nir: Delete most of the constant_initializer support

Constant initializers have been a constant (ha!) pain for quite some time.
While they're useful from a language perspective, people writing passes or
backends really don't want deal with them most of the time.  This commit
removes most of the constant initializer support from NIR.  It is expected
that you call nir_lower_constant_initializers VERY EARLY to ensure that
they're gone before you do anything interesting.

Reviewed-by: Iago Toral Quiroga <[email protected]>

1 files changed, 2 insertions, 89 deletions

diff --git a/src/compiler/nir/nir_lower_locals_to_regs.c b/src/compiler/nir/nir_lower_locals_to_regs.c
index cddd9fa9b53..25a62b3624a 100644
--- a/src/compiler/nir/nir_lower_locals_to_regs.c
+++ b/src/compiler/nir/nir_lower_locals_to_regs.c
@@ -101,6 +101,8 @@ get_reg_for_deref(nir_deref_var *deref, struct locals_to_regs_state *state)
 {
    uint32_t hash = hash_deref(deref);
 
+   assert(deref->var->constant_initializer == NULL);
+
    struct hash_entry *entry =
       _mesa_hash_table_search_pre_hashed(state->regs_table, hash, deref);
    if (entry)
@@ -269,80 +271,6 @@ lower_locals_to_regs_block(nir_block *block,
    return true;
 }
 
-static nir_block *
-compute_reg_usedef_lca(nir_register *reg)
-{
-   nir_block *lca = NULL;
-
-   list_for_each_entry(nir_dest, def_dest, &reg->defs, reg.def_link)
-      lca = nir_dominance_lca(lca, def_dest->reg.parent_instr->block);
-
-   list_for_each_entry(nir_src, use_src, &reg->uses, use_link)
-      lca = nir_dominance_lca(lca, use_src->parent_instr->block);
-
-   list_for_each_entry(nir_src, use_src, &reg->if_uses, use_link) {
-      nir_cf_node *prev_node = nir_cf_node_prev(&use_src->parent_if->cf_node);
-      lca = nir_dominance_lca(lca, nir_cf_node_as_block(prev_node));
-   }
-
-   return lca;
-}
-
-static void
-insert_constant_initializer(nir_deref_var *deref_head, nir_deref *deref_tail,
-                            nir_block *block,
-                            struct locals_to_regs_state *state)
-{
-   if (deref_tail->child) {
-      switch (deref_tail->child->deref_type) {
-      case nir_deref_type_array: {
-         unsigned array_elems = glsl_get_length(deref_tail->type);
-
-         nir_deref_array arr_deref;
-         arr_deref.deref = *deref_tail->child;
-         arr_deref.deref_array_type = nir_deref_array_type_direct;
-
-         nir_deref *old_child = deref_tail->child;
-         deref_tail->child = &arr_deref.deref;
-         for (unsigned i = 0; i < array_elems; i++) {
-            arr_deref.base_offset = i;
-            insert_constant_initializer(deref_head, &arr_deref.deref,
-                                        block, state);
-         }
-         deref_tail->child = old_child;
-         return;
-      }
-
-      case nir_deref_type_struct:
-         insert_constant_initializer(deref_head, deref_tail->child,
-                                     block, state);
-         return;
-
-      default:
-         unreachable("Invalid deref child type");
-      }
-   }
-
-   assert(deref_tail->child == NULL);
-
-   nir_load_const_instr *load =
-      nir_deref_get_const_initializer_load(state->shader, deref_head);
-   nir_instr_insert_before_block(block, &load->instr);
-
-   nir_src reg_src = get_deref_reg_src(deref_head, &load->instr, state);
-
-   nir_alu_instr *mov = nir_alu_instr_create(state->shader, nir_op_imov);
-   mov->src[0].src = nir_src_for_ssa(&load->def);
-   mov->dest.write_mask = (1 << load->def.num_components) - 1;
-   mov->dest.dest.is_ssa = false;
-   mov->dest.dest.reg.reg = reg_src.reg.reg;
-   mov->dest.dest.reg.base_offset = reg_src.reg.base_offset;
-   mov->dest.dest.reg.indirect = reg_src.reg.indirect;
-
-   nir_instr_insert_after(&load->instr, &mov->instr);
-   state->progress = true;
-}
-
 static bool
 nir_lower_locals_to_regs_impl(nir_function_impl *impl)
 {
@@ -360,21 +288,6 @@ nir_lower_locals_to_regs_impl(nir_function_impl *impl)
       lower_locals_to_regs_block(block, &state);
    }
 
-   nir_array_foreach(&state.derefs_array, nir_deref_var *, deref_ptr) {
-      nir_deref_var *deref = *deref_ptr;
-      struct hash_entry *deref_entry =
-         _mesa_hash_table_search(state.regs_table, deref);
-      assert(deref_entry && deref_entry->key == deref);
-      nir_register *reg = (nir_register *)deref_entry->data;
-
-      if (deref->var->constant_initializer == NULL)
-         continue;
-
-      nir_block *usedef_lca = compute_reg_usedef_lca(reg);
-
-      insert_constant_initializer(deref, &deref->deref, usedef_lca, &state);
-   }
-
    nir_metadata_preserve(impl, nir_metadata_block_index |
                                nir_metadata_dominance);