[Wasm GC] Fix CFG traversal of call_ref and add missing validation check (#4690)

We were missing CallRef in the CFG traversal code in a place where we
note possible exceptions. As a result we thought CallRef cannot throw, and
were missing some control flow edges.

To actually detect the problem, we need to validate non-nullable locals
properly, which we were not doing. This adds that as well.

3 files changed, 60 insertions, 0 deletions

diff --git a/test/lit/validation/nn-locals-bad-call_ref.wast b/test/lit/validation/nn-locals-bad-call_ref.wast
new file mode 100644
index 000000000..357409eef
--- /dev/null
+++ b/test/lit/validation/nn-locals-bad-call_ref.wast
@@ -0,0 +1,31 @@
+;; Test for validation of non-nullable locals
+
+;; RUN: not wasm-opt -all --enable-gc-nn-locals %s 2>&1 | filecheck %s
+
+;; CHECK: non-nullable local must not read null
+
+(module
+  (tag $tag (param i32))
+  (func $func
+    (local $0 (ref any))
+    (try
+      (do
+        (call_ref
+          (ref.func $func)
+        )
+      )
+      (catch $tag
+        (drop
+          (pop (i32))
+        )
+        ;; The path to here is from a possible exception thrown in the call_ref.
+        ;; This is a regression test for call_ref not being seen as possibly
+        ;; throwing. We should see a validation error here, as the local.get is
+        ;; of a null default, and it *is* reachable thanks to the call_ref.
+        (drop
+          (local.get $0)
+        )
+      )
+    )
+  )
+)
diff --git a/test/lit/validation/nn-locals-bad.wast b/test/lit/validation/nn-locals-bad.wast
new file mode 100644
index 000000000..17a5c1404
--- /dev/null
+++ b/test/lit/validation/nn-locals-bad.wast
@@ -0,0 +1,15 @@
+;; Test for validation of non-nullable locals
+
+;; RUN: not wasm-opt -all --enable-gc-nn-locals %s 2>&1 | filecheck %s
+
+;; CHECK: non-nullable local must not read null
+
+(module
+  (func $foo
+    (local $nn (ref any))
+    ;; It is not ok to read a non-nullable local.
+    (drop
+      (local.get $nn)
+    )
+  )
+)
diff --git a/test/lit/validation/nn-locals-ok.wast b/test/lit/validation/nn-locals-ok.wast
new file mode 100644
index 000000000..1dfd20962
--- /dev/null
+++ b/test/lit/validation/nn-locals-ok.wast
@@ -0,0 +1,14 @@
+;; Test for validation of non-nullable locals
+
+;; RUN: wasm-opt -all --enable-gc-nn-locals %s --print | filecheck %s
+
+;; CHECK: (module
+
+(module
+  (func $foo (param $nn (ref any))
+    ;; It is ok to read a non-nullable param.
+    (drop
+      (local.get $nn)
+    )
+  )
+)