nir: Add helpers for working with deref instructions

This commit adds a pass for lowering deref instructions to deref chains
as well as some smaller helpers to ease the transition.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Acked-by: Rob Clark <robdclark@gmail.com>
Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Acked-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/Makefile.sources

@@ -207,6 +207,7 @@ NIR_FILES = \
 	nir/nir_control_flow.c \
 	nir/nir_control_flow.h \
 	nir/nir_control_flow_private.h \
+	nir/nir_deref.c \
 	nir/nir_dominance.c \
 	nir/nir_format_convert.h \
 	nir/nir_from_ssa.c \

src/compiler/nir/meson.build

@@ -92,6 +92,7 @@ files_libnir = files(
   'nir_control_flow.c',
   'nir_control_flow.h',
   'nir_control_flow_private.h',
+  'nir_deref.c',
   'nir_dominance.c',
   'nir_format_convert.h',
   'nir_from_ssa.c',

src/compiler/nir/nir.h

@@ -1010,6 +1010,31 @@ nir_src_as_deref(nir_src src)
    return nir_instr_as_deref(src.ssa->parent_instr);
 }
 
+static inline nir_deref_instr *
+nir_deref_instr_parent(const nir_deref_instr *instr)
+{
+   if (instr->deref_type == nir_deref_type_var)
+      return NULL;
+   else
+      return nir_src_as_deref(instr->parent);
+}
+
+static inline nir_variable *
+nir_deref_instr_get_variable(const nir_deref_instr *instr)
+{
+   while (instr->deref_type != nir_deref_type_var) {
+      if (instr->deref_type == nir_deref_type_cast)
+         return NULL;
+
+      instr = nir_deref_instr_parent(instr);
+   }
+
+   return instr->var;
+}
+
+nir_deref_var *
+nir_deref_instr_to_deref(nir_deref_instr *instr, void *mem_ctx);
+
 typedef struct {
    nir_instr instr;
 
@@ -2647,6 +2672,18 @@ bool nir_inline_functions(nir_shader *shader);
 
 bool nir_propagate_invariant(nir_shader *shader);
 
+enum nir_lower_deref_flags {
+   nir_lower_load_store_derefs =       (1 << 0),
+   nir_lower_texture_derefs =          (1 << 1),
+   nir_lower_interp_derefs =           (1 << 2),
+   nir_lower_atomic_counter_derefs =   (1 << 3),
+   nir_lower_atomic_derefs =           (1 << 4),
+   nir_lower_image_derefs =            (1 << 5),
+};
+
+bool nir_lower_deref_instrs(nir_shader *shader,
+                            enum nir_lower_deref_flags flags);
+
 void nir_lower_var_copy_instr(nir_intrinsic_instr *copy, nir_shader *shader);
 bool nir_lower_var_copies(nir_shader *shader);
 

src/compiler/nir/nir_builder.h

@@ -644,6 +644,29 @@ nir_build_deref_cast(nir_builder *build, nir_ssa_def *parent,
    return deref;
 }
 
+static inline nir_deref_instr *
+nir_build_deref_for_chain(nir_builder *b, nir_deref_var *deref_var)
+{
+   nir_deref_instr *tail = nir_build_deref_var(b, deref_var->var);
+   for (nir_deref *d = deref_var->deref.child; d; d = d->child) {
+      if (d->deref_type == nir_deref_type_array) {
+         nir_deref_array *a = nir_deref_as_array(d);
+         assert(a->deref_array_type != nir_deref_array_type_wildcard);
+
+         nir_ssa_def *index = nir_imm_int(b, a->base_offset);
+         if (a->deref_array_type == nir_deref_array_type_indirect)
+            index = nir_iadd(b, index, nir_ssa_for_src(b, a->indirect, 1));
+
+         tail = nir_build_deref_array(b, tail, index);
+      } else {
+         nir_deref_struct *s = nir_deref_as_struct(d);
+         tail = nir_build_deref_struct(b, tail, s->index);
+      }
+   }
+
+   return tail;
+}
+
 static inline nir_ssa_def *
 nir_load_reg(nir_builder *build, nir_register *reg)
 {

