src/compiler/nir/nir_opt_copy_prop_vars.c

/*
 * 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 "nir_deref.h"

#include "util/bitscan.h"
#include "util/u_dynarray.h"

static const bool debug = false;

/**
 * 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) Removal of redundant load_deref 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.
 *
 * This pass uses an intermediate solution between being local / "per-block"
 * and a complete data-flow analysis.  It follows the control flow graph, and
 * propagate the available copy information forward, invalidating data at each
 * cf_node.
 *
 * Removal of dead writes to variables is handled by another pass.
 */

struct copies {
   struct list_head node;

   /* Hash table of copies referenced by variables */
   struct hash_table *ht;

   /* Array of derefs that can't be chased back to a variable */
   struct util_dynarray arr;
};

struct copies_dynarray {
   struct list_head node;
   struct util_dynarray arr;

   /* The copies structure this dynarray was cloned or created for */
   struct copies *owner;
};

struct vars_written {
   nir_variable_mode modes;

   /* Key is deref and value is the uintptr_t with the write mask. */
   struct hash_table *derefs;
};

struct value {
   bool is_ssa;
   union {
      struct {
         nir_def *def[NIR_MAX_VEC_COMPONENTS];
         uint8_t component[NIR_MAX_VEC_COMPONENTS];
      } ssa;
      nir_deref_and_path deref;
   };
};

static void
value_set_ssa_components(struct value *value, nir_def *def,
                         unsigned num_components)
{
   value->is_ssa = true;
   for (unsigned i = 0; i < num_components; i++) {
      value->ssa.def[i] = def;
      value->ssa.component[i] = i;
   }
}

struct copy_entry {
   struct value src;

   nir_deref_and_path dst;
};

struct copy_prop_var_state {
   nir_function_impl *impl;

   void *mem_ctx;
   linear_ctx *lin_ctx;

   /* Maps nodes to vars_written.  Used to invalidate copy entries when
    * visiting each node.
    */
   struct hash_table *vars_written_map;

   /* List of copy structures ready for reuse */
   struct list_head unused_copy_structs_list;

   bool progress;
};

static bool
value_equals_store_src(struct value *value, nir_intrinsic_instr *intrin)
{
   assert(intrin->intrinsic == nir_intrinsic_store_deref);
   nir_component_mask_t write_mask = nir_intrinsic_write_mask(intrin);

   for (unsigned i = 0; i < intrin->num_components; i++) {
      if ((write_mask & (1 << i)) &&
          (value->ssa.def[i] != intrin->src[1].ssa ||
           value->ssa.component[i] != i))
         return false;
   }

   return true;
}

static struct vars_written *
create_vars_written(struct copy_prop_var_state *state)
{
   struct vars_written *written =
      linear_zalloc_child(state->lin_ctx, sizeof(struct vars_written));
   written->derefs = _mesa_pointer_hash_table_create(state->mem_ctx);
   return written;
}

static void
gather_vars_written(struct copy_prop_var_state *state,
                    struct vars_written *written,
                    nir_cf_node *cf_node)
{
   struct vars_written *new_written = NULL;

   switch (cf_node->type) {
   case nir_cf_node_function: {
      nir_function_impl *impl = nir_cf_node_as_function(cf_node);
      foreach_list_typed_safe(nir_cf_node, cf_node, node, &impl->body)
         gather_vars_written(state, NULL, cf_node);
      break;
   }

   case nir_cf_node_block: {
      if (!written)
         break;

      nir_block *block = nir_cf_node_as_block(cf_node);
      nir_foreach_instr(instr, block) {
         if (instr->type == nir_instr_type_call) {
            written->modes |= nir_var_shader_out |
                              nir_var_shader_temp |
                              nir_var_function_temp |
                              nir_var_mem_ssbo |
                              nir_var_mem_shared |
                              nir_var_mem_global;
            continue;
         }

         if (instr->type != nir_instr_type_intrinsic)
            continue;

         nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
         switch (intrin->intrinsic) {
         case nir_intrinsic_barrier:
            if (nir_intrinsic_memory_semantics(intrin) & NIR_MEMORY_ACQUIRE)
               written->modes |= nir_intrinsic_memory_modes(intrin);
            break;

         case nir_intrinsic_emit_vertex:
         case nir_intrinsic_emit_vertex_with_counter:
            written->modes = nir_var_shader_out;
            break;

         case nir_intrinsic_trace_ray:
         case nir_intrinsic_execute_callable:
         case nir_intrinsic_rt_trace_ray:
         case nir_intrinsic_rt_execute_callable: {
            nir_deref_instr *payload =
               nir_src_as_deref(*nir_get_shader_call_payload_src(intrin));

            nir_component_mask_t mask = (1 << glsl_get_vector_elements(payload->type)) - 1;

            struct hash_entry *ht_entry =
               _mesa_hash_table_search(written->derefs, payload);
            if (ht_entry) {
               ht_entry->data = (void *)(mask | (uintptr_t)ht_entry->data);
            } else {
               _mesa_hash_table_insert(written->derefs, payload,
                                       (void *)(uintptr_t)mask);
            }
            break;
         }

         case nir_intrinsic_report_ray_intersection:
            written->modes |= nir_var_mem_ssbo |
                              nir_var_mem_global |
                              nir_var_shader_call_data |
                              nir_var_ray_hit_attrib;
            break;

         case nir_intrinsic_ignore_ray_intersection:
         case nir_intrinsic_terminate_ray:
            written->modes |= nir_var_mem_ssbo |
                              nir_var_mem_global |
                              nir_var_shader_call_data;
            break;

         case nir_intrinsic_deref_atomic:
         case nir_intrinsic_deref_atomic_swap:
         case nir_intrinsic_store_deref:
         case nir_intrinsic_copy_deref:
         case nir_intrinsic_memcpy_deref: {
            /* Destination in all of store_deref, copy_deref and the atomics is src[0]. */
            nir_deref_instr *dst = nir_src_as_deref(intrin->src[0]);

