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-rw-r--r--src/compiler/nir/nir_lower_returns.c47
1 files changed, 41 insertions, 6 deletions
diff --git a/src/compiler/nir/nir_lower_returns.c b/src/compiler/nir/nir_lower_returns.c
index cf49d5b09e3..33490b223b4 100644
--- a/src/compiler/nir/nir_lower_returns.c
+++ b/src/compiler/nir/nir_lower_returns.c
@@ -30,6 +30,13 @@ struct lower_returns_state {
struct exec_list *cf_list;
nir_loop *loop;
nir_variable *return_flag;
+
+ /* This indicates that we have a return which is predicated on some form of
+ * control-flow. Since whether or not the return happens can only be
+ * determined dynamically at run-time, everything that occurs afterwards
+ * needs to be predicated on the return flag variable.
+ */
+ bool has_predicated_return;
};
static bool lower_returns_in_cf_list(struct exec_list *cf_list,
@@ -82,8 +89,10 @@ lower_returns_in_loop(nir_loop *loop, struct lower_returns_state *state)
* flag set to true. We need to predicate everything following the loop
* on the return flag.
*/
- if (progress)
+ if (progress) {
predicate_following(&loop->cf_node, state);
+ state->has_predicated_return = true;
+ }
return progress;
}
@@ -91,10 +100,14 @@ lower_returns_in_loop(nir_loop *loop, struct lower_returns_state *state)
static bool
lower_returns_in_if(nir_if *if_stmt, struct lower_returns_state *state)
{
- bool progress;
+ bool progress, then_progress, else_progress;
+
+ bool has_predicated_return = state->has_predicated_return;
+ state->has_predicated_return = false;
- progress = lower_returns_in_cf_list(&if_stmt->then_list, state);
- progress = lower_returns_in_cf_list(&if_stmt->else_list, state) || progress;
+ then_progress = lower_returns_in_cf_list(&if_stmt->then_list, state);
+ else_progress = lower_returns_in_cf_list(&if_stmt->else_list, state);
+ progress = then_progress || else_progress;
/* If either of the recursive calls made progress, then there were
* returns inside of the body of the if. If we're in a loop, then these
@@ -106,8 +119,29 @@ lower_returns_in_if(nir_if *if_stmt, struct lower_returns_state *state)
* after a return, we need to predicate everything following on the
* return flag.
*/
- if (progress && !state->loop)
- predicate_following(&if_stmt->cf_node, state);
+ if (progress && !state->loop) {
+ if (state->has_predicated_return) {
+ predicate_following(&if_stmt->cf_node, state);
+ } else {
+ /* If there are no nested returns we can just add the instructions to
+ * the end of the branch that doesn't have the return.
+ */
+ nir_cf_list list;
+ nir_cf_extract(&list, nir_after_cf_node(&if_stmt->cf_node),
+ nir_after_cf_list(state->cf_list));
+
+ if (then_progress && else_progress) {
+ /* Both branches return so delete instructions following the if */
+ nir_cf_delete(&list);
+ } else if (then_progress) {
+ nir_cf_reinsert(&list, nir_after_cf_list(&if_stmt->else_list));
+ } else {
+ nir_cf_reinsert(&list, nir_after_cf_list(&if_stmt->then_list));
+ }
+ }
+ }
+
+ state->has_predicated_return = progress || has_predicated_return;
return progress;
}
@@ -221,6 +255,7 @@ nir_lower_returns_impl(nir_function_impl *impl)
state.cf_list = &impl->body;
state.loop = NULL;
state.return_flag = NULL;
+ state.has_predicated_return = false;
nir_builder_init(&state.builder, impl);
bool progress = lower_returns_in_cf_list(&impl->body, &state);