From 2de466331a586746c8db9136a43ee6c1f4bc01f9 Mon Sep 17 00:00:00 2001
From: alexlamsl <alexlamsl@gmail.com>
Date: Fri, 16 Jun 2017 15:37:37 +0800
Subject: [PATCH] in-place `eliminate_spurious_blocks()`

---
 lib/compress.js | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index 3231ffc2..944ad5db 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -668,7 +668,7 @@ merge(Compressor.prototype, {
         var CHANGED, max_iter = 10;
         do {
             CHANGED = false;
-            statements = eliminate_spurious_blocks(statements);
+            eliminate_spurious_blocks(statements);
             if (compressor.option("dead_code")) {
                 eliminate_dead_code(statements, compressor);
             }
@@ -890,25 +890,27 @@ merge(Compressor.prototype, {
 
         function eliminate_spurious_blocks(statements) {
             var seen_dirs = [];
-            return statements.reduce(function(a, stat){
+            for (var i = 0; i < statements.length;) {
+                var stat = statements[i];
                 if (stat instanceof AST_BlockStatement) {
                     CHANGED = true;
-                    a.push.apply(a, eliminate_spurious_blocks(stat.body));
+                    eliminate_spurious_blocks(stat.body);
+                    [].splice.apply(statements, [i, 1].concat(stat.body));
+                    i += stat.body.length;
                 } else if (stat instanceof AST_EmptyStatement) {
                     CHANGED = true;
+                    statements.splice(i, 1);
                 } else if (stat instanceof AST_Directive) {
                     if (seen_dirs.indexOf(stat.value) < 0) {
-                        a.push(stat);
+                        i++;
                         seen_dirs.push(stat.value);
                     } else {
                         CHANGED = true;
+                        statements.splice(i, 1);
                     }
-                } else {
-                    a.push(stat);
-                }
-                return a;
-            }, []);
-        };
+                } else i++;
+            }
+        }
 
         function handle_if_return(statements, compressor) {
             var self = compressor.self();