Google Git
Sign in
fuchsia / third_party / mesa / main / . / src / intel / compiler / elk / elk_fs_copy_propagation.cpp
blob: b3632a9db81648995ef893ab561d3272c07e9428 [file] [log] [blame]
/*
* 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 elk_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).
*/
#include "util/bitset.h"
#include "util/u_math.h"
#include "util/rb_tree.h"
#include "elk_fs.h"
#include "elk_fs_live_variables.h"
#include "elk_cfg.h"
#include "elk_eu.h"
using namespace elk;
namespace { /* avoid conflict with opt_copy_propagation_elements */
struct acp_entry {
struct rb_node by_dst;
struct rb_node by_src;
elk_fs_reg dst;
elk_fs_reg src;
unsigned global_idx;
unsigned size_written;
unsigned size_read;
enum elk_opcode opcode;
bool is_partial_write;
bool force_writemask_all;
};
/**
* Compare two acp_entry::src.nr
*
* This is intended to be used as the comparison function for rb_tree.
*/
static int
cmp_entry_dst_entry_dst(const struct rb_node *a_node, const struct rb_node *b_node)
{
const struct acp_entry *a_entry =
rb_node_data(struct acp_entry, a_node, by_dst);
const struct acp_entry *b_entry =
rb_node_data(struct acp_entry, b_node, by_dst);
return a_entry->dst.nr - b_entry->dst.nr;
}
static int
cmp_entry_dst_nr(const struct rb_node *a_node, const void *b_key)
{
const struct acp_entry *a_entry =
rb_node_data(struct acp_entry, a_node, by_dst);
return a_entry->dst.nr - (uintptr_t) b_key;
}
static int
cmp_entry_src_entry_src(const struct rb_node *a_node, const struct rb_node *b_node)
{
const struct acp_entry *a_entry =
rb_node_data(struct acp_entry, a_node, by_src);
const struct acp_entry *b_entry =
rb_node_data(struct acp_entry, b_node, by_src);
return a_entry->src.nr - b_entry->src.nr;
}
/**
* Compare an acp_entry::src.nr with a raw nr.
*
* This is intended to be used as the comparison function for rb_tree.
*/
static int
cmp_entry_src_nr(const struct rb_node *a_node, const void *b_key)
{
const struct acp_entry *a_entry =
rb_node_data(struct acp_entry, a_node, by_src);
return a_entry->src.nr - (uintptr_t) b_key;
}
class acp_forward_iterator {
public:
acp_forward_iterator(struct rb_node *n, unsigned offset)
: curr(n), next(nullptr), offset(offset)
{
next = rb_node_next_or_null(curr);
}
acp_forward_iterator &operator++()
{
curr = next;
next = rb_node_next_or_null(curr);
return *this;
}
bool operator!=(const acp_forward_iterator &other) const
{
return curr != other.curr;
}
struct acp_entry *operator*() const
{
/* This open-codes part of rb_node_data. */
return curr != NULL ? (struct acp_entry *)(((char *)curr) - offset)
: NULL;
}
private:
struct rb_node *curr;
struct rb_node *next;
unsigned offset;
};
struct acp {
DECLARE_LINEAR_ALLOC_CXX_OPERATORS(acp);
struct rb_tree by_dst;
struct rb_tree by_src;
acp()
{
rb_tree_init(&by_dst);
rb_tree_init(&by_src);
}
acp_forward_iterator begin()
{
return acp_forward_iterator(rb_tree_first(&by_src),
rb_tree_offsetof(struct acp_entry, by_src, 0));
}
const acp_forward_iterator end() const
{
return acp_forward_iterator(nullptr, 0);
}
unsigned length()
{
unsigned l = 0;
for (rb_node *iter = rb_tree_first(&by_src);
iter != NULL; iter = rb_node_next(iter))
l++;
return l;
}
void add(acp_entry *entry)
{
rb_tree_insert(&by_dst, &entry->by_dst, cmp_entry_dst_entry_dst);
rb_tree_insert(&by_src, &entry->by_src, cmp_entry_src_entry_src);
}
void remove(acp_entry *entry)
{
rb_tree_remove(&by_dst, &entry->by_dst);
rb_tree_remove(&by_src, &entry->by_src);
}
acp_forward_iterator find_by_src(unsigned nr)
{
struct rb_node *rbn = rb_tree_search(&by_src,
(void *)(uintptr_t) nr,
cmp_entry_src_nr);
return acp_forward_iterator(rbn, rb_tree_offsetof(struct acp_entry,
by_src, rbn));
}
acp_forward_iterator find_by_dst(unsigned nr)
{
struct rb_node *rbn = rb_tree_search(&by_dst,
(void *)(uintptr_t) nr,
cmp_entry_dst_nr);
return acp_forward_iterator(rbn, rb_tree_offsetof(struct acp_entry,
by_dst, rbn));
}
};
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;
/**
* Which entries in the fs_copy_prop_dataflow acp table are guaranteed to
* have a fully uninitialized destination at the end of this block.
*/
BITSET_WORD *undef;
/**
* Which entries in the fs_copy_prop_dataflow acp table can the
* start of this block be reached from. Note that this is a weaker
* condition than livein.
