/*
* Copyright © 2016 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.
*/
#include "nir.h"
#include "nir_builder.h"
#include "util/bitscan.h"
/**
* Variable-based copy propagation
*
* Normally, NIR trusts in SSA form for most of its copy-propagation needs.
* However, there are cases, especially when dealing with indirects, where SSA
* won't help you. This pass is for those times. Specifically, it handles
* the following things that the rest of NIR can't:
*
* 1) Copy-propagation on variables that have indirect access. This includes
* propagating from indirect stores into indirect loads.
*
* 2) Dead code elimination of store_var and copy_var intrinsics based on
* killed destination values.
*
* 3) Removal of redundant load_var intrinsics. We can't trust regular CSE
* to do this because it isn't aware of variable writes that may alias the
* value and make the former load invalid.
*
* Unfortunately, properly handling all of those cases makes this path rather
* complex. In order to avoid additional complexity, this pass is entirely
* block-local. If we tried to make it global, the data-flow analysis would
* rapidly get out of hand. Fortunately, for anything that is only ever
* accessed directly, we get SSA based copy-propagation which is extremely
* powerful so this isn't that great a loss.
*/
struct value {
bool is_ssa;
union {
nir_ssa_def *ssa[4];
nir_deref_var *deref;
};
};
struct copy_entry {
struct list_head link;
nir_instr *store_instr[4];
unsigned comps_may_be_read;
struct value src;
nir_deref_var *dst;
};
struct copy_prop_var_state {
nir_shader *shader;
void *mem_ctx;
struct list_head copies;
/* We're going to be allocating and deleting a lot of copy entries so we'll
* keep a free list to avoid thrashing malloc too badly.
*/
struct list_head copy_free_list;
bool progress;
};
static struct copy_entry *
copy_entry_create(struct copy_prop_var_state *state,
nir_deref_var *dst_deref)
{
struct copy_entry *entry;
if (!list_empty(&state->copy_free_list)) {
struct list_head *item = state->copy_free_list.next;
list_del(item);
entry = LIST_ENTRY(struct copy_entry, item, link);
memset(entry, 0, sizeof(*entry));
} else {
entry = rzalloc(state->mem_ctx, struct copy_entry);
}
entry->dst = dst_deref;
list_add(&entry->link, &state->copies);
return entry;
}
static void
copy_entry_remove(struct copy_prop_var_state *state, struct copy_entry *entry)
{
list_del(&entry->link);
list_add(&entry->link, &state->copy_free_list);
}
enum deref_compare_result {
derefs_equal_bit = (1 << 0),
derefs_may_alias_bit = (1 << 1),
derefs_a_contains_b_bit = (1 << 2),
derefs_b_contains_a_bit = (1 << 3),
};
/** Returns true if the storage referrenced to by deref completely contains
* the storage referenced by sub.
*
* NOTE: This is fairly general and could be moved to core NIR if someone else
* ever needs it.
*/
static enum deref_compare_result
compare_derefs(nir_deref_var *a, nir_deref_var *b)
{
if (a->var != b->var)
return 0;
/* Start off assuming they fully compare. We ignore equality for now. In
* the end, we'll determine that by containment.
*/
enum deref_compare_result result = derefs_may_alias_bit |
derefs_a_contains_b_bit |
derefs_b_contains_a_bit;
nir_deref *a_tail = &a->deref;
nir_deref *b_tail = &b->deref;
while (a_tail->child && b_tail->child) {
a_tail = a_tail->child;
b_tail = b_tail->child;
assert(a_tail->deref_type == b_tail->deref_type);
switch (a_tail->deref_type) {
case nir_deref_type_array: {
nir_deref_array *a_arr = nir_deref_as_array(a_tail);
nir_deref_array *b_arr = nir_deref_as_array(b_tail);
if (a_arr->deref_array_type == nir_deref_array_type_direct &&
b_arr->deref_array_type == nir_deref_array_type_direct) {
/* If they're both direct and have different offsets, they
* don't even alias much less anything else.