            uintptr_t mask = intrin->intrinsic == nir_intrinsic_store_deref ? nir_intrinsic_write_mask(intrin) : (1 << glsl_get_vector_elements(dst->type)) - 1;

            struct hash_entry *ht_entry = _mesa_hash_table_search(written->derefs, dst);
            if (ht_entry)
               ht_entry->data = (void *)(mask | (uintptr_t)ht_entry->data);
            else
               _mesa_hash_table_insert(written->derefs, dst, (void *)mask);

            break;
         }

         default:
            break;
         }
      }

      break;
   }

   case nir_cf_node_if: {
      nir_if *if_stmt = nir_cf_node_as_if(cf_node);

      new_written = create_vars_written(state);

      foreach_list_typed_safe(nir_cf_node, cf_node, node, &if_stmt->then_list)
         gather_vars_written(state, new_written, cf_node);

      foreach_list_typed_safe(nir_cf_node, cf_node, node, &if_stmt->else_list)
         gather_vars_written(state, new_written, cf_node);

      break;
   }

   case nir_cf_node_loop: {
      nir_loop *loop = nir_cf_node_as_loop(cf_node);
      assert(!nir_loop_has_continue_construct(loop));

      new_written = create_vars_written(state);

      foreach_list_typed_safe(nir_cf_node, cf_node, node, &loop->body)
         gather_vars_written(state, new_written, cf_node);

      break;
   }

   default:
      unreachable("Invalid CF node type");
   }

   if (new_written) {
      /* Merge new information to the parent control flow node. */
      if (written) {
         written->modes |= new_written->modes;
         hash_table_foreach(new_written->derefs, new_entry) {
            struct hash_entry *old_entry =
               _mesa_hash_table_search_pre_hashed(written->derefs, new_entry->hash,
                                                  new_entry->key);
            if (old_entry) {
               nir_component_mask_t merged = (uintptr_t)new_entry->data |
                                             (uintptr_t)old_entry->data;
               old_entry->data = (void *)((uintptr_t)merged);
            } else {
               _mesa_hash_table_insert_pre_hashed(written->derefs, new_entry->hash,
                                                  new_entry->key, new_entry->data);
            }
         }
      }
      _mesa_hash_table_insert(state->vars_written_map, cf_node, new_written);
   }
}

/* Creates a fresh dynarray */
static struct copies_dynarray *
get_copies_dynarray(struct copy_prop_var_state *state)
{
   struct copies_dynarray *cp_arr =
      ralloc(state->mem_ctx, struct copies_dynarray);
   util_dynarray_init(&cp_arr->arr, state->mem_ctx);
   return cp_arr;
}

/* Checks if the pointer leads to a cloned copy of the array for this hash
 * table or if the pointer was inherited from when the hash table was cloned.
 */
static bool
copies_owns_ht_entry(struct copies *copies,
                     struct hash_entry *ht_entry)
{
   assert(copies && ht_entry && ht_entry->data);
   struct copies_dynarray *copies_array = ht_entry->data;
   return copies_array->owner == copies;
}

static void
clone_copies_dynarray_from_src(struct copies_dynarray *dst,
                               struct copies_dynarray *src)
{
   util_dynarray_append_dynarray(&dst->arr, &src->arr);
}

/* Gets copies array from the hash table entry or clones the source array if
 * the hash entry contains NULL. The values are not cloned when the hash table
 * is created because its expensive to clone everything and most value will
 * never actually be accessed.
 */
static struct copies_dynarray *
get_copies_array_from_ht_entry(struct copy_prop_var_state *state,
                               struct copies *copies,
                               struct hash_entry *ht_entry)
{
   struct copies_dynarray *copies_array;
   if (copies_owns_ht_entry(copies, ht_entry)) {
      /* The array already exists so just return it */
      copies_array = (struct copies_dynarray *)ht_entry->data;
   } else {
      /* Clone the array and set the data value for future access */
      copies_array = get_copies_dynarray(state);
      copies_array->owner = copies;
      clone_copies_dynarray_from_src(copies_array, ht_entry->data);
      ht_entry->data = copies_array;
   }

   return copies_array;
}

static struct copies_dynarray *
copies_array_for_var(struct copy_prop_var_state *state,
                     struct copies *copies, nir_variable *var)
{
   struct hash_entry *entry = _mesa_hash_table_search(copies->ht, var);
   if (entry != NULL)
      return get_copies_array_from_ht_entry(state, copies, entry);

   struct copies_dynarray *copies_array = get_copies_dynarray(state);
   copies_array->owner = copies;
   _mesa_hash_table_insert(copies->ht, var, copies_array);

   return copies_array;
}

static struct util_dynarray *
copies_array_for_deref(struct copy_prop_var_state *state,
                       struct copies *copies, nir_deref_and_path *deref)
{
   nir_get_deref_path(state->mem_ctx, deref);

   struct util_dynarray *copies_array;
   if (deref->_path->path[0]->deref_type != nir_deref_type_var) {
      copies_array = &copies->arr;
   } else {
      struct copies_dynarray *cpda =
         copies_array_for_var(state, copies, deref->_path->path[0]->var);
      copies_array = &cpda->arr;
   }

   return copies_array;
}

static struct copy_entry *
copy_entry_create(struct copy_prop_var_state *state,
                  struct copies *copies, nir_deref_and_path *deref)
{
   struct util_dynarray *copies_array =
      copies_array_for_deref(state, copies, deref);

   struct copy_entry new_entry = {
      .dst = *deref,
   };
   util_dynarray_append(copies_array, struct copy_entry, new_entry);
   return util_dynarray_top_ptr(copies_array, struct copy_entry);
}

