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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 | #include |
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25 | #include "main/compiler.h" |
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26 | #include "glsl_types.h" |
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27 | #include "loop_analysis.h" |
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28 | #include "ir_hierarchical_visitor.h" |
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29 | |||
30 | /** |
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31 | * Find an initializer of a variable outside a loop |
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32 | * |
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33 | * Works backwards from the loop to find the pre-loop value of the variable. |
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34 | * This is used, for example, to find the initial value of loop induction |
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35 | * variables. |
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36 | * |
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37 | * \param loop Loop where \c var is an induction variable |
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38 | * \param var Variable whose initializer is to be found |
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39 | * |
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40 | * \return |
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41 | * The \c ir_rvalue assigned to the variable outside the loop. May return |
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42 | * \c NULL if no initializer can be found. |
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43 | */ |
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44 | ir_rvalue * |
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45 | find_initial_value(ir_loop *loop, ir_variable *var) |
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46 | { |
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47 | for (exec_node *node = loop->prev; |
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48 | !node->is_head_sentinel(); |
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49 | node = node->prev) { |
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50 | ir_instruction *ir = (ir_instruction *) node; |
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51 | |||
52 | switch (ir->ir_type) { |
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53 | case ir_type_call: |
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54 | case ir_type_loop: |
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55 | case ir_type_loop_jump: |
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56 | case ir_type_return: |
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57 | case ir_type_if: |
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58 | return NULL; |
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59 | |||
60 | case ir_type_function: |
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61 | case ir_type_function_signature: |
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62 | assert(!"Should not get here."); |
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63 | return NULL; |
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64 | |||
65 | case ir_type_assignment: { |
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66 | ir_assignment *assign = ir->as_assignment(); |
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67 | ir_variable *assignee = assign->lhs->whole_variable_referenced(); |
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68 | |||
69 | if (assignee == var) |
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70 | return (assign->condition != NULL) ? NULL : assign->rhs; |
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71 | |||
72 | break; |
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73 | } |
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74 | |||
75 | default: |
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76 | break; |
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77 | } |
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78 | } |
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79 | |||
80 | return NULL; |
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81 | } |
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82 | |||
83 | |||
84 | int |
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85 | calculate_iterations(ir_rvalue *from, ir_rvalue *to, ir_rvalue *increment, |
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86 | enum ir_expression_operation op) |
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87 | { |
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88 | if (from == NULL || to == NULL || increment == NULL) |
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89 | return -1; |
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90 | |||
91 | void *mem_ctx = ralloc_context(NULL); |
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92 | |||
93 | ir_expression *const sub = |
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94 | new(mem_ctx) ir_expression(ir_binop_sub, from->type, to, from); |
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95 | |||
96 | ir_expression *const div = |
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97 | new(mem_ctx) ir_expression(ir_binop_div, sub->type, sub, increment); |
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98 | |||
99 | ir_constant *iter = div->constant_expression_value(); |
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100 | |||
101 | if (iter == NULL) |
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102 | return -1; |
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103 | |||
104 | if (!iter->type->is_integer()) { |
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105 | const ir_expression_operation op = iter->type->is_double() |
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106 | ? ir_unop_d2i : ir_unop_f2i; |
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107 | ir_rvalue *cast = |
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108 | new(mem_ctx) ir_expression(op, glsl_type::int_type, iter, NULL); |
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109 | |||
110 | iter = cast->constant_expression_value(); |
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111 | } |
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112 | |||
113 | int iter_value = iter->get_int_component(0); |
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114 | |||
115 | /* Make sure that the calculated number of iterations satisfies the exit |
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116 | * condition. This is needed to catch off-by-one errors and some types of |
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117 | * ill-formed loops. For example, we need to detect that the following |
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118 | * loop does not have a maximum iteration count. |
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119 | * |
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120 | * for (float x = 0.0; x != 0.9; x += 0.2) |
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121 | * ; |
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122 | */ |
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123 | const int bias[] = { -1, 0, 1 }; |
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124 | bool valid_loop = false; |
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125 | |||
126 | for (unsigned i = 0; i < ARRAY_SIZE(bias); i++) { |
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127 | /* Increment may be of type int, uint or float. */ |
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128 | switch (increment->type->base_type) { |
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129 | case GLSL_TYPE_INT: |
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130 | iter = new(mem_ctx) ir_constant(iter_value + bias[i]); |
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131 | break; |
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132 | case GLSL_TYPE_UINT: |