*/
BITSET_WORD *reachin;
/**
* Which entries in the fs_copy_prop_dataflow acp table are
* overwritten by an instruction with channel masks inconsistent
* with the copy instruction (e.g. due to force_writemask_all).
* Such an overwrite can cause the copy entry to become invalid
* even if the copy instruction is subsequently re-executed for any
* given channel i, since the execution of the overwrite for
* channel i may corrupt other channels j!=i inactive for the
* subsequent copy.
*/
BITSET_WORD *exec_mismatch;
};
class fs_copy_prop_dataflow
{
public:
fs_copy_prop_dataflow(linear_ctx *lin_ctx, elk_cfg_t *cfg,
const fs_live_variables &live,
struct acp *out_acp);
void setup_initial_values();
void run();
void dump_block_data() const UNUSED;
elk_cfg_t *cfg;
const fs_live_variables &live;
acp_entry **acp;
int num_acp;
int bitset_words;
struct block_data *bd;
};
} /* anonymous namespace */
fs_copy_prop_dataflow::fs_copy_prop_dataflow(linear_ctx *lin_ctx, elk_cfg_t *cfg,
const fs_live_variables &live,
struct acp *out_acp)
: cfg(cfg), live(live)
{
bd = linear_zalloc_array(lin_ctx, struct block_data, cfg->num_blocks);
num_acp = 0;
foreach_block (block, cfg)
num_acp += out_acp[block->num].length();
bitset_words = BITSET_WORDS(num_acp);
foreach_block (block, cfg) {
bd[block->num].livein = linear_zalloc_array(lin_ctx, BITSET_WORD, bitset_words);
bd[block->num].liveout = linear_zalloc_array(lin_ctx, BITSET_WORD, bitset_words);
bd[block->num].copy = linear_zalloc_array(lin_ctx, BITSET_WORD, bitset_words);
bd[block->num].kill = linear_zalloc_array(lin_ctx, BITSET_WORD, bitset_words);
bd[block->num].undef = linear_zalloc_array(lin_ctx, BITSET_WORD, bitset_words);
bd[block->num].reachin = linear_zalloc_array(lin_ctx, BITSET_WORD, bitset_words);
bd[block->num].exec_mismatch = linear_zalloc_array(lin_ctx, BITSET_WORD, bitset_words);
}
acp = linear_zalloc_array(lin_ctx, struct acp_entry *, num_acp);
int next_acp = 0;
foreach_block (block, cfg) {
for (auto iter = out_acp[block->num].begin();
iter != out_acp[block->num].end(); ++iter) {
acp[next_acp] = *iter;
(*iter)->global_idx = next_acp;
/* opt_copy_propagation_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();
}
/**
* Like reg_offset, but register must be VGRF or FIXED_GRF.
*/
static inline unsigned
grf_reg_offset(const elk_fs_reg &r)
{
return (r.file == VGRF ? 0 : r.nr) * REG_SIZE +
r.offset +
(r.file == FIXED_GRF ? r.subnr : 0);
}
/**
* Like regions_overlap, but register must be VGRF or FIXED_GRF.
*/
static inline bool
grf_regions_overlap(const elk_fs_reg &r, unsigned dr, const elk_fs_reg &s, unsigned ds)
{
return reg_space(r) == reg_space(s) &&
!(grf_reg_offset(r) + dr <= grf_reg_offset(s) ||
grf_reg_offset(s) + ds <= grf_reg_offset(r));
}
/**
* 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. */
{
struct acp acp_table;
/* First, get all the KILLs for instructions which overwrite ACP
* destinations.
*/
for (int i = 0; i < num_acp; i++)
acp_table.add(acp[i]);
foreach_block (block, cfg) {
foreach_inst_in_block(elk_fs_inst, inst, block) {
if (inst->dst.file != VGRF &&
inst->dst.file != FIXED_GRF)
continue;
for (auto iter = acp_table.find_by_src(inst->dst.nr);
iter != acp_table.end() && (*iter)->src.nr == inst->dst.nr;
++iter) {
if (grf_regions_overlap(inst->dst, inst->size_written,
(*iter)->src, (*iter)->size_read)) {
BITSET_SET(bd[block->num].kill, (*iter)->global_idx);
if (inst->force_writemask_all && !(*iter)->force_writemask_all)
BITSET_SET(bd[block->num].exec_mismatch, (*iter)->global_idx);
}
}
if (inst->dst.file != VGRF)
continue;
for (auto iter = acp_table.find_by_dst(inst->dst.nr);
iter != acp_table.end() && (*iter)->dst.nr == inst->dst.nr;
++iter) {
if (grf_regions_overlap(inst->dst, inst->size_written,
(*iter)->dst, (*iter)->size_written)) {
BITSET_SET(bd[block->num].kill, (*iter)->global_idx);
if (inst->force_writemask_all && !(*iter)->force_writemask_all)
BITSET_SET(bd[block->num].exec_mismatch, (*iter)->global_idx);
}
}
}
}
}
/* 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 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;
}
}
}
/* Initialize the undef set. */
foreach_block (block, cfg) {
for (int i = 0; i < num_acp; i++) {
BITSET_SET(bd[block->num].undef, i);
for (unsigned off = 0; off < acp[i]->size_written; off += REG_SIZE) {
if (BITSET_TEST(live.block_data[block->num].defout,
live.var_from_reg(byte_offset(acp[i]->dst, off))))
BITSET_CLEAR(bd[block->num].undef, 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 progress;
do {
progress = false;
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];
const BITSET_WORD old_reachin = bd[block->num].reachin[i];
BITSET_WORD livein_from_any_block = 0;
/* Update livein for this block. If a copy is live out of all
* parent blocks, it's live coming in to this block.
