/*
* 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_copy_propagation.cpp
*
* Moves usage of recently-copied variables to the previous copy of
* the variable.
*
* This should reduce the number of MOV instructions in the generated
* programs unless copy propagation is also done on the LIR, and may
* help anyway by triggering other optimizations that live in the HIR.
*/
#include "ir.h"
#include "ir_visitor.h"
#include "ir_basic_block.h"
#include "ir_optimization.h"
#include "compiler/glsl_types.h"
#include "util/hash_table.h"
#include "util/set.h"
namespace {
class ir_copy_propagation_visitor : public ir_hierarchical_visitor {
public:
ir_copy_propagation_visitor()
{
progress = false;
mem_ctx = ralloc_context(0);
lin_ctx = linear_alloc_parent(mem_ctx, 0);
acp = _mesa_hash_table_create(mem_ctx, _mesa_hash_pointer,
_mesa_key_pointer_equal);
kills = _mesa_set_create(mem_ctx, _mesa_hash_pointer,
_mesa_key_pointer_equal);
killed_all = false;
}
~ir_copy_propagation_visitor()
{
ralloc_free(mem_ctx);
}
virtual ir_visitor_status visit(class ir_dereference_variable *);
void handle_loop(class ir_loop *, bool keep_acp);
virtual ir_visitor_status visit_enter(class ir_loop *);
virtual ir_visitor_status visit_enter(class ir_function_signature *);
virtual ir_visitor_status visit_enter(class ir_function *);
virtual ir_visitor_status visit_leave(class ir_assignment *);
virtual ir_visitor_status visit_enter(class ir_call *);
virtual ir_visitor_status visit_enter(class ir_if *);
void add_copy(ir_assignment *ir);
void kill(ir_variable *ir);
void handle_if_block(exec_list *instructions);
/** Hash of lhs->rhs: The available copies to propagate */
hash_table *acp;
/**
* Set of ir_variables: Whose values were killed in this block.
*/
set *kills;
bool progress;
bool killed_all;
void *mem_ctx;
void *lin_ctx;
};
} /* unnamed namespace */
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_function_signature *ir)
{
/* Treat entry into a function signature as a completely separate
* block. Any instructions at global scope will be shuffled into
* main() at link time, so they're irrelevant to us.
*/
hash_table *orig_acp = this->acp;
set *orig_kills = this->kills;
bool orig_killed_all = this->killed_all;
acp = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
_mesa_key_pointer_equal);
kills = _mesa_set_create(NULL, _mesa_hash_pointer,
_mesa_key_pointer_equal);
this->killed_all = false;
visit_list_elements(this, &ir->body);
_mesa_hash_table_destroy(acp, NULL);
_mesa_set_destroy(kills, NULL);
this->kills = orig_kills;
this->acp = orig_acp;
this->killed_all = orig_killed_all;
return visit_continue_with_parent;
}
ir_visitor_status
ir_copy_propagation_visitor::visit_leave(ir_assignment *ir)
{
kill(ir->lhs->variable_referenced());
add_copy(ir);
return visit_continue;
}
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_function *ir)
{
(void) ir;
return visit_continue;
}
/**
* Replaces dereferences of ACP RHS variables with ACP LHS variables.
*
* This is where the actual copy propagation occurs. Note that the
* rewriting of ir_dereference means that the ir_dereference instance
* must not be shared by multiple IR operations!
*/
ir_visitor_status
ir_copy_propagation_visitor::visit(ir_dereference_variable *ir)
{
if (this->in_assignee)
return visit_continue;
struct hash_entry *entry = _mesa_hash_table_search(acp, ir->var);
if (entry) {
ir->var = (ir_variable *) entry->data;
progress = true;
}
return visit_continue;
}
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_call *ir)
{
/* Do copy propagation on call parameters, but skip any out params */
foreach_two_lists(formal_node, &ir->callee->parameters,
actual_node, &ir->actual_parameters) {
ir_variable *sig_param = (ir_variable *) formal_node;
ir_rvalue *ir = (ir_rvalue *) actual_node;
if (sig_param->data.mode != ir_var_function_out
&& sig_param->data.mode != ir_var_function_inout) {
ir->accept(this);
}
}
/* Since this pass can run when unlinked, we don't (necessarily) know
* the side effects of calls. (When linked, most calls are inlined
* anyway, so it doesn't matter much.)
*
* One place where this does matter is IR intrinsics. They're never
* inlined. We also know what they do - while some have side effects
* (such as image writes), none edit random global variables. So we
* can assume they're side-effect free (other than the return value
* and out parameters).
