/* * Copyright © 2010 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. */ /** * \file opt_constant_variable.cpp * * Marks variables assigned a single constant value over the course * of the program as constant. * * The goal here is to trigger further constant folding and then dead * code elimination. This is common with vector/matrix constructors * and calls to builtin functions. */ #include "ir.h" #include "ir_visitor.h" #include "ir_optimization.h" #include "compiler/glsl_types.h" #include "util/hash_table.h" namespace { struct assignment_entry { int assignment_count; ir_variable *var; ir_constant *constval; bool our_scope; }; class ir_constant_variable_visitor : public ir_hierarchical_visitor { public: using ir_hierarchical_visitor::visit; using ir_hierarchical_visitor::visit_enter; virtual ir_visitor_status visit_enter(ir_dereference_variable *); virtual ir_visitor_status visit(ir_variable *); virtual ir_visitor_status visit_enter(ir_assignment *); virtual ir_visitor_status visit_enter(ir_call *); struct hash_table *ht; }; } /* unnamed namespace */ static struct assignment_entry * get_assignment_entry(ir_variable *var, struct hash_table *ht) { struct hash_entry *hte = _mesa_hash_table_search(ht, var); struct assignment_entry *entry; if (hte) { entry = (struct assignment_entry *) hte->data; } else { entry = (struct assignment_entry *) calloc(1, sizeof(*entry)); entry->var = var; _mesa_hash_table_insert(ht, var, entry); } return entry; } ir_visitor_status ir_constant_variable_visitor::visit(ir_variable *ir) { struct assignment_entry *entry = get_assignment_entry(ir, this->ht); entry->our_scope = true; return visit_continue; } /* Skip derefs of variables so that we can detect declarations. */ ir_visitor_status ir_constant_variable_visitor::visit_enter(ir_dereference_variable *ir) { (void)ir; return visit_continue_with_parent; } ir_visitor_status ir_constant_variable_visitor::visit_enter(ir_assignment *ir) { ir_constant *constval; struct assignment_entry *entry; entry = get_assignment_entry(ir->lhs->variable_referenced(), this->ht); assert(entry); entry->assignment_count++; /* If there's more than one assignment, don't bother - we won't do anything * with this variable anyway, and continuing just wastes memory cloning * constant expressions. */ if (entry->assignment_count > 1) return visit_continue; /* If it's already constant, don't do the work. */ if (entry->var->constant_value) return visit_continue; /* OK, now find if we actually have all the right conditions for * this to be a constant value assigned to the var. */ if (ir->condition) return visit_continue; ir_variable *var = ir->whole_variable_written(); if (!var) return visit_continue; /* Ignore buffer variables, since the underlying storage is shared * and we can't be sure that this variable won't be written by another * thread. */ if (var->data.mode == ir_var_shader_storage || var->data.mode == ir_var_shader_shared) return visit_continue; constval = ir->rhs->constant_expression_value(ralloc_parent(ir)); if (!constval) return visit_continue; /* Mark this entry as having a constant assignment (if the * assignment count doesn't go >1). do_constant_variable will fix * up the variable with the constant value later. */ entry->constval = constval; return visit_continue; } ir_visitor_status ir_constant_variable_visitor::visit_enter(ir_call *ir) { /* Mark any out parameters as assigned to */ foreach_two_lists(formal_node, &ir->callee->parameters, actual_node, &ir->actual_parameters) { ir_rvalue *param_rval = (ir_rvalue *) actual_node; ir_variable *param = (ir_variable *) formal_node; if (param->data.mode == ir_var_function_out || param->data.mode == ir_var_function_inout) { ir_variable *var = param_rval->variable_referenced(); struct assignment_entry *entry; assert(var); entry = get_assignment_entry(var, this->ht); entry->assignment_count++; } } /* Mark the return storage as having been assigned to */ if (ir->return_deref != NULL) { ir_variable *var = ir->return_deref->variable_referenced(); struct assignment_entry *entry; assert(var); entry = get_assignment_entry(var, this->ht); entry->assignment_count++; } return visit_continue; } /** * Does a copy propagation pass on the code present in the instruction stream. */ bool do_constant_variable(exec_list *instructions) { bool progress = false; ir_constant_variable_visitor v; v.ht = _mesa_pointer_hash_table_create(NULL); v.run(instructions); hash_table_foreach(v.ht, hte) { struct assignment_entry *entry = (struct assignment_entry *) hte->data; if (entry->assignment_count == 1 && entry->constval && entry->our_scope) { entry->var->constant_value = entry->constval; progress = true; } hte->data = NULL; free(entry); } _mesa_hash_table_destroy(v.ht, NULL); return progress; } bool do_constant_variable_unlinked(exec_list *instructions) { bool progress = false; foreach_in_list(ir_instruction, ir, instructions) { ir_function *f = ir->as_function(); if (f) { foreach_in_list(ir_function_signature, sig, &f->signatures) { if (do_constant_variable(&sig->body)) progress = true; } } } return progress; }