/*
* 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 Muchnick's Advanced Compiler Design and Implementation, section
* 12.5 (p356).
*/
#define ACP_HASH_SIZE 16
#include "util/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;
uint8_t regs_written;
enum opcode opcode;
bool saturate;
};
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 generated by
* instructions in this block which reach the end of the block without
* being killed.
*/
BITSET_WORD *copy;
/**
* 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_initial_values();
void run();
void dump_block_data() const;
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;
foreach_block (block, cfg) {
for (int i = 0; i < ACP_HASH_SIZE; i++) {
num_acp += out_acp[block->num][i].length();
}
}
acp = rzalloc_array(mem_ctx, struct acp_entry *, num_acp);
bitset_words = BITSET_WORDS(num_acp);
int next_acp = 0;
foreach_block (block, cfg) {
bd[block->num].livein = rzalloc_array(bd, BITSET_WORD, bitset_words);
bd[block->num].liveout = rzalloc_array(bd, BITSET_WORD, bitset_words);
bd[block->num].copy = rzalloc_array(bd, BITSET_WORD, bitset_words);
bd[block->num].kill = rzalloc_array(bd, BITSET_WORD, bitset_words);
for (int i = 0; i < ACP_HASH_SIZE; i++) {
foreach_in_list(acp_entry, entry, &out_acp[block->num][i]) {
acp[next_acp] = entry;
/* opt_copy_propagate_local populates out_acp with copies created
* in a block which are still live at the end of the block. This
* is exactly what we want in the COPY set.
*/
BITSET_SET(bd[block->num].copy, next_acp);
next_acp++;
}
}
}
assert(next_acp == num_acp);
setup_initial_values();
run();
}
/**
* Set up initial values for each of the data flow sets, prior to running
* the fixed-point algorithm.
*/
void
fs_copy_prop_dataflow::setup_initial_values()
{
/* Initialize the COPY and KILL sets. */
foreach_block (block, cfg) {
foreach_inst_in_block(fs_inst, inst, block) {
if (inst->dst.file != GRF)
continue;
/* Mark ACP entries which are killed by this instruction. */
for (int i = 0; i < num_acp; i++) {
if (inst->overwrites_reg(acp[i]->dst) ||
inst->overwrites_reg(acp[i]->src)) {
BITSET_SET(bd[block->num].kill, i);
}
}
}
}
/* Populate the initial values for the livein and liveout sets. For the
* block at the start of the program, livein = 0 and liveout = copy.
* For the others, set liveout to 0 (the empty set) and livein to ~0
* (the universal set).
*/
foreach_block (block, cfg) {
if (block->parents.is_empty()) {
for (int i = 0; i < bitset_words; i++) {
bd[block->num].livein[i] = 0u;
bd[block->num].liveout[i] = bd[block->num].copy[i];
}
} else {
for (int i = 0; i < bitset_words; i++) {
bd[block->num].liveout[i] = 0u;
bd[block->num].livein[i] = ~0u;
}
}
}
}
/**
* 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 progress;
do {
progress = false;
/* Update liveout for all blocks. */
foreach_block (block, cfg) {
if (block->parents.is_empty())
continue;
for (int i = 0; i < bitset_words; i++) {
const BITSET_WORD old_liveout = bd[block->num].liveout[i];
bd[block->num].liveout[i] =
bd[block->num].copy[i] | (bd[block->num].livein[i] &
~bd[block->num].kill[i]);
if (old_liveout != bd[block->num].liveout[i])
progress = true;
}
}
/* Update livein for all blocks. If a copy is live out of all parent
* blocks, it's live coming in to this block.