*/
bd[block->num].livein[i] = ~0u;
foreach_list_typed(elk_bblock_link, parent_link, link, &block->parents) {
elk_bblock_t *parent = parent_link->block;
/* Consider ACP entries with a known-undefined destination to
* be available from the parent. This is valid because we're
* free to set the undefined variable equal to the source of
* the ACP entry without breaking the application's
* expectations, since the variable is undefined.
*/
bd[block->num].livein[i] &= (bd[parent->num].liveout[i] |
bd[parent->num].undef[i]);
livein_from_any_block |= bd[parent->num].liveout[i];
/* Update reachin for this block. If the end of any
* parent block is reachable from the copy, the start
* of this block is reachable from it as well.
*/
bd[block->num].reachin[i] |= (bd[parent->num].reachin[i] |
bd[parent->num].copy[i]);
}
/* Limit to the set of ACP entries that can possibly be available
* at the start of the block, since propagating from a variable
* which is guaranteed to be undefined (rather than potentially
* undefined for some dynamic control-flow paths) doesn't seem
* particularly useful.
*/
bd[block->num].livein[i] &= livein_from_any_block;
/* Update liveout for this block. */
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] ||
old_reachin != bd[block->num].reachin[i])
progress = true;
}
}
} while (progress);
/* Perform a second fixed-point pass in order to propagate the
* exec_mismatch bitsets. Note that this requires an accurate
* value of the reachin bitsets as input, which isn't available
* until the end of the first propagation pass, so this loop cannot
* be folded into the previous one.
*/
do {
progress = false;
foreach_block (block, cfg) {
for (int i = 0; i < bitset_words; i++) {
const BITSET_WORD old_exec_mismatch = bd[block->num].exec_mismatch[i];
/* Update exec_mismatch for this block. If the end of a
* parent block is reachable by an overwrite with
* inconsistent execution masking, the start of this block
* is reachable by such an overwrite as well.
*/
foreach_list_typed(elk_bblock_link, parent_link, link, &block->parents) {
elk_bblock_t *parent = parent_link->block;
bd[block->num].exec_mismatch[i] |= (bd[parent->num].exec_mismatch[i] &
bd[parent->num].reachin[i]);
}
/* Only consider overwrites with inconsistent execution
* masking if they are reachable from the copy, since
* overwrites unreachable from a copy are harmless to that
* copy.
*/
bd[block->num].exec_mismatch[i] &= bd[block->num].reachin[i];
if (old_exec_mismatch != bd[block->num].exec_mismatch[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(elk_bblock_link, link, link, &block->parents) {
elk_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 elk_opcode opcode)
{
return (opcode == ELK_OPCODE_AND ||
opcode == ELK_OPCODE_OR ||
opcode == ELK_OPCODE_XOR ||
opcode == ELK_OPCODE_NOT);
}
static bool
can_take_stride(elk_fs_inst *inst, elk_reg_type dst_type,
unsigned arg, unsigned stride,
const struct elk_compiler *compiler)
{
const struct intel_device_info *devinfo = compiler->devinfo;
if (stride > 4)
return false;
/* Bail if the channels of the source need to be aligned to the byte offset
* of the corresponding channel of the destination, and the provided stride
* would break this restriction.
*/
if (has_dst_aligned_region_restriction(devinfo, inst, dst_type) &&
!(type_sz(inst->src[arg].type) * stride ==
type_sz(dst_type) * inst->dst.stride ||
stride == 0))
return false;
/* 3-source instructions can only be Align16, which restricts what strides
* they can take. They can only take a stride of 1 (the usual case), or 0
* with a special "repctrl" bit. But the repctrl bit doesn't work for
* 64-bit datatypes, so if the source type is 64-bit then only a stride of
* 1 is allowed. From the Broadwell PRM, Volume 7 "3D Media GPGPU", page
* 944:
*
* This is applicable to 32b datatypes and 16b datatype. 64b datatypes
* cannot use the replicate control.
*/
if (inst->elk_is_3src(compiler)) {
if (type_sz(inst->src[arg].type) > 4)
return stride == 1;
else
return stride == 1 || stride == 0;
}
/* From the Broadwell PRM, Volume 2a "Command Reference - Instructions",
* page 391 ("Extended Math Function"):
*
* The following restrictions apply for align1 mode: Scalar source is
* supported. Source and destination horizontal stride must be the
* same.
*
* From the Haswell PRM Volume 2b "Command Reference - Instructions", page
* 134 ("Extended Math Function"):
*
* Scalar source is supported. Source and destination horizontal stride
* must be 1.
*
* and similar language exists for IVB and SNB. Pre-SNB, math instructions
* are sends, so the sources are moved to MRF's and there are no
* restrictions.
