nir: add variant of lower_io_to_scalar to be called earlier

This is intended to be called before nir_lower_io() so that we
can do some linking optimisations with the results. It can also
be used with drivers that don't use nir_lower_io() at all such
as RADV.

v2: pass mode mask rather than first and last stage integer.

Reviewed-by: Eric Anholt <[email protected]>

2 files changed, 255 insertions, 0 deletions

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 5af150310f2..bd6035e1f90 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2454,6 +2454,7 @@ bool nir_lower_load_const_to_scalar(nir_shader *shader);
 bool nir_lower_read_invocation_to_scalar(nir_shader *shader);
 bool nir_lower_phis_to_scalar(nir_shader *shader);
 void nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask);
+void nir_lower_io_to_scalar_early(nir_shader *shader, nir_variable_mode mask);
 
 bool nir_lower_samplers(nir_shader *shader,
                         const struct gl_shader_program *shader_program);
diff --git a/src/compiler/nir/nir_lower_io_to_scalar.c b/src/compiler/nir/nir_lower_io_to_scalar.c
index fffd1d3d2bb..7774c2d2458 100644
--- a/src/compiler/nir/nir_lower_io_to_scalar.c
+++ b/src/compiler/nir/nir_lower_io_to_scalar.c
@@ -127,3 +127,257 @@ nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask)
       }
    }
 }
+
+static nir_variable **
+get_channel_variables(struct hash_table *ht, nir_variable *var)
+{
+   nir_variable **chan_vars;
+   struct hash_entry *entry = _mesa_hash_table_search(ht, var);
+   if (!entry) {
+      chan_vars = (nir_variable **) calloc(4, sizeof(nir_variable *));
+      _mesa_hash_table_insert(ht, var, chan_vars);
+   } else {
+      chan_vars = (nir_variable **) entry->data;
+   }
+
+   return chan_vars;
+}
+
+/*
+ * This function differs from nir_deref_clone() in that it gets its type from
+ * the parent deref rather than our source deref. This is useful when splitting
+ * vectors because we want to use the scalar type of the new parent rather than
+ * then the old vector type.
+ */
+static nir_deref_array *
+clone_deref_array(const nir_deref_array *darr, nir_deref *parent)
+{
+   nir_deref_array *ndarr = nir_deref_array_create(parent);
+
+   ndarr->deref.type = glsl_get_array_element(parent->type);
+   if (darr->deref.child)
+      ndarr->deref.child =
+         &clone_deref_array(nir_deref_as_array(darr->deref.child),
+                            &ndarr->deref)->deref;
+
+   ndarr->deref_array_type = darr->deref_array_type;
+   ndarr->base_offset = darr->base_offset;
+   if (ndarr->deref_array_type == nir_deref_array_type_indirect)
+     nir_src_copy(&ndarr->indirect, &darr->indirect, parent);
+
+   return ndarr;
+}
+
+static void
+lower_load_to_scalar_early(nir_builder *b, nir_intrinsic_instr *intr,
+                           nir_variable *var, struct hash_table *split_inputs,
+                           struct hash_table *split_outputs)
+{
+   b->cursor = nir_before_instr(&intr->instr);
+
+   assert(intr->dest.is_ssa);
+
+   nir_ssa_def *loads[4];
+
+   nir_variable **chan_vars;
+   if (var->data.mode == nir_var_shader_in) {
+      chan_vars = get_channel_variables(split_inputs, var);
+   } else {
+      chan_vars = get_channel_variables(split_outputs, var);
+   }
+
+   for (unsigned i = 0; i < intr->num_components; i++) {
+      nir_variable *chan_var = chan_vars[var->data.location_frac + i];
+      if (!chan_vars[var->data.location_frac + i]) {
+         chan_var = nir_variable_clone(var, b->shader);
+         chan_var->data.location_frac =  var->data.location_frac + i;
+         chan_var->type = glsl_channel_type(chan_var->type);
+
+         chan_vars[var->data.location_frac + i] = chan_var;
+
+         nir_shader_add_variable(b->shader, chan_var);
+      }
+
+      nir_intrinsic_instr *chan_intr =
+         nir_intrinsic_instr_create(b->shader, intr->intrinsic);
+      nir_ssa_dest_init(&chan_intr->instr, &chan_intr->dest,
+                        1, intr->dest.ssa.bit_size, NULL);
+      chan_intr->num_components = 1;
+      chan_intr->variables[0] = nir_deref_var_create(chan_intr, chan_var);
+
+      if (intr->variables[0]->deref.child) {
+         chan_intr->variables[0]->deref.child =
+            &clone_deref_array(nir_deref_as_array(intr->variables[0]->deref.child),
+                               &chan_intr->variables[0]->deref)->deref;
+      }
+
+      if (intr->intrinsic == nir_intrinsic_interp_var_at_offset ||
+          intr->intrinsic == nir_intrinsic_interp_var_at_sample)
+         nir_src_copy(chan_intr->src, intr->src, &chan_intr->instr);
+
+      nir_builder_instr_insert(b, &chan_intr->instr);
+
+      loads[i] = &chan_intr->dest.ssa;
+   }
+
+   nir_ssa_def_rewrite_uses(&intr->dest.ssa,
+                            nir_src_for_ssa(nir_vec(b, loads,
+                                                    intr->num_components)));
+
+   /* Remove the old load intrinsic */
+   nir_instr_remove(&intr->instr);
+}
+
+static void
+lower_store_output_to_scalar_early(nir_builder *b, nir_intrinsic_instr *intr,
+                                   nir_variable *var,
+                                   struct hash_table *split_outputs)
+{
+   b->cursor = nir_before_instr(&intr->instr);
+
+   nir_ssa_def *value = nir_ssa_for_src(b, intr->src[0], intr->num_components);
+
+   nir_variable **chan_vars = get_channel_variables(split_outputs, var);
