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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.
*/
/** @file brw_dead_control_flow.cpp
*
* This file implements the dead control flow elimination optimization pass.
*/
#include "brw_shader.h"
#include "brw_cfg.h"
/* Look for and eliminate dead control flow:
*
* - if/endif
* - if/else/endif
*/
bool
dead_control_flow_eliminate(backend_visitor *v)
{
bool progress = false;
cfg_t cfg(v);
for (int b = 0; b < cfg.num_blocks; b++) {
bblock_t *block = cfg.blocks[b];
bool found = false;
/* ENDIF instructions, by definition, can only be found at the ends of
* basic blocks.
*/
backend_instruction *endif_inst = block->end;
if (endif_inst->opcode != BRW_OPCODE_ENDIF)
continue;
backend_instruction *if_inst = NULL, *else_inst = NULL;
backend_instruction *prev_inst = (backend_instruction *) endif_inst->prev;
if (prev_inst->opcode == BRW_OPCODE_IF) {
if_inst = prev_inst;
found = true;
} else if (prev_inst->opcode == BRW_OPCODE_ELSE) {
else_inst = prev_inst;
prev_inst = (backend_instruction *) prev_inst->prev;
if (prev_inst->opcode == BRW_OPCODE_IF) {
if_inst = prev_inst;
found = true;
}
}
if (found) {
if_inst->remove();
if (else_inst)
else_inst->remove();
endif_inst->remove();
progress = true;
}
}
if (progress)
v->invalidate_live_intervals();
return progress;
}
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