*/
if (inst->is_math()) {
if (devinfo->ver == 6 || devinfo->ver == 7) {
assert(inst->dst.stride == 1);
return stride == 1 || stride == 0;
} else if (devinfo->ver >= 8) {
return stride == inst->dst.stride || stride == 0;
}
}
return true;
}
static bool
instruction_requires_packed_data(elk_fs_inst *inst)
{
switch (inst->opcode) {
case ELK_FS_OPCODE_DDX_FINE:
case ELK_FS_OPCODE_DDX_COARSE:
case ELK_FS_OPCODE_DDY_FINE:
case ELK_FS_OPCODE_DDY_COARSE:
case ELK_SHADER_OPCODE_QUAD_SWIZZLE:
return true;
default:
return false;
}
}
static bool
try_copy_propagate(const elk_compiler *compiler, elk_fs_inst *inst,
acp_entry *entry, int arg,
const elk::simple_allocator &alloc)
{
if (inst->src[arg].file != VGRF)
return false;
const struct intel_device_info *devinfo = compiler->devinfo;
assert(entry->src.file == VGRF || entry->src.file == UNIFORM ||
entry->src.file == ATTR || entry->src.file == FIXED_GRF);
/* Avoid propagating a LOAD_PAYLOAD instruction into another if there is a
* good chance that we'll be able to eliminate the latter through register
* coalescing. If only part of the sources of the second LOAD_PAYLOAD can
* be simplified through copy propagation we would be making register
* coalescing impossible, ending up with unnecessary copies in the program.
* This is also the case for is_multi_copy_payload() copies that can only
* be coalesced when the instruction is lowered into a sequence of MOVs.
*
* Worse -- In cases where the ACP entry was the result of CSE combining
* multiple LOAD_PAYLOAD subexpressions, propagating the first LOAD_PAYLOAD
* into the second would undo the work of CSE, leading to an infinite
* optimization loop. Avoid this by detecting LOAD_PAYLOAD copies from CSE
* temporaries which should match is_coalescing_payload().
*/
if (entry->opcode == ELK_SHADER_OPCODE_LOAD_PAYLOAD &&
(is_coalescing_payload(alloc, inst) || is_multi_copy_payload(inst)))
return false;
assert(entry->dst.file == VGRF);
if (inst->src[arg].nr != entry->dst.nr)
return false;
/* Bail if inst is reading a range that isn't contained in the range
* that entry is writing.
*/
if (!region_contained_in(inst->src[arg], inst->size_read(arg),
entry->dst, entry->size_written))
return false;
/* Send messages with EOT set are restricted to use g112-g127 (and we
* sometimes need g127 for other purposes), so avoid copy propagating
* anything that would make it impossible to satisfy that restriction.
*/
if (inst->eot) {
/* Avoid propagating a FIXED_GRF register, as that's already pinned. */
if (entry->src.file == FIXED_GRF)
return false;
/* We might be propagating from a large register, while the SEND only
* is reading a portion of it (say the .A channel in an RGBA value).
* We need to pin both split SEND sources in g112-g126/127, so only
* allow this if the registers aren't too large.
*/
if (inst->opcode == ELK_SHADER_OPCODE_SEND && entry->src.file == VGRF) {
unsigned prop_src_size = alloc.sizes[entry->src.nr];
if (prop_src_size > 15)
return false;
}
}
/* Avoid propagating odd-numbered FIXED_GRF registers into the first source
* of a LINTERP instruction on platforms where the PLN instruction has
* register alignment restrictions.
*/
if (devinfo->has_pln && devinfo->ver <= 6 &&
entry->src.file == FIXED_GRF && (entry->src.nr & 1) &&
inst->opcode == ELK_FS_OPCODE_LINTERP && arg == 0)
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
* elk_fs_generator::generate_code.
*/
if (entry->src.type == ELK_REGISTER_TYPE_UD &&
entry->src.negate)
return false;
bool has_source_modifiers = entry->src.abs || entry->src.negate;
if (has_source_modifiers && !inst->can_do_source_mods(devinfo))
return false;
/* Reject cases that would violate register regioning restrictions. */
if ((entry->src.file == UNIFORM || !entry->src.is_contiguous()) &&
((devinfo->ver == 6 && inst->is_math()) ||
inst->is_send_from_grf() ||
inst->uses_indirect_addressing())) {
return false;
}
if (has_source_modifiers &&
inst->opcode == ELK_SHADER_OPCODE_GFX4_SCRATCH_WRITE)
return false;
/* Some instructions implemented in the generator backend, such as
* derivatives, assume that their operands are packed so we can't
* generally propagate strided regions to them.
*/
const unsigned entry_stride = (entry->src.file == FIXED_GRF ? 1 :
entry->src.stride);
if (instruction_requires_packed_data(inst) && entry_stride != 1)
return false;
const elk_reg_type dst_type = (has_source_modifiers &&
entry->dst.type != inst->src[arg].type) ?
entry->dst.type : inst->dst.type;
/* Bail if the result of composing both strides would exceed the
* hardware limit.