src/compiler/nir/nir_deref.c

@@ -0,0 +1,301 @@
+/*
+ * Copyright © 2018 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"
+
+nir_deref_var *
+nir_deref_instr_to_deref(nir_deref_instr *instr, void *mem_ctx)
+{
+   nir_deref *deref = NULL;
+
+   while (instr->deref_type != nir_deref_type_var) {
+      nir_deref *nderef;
+      switch (instr->deref_type) {
+      case nir_deref_type_array:
+      case nir_deref_type_array_wildcard: {
+         nir_deref_array *deref_arr = nir_deref_array_create(mem_ctx);
+         if (instr->deref_type == nir_deref_type_array) {
+            nir_const_value *const_index =
+               nir_src_as_const_value(instr->arr.index);
+            if (const_index) {
+               deref_arr->deref_array_type = nir_deref_array_type_direct;
+               deref_arr->base_offset = const_index->u32[0];
+            } else {
+               deref_arr->deref_array_type = nir_deref_array_type_indirect;
+               deref_arr->base_offset = 0;
+               nir_src_copy(&deref_arr->indirect, &instr->arr.index, mem_ctx);
+            }
+         } else {
+            deref_arr->deref_array_type = nir_deref_array_type_wildcard;
+         }
+         nderef = &deref_arr->deref;
+         break;
+      }
+
+      case nir_deref_type_struct:
+         nderef = &nir_deref_struct_create(mem_ctx, instr->strct.index)->deref;
+         break;
+
+      default:
+         unreachable("Invalid deref instruction type");
+      }
+
+      nderef->child = deref;
+      ralloc_steal(nderef, deref);
+      nderef->type = instr->type;
+
+      deref = nderef;
+      assert(instr->parent.is_ssa);
+      instr = nir_src_as_deref(instr->parent);
+   }
+
+   assert(instr->deref_type == nir_deref_type_var);
+   nir_deref_var *deref_var = nir_deref_var_create(mem_ctx, instr->var);
+   deref_var->deref.child = deref;
+   ralloc_steal(deref_var, deref);
+
+   return deref_var;
+}
+
+static nir_deref_var *
+nir_deref_src_to_deref(nir_src src, void *mem_ctx)
+{
+   return nir_deref_instr_to_deref(nir_src_as_deref(src), mem_ctx);
+}
+
+static bool
+nir_lower_deref_instrs_tex(nir_tex_instr *tex)
+{
+   bool progress = false;
+
+   /* Remove the instruction before we modify it.  This way we won't mess up
+    * use-def chains when we move sources around.
+    */
+   nir_cursor cursor = nir_instr_remove(&tex->instr);
+
+   unsigned new_num_srcs = 0;
+   for (unsigned i = 0; i < tex->num_srcs; i++) {
+      if (tex->src[i].src_type == nir_tex_src_texture_deref) {
+         tex->texture = nir_deref_src_to_deref(tex->src[i].src, tex);
+         progress = true;
+         continue;
+      } else if (tex->src[i].src_type == nir_tex_src_sampler_deref) {
+         tex->sampler = nir_deref_src_to_deref(tex->src[i].src, tex);
+         progress = true;
+         continue;
+      }
+
+      /* Compact the sources down to remove the deref sources */
+      assert(new_num_srcs <= i);
+      tex->src[new_num_srcs++] = tex->src[i];
+   }
+   tex->num_srcs = new_num_srcs;
+
+   nir_instr_insert(cursor, &tex->instr);
+
+   return progress;
+}
+
+static bool
+nir_lower_deref_instrs_intrin(nir_intrinsic_instr *intrin,
+                              enum nir_lower_deref_flags flags)
+{
+   nir_intrinsic_op deref_op = intrin->intrinsic;
+   nir_intrinsic_op var_op;
+
+   switch (deref_op) {
+#define CASE(a) \
+   case nir_intrinsic_##a##_deref: \
+      if (!(flags & nir_lower_load_store_derefs)) \
+         return false; \
+      var_op = nir_intrinsic_##a##_var; \
+      break;
+   CASE(load)
+   CASE(store)
+   CASE(copy)
+#undef CASE
+
+#define CASE(a) \
+   case nir_intrinsic_interp_deref_##a: \
+      if (!(flags & nir_lower_interp_derefs)) \
+         return false; \
+      var_op = nir_intrinsic_interp_var_##a; \
+      break;
+   CASE(at_centroid)
+   CASE(at_sample)
+   CASE(at_offset)
+#undef CASE
+
+#define CASE(a) \
+   case nir_intrinsic_atomic_counter_##a##_deref: \
+      if (!(flags & nir_lower_atomic_counter_derefs)) \
+         return false; \
