Add proper support for "use asm"; blocks. Disable -c optimization within "use asm"; sections and preserve floating point literals in their original form. Non-asm.js sections are optimized as before. Asm.js sections can still be mangled and minified of whitespace. No special command line flags are required.

bin/uglifyjs

@@ -401,7 +401,7 @@ async.eachLimit(files, 1, function (file, cb) {
         writeNameCache("props", cache);
     })();
 
-    var SCOPE_IS_NEEDED = COMPRESS || MANGLE || ARGS.lint;
+    var SCOPE_IS_NEEDED = COMPRESS || MANGLE || BEAUTIFY || ARGS.lint;
     var TL_CACHE = readNameCache("vars");
 
     if (SCOPE_IS_NEEDED) {

lib/compress.js

@@ -111,6 +111,7 @@ merge(Compressor.prototype, {
         node.DEFMETHOD("optimize", function(compressor){
             var self = this;
             if (self._optimized) return self;
+            if (compressor.has_directive("use asm")) return self;
             var opt = optimizer(self, compressor);
             opt._optimized = true;
             if (opt === self) return opt;
@@ -1026,6 +1027,7 @@ merge(Compressor.prototype, {
 
     AST_Scope.DEFMETHOD("drop_unused", function(compressor){
         var self = this;
+        if (compressor.has_directive("use asm")) return self;
         if (compressor.option("unused")
             && !(self instanceof AST_Toplevel)
             && !self.uses_eval
@@ -1205,9 +1207,10 @@ merge(Compressor.prototype, {
     });
 
     AST_Scope.DEFMETHOD("hoist_declarations", function(compressor){
+        var self = this;
+        if (compressor.has_directive("use asm")) return self;
         var hoist_funs = compressor.option("hoist_funs");
         var hoist_vars = compressor.option("hoist_vars");
-        var self = this;
         if (hoist_funs || hoist_vars) {
             var dirs = [];
             var hoisted = [];
@@ -2028,15 +2031,14 @@ merge(Compressor.prototype, {
     var commutativeOperators = makePredicate("== === != !== * & | ^");
 
     OPT(AST_Binary, function(self, compressor){
-        var reverse = compressor.has_directive("use asm") ? noop
+        function reverse(op, force) {
-            : function(op, force) {
+            if (force || !(self.left.has_side_effects(compressor) || self.right.has_side_effects(compressor))) {
-                if (force || !(self.left.has_side_effects(compressor) || self.right.has_side_effects(compressor))) {
+                if (op) self.operator = op;
-                    if (op) self.operator = op;
+                var tmp = self.left;
-                    var tmp = self.left;
+                self.left = self.right;
-                    self.left = self.right;
+                self.right = tmp;
-                    self.right = tmp;
+            }
-                }
+        }
-            };
         if (commutativeOperators(self.operator)) {
             if (self.right instanceof AST_Constant
                 && !(self.left instanceof AST_Constant)) {
@@ -2104,10 +2106,10 @@ merge(Compressor.prototype, {
         if (compressor.option("conditionals")) {
             if (self.operator == "&&") {
                 var ll = self.left.evaluate(compressor);
-                var rr = self.right.evaluate(compressor);
                 if (ll.length > 1) {
                     if (ll[1]) {
                         compressor.warn("Condition left of && always true [{file}:{line},{col}]", self.start);
+                        var rr = self.right.evaluate(compressor);
                         return rr[0];
                     } else {
                         compressor.warn("Condition left of && always false [{file}:{line},{col}]", self.start);
@@ -2117,13 +2119,13 @@ merge(Compressor.prototype, {
             }
             else if (self.operator == "||") {
                 var ll = self.left.evaluate(compressor);
-                var rr = self.right.evaluate(compressor);
                 if (ll.length > 1) {
                     if (ll[1]) {
                         compressor.warn("Condition left of || always true [{file}:{line},{col}]", self.start);
                         return ll[0];
                     } else {
                         compressor.warn("Condition left of || always false [{file}:{line},{col}]", self.start);
+                        var rr = self.right.evaluate(compressor);
                         return rr[0];
                     }
                 }

lib/output.js

@@ -1158,7 +1158,11 @@ function OutputStream(options) {
         output.print_string(self.getValue(), self.quote);
     });
     DEFPRINT(AST_Number, function(self, output){
-        output.print(make_num(self.getValue()));
+        if (self.value_string !== undefined && self.scope && self.scope.has_directive('use asm')) {
+            output.print(self.value_string);
+        } else {
+            output.print(make_num(self.getValue()));
+        }
     });
 
     function regexp_safe_literal(code) {

lib/parse.js

@@ -1149,6 +1149,9 @@ function parse($TEXT, options) {
             break;
           case "num":
             ret = new AST_Number({ start: tok, end: tok, value: tok.value });
+            var value_string = $TEXT.substring(tok.pos, tok.endpos);
+            if (value_string.indexOf('.') >= 0)
+                ret.value_string = value_string;
             break;
           case "string":
             ret = new AST_String({

lib/scope.js

@@ -119,6 +119,10 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
             push_uniq(scope.directives, node.value);
             return true;
         }
+        if (node instanceof AST_Number) {
+            node.scope = scope;
+            return true;
+        }
         if (node instanceof AST_With) {
             for (var s = scope; s; s = s.parent_scope)
                 s.uses_with = true;