discard(); |
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| 143 | if (ir != NULL) |
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| 144 | return ir; |
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| 145 | } |
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| 146 | return NULL; |
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| 147 | } |
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| 148 | |||
| 149 | |||
| 150 | static void |
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| 151 | replace_discard(void *mem_ctx, ir_variable *var, ir_discard *ir) |
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| 152 | { |
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| 153 | ir_rvalue *condition = ir->condition; |
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| 154 | |||
| 155 | /* For unconditional discards, use "true" as the condition. */ |
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| 156 | if (condition == NULL) |
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| 157 | condition = new(mem_ctx) ir_constant(true); |
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| 158 | |||
| 159 | ir_assignment *assignment = |
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| 160 | new(mem_ctx) ir_assignment(new(mem_ctx) ir_dereference_variable(var), |
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| 161 | condition, NULL); |
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| 162 | |||
| 163 | ir->replace_with(assignment); |
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| 164 | } |
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| 165 | |||
| 166 | |||
| 167 | ir_visitor_status |
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| 168 | lower_discard_visitor::visit_leave(ir_if *ir) |
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| 169 | { |
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| 170 | ir_discard *then_discard = find_discard(ir->then_instructions); |
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| 171 | ir_discard *else_discard = find_discard(ir->else_instructions); |
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| 172 | |||
| 173 | if (then_discard == NULL && else_discard == NULL) |
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| 174 | return visit_continue; |
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| 175 | |||
| 176 | void *mem_ctx = ralloc_parent(ir); |
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| 177 | |||
| 178 | ir_variable *temp = new(mem_ctx) ir_variable(glsl_type::bool_type, |
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| 179 | "discard_cond_temp", |
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| 180 | ir_var_temporary); |
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| 181 | ir_assignment *temp_initializer = |
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| 182 | new(mem_ctx) ir_assignment(new(mem_ctx) ir_dereference_variable(temp), |
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| 183 | new(mem_ctx) ir_constant(false), NULL); |
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| 184 | |||
| 185 | ir->insert_before(temp); |
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| 186 | ir->insert_before(temp_initializer); |
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| 187 | |||
| 188 | if (then_discard != NULL) |
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| 189 | replace_discard(mem_ctx, temp, then_discard); |
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| 190 | |||
| 191 | if (else_discard != NULL) |
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| 192 | replace_discard(mem_ctx, temp, else_discard); |
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| 193 | |||
| 194 | ir_discard *discard = then_discard != NULL ? then_discard : else_discard; |
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| 195 | discard->condition = new(mem_ctx) ir_dereference_variable(temp); |
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| 196 | ir->insert_after(discard); |
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| 197 | |||
| 198 | this->progress = true; |
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| 199 | |||
| 200 | return visit_continue; |
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| 201 | } |