nir: Add a deref path helper struct

This commit introduces a new nir_deref.h header for helpers that are
less common and really only needed by a few heavy-duty passes.  In this
header is a new struct for representing a full deref path which can be
walked in either direction.

v2 (Jason Ekstrand):
 - Assert that deref != NULL (Caio)
 - Fill _short_path with 0xdeadbeef in debug builds when not used (Caio)
 - Make nir_deref_path a typedef (Rob)

Reviewed-by: Caio Marcelo de Oliveira Filho <[email protected]>
Acked-by: Rob Clark <[email protected]>
Acked-by: Bas Nieuwenhuizen <[email protected]>
Acked-by: Dave Airlie <[email protected]>
Reviewed-by: Kenneth Graunke <[email protected]>

1 files changed, 55 insertions, 0 deletions

diff --git a/src/compiler/nir/nir_deref.h b/src/compiler/nir/nir_deref.h
new file mode 100644
index 00000000000..0980bae7215
--- /dev/null
+++ b/src/compiler/nir/nir_deref.h
@@ -0,0 +1,55 @@
+/*
+ * 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.
+ */
+
+#ifndef NIR_DEREF_H
+#define NIR_DEREF_H
+
+#include "nir.h"
+#include "nir_builder.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct {
+   /** Short path so we can keep it on the stack most of the time. */
+   nir_deref_instr *_short_path[7];
+
+   /** A null-terminated array view of a deref chain
+    *
+    * The first element of this array will be the variable dereference
+    * followed by every deref_instr on the path to the final one.  The last
+    * element in the array is a NULL pointer which acts as a terminator.
+    */
+   nir_deref_instr **path;
+} nir_deref_path;
+
+void nir_deref_path_init(nir_deref_path *path,
+                         nir_deref_instr *deref, void *mem_ctx);
+void nir_deref_path_finish(nir_deref_path *path);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* NIR_DEREF_H */