1 files changed, 42 insertions, 0 deletions
diff --git a/third_party/rust/naga/src/proc/terminator.rs b/third_party/rust/naga/src/proc/terminator.rs
new file mode 100644
index 0000000000..5915616cc5
--- /dev/null
+++ b/third_party/rust/naga/src/proc/terminator.rs
@@ -0,0 +1,42 @@
+/// Ensure that the given block has return statements
+/// at the end of its control flow.
+///
+/// Note: we don't want to blindly append a return statement
+/// to the end, because it may be either redundant or invalid,
+/// e.g. when the user already has returns in if/else branches.
+pub fn ensure_block_returns(block: &mut crate::Block) {
+    use crate::Statement as S;
+    match block.last_mut() {
+        Some(&mut S::Block(ref mut b)) => {
+            ensure_block_returns(b);
+        }
+        Some(&mut S::If {
+            condition: _,
+            ref mut accept,
+            ref mut reject,
+        }) => {
+            ensure_block_returns(accept);
+            ensure_block_returns(reject);
+        }
+        Some(&mut S::Switch {
+            selector: _,
+            ref mut cases,
+        }) => {
+            for case in cases.iter_mut() {
+                if !case.fall_through {
+                    ensure_block_returns(&mut case.body);
+                }
+            }
+        }
+        Some(&mut (S::Emit(_) | S::Break | S::Continue | S::Return { .. } | S::Kill)) => (),
+        Some(
+            &mut (S::Loop { .. }
+            | S::Store { .. }
+            | S::ImageStore { .. }
+            | S::Call { .. }
+            | S::Atomic { .. }
+            | S::Barrier(_)),
+        )
+        | None => block.push(S::Return { value: None }, Default::default()),
+    }
+}