*/
if (a_arr->base_offset != b_arr->base_offset)
return 0;
} else if (a_arr->deref_array_type == nir_deref_array_type_wildcard) {
if (b_arr->deref_array_type != nir_deref_array_type_wildcard)
result &= ~derefs_b_contains_a_bit;
} else if (b_arr->deref_array_type == nir_deref_array_type_wildcard) {
if (a_arr->deref_array_type != nir_deref_array_type_wildcard)
result &= ~derefs_a_contains_b_bit;
} else if (a_arr->deref_array_type == nir_deref_array_type_indirect &&
b_arr->deref_array_type == nir_deref_array_type_indirect) {
assert(a_arr->indirect.is_ssa && b_arr->indirect.is_ssa);
if (a_arr->indirect.ssa == b_arr->indirect.ssa) {
/* If they're different constant offsets from the same indirect
* then they don't alias at all.
*/
if (a_arr->base_offset != b_arr->base_offset)
return 0;
/* Otherwise the indirect and base both match */
} else {
/* If they're have different indirect offsets then we can't
* prove anything about containment.
*/
result &= ~(derefs_a_contains_b_bit | derefs_b_contains_a_bit);
}
} else {
/* In this case, one is indirect and the other direct so we can't
* prove anything about containment.
*/
result &= ~(derefs_a_contains_b_bit | derefs_b_contains_a_bit);
}
break;
}
case nir_deref_type_struct: {
nir_deref_struct *a_struct = nir_deref_as_struct(a_tail);
nir_deref_struct *b_struct = nir_deref_as_struct(b_tail);
/* If they're different struct members, they don't even alias */
if (a_struct->index != b_struct->index)
return 0;
break;
}
default:
unreachable("Invalid deref type");
}
}
/* If a is longer than b, then it can't contain b */
if (a_tail->child)
result &= ~derefs_a_contains_b_bit;
if (b_tail->child)
result &= ~derefs_b_contains_a_bit;
/* If a contains b and b contains a they must be equal. */
if ((result & derefs_a_contains_b_bit) && (result & derefs_b_contains_a_bit))
result |= derefs_equal_bit;
return result;
}
static void
remove_dead_writes(struct copy_prop_var_state *state,
struct copy_entry *entry, unsigned write_mask)
{
/* We're overwriting another entry. Some of it's components may not
* have been read yet and, if that's the case, we may be able to delete
* some instructions but we have to be careful.
*/
unsigned dead_comps = write_mask & ~entry->comps_may_be_read;
for (unsigned mask = dead_comps; mask;) {
unsigned i = u_bit_scan(&mask);
nir_instr *instr = entry->store_instr[i];
/* We may have already deleted it on a previous iteration */
if (!instr)
continue;
/* See if this instr is used anywhere that it's not dead */
bool keep = false;
for (unsigned j = 0; j < 4; j++) {
if (entry->store_instr[j] == instr) {
if (dead_comps & (1 << j)) {
entry->store_instr[j] = NULL;
} else {
keep = true;
}
}
}
if (!keep) {
nir_instr_remove(instr);
state->progress = true;
}
}
}
static struct copy_entry *
lookup_entry_for_deref(struct copy_prop_var_state *state,
nir_deref_var *deref,
enum deref_compare_result allowed_comparisons)
{
list_for_each_entry(struct copy_entry, iter, &state->copies, link) {
if (compare_derefs(iter->dst, deref) & allowed_comparisons)
return iter;
}
return NULL;
}
static void
mark_aliased_entries_as_read(struct copy_prop_var_state *state,
nir_deref_var *deref, unsigned components)
{
list_for_each_entry(struct copy_entry, iter, &state->copies, link) {
if (compare_derefs(iter->dst, deref) & derefs_may_alias_bit)
iter->comps_may_be_read |= components;
}
}
static struct copy_entry *
get_entry_and_kill_aliases(struct copy_prop_var_state *state,
nir_deref_var *deref,
unsigned write_mask)
{
struct copy_entry *entry = NULL;
list_for_each_entry_safe(struct copy_entry, iter, &state->copies, link) {
if (!iter->src.is_ssa) {
/* If this write aliases the source of some entry, get rid of it */
if (compare_derefs(iter->src.deref, deref) & derefs_may_alias_bit) {
copy_entry_remove(state, iter);
continue;
}
}
enum deref_compare_result comp = compare_derefs(iter->dst, deref);
/* This is a store operation. If we completely overwrite some value, we
* want to delete any dead writes that may be present.
