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/*
* 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_fs_cfg.h"
#include "brw_fs_live_variables.h"
using namespace brw;
/** @file brw_fs_live_variables.cpp
*
* Support for computing at the basic block level which variables
* (virtual GRFs in our case) are live at entry and exit.
*
* See Muchnik's Advanced Compiler Design and Implementation, section
* 14.1 (p444).
*/
/**
* Sets up the use[] and def[] arrays.
*
* The basic-block-level live variable analysis needs to know which
* variables get used before they're completely defined, and which
* variables are completely defined before they're used.
*/
void
fs_live_variables::setup_def_use()
{
int ip = 0;
for (int b = 0; b < cfg->num_blocks; b++) {
fs_bblock *block = cfg->blocks[b];
assert(ip == block->start_ip);
if (b > 0)
assert(cfg->blocks[b - 1]->end_ip == ip - 1);
for (fs_inst *inst = block->start;
inst != block->end->next;
inst = (fs_inst *)inst->next) {
/* Set use[] for this instruction */
for (unsigned int i = 0; i < 3; i++) {
if (inst->src[i].file == GRF) {
int reg = inst->src[i].reg;
if (!bd[b].def[reg])
bd[b].use[reg] = true;
}
}
/* Check for unconditional writes to whole registers. These
* are the things that screen off preceding definitions of a
* variable, and thus qualify for being in def[].
*/
if (inst->dst.file == GRF &&
inst->regs_written() == v->virtual_grf_sizes[inst->dst.reg] &&
!inst->predicated &&
!inst->force_uncompressed &&
!inst->force_sechalf) {
int reg = inst->dst.reg;
if (!bd[b].use[reg])
bd[b].def[reg] = true;
}
ip++;
}
}
}
/**
* The algorithm incrementally sets bits in liveout and livein,
* propagating it through control flow. It will eventually terminate
* because it only ever adds bits, and stops when no bits are added in
* a pass.
*/
void
fs_live_variables::compute_live_variables()
{
bool cont = true;
while (cont) {
cont = false;
for (int b = 0; b < cfg->num_blocks; b++) {
/* Update livein */
for (int i = 0; i < num_vars; i++) {
if (bd[b].use[i] || (bd[b].liveout[i] && !bd[b].def[i])) {
if (!bd[b].livein[i]) {
bd[b].livein[i] = true;
cont = true;
}
}
}
/* Update liveout */
foreach_list(block_node, &cfg->blocks[b]->children) {
fs_bblock_link *link = (fs_bblock_link *)block_node;
fs_bblock *block = link->block;
for (int i = 0; i < num_vars; i++) {
if (bd[block->block_num].livein[i] && !bd[b].liveout[i]) {
bd[b].liveout[i] = true;
cont = true;
}
}
}
}
}
}
fs_live_variables::fs_live_variables(fs_visitor *v, fs_cfg *cfg)
: v(v), cfg(cfg)
{
mem_ctx = ralloc_context(cfg->mem_ctx);
num_vars = v->virtual_grf_next;
bd = rzalloc_array(mem_ctx, struct block_data, cfg->num_blocks);
vars = rzalloc_array(mem_ctx, struct var, num_vars);
for (int i = 0; i < cfg->num_blocks; i++) {
bd[i].def = rzalloc_array(mem_ctx, bool, num_vars);
bd[i].use = rzalloc_array(mem_ctx, bool, num_vars);
bd[i].livein = rzalloc_array(mem_ctx, bool, num_vars);
bd[i].liveout = rzalloc_array(mem_ctx, bool, num_vars);
}
setup_def_use();
compute_live_variables();
}
fs_live_variables::~fs_live_variables()
{
ralloc_free(mem_ctx);
}
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