*/
foreach_block (block, cfg) {
if (block->parents.is_empty())
continue;
for (int i = 0; i < bitset_words; i++) {
const BITSET_WORD old_livein = bd[block->num].livein[i];
bd[block->num].livein[i] = ~0u;
foreach_list_typed(bblock_link, parent_link, link, &block->parents) {
bblock_t *parent = parent_link->block;
bd[block->num].livein[i] &= bd[parent->num].liveout[i];
}
if (old_livein != bd[block->num].livein[i])
progress = true;
}
}
} while (progress);
}
void
fs_copy_prop_dataflow::dump_block_data() const
{
foreach_block (block, cfg) {
fprintf(stderr, "Block %d [%d, %d] (parents ", block->num,
block->start_ip, block->end_ip);
foreach_list_typed(bblock_link, link, link, &block->parents) {
bblock_t *parent = link->block;
fprintf(stderr, "%d ", parent->num);
}
fprintf(stderr, "):\n");
fprintf(stderr, " livein = 0x");
for (int i = 0; i < bitset_words; i++)
fprintf(stderr, "%08x", bd[block->num].livein[i]);
fprintf(stderr, ", liveout = 0x");
for (int i = 0; i < bitset_words; i++)
fprintf(stderr, "%08x", bd[block->num].liveout[i]);
fprintf(stderr, ",\n copy = 0x");
for (int i = 0; i < bitset_words; i++)
fprintf(stderr, "%08x", bd[block->num].copy[i]);
fprintf(stderr, ", kill = 0x");
for (int i = 0; i < bitset_words; i++)
fprintf(stderr, "%08x", bd[block->num].kill[i]);
fprintf(stderr, "\n");
}
}
static bool
is_logic_op(enum opcode opcode)
{
return (opcode == BRW_OPCODE_AND ||
opcode == BRW_OPCODE_OR ||
opcode == BRW_OPCODE_XOR ||
opcode == BRW_OPCODE_NOT);
}
static bool
can_change_source_types(fs_inst *inst)
{
return !inst->src[0].abs && !inst->src[0].negate &&
(inst->opcode == BRW_OPCODE_MOV ||
(inst->opcode == BRW_OPCODE_SEL &&
inst->predicate != BRW_PREDICATE_NONE &&
!inst->src[1].abs && !inst->src[1].negate));
}
bool
fs_visitor::try_copy_propagate(fs_inst *inst, int arg, acp_entry *entry)
{
if (inst->src[arg].file != GRF)
return false;
if (entry->src.file == IMM)
return false;
assert(entry->src.file == GRF || entry->src.file == UNIFORM ||
entry->src.file == ATTR);
if (entry->opcode == SHADER_OPCODE_LOAD_PAYLOAD &&
inst->opcode == SHADER_OPCODE_LOAD_PAYLOAD)
return false;
assert(entry->dst.file == GRF);
if (inst->src[arg].reg != entry->dst.reg)
return false;
/* Bail if inst is reading a range that isn't contained in the range
* that entry is writing.
*/
if (inst->src[arg].reg_offset < entry->dst.reg_offset ||
(inst->src[arg].reg_offset * 32 + inst->src[arg].subreg_offset +
inst->regs_read(arg) * inst->src[arg].stride * 32) >
(entry->dst.reg_offset + entry->regs_written) * 32)
return false;
/* we can't generally copy-propagate UD negations because we
* can end up accessing the resulting values as signed integers
* instead. See also resolve_ud_negate() and comment in
* fs_generator::generate_code.
*/
if (entry->src.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.is_contiguous()) &&
!inst->can_do_source_mods(devinfo))
return false;
if (has_source_modifiers &&
inst->opcode == SHADER_OPCODE_GEN4_SCRATCH_WRITE)
return false;
/* Bail if the result of composing both strides would exceed the
* hardware limit.
*/
if (entry->src.stride * inst->src[arg].stride > 4)
return false;
/* Bail if the result of composing both strides cannot be expressed
* as another stride. This avoids, for example, trying to transform
* this:
*
* MOV (8) rX<1>UD rY<0;1,0>UD
* FOO (8) ... rX<8;8,1>UW
*
* into this:
*
* FOO (8) ... rY<0;1,0>UW
*
* Which would have different semantics.
*/
if (entry->src.stride != 1 &&
(inst->src[arg].stride *
type_sz(inst->src[arg].type)) % type_sz(entry->src.type) != 0)
return false;
if (has_source_modifiers &&
entry->dst.type != inst->src[arg].type &&
!can_change_source_types(inst))
return false;
if (devinfo->gen >= 8 && (entry->src.negate || entry->src.abs) &&
is_logic_op(inst->opcode)) {
return false;
}
if (entry->saturate) {
switch(inst->opcode) {
case BRW_OPCODE_SEL:
if (inst->src[1].file != IMM ||
inst->src[1].fixed_hw_reg.dw1.f < 0.0 ||
inst->src[1].fixed_hw_reg.dw1.f > 1.0) {
return false;
}
break;
default:
return false;
}
}
inst->src[arg].file = entry->src.file;
inst->src[arg].reg = entry->src.reg;
inst->src[arg].stride *= entry->src.stride;
inst->saturate = inst->saturate || entry->saturate;
switch (entry->src.file) {
case UNIFORM:
assert(entry->src.width == 1);
case BAD_FILE:
case HW_REG:
inst->src[arg].width = entry->src.width;
inst->src[arg].reg_offset = entry->src.reg_offset;
inst->src[arg].subreg_offset = entry->src.subreg_offset;
break;
case ATTR:
case GRF:
{
assert(entry->src.width % inst->src[arg].width == 0);
/* In this case, we'll just leave the width alone. The source
* register could have different widths depending on how it is
* being used. For instance, if only half of the register was
* used then we want to preserve that and continue to only use
* half.
