nir: Add a pass to lower local variables to registers

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>

3 files changed, 316 insertions, 0 deletions

diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index 1d3b049..6230f49 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -22,6 +22,7 @@ NIR_FILES = \
 	$(GLSL_SRCDIR)/nir/nir_intrinsics.h \
 	$(GLSL_SRCDIR)/nir/nir_live_variables.c \
 	$(GLSL_SRCDIR)/nir/nir_lower_atomics.c \
+	$(GLSL_SRCDIR)/nir/nir_lower_locals_to_regs.c \
 	$(GLSL_SRCDIR)/nir/nir_lower_samplers.cpp \
 	$(GLSL_SRCDIR)/nir/nir_lower_system_values.c \
 	$(GLSL_SRCDIR)/nir/nir_lower_variables.c \
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 9d207bd..884cc04 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1358,6 +1358,8 @@ void nir_dump_cfg(nir_shader *shader, FILE *fp);
 
 void nir_split_var_copies(nir_shader *shader);
 
+void nir_lower_locals_to_regs(nir_shader *shader);
+
 void nir_lower_variables(nir_shader *shader);
 
 void nir_lower_variables_scalar(nir_shader *shader, bool lower_globals,
diff --git a/src/glsl/nir/nir_lower_locals_to_regs.c b/src/glsl/nir/nir_lower_locals_to_regs.c
new file mode 100644
index 0000000..715c634
--- /dev/null
+++ b/src/glsl/nir/nir_lower_locals_to_regs.c
@@ -0,0 +1,313 @@
+/*
+ * Copyright © 2014 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.
+ *
+ * Authors:
+ *    Jason Ekstrand (jason@jlekstrand.net)
+ *
+ */
+
+#include "nir.h"
+
+struct locals_to_regs_state {
+   void *mem_ctx;
+   nir_function_impl *impl;
+
+   /* A hash table mapping derefs to registers */
+   struct hash_table *regs_table;
+};
+
+/* The following two functions implement a hash and equality check for
+ * variable dreferences.  When the hash or equality function encounters an
+ * array, it ignores the offset and whether it is direct or indirect
+ * entirely.
+ */
+static uint32_t
+hash_deref(const void *void_deref)
+{
+   const nir_deref *deref = void_deref;
+
+   uint32_t hash;
+   if (deref->child) {
+      hash = hash_deref(deref->child);
+   } else {
+      hash = 2166136261ul;
+   }
+
+   switch (deref->deref_type) {
+   case nir_deref_type_var:
+      hash ^= _mesa_hash_pointer(nir_deref_as_var(deref)->var);
+      break;
+   case nir_deref_type_array: {
+      hash ^= 268435183;
+      break;
+   }
+   case nir_deref_type_struct:
+      hash ^= nir_deref_as_struct(deref)->index;
+      break;
+   }
+
+   return hash * 0x01000193;
+}
+
+static bool
+derefs_equal(const void *void_a, const void *void_b)
+{
+   const nir_deref *a = void_a;
+   const nir_deref *b = void_b;
+
+   if (a->deref_type != b->deref_type)
+      return false;
+
+   switch (a->deref_type) {
+   case nir_deref_type_var:
+      if (nir_deref_as_var(a)->var != nir_deref_as_var(b)->var)
+         return false;
+      break;
+   case nir_deref_type_array:
+      /* Do nothing.  All array derefs are the same */
+      break;
+   case nir_deref_type_struct:
+      if (nir_deref_as_struct(a)->index != nir_deref_as_struct(b)->index)
+         return false;
+      break;
+   default:
+      unreachable("Invalid dreference type");
+   }
+
+   assert((a->child == NULL) == (b->child == NULL));
+   if (a->child)
+      return derefs_equal(a->child, b->child);
+   else
+      return true;
+}
+
+static nir_register *
+get_reg_for_deref(nir_deref_var *deref, struct locals_to_regs_state *state)
+{
+   uint32_t hash = hash_deref(deref);
+
+   struct hash_entry *entry =