*/
if (!ir->callee->is_intrinsic()) {
_mesa_hash_table_clear(acp, NULL);
this->killed_all = true;
} else {
if (ir->return_deref)
kill(ir->return_deref->var);
foreach_two_lists(formal_node, &ir->callee->parameters,
actual_node, &ir->actual_parameters) {
ir_variable *sig_param = (ir_variable *) formal_node;
if (sig_param->data.mode == ir_var_function_out ||
sig_param->data.mode == ir_var_function_inout) {
ir_rvalue *ir = (ir_rvalue *) actual_node;
ir_variable *var = ir->variable_referenced();
kill(var);
}
}
}
return visit_continue_with_parent;
}
void
ir_copy_propagation_visitor::handle_if_block(exec_list *instructions)
{
hash_table *orig_acp = this->acp;
set *orig_kills = this->kills;
bool orig_killed_all = this->killed_all;
acp = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
_mesa_key_pointer_equal);
kills = _mesa_set_create(NULL, _mesa_hash_pointer,
_mesa_key_pointer_equal);
this->killed_all = false;
/* Populate the initial acp with a copy of the original */
struct hash_entry *entry;
hash_table_foreach(orig_acp, entry) {
_mesa_hash_table_insert(acp, entry->key, entry->data);
}
visit_list_elements(this, instructions);
if (this->killed_all) {
_mesa_hash_table_clear(orig_acp, NULL);
}
set *new_kills = this->kills;
this->kills = orig_kills;
_mesa_hash_table_destroy(acp, NULL);
this->acp = orig_acp;
this->killed_all = this->killed_all || orig_killed_all;
struct set_entry *s_entry;
set_foreach(new_kills, s_entry) {
kill((ir_variable *) s_entry->key);
}
_mesa_set_destroy(new_kills, NULL);
}
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_if *ir)
{
ir->condition->accept(this);
handle_if_block(&ir->then_instructions);
handle_if_block(&ir->else_instructions);
/* handle_if_block() already descended into the children. */
return visit_continue_with_parent;
}
void
ir_copy_propagation_visitor::handle_loop(ir_loop *ir, bool keep_acp)
{
hash_table *orig_acp = this->acp;
set *orig_kills = this->kills;
bool orig_killed_all = this->killed_all;
acp = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
_mesa_key_pointer_equal);
kills = _mesa_set_create(NULL, _mesa_hash_pointer,
_mesa_key_pointer_equal);
this->killed_all = false;
if (keep_acp) {
struct hash_entry *entry;
hash_table_foreach(orig_acp, entry) {
_mesa_hash_table_insert(acp, entry->key, entry->data);
}
}
visit_list_elements(this, &ir->body_instructions);
if (this->killed_all) {
_mesa_hash_table_clear(orig_acp, NULL);
}
set *new_kills = this->kills;
this->kills = orig_kills;
_mesa_hash_table_destroy(acp, NULL);
this->acp = orig_acp;
this->killed_all = this->killed_all || orig_killed_all;
struct set_entry *entry;
set_foreach(new_kills, entry) {
kill((ir_variable *) entry->key);
}
_mesa_set_destroy(new_kills, NULL);
}
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_loop *ir)
{
/* Make a conservative first pass over the loop with an empty ACP set.
* This also removes any killed entries from the original ACP set.
*/
handle_loop(ir, false);
/* Then, run it again with the real ACP set, minus any killed entries.
* This takes care of propagating values from before the loop into it.
*/
handle_loop(ir, true);
/* already descended into the children. */
return visit_continue_with_parent;
}
void
ir_copy_propagation_visitor::kill(ir_variable *var)
{
assert(var != NULL);
/* Remove any entries currently in the ACP for this kill. */
struct hash_entry *entry = _mesa_hash_table_search(acp, var);
if (entry) {
_mesa_hash_table_remove(acp, entry);
}
hash_table_foreach(acp, entry) {
if (var == (ir_variable *) entry->data) {
_mesa_hash_table_remove(acp, entry);
}
}
/* Add the LHS variable to the set of killed variables in this block. */
_mesa_set_add(kills, var);
}
/**
* Adds an entry to the available copy list if it's a plain assignment
* of a variable to a variable.
*/
void
ir_copy_propagation_visitor::add_copy(ir_assignment *ir)
{
if (ir->condition)
return;
ir_variable *lhs_var = ir->whole_variable_written();
ir_variable *rhs_var = ir->rhs->whole_variable_referenced();
/* Don't try to remove a dumb assignment of a variable to itself. Removing
* it now would mess up the loop iteration calling us.
*/
if (lhs_var != NULL && rhs_var != NULL && lhs_var != rhs_var) {
if (lhs_var->data.mode != ir_var_shader_storage &&
lhs_var->data.mode != ir_var_shader_shared &&
lhs_var->data.precise == rhs_var->data.precise) {
_mesa_hash_table_insert(acp, lhs_var, rhs_var);
}
}
}
/**
* Does a copy propagation pass on the code present in the instruction stream.
*/
bool
do_copy_propagation(exec_list *instructions)
{
ir_copy_propagation_visitor v;
visit_list_elements(&v, instructions);
return v.progress;
}