only remove seq|0 when seq is an assign value

2 files changed, 14 insertions, 11 deletions

diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index 57a3b1b3..89f65eda 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -539,16 +539,19 @@ function simplifyExpressionsPre(ast) {
             }
           }
         }
-      } else if (type == 'binary' && node[1] == '|') {
-        // canonicalize order of |0 to end
-        if (node[2][0] == 'num' && node[2][1] == 0) {
-          var temp = node[2];
-          node[2] = node[3];
-          node[3] = temp;
-        }
-        // if a seq ends in an |0, remove an external |0
-        if (node[2][0] == 'seq' && node[2][2][0] == 'binary' && node[2][2][1] in USEFUL_BINARY_OPS) {
-          return node[2];
+        var value = node[3];
+        if (value[0] == 'binary' && value[1] == '|') {
+          // canonicalize order of |0 to end
+          if (value[2][0] == 'num' && value[2][1] == 0) {
+            var temp = value[2];
+            value[2] = value[3];
+            value[3] = temp;
+          }
+          // if a seq ends in an |0, remove an external |0
+          // note that it is only safe to do this in assigns, like we are doing here (return (x, y|0); is not valid)
+          if (value[2][0] == 'seq' && value[2][2][0] == 'binary' && value[2][2][1] in USEFUL_BINARY_OPS) {
+            node[3] = value[2];
+          }
         }
       }
     });
diff --git a/tools/test-js-optimizer-asm-pre-output.js b/tools/test-js-optimizer-asm-pre-output.js
index a41ba2f8..25d521ab 100644
--- a/tools/test-js-optimizer-asm-pre-output.js
+++ b/tools/test-js-optimizer-asm-pre-output.js
@@ -8,7 +8,7 @@ function a() {
   HEAP[1024] = 5;
   whee(12, 13);
   whee(12, 13);
-  f((g = t(), g + g | 0));
+  f((g = t(), g + g | 0) | 0);
 }
 function b($this, $__n) {
   $this = $this | 0;