*/
if (!can_take_stride(inst, dst_type, arg,
entry_stride * inst->src[arg].stride,
compiler))
return false;
/* From the Cherry Trail/Braswell PRMs, Volume 7: 3D Media GPGPU:
* EU Overview
* Register Region Restrictions
* Special Requirements for Handling Double Precision Data Types :
*
* "When source or destination datatype is 64b or operation is integer
* DWord multiply, regioning in Align1 must follow these rules:
*
* 1. Source and Destination horizontal stride must be aligned to the
* same qword.
* 2. Regioning must ensure Src.Vstride = Src.Width * Src.Hstride.
* 3. Source and Destination offset must be the same, except the case
* of scalar source."
*
* Most of this is already checked in can_take_stride(), we're only left
* with checking 3.
*/
if (has_dst_aligned_region_restriction(devinfo, inst, dst_type) &&
entry_stride != 0 &&
(reg_offset(inst->dst) % REG_SIZE) != (reg_offset(entry->src) % REG_SIZE))
return false;
/* Bail if the source FIXED_GRF region of the copy cannot be trivially
* composed with the source region of the instruction -- E.g. because the
* copy uses some extended stride greater than 4 not supported natively by
* the hardware as a horizontal stride, or because instruction compression
* could require us to use a vertical stride shorter than a GRF.
*/
if (entry->src.file == FIXED_GRF &&
(inst->src[arg].stride > 4 ||
inst->dst.component_size(inst->exec_size) >
inst->src[arg].component_size(inst->exec_size)))
return false;
/* Bail if the instruction type is larger than the execution type of the
* copy, what implies that each channel is reading multiple channels of the
* destination of the copy, and simply replacing the sources would give a
* program with different semantics.
*/
if ((type_sz(entry->dst.type) < type_sz(inst->src[arg].type) ||
entry->is_partial_write) &&
inst->opcode != ELK_OPCODE_MOV) {
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_stride != 1 &&
(inst->src[arg].stride *
type_sz(inst->src[arg].type)) % type_sz(entry->src.type) != 0)
return false;
/* Since semantics of source modifiers are type-dependent we need to
* ensure that the meaning of the instruction remains the same if we
* change the type. If the sizes of the types are different the new
* instruction will read a different amount of data than the original
* and the semantics will always be different.
*/
if (has_source_modifiers &&
entry->dst.type != inst->src[arg].type &&
(!inst->can_change_types() ||
type_sz(entry->dst.type) != type_sz(inst->src[arg].type)))
return false;
if (devinfo->ver >= 8 && (entry->src.negate || entry->src.abs) &&
is_logic_op(inst->opcode)) {
return false;
}
/* Save the offset of inst->src[arg] relative to entry->dst for it to be
* applied later.
*/
const unsigned rel_offset = inst->src[arg].offset - entry->dst.offset;
/* Fold the copy into the instruction consuming it. */
inst->src[arg].file = entry->src.file;
inst->src[arg].nr = entry->src.nr;
inst->src[arg].subnr = entry->src.subnr;
inst->src[arg].offset = entry->src.offset;
/* Compose the strides of both regions. */
if (entry->src.file == FIXED_GRF) {
if (inst->src[arg].stride) {
const unsigned orig_width = 1 << entry->src.width;
const unsigned reg_width = REG_SIZE / (type_sz(inst->src[arg].type) *
inst->src[arg].stride);
inst->src[arg].width = cvt(MIN2(orig_width, reg_width)) - 1;
inst->src[arg].hstride = cvt(inst->src[arg].stride);
inst->src[arg].vstride = inst->src[arg].hstride + inst->src[arg].width;
} else {
inst->src[arg].vstride = inst->src[arg].hstride =
inst->src[arg].width = 0;
}
inst->src[arg].stride = 1;
/* Hopefully no Align16 around here... */
assert(entry->src.swizzle == ELK_SWIZZLE_XYZW);
inst->src[arg].swizzle = entry->src.swizzle;
} else {
inst->src[arg].stride *= entry->src.stride;
}
/* Compute the first component of the copy that the instruction is
* reading, and the base byte offset within that component.
*/
assert((entry->dst.offset % REG_SIZE == 0 || inst->opcode == ELK_OPCODE_MOV) &&
entry->dst.stride == 1);
const unsigned component = rel_offset / type_sz(entry->dst.type);
const unsigned suboffset = rel_offset % type_sz(entry->dst.type);
/* Calculate the byte offset at the origin of the copy of the given
* component and suboffset.
*/
inst->src[arg] = byte_offset(inst->src[arg],
component * entry_stride * type_sz(entry->src.type) + suboffset);
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.
*/
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;
}
static bool
try_constant_propagate(const elk_compiler *compiler, elk_fs_inst *inst,
acp_entry *entry, int arg)
{
const struct intel_device_info *devinfo = compiler->devinfo;
bool progress = false;
if (type_sz(entry->src.type) > 4)
return false;
if (inst->src[arg].file != VGRF)
return false;
assert(entry->dst.file == VGRF);
if (inst->src[arg].nr != entry->dst.nr)
return false;
/* Bail if inst is reading a range that isn't contained in the range
* that entry is writing.
