/*
* 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_tree_grafting.cpp
*
* Takes assignments to variables that are dereferenced only once and
* pastes the RHS expression into where the variable is dereferenced.
*
* In the process of various operations like function inlining and
* tertiary op handling, we'll end up with our expression trees having
* been chopped up into a series of assignments of short expressions
* to temps. Other passes like ir_algebraic.cpp would prefer to see
* the deepest expression trees they can to try to optimize them.
*
* This is a lot like copy propagaton. In comparison, copy
* propagation only acts on plain copies, not arbitrary expressions on
* the RHS. Generally, we wouldn't want to go pasting some
* complicated expression everywhere it got used, though, so we don't
* handle expressions in that pass.
*
* The hard part is making sure we don't move an expression across
* some other assignments that would change the value of the
* expression. So we split this into two passes: First, find the
* variables in our scope which are written to once and read once, and
* then go through basic blocks seeing if we find an opportunity to
* move those expressions safely.
*/
#include "ir.h"
#include "ir_visitor.h"
#include "ir_variable_refcount.h"
#include "ir_basic_block.h"
#include "ir_optimization.h"
#include "glsl_types.h"
namespace {
static bool debug = false;
class ir_tree_grafting_visitor : public ir_hierarchical_visitor {
public:
ir_tree_grafting_visitor(ir_assignment *graft_assign,
ir_variable *graft_var)
{
this->progress = false;
this->graft_assign = graft_assign;
this->graft_var = graft_var;
}
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_expression *);
virtual ir_visitor_status visit_enter(class ir_function *);
virtual ir_visitor_status visit_enter(class ir_function_signature *);
virtual ir_visitor_status visit_enter(class ir_if *);
virtual ir_visitor_status visit_enter(class ir_loop *);
virtual ir_visitor_status visit_enter(class ir_swizzle *);
virtual ir_visitor_status visit_enter(class ir_texture *);
ir_visitor_status check_graft(ir_instruction *ir, ir_variable *var);
bool do_graft(ir_rvalue **rvalue);
bool progress;
ir_variable *graft_var;
ir_assignment *graft_assign;
};
struct find_deref_info {
ir_variable *var;
bool found;
};
void
dereferences_variable_callback(ir_instruction *ir, void *data)
{
struct find_deref_info *info = (struct find_deref_info *)data;
ir_dereference_variable *deref = ir->as_dereference_variable();
if (deref && deref->var == info->var)
info->found = true;
}
static bool
dereferences_variable(ir_instruction *ir, ir_variable *var)
{
struct find_deref_info info;
info.var = var;
info.found = false;
visit_tree(ir, dereferences_variable_callback, &info);
return info.found;
}
bool
ir_tree_grafting_visitor::do_graft(ir_rvalue **rvalue)
{
if (!*rvalue)
return false;
ir_dereference_variable *deref = (*rvalue)->as_dereference_variable();
if (!deref || deref->var != this->graft_var)
return false;
if (debug) {
printf("GRAFTING:\n");
this->graft_assign->print();
printf("\n");
printf("TO:\n");
(*rvalue)->print();
printf("\n");
}
this->graft_assign->remove();
*rvalue = this->graft_assign->rhs;
this->progress = true;
return true;
}
ir_visitor_status
ir_tree_grafting_visitor::visit_enter(ir_loop *ir)
{
(void)ir;
/* Do not traverse into the body of the loop since that is a
* different basic block.
*/
return visit_stop;
}
/**
* Check if we can continue grafting after writing to a variable. If the
* expression we're trying to graft references the variable, we must stop.
*
* \param ir An instruction that writes to a variable.
* \param var The variable being updated.
*/
ir_visitor_status
ir_tree_grafting_visitor::check_graft(ir_instruction *ir, ir_variable *var)
{
if (dereferences_variable(this->graft_assign->rhs, var)) {
if (debug) {
printf("graft killed by: ");
ir->print();
printf("\n");
}
return visit_stop;
}
return visit_continue;
}
ir_visitor_status
ir_tree_grafting_visitor::visit_leave(ir_assignment *ir)
{
if (do_graft(&ir->rhs) ||
do_graft(&ir->condition))
return visit_stop;
/* If this assignment updates a variable used in the assignment
* we're trying to graft, then we're done.
