diff --git a/lib/compress.js b/lib/compress.js
index 2bc1c5a5..6e125e47 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -138,13 +138,15 @@ merge(Compressor.prototype, {
     },
     before: function(node, descend, in_list) {
         if (node._squeezed) return node;
-        var was_scope = false;
+        // asm.js: drop unused only, leave everything else as is inside "use asm" scope
+        var asm = this.has_directive("use asm"),
+            was_scope = false;
         if (node instanceof AST_Scope) {
-            node = node.hoist_declarations(this);
+            if (!asm) node = node.hoist_declarations(this);
             was_scope = true;
         }
         descend(node, this);
-        node = node.optimize(this);
+        if (!asm) node = node.optimize(this);
         if (was_scope && node instanceof AST_Scope) {
             node.drop_unused(this);
             descend(node, this);
@@ -1384,6 +1386,15 @@ merge(Compressor.prototype, {
         def(AST_Constant, return_false);
         def(AST_This, return_false);
 
+        // asm.js: `new stdlib.XYZ` inside "use asm" scope are always pure
+        def(AST_New, function(compressor){
+            if (compressor.has_directive("use asm")) return false;
+            // AST_Call fallback
+            var pure = compressor.option("pure_funcs");
+            if (!pure) return true;
+            return pure.indexOf(this.expression.print_to_string()) < 0;
+        });
+
         def(AST_Call, function(compressor){
             if (!this.has_pure_annotation(compressor) && compressor.pure_funcs(this)) return true;
             for (var i = this.args.length; --i >= 0;) {
diff --git a/lib/scope.js b/lib/scope.js
index 29e4103a..7c083a69 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -289,6 +289,14 @@ AST_Scope.DEFMETHOD("def_variable", function(symbol){
 
 AST_Scope.DEFMETHOD("next_mangled", function(options){
     var ext = this.enclosed;
+
+    // asm.js: don't mask module-scope names
+    var asm = this.has_directive("use asm"),
+        pasm = this.parent_scope ? this.parent_scope.has_directive("use asm") : false;
+    if (pasm) {
+        this.cname = this.parent_scope.cname;
+    }
+
     out: while (true) {
         var m = base54(++this.cname);
         if (!is_identifier(m)) continue; // skip over "do"
@@ -297,6 +305,21 @@ AST_Scope.DEFMETHOD("next_mangled", function(options){
         // shadow a name excepted from mangling.
         if (options.except.indexOf(m) >= 0) continue;
 
+        // asm.js: don't reuse module name although it is out of the current scope
+        if (asm) {
+            var sym = this.name;
+            var penc = this.parent_scope.enclosed;
+            if (sym && penc.length) {
+                for (var i = 0; i < penc.length; i++) {
+                    var psym = penc[i];
+                    if (sym.name == psym.name) {
+                        var name = psym.mangled_name || (psym.unmangleable(options) && psym.name);
+                        if (m == name) continue out;
+                    }
+                }
+            }
+        }
+
         // we must ensure that the mangled name does not shadow a name
         // from some parent scope that is referenced in this or in
         // inner scopes.