Signed-off-by: Samuel Pitoiset <samuel.pitoi...@gmail.com>
---
src/compiler/nir/nir_opt_if.c | 87 +++++++++++++++++++++++++++++++++++
1 file changed, 87 insertions(+)
diff --git a/src/compiler/nir/nir_opt_if.c
b/src/compiler/nir/nir_opt_if.c
index bc128f79f3c..47a8a65aad3 100644
--- a/src/compiler/nir/nir_opt_if.c
+++ b/src/compiler/nir/nir_opt_if.c
@@ -890,6 +890,92 @@ opt_if_loop_last_continue(nir_loop *loop)
return true;
}
+/**
+ * This optimization allows to remove continue blocks by moving the
rest of the
+ * loop to the other side. This is only applied if continue blocks
are in the
+ * top-level control flow of the loop. This turns:
+ *
+ * if (cond) {
+ * ... code ...
+ * continue
+ * } else {
+ * }
+ * ... code ...
+ *
+ * into:
+ *
+ * if (cond) {
+ * ... code ...
+ * continue
+ * } else {
+ * ... code ...
+ * }
+ */
+static bool
+opt_if_loop_remove_continue(nir_loop *loop)
+{
+ nir_block *header_block = nir_loop_first_block(loop);
+ nir_block *bottom_block = nir_loop_last_block(loop);
+ nir_block *prev_block =
+ nir_cf_node_as_block(nir_cf_node_prev(&loop->cf_node));
+
+ /* It would be insane if this were not true */
+ assert(_mesa_set_search(header_block->predecessors, prev_block));
+
+ /* The loop must have, at least, two continue blocks (including
the normal
+ * continue at the end of loop).
+ */
+ if (header_block->predecessors->entries < 3)
+ return false;
+
+ /* Scan the control flow of the loop from the last to the first
node, and
+ * optimize when an if block contains a continue.
+ */
+ nir_cf_node *last_node = &bottom_block->cf_node;
+ nir_cf_node *first_node = &header_block->cf_node;
+
+ while (last_node != first_node) {
+ last_node = nir_cf_node_prev(last_node);
+ if (last_node->type != nir_cf_node_if)
+ continue;
+
+ nir_if *nif = nir_cf_node_as_if(last_node);
+ nir_block *then_block = nir_if_last_then_block(nif);
+
+ /* Nothing to do if the block isn't a continue block. */
+ nir_instr *instr = nir_block_last_instr(then_block);
+ if (!instr ||
+ instr->type != nir_instr_type_jump ||
+ nir_instr_as_jump(instr)->type != nir_jump_continue)
+ continue;
+
+ /* Get the block immediately following the if statement. */
+ nir_block *after_if_block =
+ nir_cf_node_as_block(nir_cf_node_next(&nif->cf_node));
+
+ /* Nothing to do if the block following the if statement is
empty. */
+ if (is_block_empty(after_if_block))
+ continue;
+
+ nir_cf_node *if_first_node = &after_if_block->cf_node;
+ nir_cf_node *if_last_node = &bottom_block->cf_node;
+ nir_block *else_block = nir_if_last_else_block(nif);
+
+ /* Move all nodes following the if statement to the last else
block, in
+ * case there is complicated control flow.
+ */
+ nir_cf_list tmp;
+ nir_cf_extract(&tmp, nir_before_cf_node(if_first_node),
+ nir_after_cf_node(if_last_node));
+ nir_cf_reinsert(&tmp, nir_after_block(else_block));
+ nir_cf_delete(&tmp);
+
+ return true;
+ }
+
+ return false;
+}
+
/* Walk all the phis in the block immediately following the if
statement and
* swap the blocks.
*/
@@ -1355,6 +1441,7 @@ opt_if_cf_list(nir_builder *b, struct exec_list
*cf_list)
progress |= opt_simplify_bcsel_of_phi(b, loop);
progress |= opt_peel_loop_initial_if(loop);
progress |= opt_if_loop_last_continue(loop);
+ progress |= opt_if_loop_remove_continue(loop);
break;
}