*/
if (comp & derefs_b_contains_a_bit)
remove_dead_writes(state, iter, write_mask);
if (comp & derefs_equal_bit) {
assert(entry == NULL);
entry = iter;
} else if (comp & derefs_may_alias_bit) {
copy_entry_remove(state, iter);
}
}
if (entry == NULL)
entry = copy_entry_create(state, deref);
return entry;
}
static void
apply_barrier_for_modes(struct copy_prop_var_state *state,
nir_variable_mode modes)
{
list_for_each_entry_safe(struct copy_entry, iter, &state->copies, link) {
if ((iter->dst->var->data.mode & modes) ||
(!iter->src.is_ssa && (iter->src.deref->var->data.mode & modes)))
copy_entry_remove(state, iter);
}
}
static void
store_to_entry(struct copy_prop_var_state *state, struct copy_entry *entry,
const struct value *value, unsigned write_mask,
nir_instr *store_instr)
{
entry->comps_may_be_read &= ~write_mask;
if (value->is_ssa) {
entry->src.is_ssa = true;
/* Only overwrite the written components */
for (unsigned i = 0; i < 4; i++) {
if (write_mask & (1 << i)) {
entry->store_instr[i] = store_instr;
entry->src.ssa[i] = value->ssa[i];
}
}
} else {
/* Non-ssa stores always write everything */
entry->src.is_ssa = false;
entry->src.deref = value->deref;
for (unsigned i = 0; i < 4; i++)
entry->store_instr[i] = store_instr;
}
}
/* Remove an instruction and return a cursor pointing to where it was */
static nir_cursor
instr_remove_cursor(nir_instr *instr)
{
nir_cursor cursor;
nir_instr *prev = nir_instr_prev(instr);
if (prev) {
cursor = nir_after_instr(prev);
} else {
cursor = nir_before_block(instr->block);
}
nir_instr_remove(instr);
return cursor;
}
/* Do a "load" from an SSA-based entry return it in "value" as a value with a
* single SSA def. Because an entry could reference up to 4 different SSA
* defs, a vecN operation may be inserted to combine them into a single SSA
* def before handing it back to the caller. If the load instruction is no
* longer needed, it is removed and nir_instr::block is set to NULL. (It is
* possible, in some cases, for the load to be used in the vecN operation in
* which case it isn't deleted.)
*/
static bool
load_from_ssa_entry_value(struct copy_prop_var_state *state,
struct copy_entry *entry,
nir_builder *b, nir_intrinsic_instr *intrin,
struct value *value)
{
*value = entry->src;
assert(value->is_ssa);
const struct glsl_type *type = nir_deref_tail(&entry->dst->deref)->type;
unsigned num_components = glsl_get_vector_elements(type);
uint8_t available = 0;
bool all_same = true;
for (unsigned i = 0; i < num_components; i++) {
if (value->ssa[i])
available |= (1 << i);
if (value->ssa[i] != value->ssa[0])
all_same = false;
}
if (all_same) {
/* Our work here is done */
b->cursor = instr_remove_cursor(&intrin->instr);
intrin->instr.block = NULL;
return true;
}
if (available != (1 << num_components) - 1 &&
intrin->intrinsic == nir_intrinsic_load_var &&
(available & nir_ssa_def_components_read(&intrin->dest.ssa)) == 0) {
/* If none of the components read are available as SSA values, then we
* should just bail. Otherwise, we would end up replacing the uses of
* the load_var a vecN() that just gathers up its components.
*/
return false;
}
b->cursor = nir_after_instr(&intrin->instr);
nir_ssa_def *load_def =
intrin->intrinsic == nir_intrinsic_load_var ? &intrin->dest.ssa : NULL;
bool keep_intrin = false;
nir_ssa_def *comps[4];
for (unsigned i = 0; i < num_components; i++) {
if (value->ssa[i]) {
comps[i] = nir_channel(b, value->ssa[i], i);
} else {
/* We don't have anything for this component in our
* list. Just re-use a channel from the load.
