/*
* Copyright © 2012 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.
*
* Authors:
* Eric Anholt <eric@anholt.net>
*
*/
#include "brw_cfg.h"
/** @file brw_cfg.cpp
*
* Walks the shader instructions generated and creates a set of basic
* blocks with successor/predecessor edges connecting them.
*/
static bblock_t *
pop_stack(exec_list *list)
{
bblock_link *link = (bblock_link *)list->get_tail();
bblock_t *block = link->block;
link->link.remove();
return block;
}
static exec_node *
link(void *mem_ctx, bblock_t *block)
{
bblock_link *l = new(mem_ctx) bblock_link(block);
return &l->link;
}
bblock_t::bblock_t(cfg_t *cfg) :
cfg(cfg), idom(NULL), start_ip(0), end_ip(0), num(0)
{
instructions.make_empty();
parents.make_empty();
children.make_empty();
}
void
bblock_t::add_successor(void *mem_ctx, bblock_t *successor)
{
successor->parents.push_tail(::link(mem_ctx, this));
children.push_tail(::link(mem_ctx, successor));
}
bool
bblock_t::is_predecessor_of(const bblock_t *block) const
{
foreach_list_typed_safe (bblock_link, parent, link, &block->parents) {
if (parent->block == this) {
return true;
}
}
return false;
}
bool
bblock_t::is_successor_of(const bblock_t *block) const
{
foreach_list_typed_safe (bblock_link, child, link, &block->children) {
if (child->block == this) {
return true;
}
}
return false;
}
static bool
ends_block(const backend_instruction *inst)
{
enum opcode op = inst->opcode;
return op == BRW_OPCODE_IF ||
op == BRW_OPCODE_ELSE ||
op == BRW_OPCODE_CONTINUE ||
op == BRW_OPCODE_BREAK ||
op == BRW_OPCODE_WHILE;
}
static bool
starts_block(const backend_instruction *inst)
{
enum opcode op = inst->opcode;
return op == BRW_OPCODE_DO ||
op == BRW_OPCODE_ENDIF;
}
bool
bblock_t::can_combine_with(const bblock_t *that) const
{
if ((const bblock_t *)this->link.next != that)
return false;
if (ends_block(this->end()) ||
starts_block(that->start()))
return false;
return true;
}
void
bblock_t::combine_with(bblock_t *that)
{
assert(this->can_combine_with(that));
foreach_list_typed (bblock_link, link, link, &this->children) {
assert(link->block == that);
}
foreach_list_typed (bblock_link, link, link, &that->parents) {
assert(link->block == this);
}
this->end_ip = that->end_ip;
this->instructions.append_list(&that->instructions);
this->cfg->remove_block(that);
}
void
bblock_t::dump(backend_visitor *v) const
{
int ip = this->start_ip;
foreach_inst_in_block(backend_instruction, inst, this) {
fprintf(stderr, "%5d: ", ip);
v->dump_instruction(inst);
ip++;
}
}
cfg_t::cfg_t(exec_list *instructions)
{
mem_ctx = ralloc_context(NULL);
block_list.make_empty();
blocks = NULL;
num_blocks = 0;
idom_dirty = true;
bblock_t *cur = NULL;
int ip = 0;
bblock_t *entry = new_block();
bblock_t *cur_if = NULL; /**< BB ending with IF. */
bblock_t *cur_else = NULL; /**< BB ending with ELSE. */
bblock_t *cur_endif = NULL; /**< BB starting with ENDIF. */
bblock_t *cur_do = NULL; /**< BB starting with DO. */
bblock_t *cur_while = NULL; /**< BB immediately following WHILE. */
exec_list if_stack, else_stack, do_stack, while_stack;
bblock_t *next;
set_next_block(&cur, entry, ip);
foreach_in_list_safe(backend_instruction, inst, instructions) {
/* set_next_block wants the post-incremented ip */
ip++;
switch (inst->opcode) {
case BRW_OPCODE_IF:
inst->exec_node::remove();
cur->instructions.push_tail(inst);
/* Push our information onto a stack so we can recover from
* nested ifs.