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133 | iter = new(mem_ctx) ir_constant(unsigned(iter_value + bias[i])); |
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134 | break; |
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135 | case GLSL_TYPE_FLOAT: |
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136 | iter = new(mem_ctx) ir_constant(float(iter_value + bias[i])); |
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137 | break; |
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138 | case GLSL_TYPE_DOUBLE: |
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139 | iter = new(mem_ctx) ir_constant(double(iter_value + bias[i])); |
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140 | break; |
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141 | default: |
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142 | unreachable("Unsupported type for loop iterator."); |
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143 | } |
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144 | |||
145 | ir_expression *const mul = |
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146 | new(mem_ctx) ir_expression(ir_binop_mul, increment->type, iter, |
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147 | increment); |
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148 | |||
149 | ir_expression *const add = |
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150 | new(mem_ctx) ir_expression(ir_binop_add, mul->type, mul, from); |
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151 | |||
152 | ir_expression *const cmp = |
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153 | new(mem_ctx) ir_expression(op, glsl_type::bool_type, add, to); |
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154 | |||
155 | ir_constant *const cmp_result = cmp->constant_expression_value(); |
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156 | |||
157 | assert(cmp_result != NULL); |
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158 | if (cmp_result->get_bool_component(0)) { |
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159 | iter_value += bias[i]; |
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160 | valid_loop = true; |
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161 | break; |
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162 | } |
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163 | } |
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164 | |||
165 | ralloc_free(mem_ctx); |
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166 | return (valid_loop) ? iter_value : -1; |
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167 | } |
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168 | |||
169 | namespace { |
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170 | |||
171 | class loop_control_visitor : public ir_hierarchical_visitor { |
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172 | public: |
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173 | loop_control_visitor(loop_state *state) |
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174 | { |
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175 | this->state = state; |
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176 | this->progress = false; |
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177 | } |
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178 | |||
179 | virtual ir_visitor_status visit_leave(ir_loop *ir); |
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180 | |||
181 | loop_state *state; |
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182 | |||
183 | bool progress; |
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184 | }; |
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185 | |||
186 | } /* anonymous namespace */ |
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187 | |||
188 | ir_visitor_status |
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189 | loop_control_visitor::visit_leave(ir_loop *ir) |
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190 | { |
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191 | loop_variable_state *const ls = this->state->get(ir); |
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192 | |||
193 | /* If we've entered a loop that hasn't been analyzed, something really, |
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194 | * really bad has happened. |
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195 | */ |
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196 | if (ls == NULL) { |
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197 | assert(ls != NULL); |
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198 | return visit_continue; |
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199 | } |
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200 | |||
201 | if (ls->limiting_terminator != NULL) { |
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202 | /* If the limiting terminator has an iteration count of zero, then we've |
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203 | * proven that the loop cannot run, so delete it. |
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204 | */ |
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205 | int iterations = ls->limiting_terminator->iterations; |
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206 | if (iterations == 0) { |
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207 | ir->remove(); |
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208 | this->progress = true; |
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209 | return visit_continue; |
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210 | } |
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211 | } |
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212 | |||
213 | /* Remove the conditional break statements associated with all terminators |
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214 | * that are associated with a fixed iteration count, except for the one |
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215 | * associated with the limiting terminator--that one needs to stay, since |
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216 | * it terminates the loop. Exception: if the loop still has a normative |
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217 | * bound, then that terminates the loop, so we don't even need the limiting |
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218 | * terminator. |
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219 | */ |
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220 | foreach_in_list(loop_terminator, t, &ls->terminators) { |
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221 | if (t->iterations < 0) |
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222 | continue; |
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223 | |||
224 | if (t != ls->limiting_terminator) { |
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225 | t->ir->remove(); |
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226 | |||
227 | assert(ls->num_loop_jumps > 0); |
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228 | ls->num_loop_jumps--; |
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229 | |||
230 | this->progress = true; |
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231 | } |
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232 | } |
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233 | |||
234 | return visit_continue; |
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235 | } |
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236 | |||
237 | |||
238 | bool |
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239 | set_loop_controls(exec_list *instructions, loop_state *ls) |
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240 | { |
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241 | loop_control_visitor v(ls); |
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242 | |||
243 | v.run(instructions); |
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244 | |||
245 | return v.progress; |
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246 | }>> |