3 files changed, 96 insertions, 9 deletions
diff --git a/src/passes/CodePushing.cpp b/src/passes/CodePushing.cpp
index 397a20bab..f4beff1a8 100644
--- a/src/passes/CodePushing.cpp
+++ b/src/passes/CodePushing.cpp
@@ -115,7 +115,14 @@ private:
     auto* set = curr->dynCast<SetLocal>();
     if (!set) return nullptr;
     auto index = set->index;
-    return analyzer.isSFA(index) && numGetsSoFar[index] == analyzer.getNumGets(index) ? set : nullptr;
+    // to be pushable, this must be SFA and the right # of gets,
+    // but also have no side effects, as it may not execute if pushed.
+    if (analyzer.isSFA(index) &&
+        numGetsSoFar[index] == analyzer.getNumGets(index) &&
+        !EffectAnalyzer(set->value).hasSideEffects()) {
+      return set;
+    }
+    return nullptr;
   }
 
   // Push past conditional control flow.
diff --git a/test/passes/code-pushing.txt b/test/passes/code-pushing.txt
index b8c496210..f09d0dfb5 100644
--- a/test/passes/code-pushing.txt
+++ b/test/passes/code-pushing.txt
@@ -342,15 +342,15 @@
     (local $x i32)
     (local $y i32)
     (block $out
-      (br_if $out
-        (i32.const 2)
-      )
       (set_local $x
         (call $push-dropped)
       )
       (set_local $y
         (call $push-dropped)
       )
+      (br_if $out
+        (i32.const 2)
+      )
       (drop
         (get_local $x)
       )
@@ -388,13 +388,13 @@
     (local $y i32)
     (block $out
       (set_local $x
-        (call $push-dropped)
+        (i32.const 1)
       )
       (br_if $out
         (i32.const 2)
       )
       (set_local $y
-        (call $push-dropped)
+        (i32.const 3)
       )
       (drop
         (get_local $x)
@@ -407,4 +407,54 @@
       (get_local $x)
     )
   )
+  (func $unpushed-ignorable-side-effect (type $0)
+    (local $x i32)
+    (local $y i32)
+    (block $out
+      (set_local $x
+        (call $push-dropped)
+      )
+      (br_if $out
+        (i32.const 2)
+      )
+      (set_local $y
+        (i32.const 3)
+      )
+      (drop
+        (get_local $x)
+      )
+      (drop
+        (get_local $y)
+      )
+    )
+  )
+  (func $unpushed-side-effect-into-drop (type $0)
+    (local $x i32)
+    (block $out
+      (set_local $x
+        (call $push-dropped)
+      )
+      (br_if $out
+        (i32.const 1)
+      )
+      (drop
+        (get_local $x)
+      )
+    )
+  )
+  (func $unpushed-side-effect-into-if (type $0)
+    (local $x i32)
+    (block $out
+      (set_local $x
+        (call $push-dropped)
+      )
+      (br_if $out
+        (i32.const 1)
+      )
+      (if
+        (get_local $x)
+        (nop)
+      )
+    )
+  )
 )
diff --git a/test/passes/code-pushing.wast b/test/passes/code-pushing.wast
index ca973e182..e1cb30f4a 100644
--- a/test/passes/code-pushing.wast
+++ b/test/passes/code-pushing.wast
@@ -179,7 +179,7 @@
       (drop (get_local $x))
     )
   )
-  (func $values-might-interfere ;; but don't, as we keep the order
+  (func $values-might-interfere ;; they don't, as we keep the order - but here their side effects prevent pushing
     (local $x i32)
     (local $y i32)
     (block $out
@@ -206,13 +206,43 @@
     (local $x i32)
     (local $y i32)
     (block $out
-      (set_local $x (call $push-dropped))
-      (set_local $y (call $push-dropped))
+      (set_local $x (i32.const 1))
+      (set_local $y (i32.const 3))
       (br_if $out (i32.const 2))
       (drop (get_local $x))
       (drop (get_local $y))
     )
     (drop (get_local $x)) ;; $x can't be pushed, but y doesn't care
   )
+  (func $unpushed-ignorable-side-effect
+    (local $x i32)
+    (local $y i32)
+    (block $out
+      (set_local $x (call $push-dropped)) ;; $x can't be pushed, but y doesn't care
+      (set_local $y (i32.const 3))
+      (br_if $out (i32.const 2))
+      (drop (get_local $x))
+      (drop (get_local $y))
+    )
+  )
+  (func $unpushed-side-effect-into-drop
+    (local $x i32)
+    (block $out
+      (set_local $x (call $push-dropped))
+      (br_if $out (i32.const 1))
+      (drop (get_local $x))
+    )
+  )
+  (func $unpushed-side-effect-into-if
+    (local $x i32)
+    (block $out
+      (set_local $x (call $push-dropped))
+      (br_if $out (i32.const 1))
+      (if
+        (get_local $x)
+        (nop)
+      )
+    )
+  )
 )