*/
if (!region_contained_in(inst->src[arg], inst->size_read(arg),
entry->dst, entry->size_written))
return false;
/* If the size of the use type is larger than the size of the entry
* type, the entry doesn't contain all of the data that the user is
* trying to use.
*/
if (type_sz(inst->src[arg].type) > type_sz(entry->dst.type))
return false;
elk_fs_reg val = entry->src;
/* If the size of the use type is smaller than the size of the entry,
* clamp the value to the range of the use type. This enables constant
* copy propagation in cases like
*
*
* mov(8) g12<1>UD 0x0000000cUD
* ...
* mul(8) g47<1>D g86<8,8,1>D g12<16,8,2>W
*/
if (type_sz(inst->src[arg].type) < type_sz(entry->dst.type)) {
if (type_sz(inst->src[arg].type) != 2 || type_sz(entry->dst.type) != 4)
return false;
assert(inst->src[arg].subnr == 0 || inst->src[arg].subnr == 2);
/* When subnr is 0, we want the lower 16-bits, and when it's 2, we
* want the upper 16-bits. No other values of subnr are valid for a
* UD source.
*/
const uint16_t v = inst->src[arg].subnr == 2 ? val.ud >> 16 : val.ud;
val.ud = v | (uint32_t(v) << 16);
}
val.type = inst->src[arg].type;
if (inst->src[arg].abs) {
if ((devinfo->ver >= 8 && is_logic_op(inst->opcode)) ||
!elk_abs_immediate(val.type, &val.as_elk_reg())) {
return false;
}
}
if (inst->src[arg].negate) {
if ((devinfo->ver >= 8 && is_logic_op(inst->opcode)) ||
!elk_negate_immediate(val.type, &val.as_elk_reg())) {
return false;
}
}
switch (inst->opcode) {
case ELK_OPCODE_MOV:
case ELK_SHADER_OPCODE_LOAD_PAYLOAD:
case ELK_FS_OPCODE_PACK:
inst->src[arg] = val;
progress = true;
break;
case ELK_SHADER_OPCODE_POW:
/* Allow constant propagation into src1 (except on Gen 6 which
* doesn't support scalar source math), and let constant combining
* promote the constant on Gen < 8.
*/
if (devinfo->ver == 6)
break;
if (arg == 1) {
inst->src[arg] = val;
progress = true;
}
break;
case ELK_OPCODE_SUBB:
if (arg == 1) {
inst->src[arg] = val;
progress = true;
}
break;
case ELK_OPCODE_MACH:
case ELK_OPCODE_MUL:
case ELK_SHADER_OPCODE_MULH:
case ELK_OPCODE_ADD:
case ELK_OPCODE_XOR:
case ELK_OPCODE_ADDC:
if (arg == 1) {
inst->src[arg] = val;
progress = true;
} else if (arg == 0 && inst->src[1].file != IMM) {
/* Don't copy propagate the constant in situations like
*
* mov(8) g8<1>D 0x7fffffffD
* mul(8) g16<1>D g8<8,8,1>D g15<16,8,2>W
*
* On platforms that only have a 32x16 multiplier, this will
* result in lowering the multiply to
*
* mul(8) g15<1>D g14<8,8,1>D 0xffffUW
* mul(8) g16<1>D g14<8,8,1>D 0x7fffUW
* add(8) g15.1<2>UW g15.1<16,8,2>UW g16<16,8,2>UW
*
* On Gfx8 and Gfx9, which have the full 32x32 multiplier, it
* results in
*
* mul(8) g16<1>D g15<16,8,2>W 0x7fffffffD
*
* Volume 2a of the Skylake PRM says:
*
* When multiplying a DW and any lower precision integer, the
* DW operand must on src0.
*/
if (inst->opcode == ELK_OPCODE_MUL &&
type_sz(inst->src[1].type) < 4 &&
type_sz(val.type) == 4)
break;
/* 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 == ELK_OPCODE_MUL &&
inst->dst.is_accumulator()) ||
inst->opcode == ELK_OPCODE_MACH) &&
(inst->src[1].type == ELK_REGISTER_TYPE_D ||
inst->src[1].type == ELK_REGISTER_TYPE_UD))
break;
inst->src[0] = inst->src[1];
inst->src[1] = val;
progress = true;
}
break;
case ELK_OPCODE_CMP:
case ELK_OPCODE_IF:
if (arg == 1) {
inst->src[arg] = val;
progress = true;
} else if (arg == 0 && inst->src[1].file != IMM) {
enum elk_conditional_mod new_cmod;
new_cmod = elk_swap_cmod(inst->conditional_mod);
if (new_cmod != ELK_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 ELK_OPCODE_SEL:
if (arg == 1) {
inst->src[arg] = val;
progress = true;
} else if (arg == 0) {
if (inst->src[1].file != IMM &&
(inst->conditional_mod == ELK_CONDITIONAL_NONE ||
/* Only GE and L are commutative. */
inst->conditional_mod == ELK_CONDITIONAL_GE ||
inst->conditional_mod == ELK_CONDITIONAL_L)) {
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 == ELK_CONDITIONAL_NONE) {
inst->predicate_inverse =
!inst->predicate_inverse;
}
} else {
inst->src[0] = val;
}
progress = true;
}
break;
case ELK_FS_OPCODE_FB_WRITE_LOGICAL:
/* The omask source of ELK_FS_OPCODE_FB_WRITE_LOGICAL is
* bit-cast using a strided region so they cannot be immediates.
