/*
* Copyright © 2012 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.
*/
/** @file brw_fs_copy_propagation.cpp
*
* Support for global copy propagation in two passes: A local pass that does
* intra-block copy (and constant) propagation, and a global pass that uses
* dataflow analysis on the copies available at the end of each block to re-do
* local copy propagation with more copies available.
*
* See Muchnik's Advanced Compiler Design and Implementation, section
* 12.5 (p356).
*/
#define ACP_HASH_SIZE 16
#include "main/bitset.h"
#include "brw_fs.h"
#include "brw_cfg.h"
namespace { /* avoid conflict with opt_copy_propagation_elements */
struct acp_entry : public exec_node {
fs_reg dst;
fs_reg src;
};
struct block_data {
/**
* Which entries in the fs_copy_prop_dataflow acp table are live at the
* start of this block. This is the useful output of the analysis, since
* it lets us plug those into the local copy propagation on the second
* pass.
*/
BITSET_WORD *livein;
/**
* Which entries in the fs_copy_prop_dataflow acp table are live at the end
* of this block. This is done in initial setup from the per-block acps
* returned by the first local copy prop pass.
*/
BITSET_WORD *liveout;
/**
* Which entries in the fs_copy_prop_dataflow acp table are killed over the
* course of this block.
*/
BITSET_WORD *kill;
};
class fs_copy_prop_dataflow
{
public:
fs_copy_prop_dataflow(void *mem_ctx, cfg_t *cfg,
exec_list *out_acp[ACP_HASH_SIZE]);
void setup_kills();
void run();
void *mem_ctx;
cfg_t *cfg;
acp_entry **acp;
int num_acp;
int bitset_words;
struct block_data *bd;
};
} /* anonymous namespace */
fs_copy_prop_dataflow::fs_copy_prop_dataflow(void *mem_ctx, cfg_t *cfg,
exec_list *out_acp[ACP_HASH_SIZE])
: mem_ctx(mem_ctx), cfg(cfg)
{
bd = rzalloc_array(mem_ctx, struct block_data, cfg->num_blocks);
num_acp = 0;
for (int b = 0; b < cfg->num_blocks; b++) {
for (int i = 0; i < ACP_HASH_SIZE; i++) {
foreach_list(entry_node, &out_acp[b][i]) {
num_acp++;
}
}
}
acp = rzalloc_array(mem_ctx, struct acp_entry *, num_acp);
bitset_words = BITSET_WORDS(num_acp);
int next_acp = 0;
for (int b = 0; b < cfg->num_blocks; b++) {
bd[b].livein = rzalloc_array(bd, BITSET_WORD, bitset_words);
bd[b].liveout = rzalloc_array(bd, BITSET_WORD, bitset_words);
bd[b].kill = rzalloc_array(bd, BITSET_WORD, bitset_words);
for (int i = 0; i < ACP_HASH_SIZE; i++) {
foreach_list(entry_node, &out_acp[b][i]) {
acp_entry *entry = (acp_entry *)entry_node;
acp[next_acp] = entry;
BITSET_SET(bd[b].liveout, next_acp);
next_acp++;
}
}
}
assert(next_acp == num_acp);
setup_kills();
run();
}
/**
* Walk the set of instructions in the block, marking which entries in the acp
* are killed by the block.
*/
void
fs_copy_prop_dataflow::setup_kills()
{
for (int b = 0; b < cfg->num_blocks; b++) {
bblock_t *block = cfg->blocks[b];
for (fs_inst *inst = (fs_inst *)block->start;
inst != block->end->next;
inst = (fs_inst *)inst->next) {
if (inst->dst.file != GRF)
continue;
for (int i = 0; i < num_acp; i++) {
if (inst->overwrites_reg(acp[i]->dst) ||
inst->overwrites_reg(acp[i]->src)) {
BITSET_SET(bd[b].kill, i);
}
}
}
}
}
/**
* Walk the set of instructions in the block, marking which entries in the acp
* are killed by the block.
*/
void
fs_copy_prop_dataflow::run()
{
bool cont = true;
while (cont) {
cont = false;
for (int b = 0; b < cfg->num_blocks; b++) {
for (int i = 0; i < bitset_words; i++) {
BITSET_WORD new_liveout = (bd[b].livein[i] &
~bd[b].kill[i] &
~bd[b].liveout[i]);
if (new_liveout) {
bd[b].liveout[i] |= new_liveout;
cont = true;
}
/* Update livein: if it's live at the end of all parents, it's
* live at our start.
