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/*
* Copyright © 2013 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.
*/
#include "brw_cfg.h"
using namespace brw;
/** @file brw_predicated_break.cpp
*
* Loops are often structured as
*
* loop:
* CMP.f0
* (+f0) IF
* BREAK
* ENDIF
* ...
* WHILE loop
*
* This peephole pass removes the IF and ENDIF instructions and predicates the
* BREAK, dropping two instructions from the loop body.
*
* If the loop was a DO { ... } WHILE loop, it looks like
*
* loop:
* ...
* CMP.f0
* (+f0) IF
* BREAK
* ENDIF
* WHILE loop
*
* and we can remove the BREAK instruction and predicate the WHILE.
*/
bool
opt_predicated_break(backend_shader *s)
{
bool progress = false;
foreach_block (block, s->cfg) {
if (block->start_ip != block->end_ip)
continue;
/* BREAK and CONTINUE instructions, by definition, can only be found at
* the ends of basic blocks.
*/
backend_instruction *jump_inst = block->end();
if (jump_inst->opcode != BRW_OPCODE_BREAK &&
jump_inst->opcode != BRW_OPCODE_CONTINUE)
continue;
backend_instruction *if_inst = block->prev()->end();
if (if_inst->opcode != BRW_OPCODE_IF)
continue;
backend_instruction *endif_inst = block->next()->start();
if (endif_inst->opcode != BRW_OPCODE_ENDIF)
continue;
bblock_t *jump_block = block;
bblock_t *if_block = jump_block->prev();
bblock_t *endif_block = jump_block->next();
jump_inst->predicate = if_inst->predicate;
jump_inst->predicate_inverse = if_inst->predicate_inverse;
bblock_t *earlier_block = if_block;
if (if_block->start_ip == if_block->end_ip) {
earlier_block = if_block->prev();
}
if_inst->remove(if_block);
bblock_t *later_block = endif_block;
if (endif_block->start_ip == endif_block->end_ip) {
later_block = endif_block->next();
}
endif_inst->remove(endif_block);
if (!earlier_block->ends_with_control_flow()) {
earlier_block->children.make_empty();
earlier_block->add_successor(s->cfg->mem_ctx, jump_block);
}
if (!later_block->starts_with_control_flow()) {
later_block->parents.make_empty();
}
jump_block->add_successor(s->cfg->mem_ctx, later_block);
if (earlier_block->can_combine_with(jump_block)) {
earlier_block->combine_with(jump_block);
block = earlier_block;
}
/* Now look at the first instruction of the block following the BREAK. If
* it's a WHILE, we can delete the break, predicate the WHILE, and join
* the two basic blocks.
*/
bblock_t *while_block = earlier_block->next();
backend_instruction *while_inst = while_block->start();
if (jump_inst->opcode == BRW_OPCODE_BREAK &&
while_inst->opcode == BRW_OPCODE_WHILE &&
while_inst->predicate == BRW_PREDICATE_NONE) {
jump_inst->remove(earlier_block);
while_inst->predicate = jump_inst->predicate;
while_inst->predicate_inverse = !jump_inst->predicate_inverse;
assert(earlier_block->can_combine_with(while_block));
earlier_block->combine_with(while_block);
}
progress = true;
}
if (progress)
s->invalidate_live_intervals();
return progress;
}
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