handle an unreachable condition properly in vacuum if simplification

1 files changed, 6 insertions, 0 deletions

diff --git a/src/passes/Vacuum.cpp b/src/passes/Vacuum.cpp
index 40f4a6e59..0178a794d 100644
--- a/src/passes/Vacuum.cpp
+++ b/src/passes/Vacuum.cpp
@@ -232,6 +232,12 @@ struct Vacuum : public WalkerPass<PostWalker<Vacuum>> {
       replaceCurrent(child);
       return;
     }
+    // if the condition is unreachable, just return it
+    if (curr->condition->type == unreachable) {
+      replaceCurrent(curr->condition);
+      return;
+    }
+    // from here on, we can assume the condition executed
     if (curr->ifFalse) {
       if (curr->ifFalse->is<Nop>()) {
         curr->ifFalse = nullptr;