*/
if_stack.push_tail(link(mem_ctx, cur_if));
else_stack.push_tail(link(mem_ctx, cur_else));
cur_if = cur;
cur_else = NULL;
cur_endif = NULL;
/* Set up our immediately following block, full of "then"
* instructions.
*/
next = new_block();
cur_if->add_successor(mem_ctx, next);
set_next_block(&cur, next, ip);
break;
case BRW_OPCODE_ELSE:
inst->exec_node::remove();
cur->instructions.push_tail(inst);
cur_else = cur;
next = new_block();
cur_if->add_successor(mem_ctx, next);
set_next_block(&cur, next, ip);
break;
case BRW_OPCODE_ENDIF: {
if (cur->instructions.is_empty()) {
/* New block was just created; use it. */
cur_endif = cur;
} else {
cur_endif = new_block();
cur->add_successor(mem_ctx, cur_endif);
set_next_block(&cur, cur_endif, ip - 1);
}
inst->exec_node::remove();
cur->instructions.push_tail(inst);
if (cur_else) {
cur_else->add_successor(mem_ctx, cur_endif);
} else {
cur_if->add_successor(mem_ctx, cur_endif);
}
assert(cur_if->end()->opcode == BRW_OPCODE_IF);
assert(!cur_else || cur_else->end()->opcode == BRW_OPCODE_ELSE);
/* Pop the stack so we're in the previous if/else/endif */
cur_if = pop_stack(&if_stack);
cur_else = pop_stack(&else_stack);
break;
}
case BRW_OPCODE_DO:
/* Push our information onto a stack so we can recover from
* nested loops.
*/
do_stack.push_tail(link(mem_ctx, cur_do));
while_stack.push_tail(link(mem_ctx, cur_while));
/* Set up the block just after the while. Don't know when exactly
* it will start, yet.
*/
cur_while = new_block();
if (cur->instructions.is_empty()) {
/* New block was just created; use it. */
cur_do = cur;
} else {
cur_do = new_block();
cur->add_successor(mem_ctx, cur_do);
set_next_block(&cur, cur_do, ip - 1);
}
inst->exec_node::remove();
cur->instructions.push_tail(inst);
break;
case BRW_OPCODE_CONTINUE:
inst->exec_node::remove();
cur->instructions.push_tail(inst);
cur->add_successor(mem_ctx, cur_do);
next = new_block();
if (inst->predicate)
cur->add_successor(mem_ctx, next);
set_next_block(&cur, next, ip);
break;
case BRW_OPCODE_BREAK:
inst->exec_node::remove();
cur->instructions.push_tail(inst);
cur->add_successor(mem_ctx, cur_while);
next = new_block();
if (inst->predicate)
cur->add_successor(mem_ctx, next);
set_next_block(&cur, next, ip);
break;
case BRW_OPCODE_WHILE:
inst->exec_node::remove();
cur->instructions.push_tail(inst);
cur->add_successor(mem_ctx, cur_do);
set_next_block(&cur, cur_while, ip);
/* Pop the stack so we're in the previous loop */
cur_do = pop_stack(&do_stack);
cur_while = pop_stack(&while_stack);
break;
default:
inst->exec_node::remove();
cur->instructions.push_tail(inst);
break;
}
}
cur->end_ip = ip - 1;
make_block_array();
}
cfg_t::~cfg_t()
{
ralloc_free(mem_ctx);
}
void
cfg_t::remove_block(bblock_t *block)
{
foreach_list_typed_safe (bblock_link, predecessor, link, &block->parents) {
/* Remove block from all of its predecessors' successor lists. */
foreach_list_typed_safe (bblock_link, successor, link,
&predecessor->block->children) {
if (block == successor->block) {
successor->link.remove();
ralloc_free(successor);
}
}
/* Add removed-block's successors to its predecessors' successor lists. */
foreach_list_typed (bblock_link, successor, link, &block->children) {
if (!successor->block->is_successor_of(predecessor->block)) {
predecessor->block->children.push_tail(link(mem_ctx,
successor->block));
}
}
}
foreach_list_typed_safe (bblock_link, successor, link, &block->children) {
/* Remove block from all of its childrens' parents lists. */