/* Remove copy entry by swapping it with the last element and reducing the
 * size.  If used inside an iteration on copies, it must be a reverse
 * (backwards) iteration.  It is safe to use in those cases because the swap
 * will not affect the rest of the iteration.
 */
static void
copy_entry_remove(struct util_dynarray *copies,
                  struct copy_entry *entry,
                  struct copy_entry **relocated_entry)
{
   const struct copy_entry *src =
      util_dynarray_pop_ptr(copies, struct copy_entry);

   /* Because we're removing elements from an array, pointers to those
    * elements are not stable as we modify the array.
    * If relocated_entry != NULL, it's points to an entry we saved off earlier
    * and want to keep pointing to the right spot.
    */
   if (relocated_entry && *relocated_entry == src)
      *relocated_entry = entry;

   if (src != entry)
      *entry = *src;
}

static bool
is_array_deref_of_vector(const nir_deref_and_path *deref)
{
   if (deref->instr->deref_type != nir_deref_type_array)
      return false;
   nir_deref_instr *parent = nir_deref_instr_parent(deref->instr);
   return glsl_type_is_vector(parent->type);
}

static struct copy_entry *
lookup_entry_for_deref(struct copy_prop_var_state *state,
                       struct copies *copies,
                       nir_deref_and_path *deref,
                       nir_deref_compare_result allowed_comparisons,
                       bool *equal)
{
   struct util_dynarray *copies_array =
      copies_array_for_deref(state, copies, deref);

   struct copy_entry *entry = NULL;
   util_dynarray_foreach(copies_array, struct copy_entry, iter) {
      nir_deref_compare_result result =
         nir_compare_derefs_and_paths(state->mem_ctx, &iter->dst, deref);
      if (result & allowed_comparisons) {
         entry = iter;
         if (result & nir_derefs_equal_bit) {
            if (equal != NULL)
               *equal = true;
            break;
         }
         /* Keep looking in case we have an equal match later in the array. */
      }
   }

   return entry;
}

static void
lookup_entry_and_kill_aliases_copy_array(struct copy_prop_var_state *state,
                                         struct util_dynarray *copies_array,
                                         nir_deref_and_path *deref,
                                         unsigned write_mask,
                                         bool remove_entry,
                                         struct copy_entry **entry,
                                         bool *entry_removed)
{
   util_dynarray_foreach_reverse(copies_array, struct copy_entry, iter) {
      nir_deref_compare_result comp =
         nir_compare_derefs_and_paths(state->mem_ctx, &iter->dst, deref);

      if (comp & nir_derefs_equal_bit) {
         /* Make sure it is unique. */
         assert(!*entry && !*entry_removed);
         if (remove_entry) {
            copy_entry_remove(copies_array, iter, NULL);
            *entry_removed = true;
         } else {
            *entry = iter;
         }
      } else if (comp & nir_derefs_may_alias_bit) {
         copy_entry_remove(copies_array, iter, entry);
      }
   }
}

static struct copy_entry *
lookup_entry_and_kill_aliases(struct copy_prop_var_state *state,
                              struct copies *copies,
                              nir_deref_and_path *deref,
                              unsigned write_mask,
                              bool remove_entry)
{
   /* TODO: Take into account the write_mask. */

   bool UNUSED entry_removed = false;
   struct copy_entry *entry = NULL;

   nir_get_deref_path(state->mem_ctx, deref);

   /* For any other variable types if the variables are different,
    * they don't alias. So we only need to compare different vars and loop
    * over the hash table for ssbos and shared vars.
    */
   if (deref->_path->path[0]->deref_type != nir_deref_type_var ||
       deref->_path->path[0]->var->data.mode == nir_var_mem_ssbo ||
       deref->_path->path[0]->var->data.mode == nir_var_mem_shared) {

      hash_table_foreach(copies->ht, ht_entry) {
         nir_variable *var = (nir_variable *)ht_entry->key;
         if (deref->_path->path[0]->deref_type == nir_deref_type_var &&
             var->data.mode != deref->_path->path[0]->var->data.mode)
            continue;

         struct copies_dynarray *copies_array =
            get_copies_array_from_ht_entry(state, copies, ht_entry);

         lookup_entry_and_kill_aliases_copy_array(state, &copies_array->arr,
                                                  deref, write_mask,
                                                  remove_entry, &entry,
                                                  &entry_removed);

         if (copies_array->arr.size == 0) {
            _mesa_hash_table_remove(copies->ht, ht_entry);
         }
      }

      lookup_entry_and_kill_aliases_copy_array(state, &copies->arr, deref,
                                               write_mask, remove_entry,
                                               &entry, &entry_removed);
   } else {
      struct copies_dynarray *cpda =
         copies_array_for_var(state, copies, deref->_path->path[0]->var);
      struct util_dynarray *copies_array = &cpda->arr;

      lookup_entry_and_kill_aliases_copy_array(state, copies_array, deref,
                                               write_mask, remove_entry,
                                               &entry, &entry_removed);

      if (copies_array->size == 0) {
         _mesa_hash_table_remove_key(copies->ht, deref->_path->path[0]->var);
      }
   }

   return entry;
}

static void
kill_aliases(struct copy_prop_var_state *state,
             struct copies *copies,
             nir_deref_and_path *deref,
             unsigned write_mask)
{
   /* TODO: Take into account the write_mask. */

   lookup_entry_and_kill_aliases(state, copies, deref, write_mask, true);
}

static struct copy_entry *
get_entry_and_kill_aliases(struct copy_prop_var_state *state,
                           struct copies *copies,
                           nir_deref_and_path *deref,
                           unsigned write_mask)
{
   /* TODO: Take into account the write_mask. */

   struct copy_entry *entry =
      lookup_entry_and_kill_aliases(state, copies, deref, write_mask, false);
   if (entry == NULL)
      entry = copy_entry_create(state, copies, deref);