+      var_op = nir_intrinsic_atomic_counter_##a##_var; \
+      break;
+   CASE(inc)
+   CASE(dec)
+   CASE(read)
+   CASE(add)
+   CASE(min)
+   CASE(max)
+   CASE(and)
+   CASE(or)
+   CASE(xor)
+   CASE(exchange)
+   CASE(comp_swap)
+#undef CASE
+
+#define CASE(a) \
+   case nir_intrinsic_deref_atomic_##a: \
+      if (!(flags & nir_lower_atomic_derefs)) \
+         return false; \
+      var_op = nir_intrinsic_var_atomic_##a; \
+      break;
+   CASE(add)
+   CASE(imin)
+   CASE(umin)
+   CASE(imax)
+   CASE(umax)
+   CASE(and)
+   CASE(or)
+   CASE(xor)
+   CASE(exchange)
+   CASE(comp_swap)
+#undef CASE
+
+#define CASE(a) \
+   case nir_intrinsic_image_deref_##a: \
+      if (!(flags & nir_lower_image_derefs)) \
+         return false; \
+      var_op = nir_intrinsic_image_var_##a; \
+      break;
+   CASE(load)
+   CASE(store)
+   CASE(atomic_add)
+   CASE(atomic_min)
+   CASE(atomic_max)
+   CASE(atomic_and)
+   CASE(atomic_or)
+   CASE(atomic_xor)
+   CASE(atomic_exchange)
+   CASE(atomic_comp_swap)
+   CASE(size)
+   CASE(samples)
+#undef CASE
+
+   default:
+      return false;
+   }
+
+   /* Remove the instruction before we modify it.  This way we won't mess up
+    * use-def chains when we move sources around.
+    */
+   nir_cursor cursor = nir_instr_remove(&intrin->instr);
+
+   unsigned num_derefs = nir_intrinsic_infos[var_op].num_variables;
+   assert(nir_intrinsic_infos[var_op].num_srcs + num_derefs ==
+          nir_intrinsic_infos[deref_op].num_srcs);
+
+   /* Move deref sources to variables */
+   for (unsigned i = 0; i < num_derefs; i++)
+      intrin->variables[i] = nir_deref_src_to_deref(intrin->src[i], intrin);
+
+   /* Shift all the other sources down */
+   for (unsigned i = 0; i < nir_intrinsic_infos[var_op].num_srcs; i++)
+      nir_src_copy(&intrin->src[i], &intrin->src[i + num_derefs], intrin);
+
+   /* Rewrite the extra sources to NIR_SRC_INIT just in case */
+   for (unsigned i = 0; i < num_derefs; i++)
+      intrin->src[nir_intrinsic_infos[var_op].num_srcs + i] = NIR_SRC_INIT;
+
+   /* It's safe to just stomp the intrinsic to var intrinsic since every
+    * intrinsic has room for some variables and the number of sources only
+    * shrinks.
+    */
+   intrin->intrinsic = var_op;
+
+   nir_instr_insert(cursor, &intrin->instr);
+
+   return true;
+}
+
+static bool
+nir_lower_deref_instrs_impl(nir_function_impl *impl,
+                            enum nir_lower_deref_flags flags)
+{
+   bool progress = false;
+
+   /* Walk the instructions in reverse order so that we can safely clean up
+    * the deref instructions after we clean up their uses.
+    */
+   nir_foreach_block_reverse(block, impl) {
+      nir_foreach_instr_reverse_safe(instr, block) {
+         switch (instr->type) {
+         case nir_instr_type_deref:
+            if (list_empty(&nir_instr_as_deref(instr)->dest.ssa.uses)) {
+               nir_instr_remove(instr);
+               progress = true;
+            }
+            break;
+
+         case nir_instr_type_tex:
+            if (flags & nir_lower_texture_derefs)
+               progress |= nir_lower_deref_instrs_tex(nir_instr_as_tex(instr));
+            break;
+
+         case nir_instr_type_intrinsic:
+            progress |=
+               nir_lower_deref_instrs_intrin(nir_instr_as_intrinsic(instr),
+                                             flags);
+            break;
+
+         default:
+            break; /* Nothing to do */
+         }
+      }
+   }
+
+   if (progress) {
+      nir_metadata_preserve(impl, nir_metadata_block_index |
+                                  nir_metadata_dominance);
+   }
+
+   return progress;
+}
+
+bool
+nir_lower_deref_instrs(nir_shader *shader,
+                       enum nir_lower_deref_flags flags)
+{
+   bool progress = false;
+
+   nir_foreach_function(function, shader) {
+      if (!function->impl)
+         continue;
+
+      progress |= nir_lower_deref_instrs_impl(function->impl, flags);
+   }
+
+   return progress;
+}