MergeBlocks: Optimize all dropped blocks (#6984)

Just call optimizeDroppedBlock from visitDrop to handle that.

Followup to #6982. This optimizes the new testcase added there. Some older
tests also improve.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/passes/MergeBlocks.cpp b/src/passes/MergeBlocks.cpp
index 401d2e629..12f67329d 100644
--- a/src/passes/MergeBlocks.cpp
+++ b/src/passes/MergeBlocks.cpp
@@ -434,6 +434,15 @@ struct MergeBlocks
     optimizeBlock(curr, getModule(), getPassOptions(), branchInfo);
   }
 
+  void visitDrop(Drop* curr) {
+    if (auto* block = curr->value->dynCast<Block>()) {
+      if (optimizeDroppedBlock(
+            curr, block, *getModule(), getPassOptions(), branchInfo)) {
+        replaceCurrent(block);
+      }
+    }
+  }
+
   // given
   // (curr
   //  (block=child