1 /* 2 * Copyright 2012 Vincent Lejeune 3 * Copyright 2012 Intel Corporation 4 * 5 * Permission is hereby granted, free of charge, to any person obtaining a 6 * copy of this software and associated documentation files (the "Software"), 7 * to deal in the Software without restriction, including without limitation 8 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 9 * and/or sell copies of the Software, and to permit persons to whom the 10 * Software is furnished to do so, subject to the following conditions: 11 * 12 * The above copyright notice and this permission notice (including the next 13 * paragraph) shall be included in all copies or substantial portions of the 14 * Software. 15 * 16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 22 * DEALINGS IN THE SOFTWARE. 23 */ 24 25 #include "ir.h" 26 #include "program/hash_table.h" 27 28 /** 29 * \file lower_output_reads.cpp 30 * 31 * In GLSL, shader output variables (such as varyings) can be both read and 32 * written. However, on some hardware, reading an output register causes 33 * trouble. 34 * 35 * This pass creates temporary shadow copies of every (used) shader output, 36 * and replaces all accesses to use those instead. It also adds code to the 37 * main() function to copy the final values to the actual shader outputs. 38 */ 39 40 class output_read_remover : public ir_hierarchical_visitor { 41 protected: 42 /** 43 * A hash table mapping from the original ir_variable shader outputs 44 * (ir_var_out mode) to the new temporaries to be used instead. 45 */ 46 hash_table *replacements; 47 48 void *mem_ctx; 49 public: 50 output_read_remover(); 51 ~output_read_remover(); 52 virtual ir_visitor_status visit(class ir_dereference_variable *); 53 virtual ir_visitor_status visit_leave(class ir_return *); 54 virtual ir_visitor_status visit_leave(class ir_function_signature *); 55 }; 56 57 /** 58 * Hash function for the output variables - computes the hash of the name. 59 * NOTE: We're using the name string to ensure that the hash doesn't depend 60 * on any random factors, otherwise the output_read_remover could produce 61 * the random order of the assignments. 62 * 63 * NOTE: If you want to reuse this function please take into account that 64 * generally the names of the variables are non-unique. 65 */ 66 static unsigned 67 hash_table_var_hash(const void *key) 68 { 69 const ir_variable * var = static_cast<const ir_variable *>(key); 70 return hash_table_string_hash(var->name); 71 } 72 73 output_read_remover::output_read_remover() 74 { 75 mem_ctx = ralloc_context(NULL); 76 replacements = 77 hash_table_ctor(0, hash_table_var_hash, hash_table_pointer_compare); 78 } 79 80 output_read_remover::~output_read_remover() 81 { 82 hash_table_dtor(replacements); 83 ralloc_free(mem_ctx); 84 } 85 86 ir_visitor_status 87 output_read_remover::visit(ir_dereference_variable *ir) 88 { 89 if (ir->var->mode != ir_var_out) 90 return visit_continue; 91 92 ir_variable *temp = (ir_variable *) hash_table_find(replacements, ir->var); 93 94 /* If we don't have an existing temporary, create one. */ 95 if (temp == NULL) { 96 void *var_ctx = ralloc_parent(ir->var); 97 temp = new(var_ctx) ir_variable(ir->var->type, ir->var->name, 98 ir_var_temporary); 99 hash_table_insert(replacements, temp, ir->var); 100 } 101 102 /* Update the dereference to use the temporary */ 103 ir->var = temp; 104 105 return visit_continue; 106 } 107 108 /** 109 * Create an assignment to copy a temporary value back to the actual output. 110 */ 111 static ir_assignment * 112 copy(void *ctx, ir_variable *output, ir_variable *temp) 113 { 114 ir_dereference_variable *lhs = new(ctx) ir_dereference_variable(output); 115 ir_dereference_variable *rhs = new(ctx) ir_dereference_variable(temp); 116 return new(ctx) ir_assignment(lhs, rhs); 117 } 118 119 /** Insert a copy-back assignment before a "return" statement */ 120 static void 121 emit_return_copy(const void *key, void *data, void *closure) 122 { 123 ir_return *ir = (ir_return *) closure; 124 ir->insert_before(copy(ir, (ir_variable *) key, (ir_variable *) data)); 125 } 126 127 /** Insert a copy-back assignment at the end of the main() function */ 128 static void 129 emit_main_copy(const void *key, void *data, void *closure) 130 { 131 ir_function_signature *sig = (ir_function_signature *) closure; 132 sig->body.push_tail(copy(sig, (ir_variable *) key, (ir_variable *) data)); 133 } 134 135 ir_visitor_status 136 output_read_remover::visit_leave(ir_return *ir) 137 { 138 hash_table_call_foreach(replacements, emit_return_copy, ir); 139 return visit_continue; 140 } 141 142 ir_visitor_status 143 output_read_remover::visit_leave(ir_function_signature *sig) 144 { 145 if (strcmp(sig->function_name(), "main") != 0) 146 return visit_continue; 147 148 hash_table_call_foreach(replacements, emit_main_copy, sig); 149 return visit_continue; 150 } 151 152 void 153 lower_output_reads(exec_list *instructions) 154 { 155 output_read_remover v; 156 visit_list_elements(&v, instructions); 157 } 158
