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1901 | 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 | * constant 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, constant, 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 constantright 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 CONSTANTRIGHT 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 opt_constant_propagation.cpp |
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26 | * |
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27 | * Tracks assignments of constants to channels of variables, and |
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28 | * usage of those constant channels with direct usage of the constants. |
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29 | * |
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30 | * This can lead to constant folding and algebraic optimizations in |
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31 | * those later expressions, while causing no increase in instruction |
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32 | * count (due to constants being generally free to load from a |
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33 | * constant push buffer or as instruction immediate values) and |
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34 | * possibly reducing register pressure. |
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35 | */ |
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36 | |||
37 | #include "ir.h" |
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38 | #include "ir_visitor.h" |
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39 | #include "ir_rvalue_visitor.h" |
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40 | #include "ir_basic_block.h" |
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41 | #include "ir_optimization.h" |
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42 | #include "glsl_types.h" |
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43 | |||
44 | class acp_entry : public exec_node |
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45 | { |
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46 | public: |
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47 | acp_entry(ir_variable *var, unsigned write_mask, ir_constant *constant) |
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48 | { |
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49 | assert(var); |
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50 | assert(constant); |
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51 | this->var = var; |
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52 | this->write_mask = write_mask; |
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53 | this->constant = constant; |
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54 | } |
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55 | |||
56 | ir_variable *var; |
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57 | ir_constant *constant; |
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58 | unsigned write_mask; |
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59 | }; |
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60 | |||
61 | |||
62 | class kill_entry : public exec_node |
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63 | { |
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64 | public: |
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65 | kill_entry(ir_variable *var, unsigned write_mask) |
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66 | { |
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67 | assert(var); |
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68 | this->var = var; |
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69 | this->write_mask = write_mask; |
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70 | } |
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71 | |||
72 | ir_variable *var; |
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73 | unsigned write_mask; |
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74 | }; |
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75 | |||
76 | class ir_constant_propagation_visitor : public ir_rvalue_visitor { |
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77 | public: |
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78 | ir_constant_propagation_visitor() |
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79 | { |
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80 | progress = false; |
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81 | mem_ctx = ralloc_context(0); |
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82 | this->acp = new(mem_ctx) exec_list; |
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83 | this->kills = new(mem_ctx) exec_list; |
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84 | } |
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85 | ~ir_constant_propagation_visitor() |
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86 | { |
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87 | ralloc_free(mem_ctx); |
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88 | } |
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89 | |||
90 | virtual ir_visitor_status visit_enter(class ir_loop *); |
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91 | virtual ir_visitor_status visit_enter(class ir_function_signature *); |
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92 | virtual ir_visitor_status visit_enter(class ir_function *); |
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93 | virtual ir_visitor_status visit_leave(class ir_assignment *); |
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94 | virtual ir_visitor_status visit_enter(class ir_call *); |
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95 | virtual ir_visitor_status visit_enter(class ir_if *); |
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96 | |||
97 | void add_constant(ir_assignment *ir); |
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98 | void kill(ir_variable *ir, unsigned write_mask); |
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99 | void handle_if_block(exec_list *instructions); |
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100 | void handle_rvalue(ir_rvalue **rvalue); |
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101 | |||
102 | /** List of acp_entry: The available constants to propagate */ |
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103 | exec_list *acp; |
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104 | |||
105 | /** |
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106 | * List of kill_entry: The masks of variables whose values were |
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107 | * killed in this block. |
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108 | */ |
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109 | exec_list *kills; |
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110 | |||
111 | bool progress; |
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112 | |||
113 | bool killed_all; |
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114 | |||
115 | void *mem_ctx; |
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116 | }; |
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117 | |||
118 | |||
119 | void |
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120 | ir_constant_propagation_visitor::handle_rvalue(ir_rvalue **rvalue) |
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121 | { |
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122 | if (this->in_assignee || !*rvalue) |
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123 | return; |
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124 | |||