   return entry;
}

static void
apply_barrier_for_modes_to_dynarr(struct util_dynarray *copies_array,
                                  nir_variable_mode modes)
{
   util_dynarray_foreach_reverse(copies_array, struct copy_entry, iter) {
      if (nir_deref_mode_may_be(iter->dst.instr, modes) ||
          (!iter->src.is_ssa && nir_deref_mode_may_be(iter->src.deref.instr, modes)))
         copy_entry_remove(copies_array, iter, NULL);
   }
}

static void
apply_barrier_for_modes(struct copy_prop_var_state *state,
                        struct copies *copies, nir_variable_mode modes)
{
   hash_table_foreach(copies->ht, ht_entry) {
      struct copies_dynarray *copies_array =
         get_copies_array_from_ht_entry(state, copies, ht_entry);

      apply_barrier_for_modes_to_dynarr(&copies_array->arr, modes);
   }

   apply_barrier_for_modes_to_dynarr(&copies->arr, modes);
}

static void
value_set_from_value(struct value *value, const struct value *from,
                     unsigned base_index, unsigned write_mask)
{
   /* We can't have non-zero indexes with non-trivial write masks */
   assert(base_index == 0 || write_mask == 1);

   if (from->is_ssa) {
      /* Clear value if it was being used as non-SSA. */
      value->is_ssa = true;
      /* Only overwrite the written components */
      for (unsigned i = 0; i < NIR_MAX_VEC_COMPONENTS; i++) {
         if (write_mask & (1 << i)) {
            value->ssa.def[base_index + i] = from->ssa.def[i];
            value->ssa.component[base_index + i] = from->ssa.component[i];
         }
      }
   } else {
      /* Non-ssa stores always write everything */
      value->is_ssa = false;
      value->deref = from->deref;
   }
}

/* Try to load a single element of a vector from the copy_entry.  If the data
 * isn't available, just let the original intrinsic do the work.
 */
static bool
load_element_from_ssa_entry_value(struct copy_prop_var_state *state,
                                  struct copy_entry *entry,
                                  nir_builder *b, nir_intrinsic_instr *intrin,
                                  struct value *value, unsigned index)
{
   assert(index < glsl_get_vector_elements(entry->dst.instr->type));

   /* We don't have the element available, so let the instruction do the work. */
   if (!entry->src.ssa.def[index])
      return false;

   b->cursor = nir_instr_remove(&intrin->instr);
   intrin->instr.block = NULL;

   assert(entry->src.ssa.component[index] <
          entry->src.ssa.def[index]->num_components);
   nir_def *def = nir_channel(b, entry->src.ssa.def[index],
                              entry->src.ssa.component[index]);

   *value = (struct value){
      .is_ssa = true,
      {
         .ssa = {
            .def = { def },
            .component = { 0 },
         },
      }
   };

   return true;
}

/* 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 multiple 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,
                          nir_deref_and_path *src, struct value *value)
{
   if (is_array_deref_of_vector(src)) {
      if (nir_src_is_const(src->instr->arr.index)) {
         unsigned index = nir_src_as_uint(src->instr->arr.index);
         return load_element_from_ssa_entry_value(state, entry, b, intrin,
                                                  value, index);
      }

      /* An SSA copy_entry for the vector won't help indirect load. */
      if (glsl_type_is_vector(entry->dst.instr->type)) {
         assert(entry->dst.instr->type == nir_deref_instr_parent(src->instr)->type);
         /* TODO: If all SSA entries are there, try an if-ladder. */
         return false;
      }
   }

   *value = entry->src;

   const struct glsl_type *type = entry->dst.instr->type;
   unsigned num_components = glsl_get_vector_elements(type);

   nir_component_mask_t available = 0;
   bool all_same = true;
   for (unsigned i = 0; i < num_components; i++) {
      if (value->ssa.def[i])
         available |= (1 << i);

      if (value->ssa.def[i] != value->ssa.def[0])
         all_same = false;

      if (value->ssa.component[i] != i)
         all_same = false;
   }

   if (all_same) {
      /* Our work here is done */
      b->cursor = nir_instr_remove(&intrin->instr);
      intrin->instr.block = NULL;
      return true;
   }

   if (available != (1 << num_components) - 1 &&
       intrin->intrinsic == nir_intrinsic_load_deref &&
       (available & nir_def_components_read(&intrin->def)) == 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_deref a vecN() that just gathers up its components.
       */
      return false;
   }

   b->cursor = nir_after_instr(&intrin->instr);

   nir_def *load_def =
      intrin->intrinsic == nir_intrinsic_load_deref ? &intrin->def : NULL;

   bool keep_intrin = false;
   nir_scalar comps[NIR_MAX_VEC_COMPONENTS];
   for (unsigned i = 0; i < num_components; i++) {
      if (value->ssa.def[i]) {
         comps[i] = nir_get_scalar(value->ssa.def[i], value->ssa.component[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(b, entry->dst.instr);

         if (load_def->parent_instr == &intrin->instr)
            keep_intrin = true;

         comps[i] = nir_get_scalar(load_def, i);
      }
   }

   nir_def *vec = nir_vec_scalars(b, comps, num_components);
   value_set_ssa_components(value, vec, num_components);