*/
BITSET_WORD new_livein = ~bd[b].livein[i];
foreach_list(block_node, &cfg->blocks[b]->parents) {
bblock_link *link = (bblock_link *)block_node;
bblock_t *block = link->block;
new_livein &= bd[block->block_num].liveout[i];
if (!new_livein)
break;
}
if (new_livein) {
bd[b].livein[i] |= new_livein;
cont = true;
}
}
}
}
}
bool
fs_visitor::try_copy_propagate(fs_inst *inst, int arg, acp_entry *entry)
{
if (entry->src.file == IMM)
return false;
if (inst->src[arg].file != entry->dst.file ||
inst->src[arg].reg != entry->dst.reg ||
inst->src[arg].reg_offset != entry->dst.reg_offset) {
return false;
}
/* See resolve_ud_negate() and comment in brw_fs_emit.cpp. */
if (inst->conditional_mod &&
inst->src[arg].type == BRW_REGISTER_TYPE_UD &&
entry->src.negate)
return false;
bool has_source_modifiers = entry->src.abs || entry->src.negate;
if ((has_source_modifiers || entry->src.file == UNIFORM ||
entry->src.smear != -1) && !can_do_source_mods(inst))
return false;
if (has_source_modifiers && entry->dst.type != inst->src[arg].type)
return false;
inst->src[arg].file = entry->src.file;
inst->src[arg].reg = entry->src.reg;
inst->src[arg].reg_offset = entry->src.reg_offset;
if (entry->src.smear != -1)
inst->src[arg].smear = entry->src.smear;
if (!inst->src[arg].abs) {
inst->src[arg].abs = entry->src.abs;
inst->src[arg].negate ^= entry->src.negate;
}
return true;
}
bool
fs_visitor::try_constant_propagate(fs_inst *inst, acp_entry *entry)
{
bool progress = false;
if (entry->src.file != IMM)
return false;
for (int i = 2; i >= 0; i--) {
if (inst->src[i].file != entry->dst.file ||
inst->src[i].reg != entry->dst.reg ||
inst->src[i].reg_offset != entry->dst.reg_offset)
continue;
/* Don't bother with cases that should have been taken care of by the
* GLSL compiler's constant folding pass.
*/
if (inst->src[i].negate || inst->src[i].abs)
continue;
switch (inst->opcode) {
case BRW_OPCODE_MOV:
inst->src[i] = entry->src;
progress = true;
break;
case BRW_OPCODE_MACH:
case BRW_OPCODE_MUL:
case BRW_OPCODE_ADD:
if (i == 1) {
inst->src[i] = entry->src;
progress = true;
} else if (i == 0 && inst->src[1].file != IMM) {
/* Fit this constant in by commuting the operands.
* Exception: we can't do this for 32-bit integer MUL/MACH
* because it's asymmetric.
*/
if ((inst->opcode == BRW_OPCODE_MUL ||
inst->opcode == BRW_OPCODE_MACH) &&
(inst->src[1].type == BRW_REGISTER_TYPE_D ||
inst->src[1].type == BRW_REGISTER_TYPE_UD))
break;
inst->src[0] = inst->src[1];
inst->src[1] = entry->src;
progress = true;
}
break;
case BRW_OPCODE_CMP:
case BRW_OPCODE_IF:
if (i == 1) {
inst->src[i] = entry->src;
progress = true;
} else if (i == 0 && inst->src[1].file != IMM) {
uint32_t new_cmod;
new_cmod = brw_swap_cmod(inst->conditional_mod);
if (new_cmod != ~0u) {
/* Fit this constant in by swapping the operands and
* flipping the test
*/
inst->src[0] = inst->src[1];
inst->src[1] = entry->src;
inst->conditional_mod = new_cmod;
progress = true;
}
}
break;
case BRW_OPCODE_SEL:
if (i == 1) {
inst->src[i] = entry->src;
progress = true;
} else if (i == 0 && inst->src[1].file != IMM) {
inst->src[0] = inst->src[1];
inst->src[1] = entry->src;
/* If this was predicated, flipping operands means
* we also need to flip the predicate.
*/
if (inst->conditional_mod == BRW_CONDITIONAL_NONE) {
inst->predicate_inverse =
!inst->predicate_inverse;
}
progress = true;
}
break;
case SHADER_OPCODE_RCP:
/* The hardware doesn't do math on immediate values
* (because why are you doing that, seriously?), but
* the correct answer is to just constant fold it
* anyway.
