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/*
* Copyright © 2016 Broadcom
*
* 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 vc4_opt_peephole_sf.c
*
* Quick optimization to eliminate unused or identical SF updates.
*/
#include "vc4_qir.h"
#include "util/u_math.h"
static bool debug;
static void
dump_from(struct vc4_compile *c, struct qinst *inst, const char *type)
{
if (!debug)
return;
fprintf(stderr, "optimizing %s: ", type);
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
static void
dump_to(struct vc4_compile *c, struct qinst *inst)
{
if (!debug)
return;
fprintf(stderr, "to: ");
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
static bool
inst_srcs_updated(struct qinst *inst, struct qinst *writer)
{
/* If the sources get overwritten, stop tracking the
* last instruction writing SF.
*/
switch (writer->dst.file) {
case QFILE_TEMP:
for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
if (inst->src[i].file == QFILE_TEMP &&
inst->src[i].index == writer->dst.index) {
return true;
}
}
return false;
default:
return false;
}
}
static bool
src_file_varies_on_reread(struct qreg reg)
{
switch (reg.file) {
case QFILE_VARY:
case QFILE_VPM:
return true;
default:
return false;
}
}
static bool
inst_result_equals(struct qinst *a, struct qinst *b)
{
if (a->op != b->op ||
qir_depends_on_flags(a) ||
qir_depends_on_flags(b)) {
return false;
}
for (int i = 0; i < qir_get_op_nsrc(a->op); i++) {
if (!qir_reg_equals(a->src[i], b->src[i]) ||
src_file_varies_on_reread(a->src[i]) ||
src_file_varies_on_reread(b->src[i])) {
return false;
}
}
return true;
}
static bool
qir_opt_peephole_sf_block(struct vc4_compile *c, struct qblock *block)
{
bool progress = false;
/* We don't have liveness dataflow analysis for flags, but we also
* never generate a use of flags across control flow, so just treat
* them as unused at block exit.
*/
bool sf_live = false;
struct qinst *last_sf = NULL;
/* Walk the block from bottom to top, tracking if the SF is used, and
* removing unused or repeated ones.
*/
qir_for_each_inst_rev(inst, block) {
if (inst->sf) {
if (!sf_live) {
/* Our instruction's SF isn't read, so drop it.
*/
dump_from(c, inst, "dead SF");
inst->sf = false;
dump_to(c, inst);
progress = true;
} else if (last_sf &&
inst_result_equals(last_sf, inst)) {
/* The last_sf sets up same value as inst, so
* just drop the later one.
*/
dump_from(c, last_sf, "repeated SF");
last_sf->sf = false;
dump_to(c, last_sf);
progress = true;
last_sf = inst;
} else {
last_sf = inst;
}
sf_live = false;
}
if (last_sf) {
if (inst_srcs_updated(last_sf, inst))
last_sf = NULL;
}
if (qir_depends_on_flags(inst))
sf_live = true;
}
return progress;
}
bool
qir_opt_peephole_sf(struct vc4_compile *c)
{
bool progress = false;
qir_for_each_block(block, c)
progress = qir_opt_peephole_sf_block(c, block) || progress;
return progress;
}
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