218 lines
6.2 KiB
C++
218 lines
6.2 KiB
C++
/*
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* Copyright © 2010 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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/**
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* \file opt_constant_variable.cpp
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*
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* Marks variables assigned a single constant value over the course
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* of the program as constant.
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*
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* The goal here is to trigger further constant folding and then dead
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* code elimination. This is common with vector/matrix constructors
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* and calls to builtin functions.
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*/
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#include "ir.h"
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#include "ir_visitor.h"
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#include "ir_optimization.h"
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#include "glsl_types.h"
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#include "util/hash_table.h"
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namespace {
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struct assignment_entry {
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int assignment_count;
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ir_variable *var;
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ir_constant *constval;
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bool our_scope;
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};
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class ir_constant_variable_visitor : public ir_hierarchical_visitor {
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public:
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virtual ir_visitor_status visit_enter(ir_dereference_variable *);
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virtual ir_visitor_status visit(ir_variable *);
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virtual ir_visitor_status visit_enter(ir_assignment *);
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virtual ir_visitor_status visit_enter(ir_call *);
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struct hash_table *ht;
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};
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} /* unnamed namespace */
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static struct assignment_entry *
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get_assignment_entry(ir_variable *var, struct hash_table *ht)
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{
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struct hash_entry *hte = _mesa_hash_table_search(ht, var);
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struct assignment_entry *entry;
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if (hte) {
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entry = (struct assignment_entry *) hte->data;
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} else {
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entry = (struct assignment_entry *) calloc(1, sizeof(*entry));
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entry->var = var;
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_mesa_hash_table_insert(ht, var, entry);
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}
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return entry;
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}
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ir_visitor_status
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ir_constant_variable_visitor::visit(ir_variable *ir)
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{
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struct assignment_entry *entry = get_assignment_entry(ir, this->ht);
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entry->our_scope = true;
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return visit_continue;
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}
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/* Skip derefs of variables so that we can detect declarations. */
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ir_visitor_status
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ir_constant_variable_visitor::visit_enter(ir_dereference_variable *ir)
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{
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(void)ir;
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return visit_continue_with_parent;
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}
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ir_visitor_status
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ir_constant_variable_visitor::visit_enter(ir_assignment *ir)
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{
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ir_constant *constval;
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struct assignment_entry *entry;
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entry = get_assignment_entry(ir->lhs->variable_referenced(), this->ht);
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assert(entry);
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entry->assignment_count++;
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/* If it's already constant, don't do the work. */
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if (entry->var->constant_value)
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return visit_continue;
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/* OK, now find if we actually have all the right conditions for
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* this to be a constant value assigned to the var.
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*/
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if (ir->condition)
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return visit_continue;
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ir_variable *var = ir->whole_variable_written();
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if (!var)
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return visit_continue;
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/* Ignore buffer variables, since the underlying storage is shared
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* and we can't be sure that this variable won't be written by another
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* thread.
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*/
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if (var->data.mode == ir_var_shader_storage)
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return visit_continue;
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constval = ir->rhs->constant_expression_value();
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if (!constval)
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return visit_continue;
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/* Mark this entry as having a constant assignment (if the
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* assignment count doesn't go >1). do_constant_variable will fix
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* up the variable with the constant value later.
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*/
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entry->constval = constval;
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return visit_continue;
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}
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ir_visitor_status
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ir_constant_variable_visitor::visit_enter(ir_call *ir)
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{
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/* Mark any out parameters as assigned to */
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foreach_two_lists(formal_node, &ir->callee->parameters,
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actual_node, &ir->actual_parameters) {
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ir_rvalue *param_rval = (ir_rvalue *) actual_node;
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ir_variable *param = (ir_variable *) formal_node;
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if (param->data.mode == ir_var_function_out ||
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param->data.mode == ir_var_function_inout) {
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ir_variable *var = param_rval->variable_referenced();
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struct assignment_entry *entry;
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assert(var);
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entry = get_assignment_entry(var, this->ht);
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entry->assignment_count++;
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}
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}
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/* Mark the return storage as having been assigned to */
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if (ir->return_deref != NULL) {
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ir_variable *var = ir->return_deref->variable_referenced();
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struct assignment_entry *entry;
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assert(var);
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entry = get_assignment_entry(var, this->ht);
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entry->assignment_count++;
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}
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return visit_continue;
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}
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/**
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* Does a copy propagation pass on the code present in the instruction stream.
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*/
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bool
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do_constant_variable(exec_list *instructions)
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{
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bool progress = false;
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ir_constant_variable_visitor v;
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v.ht = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
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_mesa_key_pointer_equal);
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v.run(instructions);
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struct hash_entry *hte;
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hash_table_foreach(v.ht, hte) {
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struct assignment_entry *entry = (struct assignment_entry *) hte->data;
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if (entry->assignment_count == 1 && entry->constval && entry->our_scope) {
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entry->var->constant_value = entry->constval;
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progress = true;
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}
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hte->data = NULL;
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free(entry);
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}
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_mesa_hash_table_destroy(v.ht, NULL);
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return progress;
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}
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bool
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do_constant_variable_unlinked(exec_list *instructions)
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{
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bool progress = false;
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foreach_in_list(ir_instruction, ir, instructions) {
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ir_function *f = ir->as_function();
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if (f) {
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foreach_in_list(ir_function_signature, sig, &f->signatures) {
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if (do_constant_variable(&sig->body))
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progress = true;
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}
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}
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}
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return progress;
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}
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