+      _mesa_hash_table_search_pre_hashed(state->regs_table, hash, deref);
+   if (entry)
+      return entry->data;
+
+   unsigned array_size = 1;
+   nir_deref *tail = &deref->deref;
+   while (tail->child) {
+      if (tail->child->deref_type == nir_deref_type_array) {
+         /* Multiply by the parent's type. */
+         if (glsl_type_is_matrix(tail->type)) {
+            array_size *= glsl_get_matrix_columns(tail->type);
+         } else {
+            assert(glsl_get_length(tail->type) > 0);
+            array_size *= glsl_get_length(tail->type);
+         }
+      }
+      tail = tail->child;
+   }
+
+   assert(glsl_type_is_vector(tail->type) || glsl_type_is_scalar(tail->type));
+
+   nir_register *reg = nir_local_reg_create(state->impl);
+   reg->num_components = glsl_get_vector_elements(tail->type);
+   reg->num_array_elems = array_size > 1 ? array_size : 0;
+
+   _mesa_hash_table_insert_with_hash(state->regs_table, hash, deref, reg);
+
+   return reg;
+}
+
+static nir_src
+get_deref_reg_src(nir_deref_var *deref, nir_instr *instr,
+                  struct locals_to_regs_state *state)
+{
+   nir_src src;
+
+   src.is_ssa = false;
+   src.reg.reg = get_reg_for_deref(deref, state);
+   src.reg.base_offset = 0;
+   src.reg.indirect = NULL;
+
+   nir_deref *tail = &deref->deref;
+   while (tail->child != NULL) {
+      const struct glsl_type *parent_type = tail->type;
+      tail = tail->child;
+
+      if (tail->deref_type != nir_deref_type_array)
+         continue;
+
+      nir_deref_array *deref_array = nir_deref_as_array(tail);
+
+      src.reg.base_offset *= glsl_get_length(parent_type);
+      src.reg.base_offset += deref_array->base_offset;
+
+      if (src.reg.indirect) {
+         nir_load_const_instr *load_const =
+            nir_load_const_instr_create(state->mem_ctx);
+         load_const->num_components = 1;
+         load_const->value.u[0] = glsl_get_length(parent_type);
+         load_const->dest.is_ssa = true;
+         nir_ssa_def_init(&load_const->instr, &load_const->dest.ssa, 1, NULL);
+         nir_instr_insert_before(instr, &load_const->instr);
+
+         nir_alu_instr *mul = nir_alu_instr_create(state->mem_ctx, nir_op_imul);
+         mul->src[0].src = *src.reg.indirect;
+         mul->src[1].src.is_ssa = true;
+         mul->src[1].src.ssa = &load_const->dest.ssa;
+         mul->dest.write_mask = 1;
+         mul->dest.dest.is_ssa = true;
+         nir_ssa_def_init(&mul->instr, &mul->dest.dest.ssa, 1, NULL);
+         nir_instr_insert_before(instr, &mul->instr);
+
+         src.reg.indirect->is_ssa = true;
+         src.reg.indirect->ssa = &mul->dest.dest.ssa;
+      }
+
+      if (deref_array->deref_array_type == nir_deref_array_type_indirect) {
+         if (src.reg.indirect == NULL) {
+            src.reg.indirect = ralloc(state->mem_ctx, nir_src);
+            *src.reg.indirect = nir_src_copy(deref_array->indirect,
+                                             state->mem_ctx);
+         } else {
+            nir_alu_instr *add = nir_alu_instr_create(state->mem_ctx,
+                                                      nir_op_iadd);
+            add->src[0].src = *src.reg.indirect;
+            add->src[1].src = nir_src_copy(deref_array->indirect,
+                                           state->mem_ctx);
+            add->dest.write_mask = 1;
+            add->dest.dest.is_ssa = true;
+            nir_ssa_def_init(&add->instr, &add->dest.dest.ssa, 1, NULL);