*
* Also, we have to deal with mapping parts of vgrfs to other
* parts of vgrfs so we have to do some reg_offset magic.
*/
/* Compute the offset of inst->src[arg] relative to inst->dst */
assert(entry->dst.subreg_offset == 0);
int rel_offset = inst->src[arg].reg_offset - entry->dst.reg_offset;
int rel_suboffset = inst->src[arg].subreg_offset;
/* Compute the final register offset (in bytes) */
int offset = entry->src.reg_offset * 32 + entry->src.subreg_offset;
offset += rel_offset * 32 + rel_suboffset;
inst->src[arg].reg_offset = offset / 32;
inst->src[arg].subreg_offset = offset % 32;
}
break;
default:
unreachable("Invalid register file");
break;
}
if (has_source_modifiers) {
if (entry->dst.type != inst->src[arg].type) {
/* We are propagating source modifiers from a MOV with a different
* type. If we got here, then we can just change the source and
* destination types of the instruction and keep going.
*/
assert(can_change_source_types(inst));
for (int i = 0; i < inst->sources; i++) {
inst->src[i].type = entry->dst.type;
}
inst->dst.type = entry->dst.type;
}
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;
if (entry->saturate)
return false;
for (int i = inst->sources - 1; i >= 0; i--) {
if (inst->src[i].file != GRF)
continue;
assert(entry->dst.file == GRF);
if (inst->src[i].reg != entry->dst.reg)
continue;
/* Bail if inst is reading a range that isn't contained in the range
* that entry is writing.
*/
if (inst->src[i].reg_offset < entry->dst.reg_offset ||
(inst->src[i].reg_offset * 32 + inst->src[i].subreg_offset +
inst->regs_read(i) * inst->src[i].stride * 32) >
(entry->dst.reg_offset + entry->regs_written) * 32)
continue;
fs_reg val = entry->src;
val.type = inst->src[i].type;
if (inst->src[i].abs) {
if ((devinfo->gen >= 8 && is_logic_op(inst->opcode)) ||
!brw_abs_immediate(val.type, &val.fixed_hw_reg)) {
continue;
}
}
if (inst->src[i].negate) {
if ((devinfo->gen >= 8 && is_logic_op(inst->opcode)) ||
!brw_negate_immediate(val.type, &val.fixed_hw_reg)) {
continue;
}
}
switch (inst->opcode) {
case BRW_OPCODE_MOV:
case SHADER_OPCODE_LOAD_PAYLOAD:
inst->src[i] = val;
progress = true;
break;
case SHADER_OPCODE_INT_QUOTIENT:
case SHADER_OPCODE_INT_REMAINDER:
/* FINISHME: Promote non-float constants and remove this. */
if (devinfo->gen < 8)
break;
/* fallthrough */
case SHADER_OPCODE_POW:
/* Allow constant propagation into src1 (except on Gen 6), and let
* constant combining promote the constant on Gen < 8.
*
* While Gen 6 MATH can take a scalar source, its source and
* destination offsets must be equal and we cannot ensure that.
*/
if (devinfo->gen == 6)
break;
/* fallthrough */
case BRW_OPCODE_BFI1:
case BRW_OPCODE_ASR:
case BRW_OPCODE_SHL:
case BRW_OPCODE_SHR:
case BRW_OPCODE_SUBB:
if (i == 1) {
inst->src[i] = val;
progress = true;
}
break;
case BRW_OPCODE_MACH:
case BRW_OPCODE_MUL:
case BRW_OPCODE_ADD:
case BRW_OPCODE_OR:
case BRW_OPCODE_AND:
case BRW_OPCODE_XOR:
case BRW_OPCODE_ADDC:
if (i == 1) {
inst->src[i] = val;
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.
*
* The BSpec says for Broadwell that
*
* "When multiplying DW x DW, the dst cannot be accumulator."
*
* Integer MUL with a non-accumulator destination will be lowered
* by lower_integer_multiplication(), so don't restrict it.