125 | const glsl_type *type = (*rvalue)->type; |
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126 | if (!type->is_scalar() && !type->is_vector()) |
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127 | return; |
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128 | |||
129 | ir_swizzle *swiz = NULL; |
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130 | ir_dereference_variable *deref = (*rvalue)->as_dereference_variable(); |
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131 | if (!deref) { |
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132 | swiz = (*rvalue)->as_swizzle(); |
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133 | if (!swiz) |
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134 | return; |
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135 | |||
136 | deref = swiz->val->as_dereference_variable(); |
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137 | if (!deref) |
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138 | return; |
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139 | } |
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140 | |||
141 | ir_constant_data data; |
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142 | memset(&data, 0, sizeof(data)); |
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143 | |||
144 | for (unsigned int i = 0; i < type->components(); i++) { |
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145 | int channel; |
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146 | acp_entry *found = NULL; |
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147 | |||
148 | if (swiz) { |
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149 | switch (i) { |
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150 | case 0: channel = swiz->mask.x; break; |
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151 | case 1: channel = swiz->mask.y; break; |
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152 | case 2: channel = swiz->mask.z; break; |
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153 | case 3: channel = swiz->mask.w; break; |
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154 | default: assert(!"shouldn't be reached"); channel = 0; break; |
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155 | } |
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156 | } else { |
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157 | channel = i; |
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158 | } |
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159 | |||
160 | foreach_iter(exec_list_iterator, iter, *this->acp) { |
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161 | acp_entry *entry = (acp_entry *)iter.get(); |
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162 | if (entry->var == deref->var && entry->write_mask & (1 << channel)) { |
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163 | found = entry; |
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164 | break; |
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165 | } |
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166 | } |
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167 | |||
168 | if (!found) |
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169 | return; |
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170 | |||
171 | int rhs_channel = 0; |
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172 | for (int j = 0; j < 4; j++) { |
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173 | if (j == channel) |
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174 | break; |
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175 | if (found->write_mask & (1 << j)) |
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176 | rhs_channel++; |
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177 | } |
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178 | |||
179 | switch (type->base_type) { |
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180 | case GLSL_TYPE_FLOAT: |
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181 | data.f[i] = found->constant->value.f[rhs_channel]; |
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182 | break; |
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183 | case GLSL_TYPE_INT: |
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184 | data.i[i] = found->constant->value.i[rhs_channel]; |
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185 | break; |
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186 | case GLSL_TYPE_UINT: |
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187 | data.u[i] = found->constant->value.u[rhs_channel]; |
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188 | break; |
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189 | case GLSL_TYPE_BOOL: |
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190 | data.b[i] = found->constant->value.b[rhs_channel]; |
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191 | break; |
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192 | default: |
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193 | assert(!"not reached"); |
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194 | break; |
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195 | } |
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196 | } |
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197 | |||
198 | *rvalue = new(ralloc_parent(deref)) ir_constant(type, &data); |
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199 | this->progress = true; |
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200 | } |
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201 | |||
202 | ir_visitor_status |
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203 | ir_constant_propagation_visitor::visit_enter(ir_function_signature *ir) |
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204 | { |
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205 | /* Treat entry into a function signature as a completely separate |
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206 | * block. Any instructions at global scope will be shuffled into |
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207 | * main() at link time, so they're irrelevant to us. |
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208 | */ |
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209 | exec_list *orig_acp = this->acp; |
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210 | exec_list *orig_kills = this->kills; |
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211 | bool orig_killed_all = this->killed_all; |
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212 | |||
213 | this->acp = new(mem_ctx) exec_list; |
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214 | this->kills = new(mem_ctx) exec_list; |
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215 | this->killed_all = false; |
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216 | |||
217 | visit_list_elements(this, &ir->body); |
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218 | |||
219 | this->kills = orig_kills; |
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220 | this->acp = orig_acp; |
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221 | this->killed_all = orig_killed_all; |
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222 | |||
223 | return visit_continue_with_parent; |
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224 | } |
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225 | |||
226 | ir_visitor_status |
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227 | ir_constant_propagation_visitor::visit_leave(ir_assignment *ir) |
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228 | { |
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229 | if (this->in_assignee) |