*/
if (load_def == NULL)
load_def = nir_load_deref_var(b, entry->dst);
if (load_def->parent_instr == &intrin->instr)
keep_intrin = true;
comps[i] = nir_channel(b, load_def, i);
}
}
nir_ssa_def *vec = nir_vec(b, comps, num_components);
for (unsigned i = 0; i < num_components; i++)
value->ssa[i] = vec;
if (!keep_intrin) {
/* Removing this instruction should not touch the cursor because we
* created the cursor after the intrinsic and have added at least one
* instruction (the vec) since then.
*/
assert(b->cursor.instr != &intrin->instr);
nir_instr_remove(&intrin->instr);
intrin->instr.block = NULL;
}
return true;
}
/**
* Specialize the wildcards in a deref chain
*
* This function returns a deref chain identical to \param deref except that
* some of its wildcards are replaced with indices from \param specific. The
* process is guided by \param guide which references the same type as \param
* specific but has the same wildcard array lengths as \param deref.
*/
static nir_deref_var *
specialize_wildcards(nir_deref_var *deref,
nir_deref_var *guide,
nir_deref_var *specific,
void *mem_ctx)
{
nir_deref_var *ret = nir_deref_var_create(mem_ctx, deref->var);
nir_deref *deref_tail = deref->deref.child;
nir_deref *guide_tail = &guide->deref;
nir_deref *spec_tail = &specific->deref;
nir_deref *ret_tail = &ret->deref;
while (deref_tail) {
switch (deref_tail->deref_type) {
case nir_deref_type_array: {
nir_deref_array *deref_arr = nir_deref_as_array(deref_tail);
nir_deref_array *ret_arr = nir_deref_array_create(ret_tail);
ret_arr->deref.type = deref_arr->deref.type;
ret_arr->deref_array_type = deref_arr->deref_array_type;
switch (deref_arr->deref_array_type) {
case nir_deref_array_type_direct:
ret_arr->base_offset = deref_arr->base_offset;
break;
case nir_deref_array_type_indirect:
ret_arr->base_offset = deref_arr->base_offset;
assert(deref_arr->indirect.is_ssa);
ret_arr->indirect = deref_arr->indirect;
break;
case nir_deref_array_type_wildcard:
/* This is where things get tricky. We have to search through
* the entry deref to find its corresponding wildcard and fill
* this slot in with the value from the src.
*/
while (guide_tail->child) {
guide_tail = guide_tail->child;
spec_tail = spec_tail->child;
if (guide_tail->deref_type == nir_deref_type_array &&
nir_deref_as_array(guide_tail)->deref_array_type ==
nir_deref_array_type_wildcard)
break;
}
nir_deref_array *spec_arr = nir_deref_as_array(spec_tail);
ret_arr->deref_array_type = spec_arr->deref_array_type;
ret_arr->base_offset = spec_arr->base_offset;
ret_arr->indirect = spec_arr->indirect;
}
ret_tail->child = &ret_arr->deref;
break;
}
case nir_deref_type_struct: {
nir_deref_struct *deref_struct = nir_deref_as_struct(deref_tail);
nir_deref_struct *ret_struct =
nir_deref_struct_create(ret_tail, deref_struct->index);
ret_struct->deref.type = deref_struct->deref.type;
ret_tail->child = &ret_struct->deref;
break;
}
case nir_deref_type_var:
unreachable("Invalid deref type");
}
deref_tail = deref_tail->child;
ret_tail = ret_tail->child;
}
return ret;
}
/* Do a "load" from an deref-based entry return it in "value" as a value. The
* deref returned in "value" will always be a fresh copy so the caller can
* steal it and assign it to the instruction directly without copying it
* again.
*/
static bool
load_from_deref_entry_value(struct copy_prop_var_state *state,
struct copy_entry *entry,
nir_builder *b, nir_intrinsic_instr *intrin,
nir_deref_var *src, struct value *value)
{
*value = entry->src;
/* Walk the deref to get the two tails and also figure out if we need to
* specialize any wildcards.
