fix vacuum big where we changed an unreachable node to a nop (#728)

3 files changed, 24 insertions, 1 deletions

diff --git a/src/passes/Vacuum.cpp b/src/passes/Vacuum.cpp
index c3fed2328..8d9bb421c 100644
--- a/src/passes/Vacuum.cpp
+++ b/src/passes/Vacuum.cpp
@@ -177,7 +177,11 @@ struct Vacuum : public WalkerPass<ExpressionStackWalker<Vacuum, Visitor<Vacuum>>
         if (isConcreteWasmType(curr->type) || EffectAnalyzer(list[0]).hasSideEffects()) {
           replaceCurrent(list[0]);
         } else {
-          ExpressionManipulator::nop(curr);
+          if (curr->type == unreachable) {
+            ExpressionManipulator::convert<Block, Unreachable>(curr);
+          } else {
+            ExpressionManipulator::nop(curr);
+          }
         }
       } else if (list.size() == 0) {
         ExpressionManipulator::nop(curr);
diff --git a/test/passes/remove-unused-names_vacuum.txt b/test/passes/remove-unused-names_vacuum.txt
new file mode 100644
index 000000000..3819fcbec
--- /dev/null
+++ b/test/passes/remove-unused-names_vacuum.txt
@@ -0,0 +1,8 @@
+(module
+  (memory $0 0)
+  (type $0 (func (result i32)))
+  (func $return-i32-but-body-is-unreachable3 (type $0) (result i32)
+    (local $label i32)
+    (unreachable)
+  )
+)
diff --git a/test/passes/remove-unused-names_vacuum.wast b/test/passes/remove-unused-names_vacuum.wast
new file mode 100644
index 000000000..04b08c332
--- /dev/null
+++ b/test/passes/remove-unused-names_vacuum.wast
@@ -0,0 +1,11 @@
+(module
+  (func $return-i32-but-body-is-unreachable3 (result i32)
+    (local $label i32)
+    (block ;; without a name here, vaccum had a too-eager bug
+      (loop $while-in$1
+        (br $while-in$1)
+      )
+    )
+  )
+)
+