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230 | return visit_continue; |
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231 | |||
232 | kill(ir->lhs->variable_referenced(), ir->write_mask); |
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233 | |||
234 | add_constant(ir); |
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235 | |||
236 | return visit_continue; |
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237 | } |
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238 | |||
239 | ir_visitor_status |
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240 | ir_constant_propagation_visitor::visit_enter(ir_function *ir) |
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241 | { |
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242 | (void) ir; |
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243 | return visit_continue; |
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244 | } |
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245 | |||
246 | ir_visitor_status |
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247 | ir_constant_propagation_visitor::visit_enter(ir_call *ir) |
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248 | { |
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249 | /* Do constant propagation on call parameters, but skip any out params */ |
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250 | exec_list_iterator sig_param_iter = ir->get_callee()->parameters.iterator(); |
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251 | foreach_iter(exec_list_iterator, iter, ir->actual_parameters) { |
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252 | ir_variable *sig_param = (ir_variable *)sig_param_iter.get(); |
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253 | ir_rvalue *param = (ir_rvalue *)iter.get(); |
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254 | if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout) { |
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255 | ir_rvalue *new_param = param; |
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256 | handle_rvalue(&new_param); |
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257 | if (new_param != param) |
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258 | param->replace_with(new_param); |
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259 | else |
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260 | param->accept(this); |
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261 | } |
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262 | sig_param_iter.next(); |
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263 | } |
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264 | |||
265 | /* Since we're unlinked, we don't (necssarily) know the side effects of |
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266 | * this call. So kill all copies. |
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267 | */ |
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268 | acp->make_empty(); |
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269 | this->killed_all = true; |
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270 | |||
271 | return visit_continue_with_parent; |
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272 | } |
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273 | |||
274 | void |
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275 | ir_constant_propagation_visitor::handle_if_block(exec_list *instructions) |
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276 | { |
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277 | exec_list *orig_acp = this->acp; |
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278 | exec_list *orig_kills = this->kills; |
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279 | bool orig_killed_all = this->killed_all; |
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280 | |||
281 | this->acp = new(mem_ctx) exec_list; |
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282 | this->kills = new(mem_ctx) exec_list; |
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283 | this->killed_all = false; |
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284 | |||
285 | /* Populate the initial acp with a constant of the original */ |
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286 | foreach_iter(exec_list_iterator, iter, *orig_acp) { |
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287 | acp_entry *a = (acp_entry *)iter.get(); |
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288 | this->acp->push_tail(new(this->mem_ctx) acp_entry(a->var, a->write_mask, |
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289 | a->constant)); |
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290 | } |
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291 | |||
292 | visit_list_elements(this, instructions); |
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293 | |||
294 | if (this->killed_all) { |
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295 | orig_acp->make_empty(); |
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296 | } |
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297 | |||
298 | exec_list *new_kills = this->kills; |
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299 | this->kills = orig_kills; |
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300 | this->acp = orig_acp; |
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301 | this->killed_all = this->killed_all || orig_killed_all; |
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302 | |||
303 | foreach_iter(exec_list_iterator, iter, *new_kills) { |
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304 | kill_entry *k = (kill_entry *)iter.get(); |
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305 | kill(k->var, k->write_mask); |
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306 | } |
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307 | } |
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308 | |||
309 | ir_visitor_status |
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310 | ir_constant_propagation_visitor::visit_enter(ir_if *ir) |
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311 | { |
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312 | ir->condition->accept(this); |
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313 | handle_rvalue(&ir->condition); |
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314 | |||
315 | handle_if_block(&ir->then_instructions); |
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316 | handle_if_block(&ir->else_instructions); |
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317 | |||
318 | /* handle_if_block() already descended into the children. */ |
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319 | return visit_continue_with_parent; |
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320 | } |
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321 | |||
322 | ir_visitor_status |
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323 | ir_constant_propagation_visitor::visit_enter(ir_loop *ir) |
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324 | { |
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325 | exec_list *orig_acp = this->acp; |
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326 | exec_list *orig_kills = this->kills; |
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327 | bool orig_killed_all = this->killed_all; |
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328 | |||
329 | /* FINISHME: For now, the initial acp for loops is totally empty. |
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330 | * We could go through once, then go through again with the acp |
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331 | * cloned minus the killed entries after the first run through. |
