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/*
* Copyright © 2014 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_dead_code.c
*
* This is a simmple dead code eliminator for QIR with no control flow.
*
* It walks from the bottom of the instruction list, removing instructions
* with a destination that is never used, and marking the sources of non-dead
* instructions as used.
*/
#include "vc4_qir.h"
static bool debug;
static void
dce(struct vc4_compile *c, struct qinst *inst)
{
if (debug) {
fprintf(stderr, "Removing: ");
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
assert(!inst->sf);
qir_remove_instruction(c, inst);
}
static bool
has_nonremovable_reads(struct vc4_compile *c, struct qinst *inst)
{
for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
if (inst->src[i].file == QFILE_VPM) {
uint32_t attr = inst->src[i].index / 4;
uint32_t offset = (inst->src[i].index % 4) * 4;
if (c->vattr_sizes[attr] != offset + 4)
return true;
/* Can't get rid of the last VPM read, or the
* simulator (at least) throws an error.
*/
uint32_t total_size = 0;
for (uint32_t i = 0; i < ARRAY_SIZE(c->vattr_sizes); i++)
total_size += c->vattr_sizes[i];
if (total_size == 4)
return true;
}
if (inst->src[i].file == QFILE_VARY &&
c->input_semantics[inst->src[i].index].semantic == 0xff) {
return true;
}
}
return false;
}
bool
qir_opt_dead_code(struct vc4_compile *c)
{
bool progress = false;
bool *used = calloc(c->num_temps, sizeof(bool));
bool sf_used = false;
/* Whether we're eliminating texture setup currently. */
bool dce_tex = false;
struct list_head *node, *t;
for (node = c->instructions.prev, t = node->prev;
&c->instructions != node;
node = t, t = t->prev) {
struct qinst *inst = (struct qinst *)node;
if (inst->dst.file == QFILE_TEMP &&
!used[inst->dst.index] &&
!inst->sf &&
(!qir_has_side_effects(c, inst) ||
inst->op == QOP_TEX_RESULT) &&
!has_nonremovable_reads(c, inst)) {
if (inst->op == QOP_TEX_RESULT) {
dce_tex = true;
c->num_texture_samples--;
}
for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
if (inst->src[i].file != QFILE_VPM)
continue;
uint32_t attr = inst->src[i].index / 4;
uint32_t offset = (inst->src[i].index % 4) * 4;
if (c->vattr_sizes[attr] == offset + 4) {
c->num_inputs--;
c->vattr_sizes[attr] -= 4;
}
}
dce(c, inst);
progress = true;
continue;
}
if (qir_depends_on_flags(inst))
sf_used = true;
if (inst->sf) {
if (!sf_used) {
if (debug) {
fprintf(stderr, "Removing SF on: ");
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
inst->sf = false;
progress = true;
}
sf_used = false;
}
if (inst->op == QOP_TEX_RESULT)
dce_tex = false;
if (dce_tex && (inst->op == QOP_TEX_S ||
inst->op == QOP_TEX_T ||
inst->op == QOP_TEX_R ||
inst->op == QOP_TEX_B ||
inst->op == QOP_TEX_DIRECT)) {
dce(c, inst);
progress = true;
continue;
}
for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
if (inst->src[i].file == QFILE_TEMP)
used[inst->src[i].index] = true;
}
}
free(used);
return progress;
}
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