nir: Add a loop analysis pass

[mesa.git] / src / compiler / nir / nir_loop_analyze.h

diff --git a/src/compiler/nir/nir_loop_analyze.h b/src/compiler/nir/nir_loop_analyze.h
new file mode 100644 (file)
index 0000000..b7f862e
--- /dev/null
+++ b/src/compiler/nir/nir_loop_analyze.h
@@ -0,0 +1,92 @@
+/*
+ * Copyright © 2016 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.
+ */
+
+#pragma once
+
+#include "nir.h"
+
+/* Returns true if nir_cf_node contains a jump other than the expected_jump
+ * parameter.
+ */
+static inline bool
+contains_other_jump(nir_cf_node *node, nir_instr *expected_jump)
+{
+   switch (node->type) {
+   case nir_cf_node_block: {
+      nir_instr *lst_instr = nir_block_last_instr(nir_cf_node_as_block(node));
+
+      /* dead_cf should have eliminated any instruction after the first break
+       */
+      nir_foreach_instr(instr, nir_cf_node_as_block(node))
+         assert(instr->type != nir_instr_type_jump || instr == lst_instr);
+
+      if (lst_instr && lst_instr->type == nir_instr_type_jump &&
+          lst_instr != expected_jump)
+         return true;
+      else
+         return false;
+   }
+   case nir_cf_node_if: {
+      nir_if *if_stmt = nir_cf_node_as_if(node);
+
+      foreach_list_typed_safe(nir_cf_node, node, node, &if_stmt->then_list) {
+         if (contains_other_jump(node, expected_jump))
+            return true;
+      }
+
+      foreach_list_typed_safe(nir_cf_node, node, node, &if_stmt->else_list) {
+         if (contains_other_jump(node, expected_jump))
+            return true;
+      }
+
+      return false;
+   }
+   case nir_cf_node_loop:
+      return true;
+
+   default:
+      unreachable("Unhandled cf node type");
+   }
+}
+
+/* Here we define a trivial if as containing only a single break that must be
+ * located at the end of either the then or else branch of the top level if,
+ * there must be no other breaks or any other type of jump.  Or we pass NULL
+ * to break_block the if must contains no jumps at all.
+ */
+static inline bool
+nir_is_trivial_loop_if(nir_if *nif, nir_block *break_block)
+{
+   nir_instr *last_instr = NULL;
+
+   if (break_block) {
+      last_instr = nir_block_last_instr(break_block);
+      assert(last_instr && last_instr->type == nir_instr_type_jump &&
+             nir_instr_as_jump(last_instr)->type == nir_jump_break);
+   }
+
+   if (contains_other_jump(&nif->cf_node, last_instr))
+      return false;
+
+   return true;
+}