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/*
* Copyright © 2011 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_vec4.h"
extern "C" {
#include "main/macros.h"
#include "program/prog_parameter.h"
}
#define MAX_INSTRUCTION (1 << 30)
namespace brw {
void
vec4_visitor::calculate_live_intervals()
{
int *def = ralloc_array(mem_ctx, int, virtual_grf_count);
int *use = ralloc_array(mem_ctx, int, virtual_grf_count);
int loop_depth = 0;
int loop_start = 0;
if (this->live_intervals_valid)
return;
for (int i = 0; i < virtual_grf_count; i++) {
def[i] = MAX_INSTRUCTION;
use[i] = -1;
}
int ip = 0;
foreach_list(node, &this->instructions) {
vec4_instruction *inst = (vec4_instruction *)node;
if (inst->opcode == BRW_OPCODE_DO) {
if (loop_depth++ == 0)
loop_start = ip;
} else if (inst->opcode == BRW_OPCODE_WHILE) {
loop_depth--;
if (loop_depth == 0) {
/* Patches up the use of vars marked for being live across
* the whole loop.
*/
for (int i = 0; i < virtual_grf_count; i++) {
if (use[i] == loop_start) {
use[i] = ip;
}
}
}
} else {
for (unsigned int i = 0; i < 3; i++) {
if (inst->src[i].file == GRF) {
int reg = inst->src[i].reg;
if (!loop_depth) {
use[reg] = ip;
} else {
def[reg] = MIN2(loop_start, def[reg]);
use[reg] = loop_start;
/* Nobody else is going to go smash our start to
* later in the loop now, because def[reg] now
* points before the bb header.
*/
}
}
}
if (inst->dst.file == GRF) {
int reg = inst->dst.reg;
if (!loop_depth) {
def[reg] = MIN2(def[reg], ip);
} else {
def[reg] = MIN2(def[reg], loop_start);
}
}
}
ip++;
}
ralloc_free(this->virtual_grf_def);
ralloc_free(this->virtual_grf_use);
this->virtual_grf_def = def;
this->virtual_grf_use = use;
this->live_intervals_valid = true;
}
bool
vec4_visitor::virtual_grf_interferes(int a, int b)
{
int start = MAX2(this->virtual_grf_def[a], this->virtual_grf_def[b]);
int end = MIN2(this->virtual_grf_use[a], this->virtual_grf_use[b]);
/* We can't handle dead register writes here, without iterating
* over the whole instruction stream to find every single dead
* write to that register to compare to the live interval of the
* other register. Just assert that dead_code_eliminate() has been
* called.
*/
assert((this->virtual_grf_use[a] != -1 ||
this->virtual_grf_def[a] == MAX_INSTRUCTION) &&
(this->virtual_grf_use[b] != -1 ||
this->virtual_grf_def[b] == MAX_INSTRUCTION));
return start < end;
}
/**
* Must be called after calculate_live_intervales() to remove unused
* writes to registers -- register allocation will fail otherwise
* because something deffed but not used won't be considered to
* interfere with other regs.
*/
bool
vec4_visitor::dead_code_eliminate()
{
bool progress = false;
int pc = 0;
calculate_live_intervals();
foreach_list_safe(node, &this->instructions) {
vec4_instruction *inst = (vec4_instruction *)node;
if (inst->dst.file == GRF && this->virtual_grf_use[inst->dst.reg] <= pc) {
inst->remove();
progress = true;
}
pc++;
}
if (progress)
live_intervals_valid = false;
return progress;
}
} /* namespace brw */
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