   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_instr *
specialize_wildcards(nir_builder *b,
                     nir_deref_path *deref,
                     nir_deref_path *guide,
                     nir_deref_path *specific)
{
   nir_deref_instr **deref_p = &deref->path[1];
   nir_deref_instr *ret_tail = deref->path[0];
   for (; *deref_p; deref_p++) {
      if ((*deref_p)->deref_type == nir_deref_type_array_wildcard)
         break;
      ret_tail = *deref_p;
   }

   nir_deref_instr **guide_p = &guide->path[1];
   nir_deref_instr **spec_p = &specific->path[1];
   for (; *deref_p; deref_p++) {
      if ((*deref_p)->deref_type == nir_deref_type_array_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_p &&
                (*guide_p)->deref_type != nir_deref_type_array_wildcard) {
            guide_p++;
            spec_p++;
         }
         assert(*guide_p && *spec_p);

         ret_tail = nir_build_deref_follower(b, ret_tail, *spec_p);

         guide_p++;
         spec_p++;
      } else {
         ret_tail = nir_build_deref_follower(b, ret_tail, *deref_p);
      }
   }

   return ret_tail;
}

/* 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_and_path *src, struct value *value)
{
   *value = entry->src;

   b->cursor = nir_instr_remove(&intrin->instr);

   nir_deref_path *entry_dst_path = nir_get_deref_path(state->mem_ctx, &entry->dst);
   nir_deref_path *src_path = nir_get_deref_path(state->mem_ctx, src);

   bool need_to_specialize_wildcards = false;
   nir_deref_instr **entry_p = &entry_dst_path->path[1];
   nir_deref_instr **src_p = &src_path->path[1];
   while (*entry_p && *src_p) {
      nir_deref_instr *entry_tail = *entry_p++;
      nir_deref_instr *src_tail = *src_p++;

      if (src_tail->deref_type == nir_deref_type_array &&
          entry_tail->deref_type == nir_deref_type_array_wildcard)
         need_to_specialize_wildcards = true;
   }

   /* 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_p == NULL);

   value->deref._path = 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.
       */
      nir_deref_path *entry_src_path =
         nir_get_deref_path(state->mem_ctx, &entry->src.deref);
      value->deref.instr = specialize_wildcards(b, entry_src_path,
                                                entry_dst_path, src_path);
   }

   /* 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.
    */
   while (*src_p) {
      nir_deref_instr *src_tail = *src_p++;
      value->deref.instr = nir_build_deref_follower(b, value->deref.instr, src_tail);
   }

   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_and_path *src, struct value *value)
{
   if (entry == NULL)
      return false;

   if (entry->src.is_ssa) {
      return load_from_ssa_entry_value(state, entry, b, intrin, src, value);
   } else {
      return load_from_deref_entry_value(state, entry, b, intrin, src, value);
   }
}

static void
invalidate_copies_for_cf_node(struct copy_prop_var_state *state,
                              struct copies *copies,
                              nir_cf_node *cf_node)
{
   struct hash_entry *ht_entry = _mesa_hash_table_search(state->vars_written_map, cf_node);
   assert(ht_entry);

   struct vars_written *written = ht_entry->data;
   if (written->modes) {
      hash_table_foreach(copies->ht, ht_entry) {
         struct copies_dynarray *copies_array =
            get_copies_array_from_ht_entry(state, copies, ht_entry);

         util_dynarray_foreach_reverse(&copies_array->arr, struct copy_entry, entry) {
            if (nir_deref_mode_may_be(entry->dst.instr, written->modes))
               copy_entry_remove(&copies_array->arr, entry, NULL);
         }

         if (copies_array->arr.size == 0) {
            _mesa_hash_table_remove(copies->ht, ht_entry);
         }
      }

      util_dynarray_foreach_reverse(&copies->arr, struct copy_entry, entry) {
         if (nir_deref_mode_may_be(entry->dst.instr, written->modes))
            copy_entry_remove(&copies->arr, entry, NULL);
      }
   }

   hash_table_foreach(written->derefs, entry) {
      nir_deref_instr *deref_written = (nir_deref_instr *)entry->key;
      nir_deref_and_path deref = { deref_written, NULL };
      kill_aliases(state, copies, &deref, (uintptr_t)entry->data);
   }
}

static void
print_value(struct value *value, unsigned num_components)
{
   bool same_ssa = true;
   for (unsigned i = 0; i < num_components; i++) {
      if (value->ssa.component[i] != i ||
          (i > 0 && value->ssa.def[i - 1] != value->ssa.def[i])) {
         same_ssa = false;
         break;
      }
   }
   if (same_ssa) {
      printf(" ssa_%d", value->ssa.def[0]->index);
   } else {
      for (int i = 0; i < num_components; i++) {
         if (value->ssa.def[i])
            printf(" ssa_%d[%u]", value->ssa.def[i]->index, value->ssa.component[i]);
         else
            printf(" _");
      }
   }
}

static void
print_copy_entry(struct copy_entry *entry)
{
   printf("    %s ", glsl_get_type_name(entry->dst.instr->type));
   nir_print_deref(entry->dst.instr, stdout);
   printf(":\t");

   unsigned num_components = glsl_get_vector_elements(entry->dst.instr->type);
   print_value(&entry->src, num_components);
   printf("\n");
}

static void
dump_instr(nir_instr *instr)
{
   printf("  ");
   nir_print_instr(instr, stdout);
   printf("\n");
}

static void
dump_copy_entries(struct copies *copies)
{
   hash_table_foreach(copies->ht, ht_entry) {
      struct util_dynarray *copies_array =
         &((struct copies_dynarray *)ht_entry->data)->arr;

      util_dynarray_foreach(copies_array, struct copy_entry, iter)
         print_copy_entry(iter);
   }

   util_dynarray_foreach(&copies->arr, struct copy_entry, iter)
      print_copy_entry(iter);

   printf("\n");
}

static void
copy_prop_vars_block(struct copy_prop_var_state *state,
                     nir_builder *b, nir_block *block,
                     struct copies *copies)
{
   if (debug) {
      printf("# block%d\n", block->index);
      dump_copy_entries(copies);
   }

   nir_foreach_instr_safe(instr, block) {
      if (debug && instr->type == nir_instr_type_deref)
         dump_instr(instr);

      if (instr->type == nir_instr_type_call) {
         if (debug)
            dump_instr(instr);
         apply_barrier_for_modes(state, copies, nir_var_shader_out | nir_var_shader_temp | nir_var_function_temp | nir_var_mem_ssbo | nir_var_mem_shared | nir_var_mem_global);
         if (debug)
            dump_copy_entries(copies);
         continue;
      }

