nir: lower-io-types pass

A pass to lower complex (struct/array/mat) inputs/outputs to primitive
types.  This allows, for example, linking that removes unused components
of a larger type which is not indirectly accessed.

In the near term, it is needed for gallium (mesa/st) support for NIR,
since only used components of a type are assigned VBO slots, and we
otherwise have no way to represent that to the driver backend.  But it
should be useful for doing shader linking in NIR.

v2: use glsl_count_attribute_slots() rather than passing a type_size
    fxn pointer

Signed-off-by: Rob Clark <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>

2 files changed, 181 insertions, 0 deletions

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 51773412d20..68f948e83a5 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2293,6 +2293,7 @@ void nir_lower_io(nir_shader *shader,
 nir_src *nir_get_io_offset_src(nir_intrinsic_instr *instr);
 nir_src *nir_get_io_vertex_index_src(nir_intrinsic_instr *instr);
 
+void nir_lower_io_types(nir_shader *shader);
 void nir_lower_vars_to_ssa(nir_shader *shader);
 
 bool nir_remove_dead_variables(nir_shader *shader, nir_variable_mode modes);
diff --git a/src/compiler/nir/nir_lower_io_types.c b/src/compiler/nir/nir_lower_io_types.c
new file mode 100644
index 00000000000..6b29f819632
--- /dev/null
+++ b/src/compiler/nir/nir_lower_io_types.c
@@ -0,0 +1,180 @@
+/*
+ * Copyright © 2016 Red Hat
+ *
+ * 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"
+
+/* Lower complex (struct/array/mat) input and output vars to primitive types
+ * (vec4) for linking.  All indirect input/output access should already be
+ * lowered (ie. nir_lower_io_to_temporaries).
+ */
+
+struct lower_io_types_state {
+   nir_shader *shader;
+   struct exec_list new_ins;
+   struct exec_list new_outs;
+};
+
+static nir_variable *
+get_new_var(struct lower_io_types_state *state, nir_variable *var,
+            const struct glsl_type *deref_type, unsigned off)
+{
+   struct exec_list *list;
+
+   if (var->data.mode == nir_var_shader_in) {
+      list = &state->new_ins;
+   } else {
+      assert(var->data.mode == nir_var_shader_out);
+      list = &state->new_outs;
+   }
+
+   nir_foreach_variable(nvar, list) {
+      if (nvar->data.location == (var->data.location + off))
+         return nvar;
+   }
+
+   /* doesn't already exist, so we need to create a new one: */
+   /* TODO figure out if scalar vs vec, and if float/int/uint/(double?)
+    * do we need to fixup interpolation mode for int vs float components
+    * of a struct, etc..
+    */
+   const struct glsl_type *ntype =
+      glsl_vector_type(glsl_get_base_type(deref_type),
+                       glsl_get_vector_elements(deref_type));
+   nir_variable *nvar = nir_variable_create(state->shader, var->data.mode,
+                                            ntype, NULL);
+
+   nvar->name = ralloc_asprintf(nvar, "%s@%u", var->name, off);
+   nvar->data = var->data;
+   nvar->data.location += off;
+
+   /* nir_variable_create is too clever for it's own good: */
+   exec_node_remove(&nvar->node);
+   exec_node_self_link(&nvar->node);      /* no delinit() :-( */
+
+   exec_list_push_tail(list, &nvar->node);
+
+   /* remove existing var from input/output list: */
+   exec_node_remove(&var->node);
+   exec_node_self_link(&var->node);
+
+   return nvar;
+}
+
+static unsigned
+get_deref_offset(struct lower_io_types_state *state, nir_deref *tail, bool vs_in)
+{
+   unsigned offset = 0;
+
+   while (tail->child != NULL) {
+      const struct glsl_type *parent_type = tail->type;
+      tail = tail->child;
+
+      if (tail->deref_type == nir_deref_type_array) {
+         nir_deref_array *deref_array = nir_deref_as_array(tail);
+
+         /* indirect inputs/outputs should already be lowered! */
+         assert(deref_array->deref_array_type == nir_deref_array_type_direct);
+
+         unsigned size = glsl_count_attribute_slots(tail->type, vs_in);
+
+         offset += size * deref_array->base_offset;
+      } else if (tail->deref_type == nir_deref_type_struct) {
+         nir_deref_struct *deref_struct = nir_deref_as_struct(tail);
+
+         for (unsigned i = 0; i < deref_struct->index; i++) {
+            const struct glsl_type *ft = glsl_get_struct_field(parent_type, i);
+            offset += glsl_count_attribute_slots(ft, vs_in);
+         }
+      }
+   }
+
+   return offset;
+}
+
+static bool
+lower_io_types_block(struct lower_io_types_state *state, nir_block *block)
+{
+   nir_foreach_instr(instr, block) {
+      if (instr->type != nir_instr_type_intrinsic)
+         continue;
+
+      nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+
+      if ((intr->intrinsic != nir_intrinsic_load_var) &&
+          (intr->intrinsic != nir_intrinsic_store_var))
+         continue;
+
+      nir_variable *var = intr->variables[0]->var;
+
+      if ((var->data.mode != nir_var_shader_in) &&
+          (var->data.mode != nir_var_shader_out))
+         continue;
+
+      bool vs_in = (state->shader->stage == MESA_SHADER_VERTEX) &&
+                   (var->data.mode == nir_var_shader_in);
+      if (glsl_count_attribute_slots(var->type, vs_in) == 1)
+         continue;
+
+      unsigned off = get_deref_offset(state, &intr->variables[0]->deref, vs_in);
+      const struct glsl_type *deref_type =
+         nir_deref_tail(&intr->variables[0]->deref)->type;
+      nir_variable *nvar = get_new_var(state, var, deref_type, off);
+
+      /* and then re-write the load/store_var deref: */
+      intr->variables[0] = nir_deref_var_create(intr, nvar);
+   }
+
+   return true;
+}
+
+static void
+lower_io_types_impl(nir_function_impl *impl, struct lower_io_types_state *state)
+{
+   nir_foreach_block(block, impl) {
+      lower_io_types_block(state, block);
+   }
+
+   nir_metadata_preserve(impl, nir_metadata_block_index |
+                               nir_metadata_dominance);
+}
+
+
+void
+nir_lower_io_types(nir_shader *shader)
+{
+   struct lower_io_types_state state;
+
+   state.shader = shader;
+   exec_list_make_empty(&state.new_ins);
+   exec_list_make_empty(&state.new_outs);
+
+   nir_foreach_function(function, shader) {
+      if (function->impl)
+         lower_io_types_impl(function->impl, &state);
+   }
+
+   /* move new in/out vars to shader's lists: */
+   exec_list_append(&shader->inputs, &state.new_ins);
+   exec_list_append(&shader->outputs, &state.new_outs);
+}