*/
if (arg != FB_WRITE_LOGICAL_SRC_OMASK) {
inst->src[arg] = val;
progress = true;
}
break;
case ELK_SHADER_OPCODE_INT_QUOTIENT:
case ELK_SHADER_OPCODE_INT_REMAINDER:
/* Allow constant propagation into either source (except on Gen 6
* which doesn't support scalar source math). Constant combining
* promote the src1 constant on Gen < 8, and it will promote the src0
* constant on all platforms.
*/
if (devinfo->ver == 6)
break;
FALLTHROUGH;
case ELK_OPCODE_AND:
case ELK_OPCODE_ASR:
case ELK_OPCODE_BFE:
case ELK_OPCODE_BFI1:
case ELK_OPCODE_BFI2:
case ELK_OPCODE_SHL:
case ELK_OPCODE_SHR:
case ELK_OPCODE_OR:
case ELK_SHADER_OPCODE_TEX_LOGICAL:
case ELK_SHADER_OPCODE_TXD_LOGICAL:
case ELK_SHADER_OPCODE_TXF_LOGICAL:
case ELK_SHADER_OPCODE_TXL_LOGICAL:
case ELK_SHADER_OPCODE_TXS_LOGICAL:
case ELK_FS_OPCODE_TXB_LOGICAL:
case ELK_SHADER_OPCODE_TXF_CMS_LOGICAL:
case ELK_SHADER_OPCODE_TXF_CMS_W_LOGICAL:
case ELK_SHADER_OPCODE_TXF_CMS_W_GFX12_LOGICAL:
case ELK_SHADER_OPCODE_TXF_UMS_LOGICAL:
case ELK_SHADER_OPCODE_TXF_MCS_LOGICAL:
case ELK_SHADER_OPCODE_LOD_LOGICAL:
case ELK_SHADER_OPCODE_TG4_LOGICAL:
case ELK_SHADER_OPCODE_TG4_OFFSET_LOGICAL:
case ELK_SHADER_OPCODE_SAMPLEINFO_LOGICAL:
case ELK_SHADER_OPCODE_IMAGE_SIZE_LOGICAL:
case ELK_SHADER_OPCODE_UNTYPED_ATOMIC_LOGICAL:
case ELK_SHADER_OPCODE_UNTYPED_SURFACE_READ_LOGICAL:
case ELK_SHADER_OPCODE_UNTYPED_SURFACE_WRITE_LOGICAL:
case ELK_SHADER_OPCODE_TYPED_ATOMIC_LOGICAL:
case ELK_SHADER_OPCODE_TYPED_SURFACE_READ_LOGICAL:
case ELK_SHADER_OPCODE_TYPED_SURFACE_WRITE_LOGICAL:
case ELK_SHADER_OPCODE_BYTE_SCATTERED_WRITE_LOGICAL:
case ELK_SHADER_OPCODE_BYTE_SCATTERED_READ_LOGICAL:
case ELK_FS_OPCODE_UNIFORM_PULL_CONSTANT_LOAD:
case ELK_SHADER_OPCODE_BROADCAST:
case ELK_OPCODE_MAD:
case ELK_OPCODE_LRP:
case ELK_FS_OPCODE_PACK_HALF_2x16_SPLIT:
case ELK_SHADER_OPCODE_SHUFFLE:
inst->src[arg] = val;
progress = true;
break;
default:
break;
}
return progress;
}
static bool
can_propagate_from(elk_fs_inst *inst)
{
return (inst->opcode == ELK_OPCODE_MOV &&
inst->dst.file == VGRF &&
((inst->src[0].file == VGRF &&
!grf_regions_overlap(inst->dst, inst->size_written,
inst->src[0], inst->size_read(0))) ||
inst->src[0].file == ATTR ||
inst->src[0].file == UNIFORM ||
inst->src[0].file == IMM ||
(inst->src[0].file == FIXED_GRF &&
inst->src[0].is_contiguous())) &&
inst->src[0].type == inst->dst.type &&
!inst->saturate &&
/* Subset of !is_partial_write() conditions. */
!inst->predicate && inst->dst.is_contiguous()) ||
is_identity_payload(FIXED_GRF, inst);
}
/* Walks a basic block and does copy propagation on it using the acp
* list.
*/
static bool
opt_copy_propagation_local(const elk_compiler *compiler, linear_ctx *lin_ctx,
elk_bblock_t *block, struct acp &acp,
const elk::simple_allocator &alloc)
{
bool progress = false;
foreach_inst_in_block(elk_fs_inst, inst, block) {
/* Try propagating into this instruction. */
bool instruction_progress = false;
for (int i = inst->sources - 1; i >= 0; i--) {
if (inst->src[i].file != VGRF)
continue;
for (auto iter = acp.find_by_dst(inst->src[i].nr);
iter != acp.end() && (*iter)->dst.nr == inst->src[i].nr;
++iter) {
if ((*iter)->src.file == IMM) {
if (try_constant_propagate(compiler, inst, *iter, i)) {
instruction_progress = true;
break;
}
} else {
if (try_copy_propagate(compiler, inst, *iter, i, alloc)) {
instruction_progress = true;
break;
}
}
}
}
if (instruction_progress) {
progress = true;
/* If only one of the sources of a 2-source, commutative instruction (e.g.,
* AND) is immediate, it must be src1. If both are immediate, opt_algebraic
* should fold it away.