      if (instr->type != nir_instr_type_intrinsic)
         continue;

      nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
      switch (intrin->intrinsic) {
      case nir_intrinsic_barrier:
         if (debug)
            dump_instr(instr);

         if (nir_intrinsic_memory_semantics(intrin) & NIR_MEMORY_ACQUIRE)
            apply_barrier_for_modes(state, copies, nir_intrinsic_memory_modes(intrin));
         break;

      case nir_intrinsic_emit_vertex:
      case nir_intrinsic_emit_vertex_with_counter:
         if (debug)
            dump_instr(instr);

         apply_barrier_for_modes(state, copies, nir_var_shader_out);
         break;

      case nir_intrinsic_report_ray_intersection:
         apply_barrier_for_modes(state, copies, nir_var_mem_ssbo | nir_var_mem_global | nir_var_shader_call_data | nir_var_ray_hit_attrib);
         break;

      case nir_intrinsic_ignore_ray_intersection:
      case nir_intrinsic_terminate_ray:
         apply_barrier_for_modes(state, copies, nir_var_mem_ssbo | nir_var_mem_global | nir_var_shader_call_data);
         break;

      case nir_intrinsic_load_deref: {
         if (debug)
            dump_instr(instr);

         if (nir_intrinsic_access(intrin) & ACCESS_VOLATILE)
            break;

         nir_deref_and_path src = { nir_src_as_deref(intrin->src[0]), NULL };

         /* If this is a load from a read-only mode, then all this pass would
          * do is combine redundant loads and CSE should be more efficient for
          * that.
          */
         nir_variable_mode ignore = nir_var_read_only_modes & ~nir_var_vec_indexable_modes;
         if (nir_deref_mode_must_be(src.instr, ignore))
            break;

         /* Ignore trivial casts. If trivial casts are applied to array derefs of vectors,
          * not doing this causes is_array_deref_of_vector to (wrongly) return false. */
         while (src.instr->deref_type == nir_deref_type_cast &&
                nir_deref_instr_parent(src.instr) && nir_deref_cast_is_trivial(src.instr))
            src.instr = nir_deref_instr_parent(src.instr);

         /* Direct array_derefs of vectors operate on the vectors (the parent
          * deref).  Indirects will be handled like other derefs.
          */
         int vec_index = 0;
         nir_deref_and_path vec_src = src;
         if (is_array_deref_of_vector(&src) && nir_src_is_const(src.instr->arr.index)) {
            vec_src.instr = nir_deref_instr_parent(src.instr);
            unsigned vec_comps = glsl_get_vector_elements(vec_src.instr->type);
            vec_index = nir_src_as_uint(src.instr->arr.index);

            /* Loading from an invalid index yields an undef */
            if (vec_index >= vec_comps) {
               b->cursor = nir_instr_remove(instr);
               nir_def *u = nir_undef(b, 1, intrin->def.bit_size);
               nir_def_rewrite_uses(&intrin->def, u);
               state->progress = true;
               break;
            }
         }

         bool src_entry_equal = false;
         struct copy_entry *src_entry =
            lookup_entry_for_deref(state, copies, &src,
                                   nir_derefs_a_contains_b_bit, &src_entry_equal);
         struct value value = { 0 };
         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.  Note for array derefs of vectors, the
                * channel 0 is used.
                */
               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_def_rewrite_uses_after(&intrin->def,
                                             value.ssa.def[0],
                                             value.ssa.def[0]->parent_instr);
               } else {
                  nir_def_rewrite_uses(&intrin->def,
                                       value.ssa.def[0]);
               }
            } else {
               /* We're turning it into a load of a different variable */
               intrin->src[0] = nir_src_for_ssa(&value.deref.instr->def);

               /* Put it back in again. */
               nir_builder_instr_insert(b, instr);
               value_set_ssa_components(&value, &intrin->def,
                                        intrin->num_components);
            }
            state->progress = true;
         } else {
            value_set_ssa_components(&value, &intrin->def,
                                     intrin->num_components);
         }

         /* 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.
          *
          * We avoid doing another lookup if src.instr == vec_src.instr.
          */
         struct copy_entry *entry = src_entry;
         if (src.instr != vec_src.instr)
            entry = lookup_entry_for_deref(state, copies, &vec_src,
                                           nir_derefs_equal_bit, NULL);
         else if (!src_entry_equal)
            entry = NULL;

         if (!entry)
            entry = copy_entry_create(state, copies, &vec_src);

         /* Update the entry with the value of the load.  This way
          * we can potentially remove subsequent loads.
          */
         value_set_from_value(&entry->src, &value, vec_index,
                              (1 << intrin->num_components) - 1);
         break;
      }

      case nir_intrinsic_store_deref: {
         if (debug)
            dump_instr(instr);

         nir_deref_and_path dst = { nir_src_as_deref(intrin->src[0]), NULL };
         assert(glsl_type_is_vector_or_scalar(dst.instr->type));

         /* Ignore trivial casts. If trivial casts are applied to array derefs of vectors,
          * not doing this causes is_array_deref_of_vector to (wrongly) return false. */
         while (dst.instr->deref_type == nir_deref_type_cast &&
                nir_deref_instr_parent(dst.instr) && nir_deref_cast_is_trivial(dst.instr))
            dst.instr = nir_deref_instr_parent(dst.instr);

         /* Direct array_derefs of vectors operate on the vectors (the parent
          * deref).  Indirects will be handled like other derefs.
          */
         int vec_index = 0;
         nir_deref_and_path vec_dst = dst;
         if (is_array_deref_of_vector(&dst) && nir_src_is_const(dst.instr->arr.index)) {
            vec_dst.instr = nir_deref_instr_parent(dst.instr);
            unsigned vec_comps = glsl_get_vector_elements(vec_dst.instr->type);

            vec_index = nir_src_as_uint(dst.instr->arr.index);