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332 | */ |
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333 | this->acp = new(mem_ctx) exec_list; |
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334 | this->kills = new(mem_ctx) exec_list; |
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335 | this->killed_all = false; |
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336 | |||
337 | visit_list_elements(this, &ir->body_instructions); |
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338 | |||
339 | if (this->killed_all) { |
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340 | orig_acp->make_empty(); |
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341 | } |
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342 | |||
343 | exec_list *new_kills = this->kills; |
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344 | this->kills = orig_kills; |
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345 | this->acp = orig_acp; |
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346 | this->killed_all = this->killed_all || orig_killed_all; |
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347 | |||
348 | foreach_iter(exec_list_iterator, iter, *new_kills) { |
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349 | kill_entry *k = (kill_entry *)iter.get(); |
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350 | kill(k->var, k->write_mask); |
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351 | } |
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352 | |||
353 | /* already descended into the children. */ |
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354 | return visit_continue_with_parent; |
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355 | } |
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356 | |||
357 | void |
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358 | ir_constant_propagation_visitor::kill(ir_variable *var, unsigned write_mask) |
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359 | { |
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360 | assert(var != NULL); |
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361 | |||
362 | /* We don't track non-vectors. */ |
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363 | if (!var->type->is_vector() && !var->type->is_scalar()) |
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364 | return; |
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365 | |||
366 | /* Remove any entries currently in the ACP for this kill. */ |
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367 | foreach_iter(exec_list_iterator, iter, *this->acp) { |
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368 | acp_entry *entry = (acp_entry *)iter.get(); |
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369 | |||
370 | if (entry->var == var) { |
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371 | entry->write_mask &= ~write_mask; |
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372 | if (entry->write_mask == 0) |
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373 | entry->remove(); |
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374 | } |
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375 | } |
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376 | |||
377 | /* Add this writemask of the variable to the list of killed |
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378 | * variables in this block. |
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379 | */ |
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380 | foreach_iter(exec_list_iterator, iter, *this->kills) { |
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381 | kill_entry *entry = (kill_entry *)iter.get(); |
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382 | |||
383 | if (entry->var == var) { |
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384 | entry->write_mask |= write_mask; |
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385 | return; |
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386 | } |
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387 | } |
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388 | /* Not already in the list. Make new entry. */ |
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389 | this->kills->push_tail(new(this->mem_ctx) kill_entry(var, write_mask)); |
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390 | } |
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391 | |||
392 | /** |
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393 | * Adds an entry to the available constant list if it's a plain assignment |
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394 | * of a variable to a variable. |
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395 | */ |
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396 | void |
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397 | ir_constant_propagation_visitor::add_constant(ir_assignment *ir) |
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398 | { |
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399 | acp_entry *entry; |
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400 | |||
401 | if (ir->condition) { |
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402 | ir_constant *condition = ir->condition->as_constant(); |
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403 | if (!condition || !condition->value.b[0]) |
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404 | return; |
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405 | } |
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406 | |||
407 | if (!ir->write_mask) |
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408 | return; |
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409 | |||
410 | ir_dereference_variable *deref = ir->lhs->as_dereference_variable(); |
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411 | ir_constant *constant = ir->rhs->as_constant(); |
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412 | |||
413 | if (!deref || !constant) |
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414 | return; |
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415 | |||
416 | /* Only do constant propagation on vectors. Constant matrices, |
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417 | * arrays, or structures would require more work elsewhere. |
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418 | */ |
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419 | if (!deref->var->type->is_vector() && !deref->var->type->is_scalar()) |
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420 | return; |
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421 | |||
422 | entry = new(this->mem_ctx) acp_entry(deref->var, ir->write_mask, constant); |
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423 | this->acp->push_tail(entry); |
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424 | } |
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425 | |||
426 | /** |
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427 | * Does a constant propagation pass on the code present in the instruction stream. |
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428 | */ |
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429 | bool |
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430 | do_constant_propagation(exec_list *instructions) |
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431 | { |
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432 | ir_constant_propagation_visitor v; |
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433 | |||
434 | visit_list_elements(&v, instructions); |
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435 | |||
436 | return v.progress; |
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437 | }><>>><>> |