*/
if (inst->sources == 2 && inst->is_commutative() &&
inst->src[0].file == IMM && inst->src[1].file != IMM) {
const auto src1 = inst->src[1];
inst->src[1] = inst->src[0];
inst->src[0] = src1;
}
}
/* kill the destination from the ACP */
if (inst->dst.file == VGRF || inst->dst.file == FIXED_GRF) {
for (auto iter = acp.find_by_dst(inst->dst.nr);
iter != acp.end() && (*iter)->dst.nr == inst->dst.nr;
++iter) {
if (grf_regions_overlap((*iter)->dst, (*iter)->size_written,
inst->dst, inst->size_written))
acp.remove(*iter);
}
for (auto iter = acp.find_by_src(inst->dst.nr);
iter != acp.end() && (*iter)->src.nr == inst->dst.nr;
++iter) {
/* Make sure we kill the entry if this instruction overwrites
* _any_ of the registers that it reads
*/
if (grf_regions_overlap((*iter)->src, (*iter)->size_read,
inst->dst, inst->size_written))
acp.remove(*iter);
}
}
/* 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 = linear_zalloc(lin_ctx, acp_entry);
entry->dst = inst->dst;
entry->src = inst->src[0];
entry->size_written = inst->size_written;
for (unsigned i = 0; i < inst->sources; i++)
entry->size_read += inst->size_read(i);
entry->opcode = inst->opcode;
entry->is_partial_write = inst->is_partial_write();
entry->force_writemask_all = inst->force_writemask_all;
acp.add(entry);
} else if (inst->opcode == ELK_SHADER_OPCODE_LOAD_PAYLOAD &&
inst->dst.file == VGRF) {
int offset = 0;
for (int i = 0; i < inst->sources; i++) {
int effective_width = i < inst->header_size ? 8 : inst->exec_size;
const unsigned size_written = effective_width *
type_sz(inst->src[i].type);
if (inst->src[i].file == VGRF ||
(inst->src[i].file == FIXED_GRF &&
inst->src[i].is_contiguous())) {
const elk_reg_type t = i < inst->header_size ?
ELK_REGISTER_TYPE_UD : inst->src[i].type;
elk_fs_reg dst = byte_offset(retype(inst->dst, t), offset);
if (!dst.equals(inst->src[i])) {
acp_entry *entry = linear_zalloc(lin_ctx, acp_entry);
entry->dst = dst;
entry->src = retype(inst->src[i], t);
entry->size_written = size_written;
entry->size_read = inst->size_read(i);
entry->opcode = inst->opcode;
entry->force_writemask_all = inst->force_writemask_all;
acp.add(entry);
}
}
offset += size_written;
}
}
}
return progress;
}
bool
elk_fs_visitor::opt_copy_propagation()
{
bool progress = false;
void *copy_prop_ctx = ralloc_context(NULL);
linear_ctx *lin_ctx = linear_context(copy_prop_ctx);
struct acp *out_acp = new (lin_ctx) acp[cfg->num_blocks];
const fs_live_variables &live = live_analysis.require();
/* 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_propagation_local(compiler, lin_ctx, block,
out_acp[block->num], alloc) || progress;
/* If the destination of an ACP entry exists only within this block,
* then there's no need to keep it for dataflow analysis. We can delete
* it from the out_acp table and avoid growing the bitsets any bigger
* than we absolutely have to.
*
* Because nothing in opt_copy_propagation_local touches the block
* start/end IPs and opt_copy_propagation_local is incapable of
* extending the live range of an ACP destination beyond the block,
* it's safe to use the liveness information in this way.
*/
for (auto iter = out_acp[block->num].begin();
iter != out_acp[block->num].end(); ++iter) {
assert((*iter)->dst.file == VGRF);
if (block->start_ip <= live.vgrf_start[(*iter)->dst.nr] &&
live.vgrf_end[(*iter)->dst.nr] <= block->end_ip) {
out_acp[block->num].remove(*iter);
}
}
}
/* Do dataflow analysis for those available copies. */
fs_copy_prop_dataflow dataflow(lin_ctx, cfg, live, 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) {
struct acp in_acp;
for (int i = 0; i < dataflow.num_acp; i++) {
if (BITSET_TEST(dataflow.bd[block->num].livein, i) &&
!BITSET_TEST(dataflow.bd[block->num].exec_mismatch, i)) {
struct acp_entry *entry = dataflow.acp[i];
in_acp.add(entry);
}
}
progress = opt_copy_propagation_local(compiler, lin_ctx, block,
in_acp, alloc) ||
progress;
}
ralloc_free(copy_prop_ctx);
if (progress)
invalidate_analysis(DEPENDENCY_INSTRUCTION_DATA_FLOW |
DEPENDENCY_INSTRUCTION_DETAIL);
return progress;
}