            /* Storing to an invalid index is a no-op. */
            if (vec_index >= vec_comps) {
               nir_instr_remove(instr);
               state->progress = true;
               break;
            }
         }

         if (nir_intrinsic_access(intrin) & ACCESS_VOLATILE) {
            unsigned wrmask = nir_intrinsic_write_mask(intrin);
            kill_aliases(state, copies, &dst, wrmask);
            break;
         }

         struct copy_entry *entry =
            lookup_entry_for_deref(state, copies, &dst, nir_derefs_equal_bit, NULL);
         if (entry && value_equals_store_src(&entry->src, intrin)) {
            /* If we are storing the value from a load of the same var the
             * store is redundant so remove it.
             */
            nir_instr_remove(instr);
            state->progress = true;
         } else {
            struct value value = { 0 };
            value_set_ssa_components(&value, intrin->src[1].ssa,
                                     intrin->num_components);
            unsigned wrmask = nir_intrinsic_write_mask(intrin);
            struct copy_entry *entry =
               get_entry_and_kill_aliases(state, copies, &vec_dst, wrmask);
            value_set_from_value(&entry->src, &value, vec_index, wrmask);
         }

         break;
      }

      case nir_intrinsic_copy_deref: {
         if (debug)
            dump_instr(instr);

         nir_deref_and_path dst = { nir_src_as_deref(intrin->src[0]), NULL };
         nir_deref_and_path src = { nir_src_as_deref(intrin->src[1]), NULL };

         /* The copy_deref intrinsic doesn't keep track of num_components, so
          * get it ourselves.
          */
         unsigned num_components = glsl_get_vector_elements(dst.instr->type);
         unsigned full_mask = (1 << num_components) - 1;

         if ((nir_intrinsic_src_access(intrin) & ACCESS_VOLATILE) ||
             (nir_intrinsic_dst_access(intrin) & ACCESS_VOLATILE)) {
            kill_aliases(state, copies, &dst, full_mask);
            break;
         }

         nir_deref_compare_result comp =
            nir_compare_derefs_and_paths(state->mem_ctx, &src, &dst);
         if (comp & nir_derefs_equal_bit) {
            /* This is a no-op self-copy.  Get rid of it */
            nir_instr_remove(instr);
            state->progress = true;
            continue;
         }

         /* Copy of direct array derefs of vectors are not handled.  Just
          * invalidate what's written and bail.
          */
         if ((is_array_deref_of_vector(&src) && nir_src_is_const(src.instr->arr.index)) ||
             (is_array_deref_of_vector(&dst) && nir_src_is_const(dst.instr->arr.index))) {
            kill_aliases(state, copies, &dst, full_mask);
            break;
         }

         struct copy_entry *src_entry =
            lookup_entry_for_deref(state, copies, &src, nir_derefs_a_contains_b_bit, NULL);
         struct value value;
         if (try_load_from_entry(state, src_entry, b, intrin, &src, &value)) {
            /* If load works, intrin (the copy_deref) is removed. */
            if (value.is_ssa) {
               nir_store_deref(b, dst.instr, value.ssa.def[0], full_mask);
            } else {
               /* If this would be a no-op self-copy, don't bother. */
               comp = nir_compare_derefs_and_paths(state->mem_ctx, &value.deref, &dst);
               if (comp & nir_derefs_equal_bit)
                  continue;

               /* Just turn it into a copy of a different deref */
               intrin->src[1] = nir_src_for_ssa(&value.deref.instr->def);

               /* Put it back in again. */
               nir_builder_instr_insert(b, instr);
            }

            state->progress = true;
         } else {
            value = (struct value){
               .is_ssa = false,
               { .deref = src },
            };
         }

         nir_variable *src_var = nir_deref_instr_get_variable(src.instr);
         if (src_var && src_var->data.cannot_coalesce) {
            /* The source cannot be coaleseced, which means we can't propagate
             * this copy.
             */
            break;
         }

         struct copy_entry *dst_entry =
            get_entry_and_kill_aliases(state, copies, &dst, full_mask);
         value_set_from_value(&dst_entry->src, &value, 0, full_mask);
         break;
      }

      case nir_intrinsic_trace_ray:
      case nir_intrinsic_execute_callable:
      case nir_intrinsic_rt_trace_ray:
      case nir_intrinsic_rt_execute_callable: {
         if (debug)
            dump_instr(instr);

         nir_deref_and_path payload = {
            nir_src_as_deref(*nir_get_shader_call_payload_src(intrin)), NULL
         };
         nir_component_mask_t full_mask = (1 << glsl_get_vector_elements(payload.instr->type)) - 1;
         kill_aliases(state, copies, &payload, full_mask);
         break;
      }

      case nir_intrinsic_memcpy_deref:
      case nir_intrinsic_deref_atomic:
      case nir_intrinsic_deref_atomic_swap:
         if (debug)
            dump_instr(instr);

         nir_deref_and_path dst = { nir_src_as_deref(intrin->src[0]), NULL };
         unsigned num_components = glsl_get_vector_elements(dst.instr->type);
         unsigned full_mask = (1 << num_components) - 1;
         kill_aliases(state, copies, &dst, full_mask);
         break;

      case nir_intrinsic_store_deref_block_intel: {
         if (debug)
            dump_instr(instr);

