[Mesa-dev] [PATCH 094/133] nir: Add a pass to lower global variables to local variables

[Jason Ekstrand]

---
 src/glsl/Makefile.sources                     |   1 +
 src/glsl/nir/nir.h                            |   2 +
 src/glsl/nir/nir_lower_global_vars_to_local.c | 107 ++++++++++++++++++++++++++
 3 files changed, 110 insertions(+)
 create mode 100644 src/glsl/nir/nir_lower_global_vars_to_local.c

diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index 53c3e98..3f5c0bd 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_global_vars_to_local.c \
 	$(GLSL_SRCDIR)/nir/nir_lower_locals_to_regs.c \
 	$(GLSL_SRCDIR)/nir/nir_lower_io.c \
 	$(GLSL_SRCDIR)/nir/nir_lower_samplers.cpp \
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index ec9ce07..30146d6 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_global_vars_to_local(nir_shader *shader);
+
 void nir_lower_locals_to_regs(nir_shader *shader);
 
 void nir_lower_io(nir_shader *shader);
diff --git a/src/glsl/nir/nir_lower_global_vars_to_local.c b/src/glsl/nir/nir_lower_global_vars_to_local.c
new file mode 100644
index 0000000..ec23a0a
--- /dev/null
+++ b/src/glsl/nir/nir_lower_global_vars_to_local.c
@@ -0,0 +1,107 @@
+/*
+ * 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 at jlekstrand.net)
+ *
+ */
+
+/*
+ * This lowering pass detects when a global variable is only being used by
+ * one function and makes it local to that function
+ */
+
+#include "nir.h"
+
+struct global_to_local_state {
+   nir_function_impl *impl;
+   /* A hash table keyed on variable pointers that stores the unique
+    * nir_function_impl that uses the given variable.  If a variable is
+    * used in multiple functions, the data for the given key will be NULL.
+    */
+   struct hash_table *var_func_table;
+};
+
+static bool
+mark_global_var_uses_block(nir_block *block, void *void_state)
+{
+   struct global_to_local_state *state = void_state;
+
+   nir_foreach_instr(block, instr) {
+      if (instr->type != nir_instr_type_intrinsic)
+         continue;
+
+      nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+      unsigned num_vars = nir_intrinsic_infos[intrin->intrinsic].num_variables;
+
+      for (unsigned i = 0; i < num_vars; i++) {
+         nir_variable *var = intrin->variables[i]->var;
+         if (var->data.mode != nir_var_global)
+            continue;
+
+         uint32_t hash = _mesa_hash_pointer(var);
+         struct hash_entry *entry =
+            _mesa_hash_table_search(state->var_func_table, hash, var);
+
+         if (entry) {
+            if (entry->data != state->impl)
+               entry->data = NULL;
+         }
+
+         _mesa_hash_table_insert(state->var_func_table, hash, var, state->impl);
+      }
+   }
+
+   return true;
+}
+
+void
+nir_lower_global_vars_to_local(nir_shader *shader)
+{
+   struct global_to_local_state state;
+
+   state.var_func_table = _mesa_hash_table_create(NULL,
+                                                  _mesa_key_pointer_equal);
+
+   nir_foreach_overload(shader, overload) {
+      if (overload->impl) {
+         state.impl = overload->impl;
+         nir_foreach_block(overload->impl, mark_global_var_uses_block, &state);
+      }
+   }
+
+   struct hash_entry *entry;
+   hash_table_foreach(state.var_func_table, entry) {
+      nir_variable *var = (void *)entry->key;
+      nir_function_impl *impl = entry->data;
+
+      assert(var->data.mode == nir_var_global);
+
+      if (impl != NULL) {
+         exec_node_remove(&var->node);
+         var->data.mode = nir_var_local;
+         exec_list_push_tail(&impl->locals, &var->node);
+      }
+   }
+
+   _mesa_hash_table_destroy(state.var_func_table, NULL);
+}
-- 
2.2.0