[Mesa-dev] [PATCH 16/21] nir/cf: add a cursor structure

[Connor Abbott]

For now, it allows us to refactor the control flow insertion API's so
that there's a single entrypoint (with some wrappers). More importantly,
it will allow us to reduce the combinatorial explosion in the extract
function. There, we need to specify two points to extract, which may be
at the beginning of a block, the end of a block, or in the middle of a
block. And then there are various wrappers based off of that (before a
control flow node, before a control flow list, etc.). Rather than having
9 different functions, we can have one function and push the actual
logic of determining which variant to use down to the split function,
which will be shared with nir_cf_node_insert().

In the future, we may want to make the instruction insertion API's as
well as the builder use this, but that's a future cleanup.

Signed-off-by: Connor Abbott <connor.w.abbott at intel.com>
---
 src/glsl/nir/nir_control_flow.h | 91 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/src/glsl/nir/nir_control_flow.h b/src/glsl/nir/nir_control_flow.h
index 20cd2bf..407b258 100644
--- a/src/glsl/nir/nir_control_flow.h
+++ b/src/glsl/nir/nir_control_flow.h
@@ -39,6 +39,97 @@ extern "C" {
  * while maintaining the invariants checked by the validator, much easier.
  */
 
+/* Helper struct for representing a point to extract/insert. Helps reduce the
+ * combinatorial explosion of possible points to extract.
+ */
+
+typedef enum {
+   nir_cursor_before_block,
+   nir_cursor_after_block,
+   nir_cursor_before_instr,
+   nir_cursor_after_instr,
+} nir_cursor_option;
+
+typedef struct {
+   nir_cursor_option option;
+   union {
+      nir_block *block;
+      nir_instr *instr;
+   };
+} nir_cursor;
+
+static inline nir_cursor
+nir_before_block(nir_block *block)
+{
+   nir_cursor cursor;
+   cursor.option = nir_cursor_before_block;
+   cursor.block = block;
+   return cursor;
+}
+
+static inline nir_cursor
+nir_after_block(nir_block *block)
+{
+   nir_cursor cursor;
+   cursor.option = nir_cursor_after_block;
+   cursor.block = block;
+   return cursor;
+}
+
+static inline nir_cursor
+nir_before_instr(nir_instr *instr)
+{
+   nir_cursor cursor;
+   cursor.option = nir_cursor_before_instr;
+   cursor.instr = instr;
+   return cursor;
+}
+
+static inline nir_cursor
+nir_after_instr(nir_instr *instr)
+{
+   nir_cursor cursor;
+   cursor.option = nir_cursor_after_instr;
+   cursor.instr = instr;
+   return cursor;
+}
+
+static inline nir_cursor
+nir_before_cf_node(nir_cf_node *node)
+{
+   if (node->type == nir_cf_node_block)
+      return nir_before_block(nir_cf_node_as_block(node));
+
+   return nir_after_block(nir_cf_node_as_block(nir_cf_node_prev(node)));
+}
+
+static inline nir_cursor
+nir_after_cf_node(nir_cf_node *node)
+{
+   if (node->type == nir_cf_node_block)
+      return nir_after_block(nir_cf_node_as_block(node));
+
+   return nir_before_block(nir_cf_node_as_block(nir_cf_node_next(node)));
+}
+
+static inline nir_cursor
+nir_before_cf_list(struct exec_list *cf_list)
+{
+   nir_cf_node *first_node = exec_node_data(nir_cf_node,
+                                            exec_list_get_head(cf_list), node);
+   return nir_before_cf_node(first_node);
+}
+
+static inline nir_cursor
+nir_after_cf_list(struct exec_list *cf_list)
+{
+   nir_cf_node *last_node = exec_node_data(nir_cf_node,
+                                           exec_list_get_tail(cf_list), node);
+   return nir_after_cf_node(last_node);
+}
+
+/** Control flow insertion. */
+
 /** puts a control flow node immediately after another control flow node */
 void nir_cf_node_insert_after(nir_cf_node *node, nir_cf_node *after);
 
-- 
2.4.3