         /* Invalidate the whole variable (or cast) and anything that alias
          * with it.
          */
         nir_deref_and_path dst = { nir_src_as_deref(intrin->src[0]), NULL };
         while (nir_deref_instr_parent(dst.instr))
            dst.instr = nir_deref_instr_parent(dst.instr);
         assert(dst.instr->deref_type == nir_deref_type_var ||
                dst.instr->deref_type == nir_deref_type_cast);

         unsigned num_components = glsl_get_vector_elements(dst.instr->type);
         unsigned full_mask = (1 << num_components) - 1;
         kill_aliases(state, copies, &dst, full_mask);
         break;
      }

      default:
         continue; /* To skip the debug below. */
      }

      if (debug)
         dump_copy_entries(copies);
   }
}

static void
clone_copies(struct copy_prop_var_state *state, struct copies *clones,
             struct copies *copies)
{
   /* Simply clone the entire hash table. This is much faster than trying to
    * rebuild it and is needed to avoid slow compilation of very large shaders.
    * If needed we will clone the data later if it is ever looked up.
    */
   assert(clones->ht == NULL);
   clones->ht = _mesa_hash_table_clone(copies->ht, state->mem_ctx);

   util_dynarray_clone(&clones->arr, state->mem_ctx, &copies->arr);
}

/* Returns an existing struct for reuse or creates a new on if they are
 * all in use. This greatly reduces the time spent allocating memory if we
 * were to just creating a fresh one each time.
 */
static struct copies *
get_copies_structure(struct copy_prop_var_state *state)
{
   struct copies *copies;
   if (list_is_empty(&state->unused_copy_structs_list)) {
      copies = ralloc(state->mem_ctx, struct copies);
      copies->ht = NULL;
      util_dynarray_init(&copies->arr, state->mem_ctx);
   } else {
      copies = list_entry(state->unused_copy_structs_list.next,
                          struct copies, node);
      list_del(&copies->node);
   }

   return copies;
}

static void
clear_copies_structure(struct copy_prop_var_state *state,
                       struct copies *copies)
{
   ralloc_free(copies->ht);
   copies->ht = NULL;

   list_add(&copies->node, &state->unused_copy_structs_list);
}

static void
copy_prop_vars_cf_node(struct copy_prop_var_state *state,
                       struct copies *copies, nir_cf_node *cf_node)
{
   switch (cf_node->type) {
   case nir_cf_node_function: {
      nir_function_impl *impl = nir_cf_node_as_function(cf_node);

      struct copies *impl_copies = get_copies_structure(state);
      impl_copies->ht = _mesa_hash_table_create(state->mem_ctx,
                                                _mesa_hash_pointer,
                                                _mesa_key_pointer_equal);

      foreach_list_typed_safe(nir_cf_node, cf_node, node, &impl->body)
         copy_prop_vars_cf_node(state, impl_copies, cf_node);

      clear_copies_structure(state, impl_copies);

      break;
   }

   case nir_cf_node_block: {
      nir_block *block = nir_cf_node_as_block(cf_node);
      nir_builder b = nir_builder_create(state->impl);
      copy_prop_vars_block(state, &b, block, copies);
      break;
   }

   case nir_cf_node_if: {
      nir_if *if_stmt = nir_cf_node_as_if(cf_node);

      /* Create new hash tables for tracking vars and fill it with clones of
       * the copy arrays for each variable we are tracking.
       *
       * We clone the copies for each branch of the if statement.  The idea is
       * that they both see the same state of available copies, but do not
       * interfere to each other.
       */
      if (!exec_list_is_empty(&if_stmt->then_list)) {
         struct copies *then_copies = get_copies_structure(state);
         clone_copies(state, then_copies, copies);

         foreach_list_typed_safe(nir_cf_node, cf_node, node, &if_stmt->then_list)
            copy_prop_vars_cf_node(state, then_copies, cf_node);

         clear_copies_structure(state, then_copies);
      }

      if (!exec_list_is_empty(&if_stmt->else_list)) {
         struct copies *else_copies = get_copies_structure(state);
         clone_copies(state, else_copies, copies);

         foreach_list_typed_safe(nir_cf_node, cf_node, node, &if_stmt->else_list)
            copy_prop_vars_cf_node(state, else_copies, cf_node);

         clear_copies_structure(state, else_copies);
      }

      /* Both branches copies can be ignored, since the effect of running both
       * branches was captured in the first pass that collects vars_written.
       */

      invalidate_copies_for_cf_node(state, copies, cf_node);

      break;
   }

   case nir_cf_node_loop: {
      nir_loop *loop = nir_cf_node_as_loop(cf_node);
      assert(!nir_loop_has_continue_construct(loop));

      /* Invalidate before cloning the copies for the loop, since the loop
       * body can be executed more than once.
       */

      invalidate_copies_for_cf_node(state, copies, cf_node);

      struct copies *loop_copies = get_copies_structure(state);
      clone_copies(state, loop_copies, copies);

      foreach_list_typed_safe(nir_cf_node, cf_node, node, &loop->body)
         copy_prop_vars_cf_node(state, loop_copies, cf_node);

      clear_copies_structure(state, loop_copies);

      break;
   }

   default:
      unreachable("Invalid CF node type");
   }
}

static bool
nir_copy_prop_vars_impl(nir_function_impl *impl)
{
   void *mem_ctx = ralloc_context(NULL);

   if (debug) {
      nir_metadata_require(impl, nir_metadata_block_index);
      printf("## nir_copy_prop_vars_impl for %s\n", impl->function->name);
   }

   struct copy_prop_var_state state = {
      .impl = impl,
      .mem_ctx = mem_ctx,
      .lin_ctx = linear_context(mem_ctx),

      .vars_written_map = _mesa_pointer_hash_table_create(mem_ctx),
   };
   list_inithead(&state.unused_copy_structs_list);

   gather_vars_written(&state, NULL, &impl->cf_node);

   copy_prop_vars_cf_node(&state, NULL, &impl->cf_node);

   bool impl_progress = state.progress;
   nir_progress(impl_progress, impl, nir_metadata_control_flow);

   ralloc_free(mem_ctx);
   return state.progress;
}

bool
nir_opt_copy_prop_vars(nir_shader *shader)
{
   bool progress = false;

   nir_foreach_function_impl(impl, shader) {
      progress |= nir_copy_prop_vars_impl(impl);
   }

   return progress;
}