Fix reuse of constant nodes in Precompute (#2764)

Previously we tried to reuse `Const` node if a precomputed value is a
constant node. But now we have two more kinds of constant node
(`RefNull` and `RefFunc`), so we shouldn't reuse them interchangeably,
meaning we shouldn't try to reuse a `Const` node when the value at hand
is a `RefNull`. This correctly checks the type of node and tries to
reuse only if the types of nodes match.

Fixes #2759.

1 files changed, 73 insertions, 0 deletions

diff --git a/test/passes/precompute_all-features.wast b/test/passes/precompute_all-features.wast
index da755bde6..2a59ea290 100644
--- a/test/passes/precompute_all-features.wast
+++ b/test/passes/precompute_all-features.wast
@@ -381,4 +381,77 @@
   (func $reftype-test (result nullref)
     (ref.null)
   )
+
+  ;; Check if constant nodes (const, ref.null, and ref.func) are correctly
+  ;; reused. (We shouldn't reuse a const node for something like ref.null, which
+  ;; will incorrectly cause an expression like 'nullref.const'.)
+  (func $dummy)
+  (func $br_reuse_node
+   (drop
+    (block $l0 (result f32)
+     (drop
+      (block $l1 (result i32)
+       (global.set $global-mut
+        (i32.const 1)
+       )
+       (br_if $l1
+        (i32.const 1)
+        (f32.lt
+         (br_if $l0
+          (f32.const 3.5)
+          (i32.const 1)
+         )
+         (f32.const 3)
+        )
+       )
+      )
+     )
+     (f32.const 0)
+    )
+   )
+
+   (drop
+    (block $l2 (result nullref)
+     (drop
+      (block $l3 (result i32)
+       (global.set $global-mut
+        (i32.const 1)
+       )
+       (br_if $l3
+        (i32.const 1)
+        (ref.is_null
+         (br_if $l2
+          (ref.null)
+          (i32.const 3)
+         )
+        )
+       )
+      )
+     )
+     (ref.null)
+    )
+   )
+
+   (drop
+    (block $l4 (result funcref)
+     (drop
+      (block $l5 (result i32)
+       (global.set $global-mut
+        (i32.const 1)
+       )
+       (br_if $l5
+        (i32.const 1)
+        (ref.is_null
+         (br_if $l4
+          (ref.func $dummy)
+          (i32.const 3)
+         )
+        )
+       )
+      )
+     )
+     (ref.null)
+    )
+   )
+  )
 )