*/
if (((inst->opcode == BRW_OPCODE_MUL &&
inst->dst.is_accumulator()) ||
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] = val;
progress = true;
}
break;
case BRW_OPCODE_CMP:
case BRW_OPCODE_IF:
if (i == 1) {
inst->src[i] = val;
progress = true;
} else if (i == 0 && inst->src[1].file != IMM) {
enum brw_conditional_mod new_cmod;
new_cmod = brw_swap_cmod(inst->conditional_mod);
if (new_cmod != BRW_CONDITIONAL_NONE) {
/* Fit this constant in by swapping the operands and
* flipping the test
*/
inst->src[0] = inst->src[1];
inst->src[1] = val;
inst->conditional_mod = new_cmod;
progress = true;
}
}
break;
case BRW_OPCODE_SEL:
if (i == 1) {
inst->src[i] = val;
progress = true;
} else if (i == 0 && inst->src[1].file != IMM) {
inst->src[0] = inst->src[1];
inst->src[1] = val;
/* 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].fixed_hw_reg.dw1.f != 0.0f) {
inst->opcode = BRW_OPCODE_MOV;
inst->src[0] = val;
inst->src[0].fixed_hw_reg.dw1.f = 1.0f / inst->src[0].fixed_hw_reg.dw1.f;
progress = true;
}
break;
case FS_OPCODE_UNIFORM_PULL_CONSTANT_LOAD:
case SHADER_OPCODE_BROADCAST:
inst->src[i] = val;
progress = true;
break;
case BRW_OPCODE_MAD:
case BRW_OPCODE_LRP:
inst->src[i] = val;
progress = true;
break;
default:
break;
}
}
return progress;
}
static bool
can_propagate_from(fs_inst *inst)
{
return (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 == ATTR ||
inst->src[0].file == UNIFORM ||
inst->src[0].file == IMM) &&
inst->src[0].type == inst->dst.type &&
!inst->is_partial_write());
}
/* Walks a basic block and does copy propagation on it using the acp
* list.
*/
bool
fs_visitor::opt_copy_propagate_local(void *copy_prop_ctx, bblock_t *block,
exec_list *acp)
{
bool progress = false;
foreach_inst_in_block(fs_inst, inst, block) {
/* Try propagating into this instruction. */
for (int i = 0; i < inst->sources; i++) {
if (inst->src[i].file != GRF)
continue;
foreach_in_list(acp_entry, entry, &acp[inst->src[i].reg % ACP_HASH_SIZE]) {
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_in_list_safe(acp_entry, entry, &acp[inst->dst.reg % ACP_HASH_SIZE]) {
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_in_list_safe(acp_entry, entry, &acp[i]) {
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 (can_propagate_from(inst)) {
acp_entry *entry = ralloc(copy_prop_ctx, acp_entry);
entry->dst = inst->dst;
entry->src = inst->src[0];
entry->regs_written = inst->regs_written;
entry->opcode = inst->opcode;
entry->saturate = inst->saturate;
acp[entry->dst.reg % ACP_HASH_SIZE].push_tail(entry);
} else if (inst->opcode == SHADER_OPCODE_LOAD_PAYLOAD &&
inst->dst.file == GRF) {
int offset = 0;
for (int i = 0; i < inst->sources; i++) {
int effective_width = i < inst->header_size ? 8 : inst->exec_size;
int regs_written = effective_width / 8;
if (inst->src[i].file == GRF) {
acp_entry *entry = ralloc(copy_prop_ctx, acp_entry);
entry->dst = inst->dst;
entry->dst.reg_offset = offset;
entry->dst.width = effective_width;
entry->src = inst->src[i];
entry->regs_written = regs_written;
entry->opcode = inst->opcode;
if (!entry->dst.equals(inst->src[i])) {
acp[entry->dst.reg % ACP_HASH_SIZE].push_tail(entry);
} else {
ralloc_free(entry);
}
}
offset += regs_written;
}
}
}
return progress;
}
bool
fs_visitor::opt_copy_propagate()
{
bool progress = false;
void *copy_prop_ctx = ralloc_context(NULL);
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.
*/
foreach_block (block, cfg) {
progress = opt_copy_propagate_local(copy_prop_ctx, block,
out_acp[block->num]) || progress;
}
/* Do dataflow analysis for those available copies. */
fs_copy_prop_dataflow dataflow(copy_prop_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.
*/
foreach_block (block, cfg) {
exec_list in_acp[ACP_HASH_SIZE];
for (int i = 0; i < dataflow.num_acp; i++) {
if (BITSET_TEST(dataflow.bd[block->num].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(copy_prop_ctx, block, in_acp) || progress;
}
for (int i = 0; i < cfg->num_blocks; i++)
delete [] out_acp[i];
ralloc_free(copy_prop_ctx);
if (progress)
invalidate_live_intervals();
return progress;
}