From 68bf64141dc4d35e6ff174fb68ce5bc50ff27c79 Mon Sep 17 00:00:00 2001
From: Alon Zakai <alonzakai@gmail.com>
Date: Sat, 29 Oct 2016 11:02:28 -0700
Subject: fix break value removal in merge-blocks: a br_if's type changes
 without a value, so finalize the node, and remove the drop

---
 src/passes/MergeBlocks.cpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/passes/MergeBlocks.cpp b/src/passes/MergeBlocks.cpp
index f7fac9594..edfa1336b 100644
--- a/src/passes/MergeBlocks.cpp
+++ b/src/passes/MergeBlocks.cpp
@@ -116,8 +116,17 @@ struct BreakValueDropper : public ControlFlowWalker<BreakValueDropper, Visitor<B
   void visitBreak(Break* curr) {
     if (curr->value && curr->name == origin) {
       Builder builder(*getModule());
-      replaceCurrent(builder.makeSequence(builder.makeDrop(curr->value), curr));
+      auto* value = curr->value;
       curr->value = nullptr;
+      curr->finalize();
+      replaceCurrent(builder.makeSequence(builder.makeDrop(value), curr));
+    }
+  }
+
+  void visitDrop(Drop* curr) {
+    // if we dropped a br_if whose value we removed, then we are now dropping a (block (drop value) (br_if)) with type none, which does not need a drop
+    if (curr->value->type == none) {
+      replaceCurrent(curr->value);
     }
   }
 };
-- 
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