*/
assert(i == 0);
if (inst->src[0].imm.f != 0.0f) {
inst->opcode = BRW_OPCODE_MOV;
inst->src[0] = entry->src;
inst->src[0].imm.f = 1.0f / inst->src[0].imm.f;
progress = true;
}
break;
case FS_OPCODE_UNIFORM_PULL_CONSTANT_LOAD:
inst->src[i] = entry->src;
progress = true;
break;
default:
break;
}
}
return progress;
}
/* Walks a basic block and does copy propagation on it using the acp
* list.
*/
bool
fs_visitor::opt_copy_propagate_local(void *mem_ctx, bblock_t *block,
exec_list *acp)
{
bool progress = false;
for (fs_inst *inst = (fs_inst *)block->start;
inst != block->end->next;
inst = (fs_inst *)inst->next) {
/* Try propagating into this instruction. */
for (int i = 0; i < 3; i++) {
if (inst->src[i].file != GRF)
continue;
foreach_list(entry_node, &acp[inst->src[i].reg % ACP_HASH_SIZE]) {
acp_entry *entry = (acp_entry *)entry_node;
if (try_constant_propagate(inst, entry))
progress = true;
if (try_copy_propagate(inst, i, entry))
progress = true;
}
}
/* kill the destination from the ACP */
if (inst->dst.file == GRF) {
foreach_list_safe(entry_node, &acp[inst->dst.reg % ACP_HASH_SIZE]) {
acp_entry *entry = (acp_entry *)entry_node;
if (inst->overwrites_reg(entry->dst)) {
entry->remove();
}
}
/* Oops, we only have the chaining hash based on the destination, not
* the source, so walk across the entire table.
*/
for (int i = 0; i < ACP_HASH_SIZE; i++) {
foreach_list_safe(entry_node, &acp[i]) {
acp_entry *entry = (acp_entry *)entry_node;
if (inst->overwrites_reg(entry->src))
entry->remove();
}
}
}
/* If this instruction's source could potentially be folded into the
* operand of another instruction, add it to the ACP.
*/
if (inst->opcode == BRW_OPCODE_MOV &&
inst->dst.file == GRF &&
((inst->src[0].file == GRF &&
(inst->src[0].reg != inst->dst.reg ||
inst->src[0].reg_offset != inst->dst.reg_offset)) ||
inst->src[0].file == UNIFORM ||
inst->src[0].file == IMM) &&
inst->src[0].type == inst->dst.type &&
!inst->saturate &&
!inst->is_partial_write()) {
acp_entry *entry = ralloc(mem_ctx, acp_entry);
entry->dst = inst->dst;
entry->src = inst->src[0];
acp[entry->dst.reg % ACP_HASH_SIZE].push_tail(entry);
}
}
return progress;
}
bool
fs_visitor::opt_copy_propagate()
{
bool progress = false;
void *mem_ctx = ralloc_context(this->mem_ctx);
cfg_t cfg(this);
exec_list *out_acp[cfg.num_blocks];
for (int i = 0; i < cfg.num_blocks; i++)
out_acp[i] = new exec_list [ACP_HASH_SIZE];
/* First, walk through each block doing local copy propagation and getting
* the set of copies available at the end of the block.
*/
for (int b = 0; b < cfg.num_blocks; b++) {
bblock_t *block = cfg.blocks[b];
progress = opt_copy_propagate_local(mem_ctx, block,
out_acp[b]) || progress;
}
/* Do dataflow analysis for those available copies. */
fs_copy_prop_dataflow dataflow(mem_ctx, &cfg, out_acp);
/* Next, re-run local copy propagation, this time with the set of copies
* provided by the dataflow analysis available at the start of a block.
*/
for (int b = 0; b < cfg.num_blocks; b++) {
bblock_t *block = cfg.blocks[b];
exec_list in_acp[ACP_HASH_SIZE];
for (int i = 0; i < dataflow.num_acp; i++) {
if (BITSET_TEST(dataflow.bd[b].livein, i)) {
struct acp_entry *entry = dataflow.acp[i];
in_acp[entry->dst.reg % ACP_HASH_SIZE].push_tail(entry);
}
}
progress = opt_copy_propagate_local(mem_ctx, block, in_acp) || progress;
}
for (int i = 0; i < cfg.num_blocks; i++)
delete [] out_acp[i];
ralloc_free(mem_ctx);
if (progress)
live_intervals_valid = false;
return progress;
}