foreach_list_typed_safe (bblock_link, predecessor, link,
&successor->block->parents) {
if (block == predecessor->block) {
predecessor->link.remove();
ralloc_free(predecessor);
}
}
/* Add removed-block's predecessors to its successors' predecessor lists. */
foreach_list_typed (bblock_link, predecessor, link, &block->parents) {
if (!predecessor->block->is_predecessor_of(successor->block)) {
successor->block->parents.push_tail(link(mem_ctx,
predecessor->block));
}
}
}
block->link.remove();
for (int b = block->num; b < this->num_blocks - 1; b++) {
this->blocks[b] = this->blocks[b + 1];
this->blocks[b]->num = b;
}
this->blocks[this->num_blocks - 1]->num = this->num_blocks - 2;
this->num_blocks--;
idom_dirty = true;
}
bblock_t *
cfg_t::new_block()
{
bblock_t *block = new(mem_ctx) bblock_t(this);
return block;
}
void
cfg_t::set_next_block(bblock_t **cur, bblock_t *block, int ip)
{
if (*cur) {
(*cur)->end_ip = ip - 1;
}
block->start_ip = ip;
block->num = num_blocks++;
block_list.push_tail(&block->link);
*cur = block;
}
void
cfg_t::make_block_array()
{
blocks = ralloc_array(mem_ctx, bblock_t *, num_blocks);
int i = 0;
foreach_block (block, this) {
blocks[i++] = block;
}
assert(i == num_blocks);
}
void
cfg_t::dump(backend_visitor *v)
{
if (idom_dirty)
calculate_idom();
foreach_block (block, this) {
fprintf(stderr, "START B%d IDOM(B%d)", block->num, block->idom->num);
foreach_list_typed(bblock_link, link, link, &block->parents) {
fprintf(stderr, " <-B%d",
link->block->num);
}
fprintf(stderr, "\n");
if (v != NULL)
block->dump(v);
fprintf(stderr, "END B%d", block->num);
foreach_list_typed(bblock_link, link, link, &block->children) {
fprintf(stderr, " ->B%d",
link->block->num);
}
fprintf(stderr, "\n");
}
}
/* Calculates the immediate dominator of each block, according to "A Simple,
* Fast Dominance Algorithm" by Keith D. Cooper, Timothy J. Harvey, and Ken
* Kennedy.
*
* The authors claim that for control flow graphs of sizes normally encountered
* (less than 1000 nodes) that this algorithm is significantly faster than
* others like Lengauer-Tarjan.
*/
void
cfg_t::calculate_idom()
{
foreach_block(block, this) {
block->idom = NULL;
}
blocks[0]->idom = blocks[0];
bool changed;
do {
changed = false;
foreach_block(block, this) {
if (block->num == 0)
continue;
bblock_t *new_idom = NULL;
foreach_list_typed(bblock_link, parent, link, &block->parents) {
if (parent->block->idom) {
if (new_idom == NULL) {
new_idom = parent->block;
} else if (parent->block->idom != NULL) {
new_idom = intersect(parent->block, new_idom);
}
}
}
if (block->idom != new_idom) {
block->idom = new_idom;
changed = true;
}
}
} while (changed);
idom_dirty = false;
}
bblock_t *
cfg_t::intersect(bblock_t *b1, bblock_t *b2)
{
/* Note, the comparisons here are the opposite of what the paper says
* because we index blocks from beginning -> end (i.e. reverse post-order)
* instead of post-order like they assume.
*/
while (b1->num != b2->num) {
while (b1->num > b2->num)
b1 = b1->idom;
while (b2->num > b1->num)
b2 = b2->idom;
}
assert(b1);
return b1;
}
void
cfg_t::dump_cfg()
{
printf("digraph CFG {\n");
for (int b = 0; b < num_blocks; b++) {
bblock_t *block = this->blocks[b];
foreach_list_typed_safe (bblock_link, child, link, &block->children) {
printf("\t%d -> %d\n", b, child->block->num);
}
}
printf("}\n");
}
void
cfg_t::dump_domtree()
{
printf("digraph DominanceTree {\n");
foreach_block(block, this) {
printf("\t%d -> %d\n", block->idom->num, block->num);
}
printf("}\n");
}