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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_cse.c
*
* Implements CSE for QIR without control flow.
*
* For each operation that writes a destination (and isn't just a MOV), put it
* in the hash table of all instructions that do so. When faced with another
* one, look it up in the hash table by its opcode and operands. If there's
* an entry in the table, then just reuse the entry's destination as the
* source of a MOV instead of reproducing the computation. That MOV will then
* get cleaned up by copy propagation.
*/
#include "vc4_qir.h"
#include "util/hash_table.h"
#include "util/ralloc.h"
static bool debug;
struct inst_key {
enum qop op;
struct qreg src[4];
/**
* If the instruction depends on the flags, how many SFs have been
* seen before this instruction, or if it depends on r4, how many r4
* writes have been seen.
*/
uint32_t implicit_arg_update_count;
};
static bool
inst_key_equals(const void *a, const void *b)
{
const struct inst_key *key_a = a;
const struct inst_key *key_b = b;
return memcmp(key_a, key_b, sizeof(*key_a)) == 0;
}
static struct qinst *
vc4_find_cse(struct vc4_compile *c, struct hash_table *ht,
struct qinst *inst, uint32_t sf_count,
uint32_t r4_count)
{
if (inst->dst.file != QFILE_TEMP ||
inst->op == QOP_MOV ||
qir_get_op_nsrc(inst->op) > 4) {
return NULL;
}
struct inst_key key;
memset(&key, 0, sizeof(key));
key.op = inst->op;
memcpy(key.src, inst->src,
qir_get_op_nsrc(inst->op) * sizeof(key.src[0]));
if (qir_depends_on_flags(inst))
key.implicit_arg_update_count = sf_count;
if (qir_reads_r4(inst))
key.implicit_arg_update_count = r4_count;
uint32_t hash = _mesa_hash_data(&key, sizeof(key));
struct hash_entry *entry =
_mesa_hash_table_search_pre_hashed(ht, hash, &key);
if (entry) {
if (debug) {
fprintf(stderr, "CSE found match:\n");
fprintf(stderr, " Original inst: ");
qir_dump_inst(c, entry->data);
fprintf(stderr, "\n");
fprintf(stderr, " Our inst: ");
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
return entry->data;
}
struct inst_key *alloc_key = ralloc(ht, struct inst_key);
if (!alloc_key)
return NULL;
memcpy(alloc_key, &key, sizeof(*alloc_key));
_mesa_hash_table_insert_pre_hashed(ht, hash, alloc_key, inst);
if (debug) {
fprintf(stderr, "Added to CSE HT: ");
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
return NULL;
}
bool
qir_opt_cse(struct vc4_compile *c)
{
bool progress = false;
uint32_t sf_count = 0, r4_count = 0;
struct hash_table *ht = _mesa_hash_table_create(NULL, NULL,
inst_key_equals);
if (!ht)
return false;
list_for_each_entry(struct qinst, inst, &c->instructions, link) {
if (qir_has_side_effects(c, inst) ||
qir_has_side_effect_reads(c, inst)) {
continue;
}
if (inst->sf) {
sf_count++;
} else {
struct qinst *cse = vc4_find_cse(c, ht, inst,
sf_count, r4_count);
if (cse) {
inst->src[0] = cse->dst;
for (int i = 1; i < qir_get_op_nsrc(inst->op);
i++)
inst->src[i] = c->undef;
inst->op = QOP_MOV;
progress = true;
if (debug) {
fprintf(stderr, " Turned into: ");
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
}
}
if (qir_writes_r4(inst))
r4_count++;
}
ralloc_free(ht);
return progress;
}
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