3 files changed, 46 insertions, 0 deletions
diff --git a/src/passes/Vacuum.cpp b/src/passes/Vacuum.cpp
index 12565f603..dd88fa0eb 100644
--- a/src/passes/Vacuum.cpp
+++ b/src/passes/Vacuum.cpp
@@ -21,6 +21,7 @@
 #include <wasm.h>
 #include <pass.h>
 #include <ast_utils.h>
+#include <wasm-builder.h>
 
 namespace wasm {
 
@@ -62,6 +63,25 @@ struct Vacuum : public WalkerPass<PostWalker<Vacuum, Visitor<Vacuum>>> {
       }
     }
   }
+
+  void visitIf(If* curr) {
+    if (curr->ifFalse) {
+      if (curr->ifFalse->is<Nop>()) {
+        curr->ifFalse = nullptr;
+      } else if (curr->ifTrue->is<Nop>()) {
+        curr->ifTrue = curr->ifFalse;
+        curr->ifFalse = nullptr;
+        curr->condition = Builder(*getModule()).makeUnary(EqZ, curr->condition, curr->condition->type);
+      }
+    }
+    if (!curr->ifFalse) {
+      // no else
+      if (curr->ifTrue->is<Nop>()) {
+        // no nothing
+        replaceCurrent(curr->condition);
+      }
+    }
+  }
 };
 
 static RegisterPass<Vacuum> registerPass("vacuum", "removes obviously unneeded code");
diff --git a/test/passes/vacuum.txt b/test/passes/vacuum.txt
index 103dbc6bc..d604cfa08 100644
--- a/test/passes/vacuum.txt
+++ b/test/passes/vacuum.txt
@@ -16,5 +16,16 @@
         (i32.const 57)
       )
     )
+    (if
+      (i32.eqz
+        (i32.const 100)
+      )
+      (i32.const 101)
+    )
+    (if
+      (i32.const 102)
+      (i32.const 103)
+    )
+    (i32.const 104)
   )
 )
diff --git a/test/passes/vacuum.wast b/test/passes/vacuum.wast
index a0c638eb8..28125b969 100644
--- a/test/passes/vacuum.wast
+++ b/test/passes/vacuum.wast
@@ -23,6 +23,21 @@
       )
       (i32.const 58)
     )
+    (if
+      (i32.const 100)
+      (nop)
+      (i32.const 101)
+    )
+    (if
+      (i32.const 102)
+      (i32.const 103)
+      (nop)
+    )
+    (if
+      (i32.const 104)
+      (nop)
+      (nop)
+    )
   )
 )