+            nir_instr_insert_before(instr, &add->instr);
+
+            src.reg.indirect->is_ssa = true;
+            src.reg.indirect->ssa = &add->dest.dest.ssa;
+         }
+      }
+   }
+
+   return src;
+}
+
+static bool
+lower_locals_to_regs_block(nir_block *block, void *void_state)
+{
+   struct locals_to_regs_state *state = void_state;
+
+   nir_foreach_instr_safe(block, instr) {
+      if (instr->type != nir_instr_type_intrinsic)
+         continue;
+
+      nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+
+      switch (intrin->intrinsic) {
+      case nir_intrinsic_load_var_vec1:
+      case nir_intrinsic_load_var_vec2:
+      case nir_intrinsic_load_var_vec3:
+      case nir_intrinsic_load_var_vec4: {
+         if (intrin->variables[0]->var->data.mode != nir_var_local)
+            continue;
+
+         nir_alu_instr *mov = nir_alu_instr_create(state->mem_ctx, nir_op_imov);
+         mov->src[0].src = get_deref_reg_src(intrin->variables[0],
+                                             &intrin->instr, state);
+         unsigned num_components = mov->src[0].src.reg.reg->num_components;
+         mov->dest.write_mask = (1 << num_components) - 1;
+         if (intrin->dest.is_ssa) {
+            mov->dest.dest.is_ssa = true;
+            nir_ssa_def_init(&mov->instr, &mov->dest.dest.ssa,
+                             num_components, NULL);
+
+            nir_src new_src = {
+               .is_ssa = true,
+               .ssa = &mov->dest.dest.ssa,
+            };
+
+            nir_ssa_def_rewrite_uses(&intrin->dest.ssa, new_src,
+                                     state->mem_ctx);
+         } else {
+            mov->dest.dest = nir_dest_copy(intrin->dest, state->mem_ctx);
+         }
+         nir_instr_insert_before(&intrin->instr, &mov->instr);
+
+         nir_instr_remove(&intrin->instr);
+         break;
+      }
+
+      case nir_intrinsic_store_var_vec1:
+      case nir_intrinsic_store_var_vec2:
+      case nir_intrinsic_store_var_vec3:
+      case nir_intrinsic_store_var_vec4: {
+         if (intrin->variables[0]->var->data.mode != nir_var_local)
+            continue;
+
+         nir_src reg_src = get_deref_reg_src(intrin->variables[0],
+                                             &intrin->instr, state);
+         unsigned num_components = reg_src.reg.reg->num_components;
+
+         nir_alu_instr *mov = nir_alu_instr_create(state->mem_ctx, nir_op_imov);
+         mov->src[0].src = nir_src_copy(intrin->src[0], state->mem_ctx);
+         mov->dest.write_mask = (1 << 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_before(&intrin->instr, &mov->instr);
+
+         nir_instr_remove(&intrin->instr);
+         break;
+      }
+
+      case nir_intrinsic_copy_var:
+         unreachable("There should be no copies whatsoever at this point");
+         break;
+
+      default:
+         continue;
+      }
+   }
+
+   return true;
+}
+
+static void
+nir_lower_locals_to_regs_impl(nir_function_impl *impl)
+{
+   struct locals_to_regs_state state;
+
+   state.mem_ctx = ralloc_parent(impl);
+   state.impl = impl;
+   state.regs_table = _mesa_hash_table_create(NULL, hash_deref, derefs_equal);
+
+   nir_foreach_block(impl, lower_locals_to_regs_block, &state);
+
+   _mesa_hash_table_destroy(state.regs_table, NULL);
+}
+
+void
+nir_lower_locals_to_regs(nir_shader *shader)
+{
+   nir_foreach_overload(shader, overload) {
+      if (overload->impl)
+         nir_lower_locals_to_regs_impl(overload->impl);
+   }
+}