*/
return check_graft(ir, ir->lhs->variable_referenced());
}
ir_visitor_status
ir_tree_grafting_visitor::visit_enter(ir_function *ir)
{
(void) ir;
return visit_continue_with_parent;
}
ir_visitor_status
ir_tree_grafting_visitor::visit_enter(ir_function_signature *ir)
{
(void)ir;
return visit_continue_with_parent;
}
ir_visitor_status
ir_tree_grafting_visitor::visit_enter(ir_call *ir)
{
exec_list_iterator sig_iter = ir->callee->parameters.iterator();
/* Reminder: iterating ir_call iterates its parameters. */
foreach_iter(exec_list_iterator, iter, *ir) {
ir_variable *sig_param = (ir_variable *)sig_iter.get();
ir_rvalue *ir = (ir_rvalue *)iter.get();
ir_rvalue *new_ir = ir;
if (sig_param->mode != ir_var_in && sig_param->mode != ir_var_const_in) {
if (check_graft(ir, sig_param) == visit_stop)
return visit_stop;
continue;
}
if (do_graft(&new_ir)) {
ir->replace_with(new_ir);
return visit_stop;
}
sig_iter.next();
}
if (ir->return_deref && check_graft(ir, ir->return_deref->var) == visit_stop)
return visit_stop;
return visit_continue;
}
ir_visitor_status
ir_tree_grafting_visitor::visit_enter(ir_expression *ir)
{
for (unsigned int i = 0; i < ir->get_num_operands(); i++) {
if (do_graft(&ir->operands[i]))
return visit_stop;
}
return visit_continue;
}
ir_visitor_status
ir_tree_grafting_visitor::visit_enter(ir_if *ir)
{
if (do_graft(&ir->condition))
return visit_stop;
/* Do not traverse into the body of the if-statement since that is a
* different basic block.
*/
return visit_continue_with_parent;
}
ir_visitor_status
ir_tree_grafting_visitor::visit_enter(ir_swizzle *ir)
{
if (do_graft(&ir->val))
return visit_stop;
return visit_continue;
}
ir_visitor_status
ir_tree_grafting_visitor::visit_enter(ir_texture *ir)
{
if (do_graft(&ir->coordinate) ||
do_graft(&ir->projector) ||
do_graft(&ir->offset) ||
do_graft(&ir->shadow_comparitor))
return visit_stop;
switch (ir->op) {
case ir_tex:
break;
case ir_txb:
if (do_graft(&ir->lod_info.bias))
return visit_stop;
break;
case ir_txf:
case ir_txl:
case ir_txs:
if (do_graft(&ir->lod_info.lod))
return visit_stop;
break;
case ir_txd:
if (do_graft(&ir->lod_info.grad.dPdx) ||
do_graft(&ir->lod_info.grad.dPdy))
return visit_stop;
break;
}
return visit_continue;
}
struct tree_grafting_info {
ir_variable_refcount_visitor *refs;
bool progress;
};
static bool
try_tree_grafting(ir_assignment *start,
ir_variable *lhs_var,
ir_instruction *bb_last)
{
ir_tree_grafting_visitor v(start, lhs_var);
if (debug) {
printf("trying to graft: ");
lhs_var->print();
printf("\n");
}
for (ir_instruction *ir = (ir_instruction *)start->next;
ir != bb_last->next;
ir = (ir_instruction *)ir->next) {
if (debug) {
printf("- ");
ir->print();
printf("\n");
}
ir_visitor_status s = ir->accept(&v);
if (s == visit_stop)
return v.progress;
}
return false;
}
static void
tree_grafting_basic_block(ir_instruction *bb_first,
ir_instruction *bb_last,
void *data)
{
struct tree_grafting_info *info = (struct tree_grafting_info *)data;
ir_instruction *ir, *next;
for (ir = bb_first, next = (ir_instruction *)ir->next;
ir != bb_last->next;
ir = next, next = (ir_instruction *)ir->next) {
ir_assignment *assign = ir->as_assignment();
if (!assign)
continue;
ir_variable *lhs_var = assign->whole_variable_written();
if (!lhs_var)
continue;
if (lhs_var->mode == ir_var_out ||
lhs_var->mode == ir_var_inout)
continue;
ir_variable_refcount_entry *entry = info->refs->get_variable_entry(lhs_var);
if (!entry->declaration ||
entry->assigned_count != 1 ||
entry->referenced_count != 2)
continue;
assert(assign == entry->assign);
/* Found a possibly graftable assignment. Now, walk through the
* rest of the BB seeing if the deref is here, and if nothing interfered with
* pasting its expression's values in between.
*/
info->progress |= try_tree_grafting(assign, lhs_var, bb_last);
}
}
} /* unnamed namespace */
/**
* Does a copy propagation pass on the code present in the instruction stream.
*/
bool
do_tree_grafting(exec_list *instructions)
{
ir_variable_refcount_visitor refs;
struct tree_grafting_info info;
info.progress = false;
info.refs = &refs;
visit_list_elements(info.refs, instructions);
call_for_basic_blocks(instructions, tree_grafting_basic_block, &info);
return info.progress;
}