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/*
* Copyright (C) 2021 Valve 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 "ir3_ra.h"
#include "ir3_shader.h"
#include "ralloc.h"
/* A note on how phi node uses are handled:
*
* - Phi node sources are considered to happen after the end of the
* predecessor block, so the live_out for that block contains phi sources.
* - On the other hand, phi destinations are considered to happen at the start
* of the block, so that live_in does *not* contain phi destinations. This
* is mainly because phi destinations and live-through values have to be
* treated very differently by RA at the beginning of a block.
*/
static bool
compute_block_liveness(struct ir3_liveness *live, struct ir3_block *block,
BITSET_WORD *tmp_live, unsigned bitset_words)
{
memcpy(tmp_live, live->live_out[block->index], bitset_words *
sizeof(BITSET_WORD));
/* Process instructions */
foreach_instr_rev (instr, &block->instr_list) {
ra_foreach_dst(dst, instr) {
if (BITSET_TEST(tmp_live, dst->name))
dst->flags &= ~IR3_REG_UNUSED;
else
dst->flags |= IR3_REG_UNUSED;
BITSET_CLEAR(tmp_live, dst->name);
}
/* Phi node uses occur after the predecessor block */
if (instr->opc != OPC_META_PHI) {
ra_foreach_src(src, instr) {
if (BITSET_TEST(tmp_live, src->def->name))
src->flags &= ~IR3_REG_KILL;
else
src->flags |= IR3_REG_KILL;
}
ra_foreach_src(src, instr) {
if (BITSET_TEST(tmp_live, src->def->name))
src->flags &= ~IR3_REG_FIRST_KILL;
else
src->flags |= IR3_REG_FIRST_KILL;
BITSET_SET(tmp_live, src->def->name);
}
}
}
memcpy(live->live_in[block->index], tmp_live,
bitset_words * sizeof(BITSET_WORD));
bool progress = false;
for (unsigned i = 0; i < block->predecessors_count; i++) {
const struct ir3_block *pred = block->predecessors[i];
for (unsigned j = 0; j < bitset_words; j++) {
if (tmp_live[j] & ~live->live_out[pred->index][j])
progress = true;
live->live_out[pred->index][j] |= tmp_live[j];
}
/* Process phi sources. */
foreach_instr (phi, &block->instr_list) {
if (phi->opc != OPC_META_PHI)
break;
if (!phi->regs[1 + i]->def)
continue;
unsigned name = phi->regs[1 + i]->def->name;
if (!BITSET_TEST(live->live_out[pred->index], name)) {
progress = true;
BITSET_SET(live->live_out[pred->index], name);
}
}
}
return progress;
}
struct ir3_liveness *ir3_calc_liveness(struct ir3_shader_variant *v)
{
struct ir3_liveness *live = rzalloc(NULL, struct ir3_liveness);
/* Reserve name 0 to mean "doesn't have a name yet" to make the debug
* output nicer.
*/
array_insert(live, live->definitions, NULL);
/* Build definition <-> name mapping */
unsigned block_count = 0;
foreach_block (block, &v->ir->block_list) {
block->index = block_count++;
foreach_instr (instr, &block->instr_list) {
ra_foreach_dst(dst, instr) {
dst->name = live->definitions_count;
array_insert(live, live->definitions, dst);
}
}
}
live->block_count = block_count;
unsigned bitset_words = BITSET_WORDS(live->definitions_count);
BITSET_WORD *tmp_live = ralloc_array(live, BITSET_WORD, bitset_words);
live->live_in = ralloc_array(live, BITSET_WORD *, block_count);
live->live_out = ralloc_array(live, BITSET_WORD *, block_count);
unsigned i = 0;
foreach_block (block, &v->ir->block_list) {
block->index = i++;
live->live_in[block->index] = rzalloc_array(live, BITSET_WORD, bitset_words);
live->live_out[block->index] = rzalloc_array(live, BITSET_WORD, bitset_words);
}
bool progress = true;
while (progress) {
progress = false;
foreach_block_rev (block, &v->ir->block_list) {
progress |=
compute_block_liveness(live, block, tmp_live, bitset_words);
}
}
return live;
}
/* Return true if "def" is live after "instr". It's assumed that "def"
* dominates "instr".
*/
bool
ir3_def_live_after(struct ir3_liveness *live, struct ir3_register *def,
struct ir3_instruction *instr)
{
/* If it's live out then it's definitely live at the instruction. */
if (BITSET_TEST(live->live_out[instr->block->index], def->name))
return true;
/* If it's not live in and not defined in the same block then the live
* range can't extend to the instruction.
*/
if (def->instr->block != instr->block &&
!BITSET_TEST(live->live_in[instr->block->index], def->name))
return false;
/* Ok, now comes the tricky case, where "def" is killed somewhere in
* "instr"'s block and we have to check if it's before or after.
*/
foreach_instr_rev (test_instr, &instr->block->instr_list) {
if (test_instr == instr)
break;
for (unsigned i = 0; i < test_instr->regs_count; i++) {
if (test_instr->regs[i]->flags & IR3_REG_DEST)
continue;
if (test_instr->regs[i]->def == def)
return true;
}
}
return false;
}
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