From 96ae0dda155b47299245a89e6a68fbb97ccda33f Mon Sep 17 00:00:00 2001
From: Alon Zakai <alonzakai@gmail.com>
Date: Tue, 6 Sep 2016 16:44:50 -0700
Subject: optimize out a set of a get of a global

---
 src/passes/OptimizeInstructions.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'src')

diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 003d2ff60..2315b9e8e 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -24,6 +24,7 @@
 #include <pass.h>
 #include <wasm-s-parser.h>
 #include <support/threads.h>
+#include <ast_utils.h>
 
 namespace wasm {
 
@@ -208,6 +209,13 @@ struct OptimizeInstructions : public WalkerPass<PostWalker<OptimizeInstructions,
           }
         }
       }
+    } else if (auto* set = curr->dynCast<SetGlobal>()) {
+      // optimize out a set of a get
+      auto* get = set->value->dynCast<GetGlobal>();
+      if (get && get->name == set->name) {
+        ExpressionManipulator::nop(curr);
+        return curr;
+      }
     }
     return nullptr;
   }
-- 
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