introduce eager evaluation (#3587)

1 files changed, 25 insertions, 44 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 9d844b81..f82a165e 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -96,6 +96,8 @@ function Compressor(options, false_by_default) {
         unsafe_undefined: false,
         unused          : !false_by_default,
     }, true);
+    var evaluate = this.options["evaluate"];
+    this.eval_threshold = /eager/.test(evaluate) ? 1 / 0 : +evaluate;
     var global_defs = this.options["global_defs"];
     if (typeof global_defs == "object") for (var key in global_defs) {
         if (/^@/.test(key) && HOP(global_defs, key)) {
@@ -2676,22 +2678,21 @@ merge(Compressor.prototype, {
         node.DEFMETHOD("_find_defs", func);
     });
 
-    function best_of_expression(ast1, ast2) {
-        return ast1.print_to_string().length >
-            ast2.print_to_string().length
-            ? ast2 : ast1;
+    function best_of_expression(ast1, ast2, threshold) {
+        var delta = ast2.print_to_string().length - ast1.print_to_string().length;
+        return delta < (threshold || 0) ? ast2 : ast1;
     }
 
-    function best_of_statement(ast1, ast2) {
+    function best_of_statement(ast1, ast2, threshold) {
         return best_of_expression(make_node(AST_SimpleStatement, ast1, {
             body: ast1
         }), make_node(AST_SimpleStatement, ast2, {
             body: ast2
-        })).body;
+        }), threshold).body;
     }
 
-    function best_of(compressor, ast1, ast2) {
-        return (first_in_statement(compressor) ? best_of_statement : best_of_expression)(ast1, ast2);
+    function best_of(compressor, ast1, ast2, threshold) {
+        return (first_in_statement(compressor) ? best_of_statement : best_of_expression)(ast1, ast2, threshold);
     }
 
     function convert_to_predicate(obj) {
@@ -2700,6 +2701,13 @@ merge(Compressor.prototype, {
         });
     }
 
+    function try_evaluate(compressor, node) {
+        var ev = node.evaluate(compressor);
+        if (ev === node) return node;
+        ev = make_node_from_constant(ev, node).optimize(compressor);
+        return best_of(compressor, node, ev, compressor.eval_threshold);
+    }
+
     var object_fns = [
         "constructor",
         "toString",
@@ -5366,12 +5374,7 @@ merge(Compressor.prototype, {
             && is_iife_call(self)) {
             return self.negate(compressor, true);
         }
-        var ev = self.evaluate(compressor);
-        if (ev !== self) {
-            ev = make_node_from_constant(ev, self).optimize(compressor);
-            return best_of(compressor, ev, self);
-        }
-        return self;
+        return try_evaluate(compressor, self);
 
         function return_value(stat) {
             if (!stat) return make_node(AST_Undefined, self);
@@ -5702,15 +5705,8 @@ merge(Compressor.prototype, {
             });
         }
         // avoids infinite recursion of numerals
-        if (self.operator != "-"
-            || !(e instanceof AST_Number || e instanceof AST_Infinity)) {
-            var ev = self.evaluate(compressor);
-            if (ev !== self) {
-                ev = make_node_from_constant(ev, self).optimize(compressor);
-                return best_of(compressor, ev, self);
-            }
-        }
-        return self;
+        return self.operator == "-" && (e instanceof AST_Number || e instanceof AST_Infinity)
+            ? self : try_evaluate(compressor, self);
     });
 
     AST_Binary.DEFMETHOD("lift_sequences", function(compressor) {
@@ -6274,12 +6270,7 @@ merge(Compressor.prototype, {
             self.right = self.right.right;
             return self.transform(compressor);
         }
-        var ev = self.evaluate(compressor);
-        if (ev !== self) {
-            ev = make_node_from_constant(ev, self).optimize(compressor);
-            return best_of(compressor, ev, self);
-        }
-        return self;
+        return try_evaluate(compressor, self);
 
         function align(ref, op) {
             switch (ref) {
@@ -6448,11 +6439,11 @@ merge(Compressor.prototype, {
                         };
                     }
                     var name_length = def.name.length;
-                    var overhead = 0;
                     if (compressor.option("unused") && !compressor.exposed(def)) {
-                        overhead = (name_length + 2 + value_length) / (def.references.length - def.assignments);
+                        name_length += (name_length + 2 + value_length) / (def.references.length - def.assignments);
                     }
-                    def.should_replace = value_length <= name_length + overhead ? fn : false;
+                    var delta = value_length - Math.floor(name_length);
+                    def.should_replace = delta < compressor.eval_threshold ? fn : false;
                 } else {
                     def.should_replace = false;
                 }
@@ -7046,12 +7037,7 @@ merge(Compressor.prototype, {
                 });
             }
         }
-        var ev = self.evaluate(compressor);
-        if (ev !== self) {
-            ev = make_node_from_constant(ev, self).optimize(compressor);
-            return best_of(compressor, ev, self);
-        }
-        return self;
+        return try_evaluate(compressor, self);
 
         function find_lambda() {
             var i = 0, p;
@@ -7152,12 +7138,7 @@ merge(Compressor.prototype, {
         }
         var sub = self.flatten_object(self.property, compressor);
         if (sub) return sub.optimize(compressor);
-        var ev = self.evaluate(compressor);
-        if (ev !== self) {
-            ev = make_node_from_constant(ev, self).optimize(compressor);
-            return best_of(compressor, ev, self);
-        }
-        return self;
+        return try_evaluate(compressor, self);
     });
 
     OPT(AST_Object, function(self, compressor) {