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/*
* 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++;
}
/* We don't know if the variable passed to this function has been
* assigned a value or if it is undefined, so for now we always assume
* it has been assigned a value. Once functions have been inlined any
* further potential optimisations will be taken care of.
*/
struct assignment_entry *entry;
entry = get_assignment_entry(param, 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;
}