+   for (unsigned i = 0; i < intr->num_components; i++) {
+      if (!(nir_intrinsic_write_mask(intr) & (1 << i)))
+         continue;
+
+      nir_variable *chan_var = chan_vars[var->data.location_frac + i];
+      if (!chan_vars[var->data.location_frac + i]) {
+         chan_var = nir_variable_clone(var, b->shader);
+         chan_var->data.location_frac =  var->data.location_frac + i;
+         chan_var->type = glsl_channel_type(chan_var->type);
+
+         chan_vars[var->data.location_frac + i] = chan_var;
+
+         nir_shader_add_variable(b->shader, chan_var);
+      }
+
+      nir_intrinsic_instr *chan_intr =
+         nir_intrinsic_instr_create(b->shader, intr->intrinsic);
+      chan_intr->num_components = 1;
+
+      nir_intrinsic_set_write_mask(chan_intr, 0x1);
+
+      chan_intr->variables[0] = nir_deref_var_create(chan_intr, chan_var);
+      chan_intr->src[0] = nir_src_for_ssa(nir_channel(b, value, i));
+
+      if (intr->variables[0]->deref.child) {
+         chan_intr->variables[0]->deref.child =
+            &clone_deref_array(nir_deref_as_array(intr->variables[0]->deref.child),
+                               &chan_intr->variables[0]->deref)->deref;
+      }
+
+      nir_builder_instr_insert(b, &chan_intr->instr);
+   }
+
+   /* Remove the old store intrinsic */
+   nir_instr_remove(&intr->instr);
+}
+
+/*
+ * This function is intended to be called earlier than nir_lower_io_to_scalar()
+ * i.e. before nir_lower_io() is called.
+ */
+void
+nir_lower_io_to_scalar_early(nir_shader *shader, nir_variable_mode mask)
+{
+   struct hash_table *split_inputs =
+      _mesa_hash_table_create(NULL, _mesa_hash_pointer,
+                              _mesa_key_pointer_equal);
+   struct hash_table *split_outputs =
+      _mesa_hash_table_create(NULL, _mesa_hash_pointer,
+                              _mesa_key_pointer_equal);
+
+   nir_foreach_function(function, shader) {
+      if (function->impl) {
+         nir_builder b;
+         nir_builder_init(&b, function->impl);
+
+         nir_foreach_block(block, function->impl) {
+            nir_foreach_instr_safe(instr, block) {
+               if (instr->type != nir_instr_type_intrinsic)
+                  continue;
+
+               nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+
+               if (intr->num_components == 1)
+                  continue;
+
+               if (intr->intrinsic != nir_intrinsic_load_var &&
+                   intr->intrinsic != nir_intrinsic_store_var &&
+                   intr->intrinsic != nir_intrinsic_interp_var_at_centroid &&
+                   intr->intrinsic != nir_intrinsic_interp_var_at_sample &&
+                   intr->intrinsic != nir_intrinsic_interp_var_at_offset)
+                  continue;
+
+               nir_variable *var = intr->variables[0]->var;
+               nir_variable_mode mode = var->data.mode;
+
+               /* TODO: add patch support */
+               if (var->data.patch)
+                  continue;
+
+               /* TODO: add doubles support */
+               if (glsl_type_is_64bit(glsl_without_array(var->type)))
+                  continue;
+
+               if (var->data.location < VARYING_SLOT_VAR0 &&
+                   var->data.location >= 0)
+                  continue;
+
+               /* Don't bother splitting if we can't opt away any unused
+                * components.
+                */
+               if (var->data.always_active_io)
+                  continue;
+
+              /* Skip types we cannot split */
+              if (glsl_type_is_matrix(glsl_without_array(var->type)) ||
+                  glsl_type_is_struct(glsl_without_array(var->type)))
+                 continue;
+
+               switch (intr->intrinsic) {
+               case nir_intrinsic_interp_var_at_centroid:
+               case nir_intrinsic_interp_var_at_sample:
+               case nir_intrinsic_interp_var_at_offset:
+               case nir_intrinsic_load_var:
+                  if ((mask & nir_var_shader_in && mode == nir_var_shader_in) ||
+                      (mask & nir_var_shader_out && mode == nir_var_shader_out))
+                     lower_load_to_scalar_early(&b, intr, var, split_inputs,
+                                                split_outputs);
+                  break;
+               case nir_intrinsic_store_var:
+                  if (mask & nir_var_shader_out &&
+                      mode == nir_var_shader_out)
+                     lower_store_output_to_scalar_early(&b, intr, var,
+                                                        split_outputs);
+                  break;
+               default:
+                  break;
+               }
+            }
+         }
+      }
+   }
+
+   /* Remove old input from the shaders inputs list */
+   struct hash_entry *entry;
+   hash_table_foreach(split_inputs, entry) {
+      nir_variable *var = (nir_variable *) entry->key;
+      exec_node_remove(&var->node);
+
+      free(entry->data);
+   }
+
+   /* Remove old output from the shaders outputs list */
+   hash_table_foreach(split_outputs, entry) {
+      nir_variable *var = (nir_variable *) entry->key;
+      exec_node_remove(&var->node);
+
+      free(entry->data);
+   }
+
+   _mesa_hash_table_destroy(split_inputs, NULL);
+   _mesa_hash_table_destroy(split_outputs, NULL);
+}