*/
bool need_to_specialize_wildcards = false;
nir_deref *entry_tail = &entry->dst->deref;
nir_deref *src_tail = &src->deref;
while (entry_tail->child && src_tail->child) {
assert(src_tail->child->deref_type == entry_tail->child->deref_type);
if (src_tail->child->deref_type == nir_deref_type_array) {
nir_deref_array *entry_arr = nir_deref_as_array(entry_tail->child);
nir_deref_array *src_arr = nir_deref_as_array(src_tail->child);
if (src_arr->deref_array_type != nir_deref_array_type_wildcard &&
entry_arr->deref_array_type == nir_deref_array_type_wildcard)
need_to_specialize_wildcards = true;
}
entry_tail = entry_tail->child;
src_tail = src_tail->child;
}
/* If the entry deref is longer than the source deref then it refers to a
* smaller type and we can't source from it.
*/
assert(entry_tail->child == NULL);
if (need_to_specialize_wildcards) {
/* The entry has some wildcards that are not in src. This means we need
* to construct a new deref based on the entry but using the wildcards
* from the source and guided by the entry dst. Oof.
*/
value->deref = specialize_wildcards(entry->src.deref, entry->dst, src,
state->mem_ctx);
} else {
/* We're going to need to make a copy in case we modify it below */
value->deref = nir_deref_var_clone(value->deref, state->mem_ctx);
}
if (src_tail->child) {
/* If our source deref is longer than the entry deref, that's ok because
* it just means the entry deref needs to be extended a bit.
*/
nir_deref *value_tail = nir_deref_tail(&value->deref->deref);
value_tail->child = nir_deref_clone(src_tail->child, value_tail);
}
b->cursor = instr_remove_cursor(&intrin->instr);
return true;
}
static bool
try_load_from_entry(struct copy_prop_var_state *state, struct copy_entry *entry,
nir_builder *b, nir_intrinsic_instr *intrin,
nir_deref_var *src, struct value *value)
{
if (entry == NULL)
return false;
if (entry->src.is_ssa) {
return load_from_ssa_entry_value(state, entry, b, intrin, value);
} else {
return load_from_deref_entry_value(state, entry, b, intrin, src, value);
}
}
static void
copy_prop_vars_block(struct copy_prop_var_state *state,
nir_builder *b, nir_block *block)
{
/* Start each block with a blank slate */
list_for_each_entry_safe(struct copy_entry, iter, &state->copies, link)
copy_entry_remove(state, iter);
nir_foreach_instr_safe(instr, block) {
if (instr->type != nir_instr_type_intrinsic)
continue;
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
switch (intrin->intrinsic) {
case nir_intrinsic_barrier:
case nir_intrinsic_memory_barrier:
/* If we hit a barrier, we need to trash everything that may possibly
* be accessible to another thread. Locals, globals, and things of
* the like are safe, however.
*/
apply_barrier_for_modes(state, ~(nir_var_local | nir_var_global |
nir_var_shader_in | nir_var_uniform));
break;
case nir_intrinsic_emit_vertex:
case nir_intrinsic_emit_vertex_with_counter:
apply_barrier_for_modes(state, nir_var_shader_out);
break;
case nir_intrinsic_load_var: {
nir_deref_var *src = intrin->variables[0];
uint8_t comps_read = nir_ssa_def_components_read(&intrin->dest.ssa);
mark_aliased_entries_as_read(state, src, comps_read);
struct copy_entry *src_entry =
lookup_entry_for_deref(state, src, derefs_a_contains_b_bit);
struct value value;
if (try_load_from_entry(state, src_entry, b, intrin, src, &value)) {
if (value.is_ssa) {
/* lookup_load has already ensured that we get a single SSA
* value that has all of the channels. We just have to do the
* rewrite operation.
*/
if (intrin->instr.block) {
/* The lookup left our instruction in-place. This means it
* must have used it to vec up a bunch of different sources.
* We need to be careful when rewriting uses so we don't
* rewrite the vecN itself.
