Bysyncify: fix skipping of flattened if condition (#2187)

We assigned it to a local, but didn't run maybeSkip on it. As a result, it was executed during rewinding, which broke restoring the saved value.

Found by the fuzzer.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/passes/Bysyncify.cpp b/src/passes/Bysyncify.cpp
index 416869194..5e2f73e5c 100644
--- a/src/passes/Bysyncify.cpp
+++ b/src/passes/Bysyncify.cpp
@@ -658,7 +658,10 @@ private:
         return iff;
       }
       auto conditionTemp = builder->addVar(func, i32);
-      iff->condition = builder->makeLocalTee(conditionTemp, iff->condition);
+      // TODO: can avoid pre if the condition is a get or a const
+      auto* pre =
+        makeMaybeSkip(builder->makeLocalSet(conditionTemp, iff->condition));
+      iff->condition = builder->makeLocalGet(conditionTemp, i32);
       iff->condition = builder->makeBinary(
         OrInt32, iff->condition, builder->makeStateCheck(State::Rewinding));
       iff->ifTrue = process(iff->ifTrue);
@@ -674,7 +677,7 @@ private:
           builder->makeStateCheck(State::Rewinding)),
         process(otherArm));
       otherIf->finalize();
-      return builder->makeSequence(iff, otherIf);
+      return builder->makeBlock({pre, iff, otherIf});
     } else if (auto* loop = curr->dynCast<Loop>()) {
       loop->body = process(loop->body);
       return loop;