/* * Copyright © 2012 Vincent Lejeune * Copyright © 2012 Intel Corporation * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER * DEALINGS IN THE SOFTWARE. */ #include "ir.h" #include "util/hash_table.h" /** * \file lower_output_reads.cpp * * In GLSL, shader output variables (such as varyings) can be both read and * written. However, on some hardware, reading an output register causes * trouble. * * This pass creates temporary shadow copies of every (used) shader output, * and replaces all accesses to use those instead. It also adds code to the * main() function to copy the final values to the actual shader outputs. */ namespace { class output_read_remover : public ir_hierarchical_visitor { protected: /** * A hash table mapping from the original ir_variable shader outputs * (ir_var_shader_out mode) to the new temporaries to be used instead. */ hash_table *replacements; unsigned stage; public: output_read_remover(unsigned stage); ~output_read_remover(); virtual ir_visitor_status visit(class ir_dereference_variable *); virtual ir_visitor_status visit_leave(class ir_emit_vertex *); virtual ir_visitor_status visit_leave(class ir_return *); virtual ir_visitor_status visit_leave(class ir_function_signature *); }; } /* anonymous namespace */ /** * Hash function for the output variables - computes the hash of the name. * NOTE: We're using the name string to ensure that the hash doesn't depend * on any random factors, otherwise the output_read_remover could produce * the random order of the assignments. * * NOTE: If you want to reuse this function please take into account that * generally the names of the variables are non-unique. */ static unsigned hash_table_var_hash(const void *key) { const ir_variable * var = static_cast(key); return _mesa_key_hash_string(var->name); } output_read_remover::output_read_remover(unsigned stage) { this->stage = stage; replacements = _mesa_hash_table_create(NULL, hash_table_var_hash, _mesa_key_pointer_equal); } output_read_remover::~output_read_remover() { _mesa_hash_table_destroy(replacements, NULL); } ir_visitor_status output_read_remover::visit(ir_dereference_variable *ir) { if (ir->var->data.mode != ir_var_shader_out || ir->var->data.fb_fetch_output) return visit_continue; hash_entry *entry = _mesa_hash_table_search(replacements, ir->var); ir_variable *temp = entry ? (ir_variable *) entry->data : NULL; /* If we don't have an existing temporary, create one. */ if (temp == NULL) { void *var_ctx = ralloc_parent(ir->var); temp = new(var_ctx) ir_variable(ir->var->type, ir->var->name, ir_var_temporary); _mesa_hash_table_insert(replacements, ir->var, temp); ir->var->insert_after(temp); } /* Update the dereference to use the temporary */ ir->var = temp; return visit_continue; } /** * Create an assignment to copy a temporary value back to the actual output. */ static ir_assignment * copy(void *ctx, ir_variable *output, ir_variable *temp) { ir_dereference_variable *lhs = new(ctx) ir_dereference_variable(output); ir_dereference_variable *rhs = new(ctx) ir_dereference_variable(temp); return new(ctx) ir_assignment(lhs, rhs); } /** Insert a copy-back assignment before a "return" statement or a call to * EmitVertex(). */ static void emit_return_copy(const void *key, void *data, void *closure) { ir_return *ir = (ir_return *) closure; ir->insert_before(copy(ir, (ir_variable *) key, (ir_variable *) data)); } /** Insert a copy-back assignment at the end of the main() function */ static void emit_main_copy(const void *key, void *data, void *closure) { ir_function_signature *sig = (ir_function_signature *) closure; sig->body.push_tail(copy(sig, (ir_variable *) key, (ir_variable *) data)); } ir_visitor_status output_read_remover::visit_leave(ir_return *ir) { hash_table_call_foreach(replacements, emit_return_copy, ir); return visit_continue; } ir_visitor_status output_read_remover::visit_leave(ir_emit_vertex *ir) { hash_table_call_foreach(replacements, emit_return_copy, ir); return visit_continue; } ir_visitor_status output_read_remover::visit_leave(ir_function_signature *sig) { if (strcmp(sig->function_name(), "main") != 0) return visit_continue; hash_table_call_foreach(replacements, emit_main_copy, sig); return visit_continue; } void lower_output_reads(unsigned stage, exec_list *instructions) { /* Due to the possible interactions between multiple tessellation control * shader invocations, we leave output variables as-is. */ if (stage == MESA_SHADER_TESS_CTRL) return; output_read_remover v(stage); visit_list_elements(&v, instructions); }