*/
nir_ssa_def_rewrite_uses_after(&intrin->dest.ssa,
nir_src_for_ssa(value.ssa[0]),
value.ssa[0]->parent_instr);
} else {
nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
nir_src_for_ssa(value.ssa[0]));
}
} else {
/* We're turning it into a load of a different variable */
ralloc_steal(intrin, value.deref);
intrin->variables[0] = value.deref;
/* Put it back in again. */
nir_builder_instr_insert(b, instr);
value.is_ssa = true;
for (unsigned i = 0; i < intrin->num_components; i++)
value.ssa[i] = &intrin->dest.ssa;
}
state->progress = true;
} else {
value.is_ssa = true;
for (unsigned i = 0; i < intrin->num_components; i++)
value.ssa[i] = &intrin->dest.ssa;
}
/* Now that we have a value, we're going to store it back so that we
* have the right value next time we come looking for it. In order
* to do this, we need an exact match, not just something that
* contains what we're looking for.
*/
struct copy_entry *store_entry =
lookup_entry_for_deref(state, src, derefs_equal_bit);
if (!store_entry)
store_entry = copy_entry_create(state, src);
/* Set up a store to this entry with the value of the load. This way
* we can potentially remove subsequent loads. However, we use a
* NULL instruction so we don't try and delete the load on a
* subsequent store.
*/
store_to_entry(state, store_entry, &value,
((1 << intrin->num_components) - 1), NULL);
break;
}
case nir_intrinsic_store_var: {
struct value value = {
.is_ssa = true
};
for (unsigned i = 0; i < intrin->num_components; i++)
value.ssa[i] = intrin->src[0].ssa;
nir_deref_var *dst = intrin->variables[0];
unsigned wrmask = nir_intrinsic_write_mask(intrin);
struct copy_entry *entry =
get_entry_and_kill_aliases(state, dst, wrmask);
store_to_entry(state, entry, &value, wrmask, &intrin->instr);
break;
}
case nir_intrinsic_copy_var: {
nir_deref_var *dst = intrin->variables[0];
nir_deref_var *src = intrin->variables[1];
if (compare_derefs(src, dst) & derefs_equal_bit) {
/* This is a no-op self-copy. Get rid of it */
nir_instr_remove(instr);
continue;
}
mark_aliased_entries_as_read(state, src, 0xf);
struct copy_entry *src_entry =
lookup_entry_for_deref(state, src, derefs_a_contains_b_bit);
struct value value;
if (try_load_from_entry(state, src_entry, b, intrin, src, &value)) {
if (value.is_ssa) {
nir_store_deref_var(b, dst, value.ssa[0], 0xf);
intrin = nir_instr_as_intrinsic(nir_builder_last_instr(b));
} else {
/* If this would be a no-op self-copy, don't bother. */
if (compare_derefs(value.deref, dst) & derefs_equal_bit)
continue;
/* Just turn it into a copy of a different deref */
ralloc_steal(intrin, value.deref);
intrin->variables[1] = value.deref;
/* Put it back in again. */
nir_builder_instr_insert(b, instr);
}
state->progress = true;
} else {
value = (struct value) {
.is_ssa = false,
{ .deref = src },
};
}
struct copy_entry *dst_entry =
get_entry_and_kill_aliases(state, dst, 0xf);
store_to_entry(state, dst_entry, &value, 0xf, &intrin->instr);
break;
}
default:
break;
}
}
}
bool
nir_opt_copy_prop_vars(nir_shader *shader)
{
struct copy_prop_var_state state;
state.shader = shader;
state.mem_ctx = ralloc_context(NULL);
list_inithead(&state.copies);
list_inithead(&state.copy_free_list);
bool global_progress = false;
nir_foreach_function(function, shader) {
if (!function->impl)
continue;
nir_builder b;
nir_builder_init(&b, function->impl);
state.progress = false;
nir_foreach_block(block, function->impl)
copy_prop_vars_block(&state, &b, block);
if (state.progress) {
nir_metadata_preserve(function->impl, nir_metadata_block_index |
nir_metadata_dominance);
global_progress = true;
}
}
ralloc_free(state.mem_ctx);
return global_progress;
}