enhance reduce_vars (#3942)

lib/compress.js

@@ -447,7 +447,7 @@ merge(Compressor.prototype, {
         }
 
         function mark(tw, def, safe) {
-            tw.safe_ids[def.id] = safe;
+            tw.safe_ids[def.id] = safe && {};
         }
 
         function push_ref(def, ref) {
@@ -455,44 +455,37 @@ merge(Compressor.prototype, {
             def.last_ref = ref;
         }
 
-        function add_assign(tw, def, node) {
-            if (def.fixed === false) return;
-            tw.assigns.add(def.id, node);
-        }
-
-        function set_assign(tw, def, node) {
-            if (def.fixed === false) return;
-            var assigns = tw.assigns.get(def.id);
-            if (assigns) assigns.forEach(function(node) {
-                node.assigns = assigns;
-            });
-            tw.assigns.set(def.id, def.assigns = [ node ]);
-        }
-
         function safe_to_read(tw, def) {
             if (def.single_use == "m") return false;
-            if (tw.safe_ids[def.id]) {
+            var safe = tw.safe_ids[def.id];
+            if (safe) {
+                if (!HOP(tw.safe_ids, def.id)) safe.read = safe.read ? true : tw.safe_ids;
                 if (def.fixed == null) {
                     if (is_arguments(def)) return false;
                     if (def.global && def.name == "arguments") return false;
                     def.fixed = make_node(AST_Undefined, def.orig[0]);
-                }
                     return true;
                 }
+                return !safe.assign || safe.assign === tw.safe_ids;
+            }
             return def.fixed instanceof AST_Defun;
         }
 
-        function safe_to_assign(tw, def, value) {
+        function safe_to_assign(tw, def) {
             if (def.fixed === undefined) return true;
             if (def.fixed === null && def.safe_ids) {
                 def.safe_ids[def.id] = false;
                 delete def.safe_ids;
                 return true;
             }
-            if (!HOP(tw.safe_ids, def.id)) return false;
+            var safe = tw.safe_ids[def.id];
+            if (!HOP(tw.safe_ids, def.id)) {
+                if (!safe) return false;
+                safe.assign = safe.assign ? true : tw.safe_ids;
+            }
             if (!safe_to_read(tw, def)) return false;
             if (def.fixed === false) return false;
-            if (def.fixed != null && (!value || def.references.length > def.assignments)) return false;
+            if (def.fixed != null && safe.read && safe.read !== tw.safe_ids) return false;
             return all(def.orig, function(sym) {
                 return !(sym instanceof AST_SymbolLambda);
             });
@@ -573,18 +566,30 @@ merge(Compressor.prototype, {
                 mark_assignment_to_arguments(sym);
                 return;
             }
-            if (sym.fixed) delete sym.fixed;
             var d = sym.definition();
-            var safe = safe_to_assign(tw, d, node.right);
             d.assignments++;
-            var fixed = d.fixed;
-            if (!fixed && node.operator != "=") return;
             var eq = node.operator == "=";
             var value = eq ? node.right : node;
             if (is_modified(compressor, tw, node, value, 0)) return;
-            sym.fixed = d.fixed = eq ? function() {
+            var safe = (eq || safe_to_read(tw, d)) && safe_to_assign(tw, d);
+            var fixed = d.fixed;
+            if (safe) {
+                push_ref(d, sym);
+                mark(tw, d, false);
+                node.right.walk(tw);
+                mark(tw, d, true);
+                if (eq) mark_escaped(tw, d, sym.scope, node, value, 0, 1);
+            } else {
+                descend();
+            }
+            if (fixed !== false && d.fixed !== false) {
+                if (eq) {
+                    sym.fixed = d.fixed = function() {
                         return node.right;
-            } : function() {
+                    };
+                } else {
+                    if (fixed == null) fixed = make_node(AST_Undefined, d.orig[0]);
+                    sym.fixed = d.fixed = function() {
                         var value = fixed instanceof AST_Node ? fixed : fixed();
                         return value && make_node(AST_Binary, node, {
                             operator: node.operator.slice(0, -1),
@@ -592,16 +597,9 @@ merge(Compressor.prototype, {
                             right: node.right
                         });
                     };
-            if (!safe) return;
+                }
-            push_ref(d, sym);
+                sym.fixed.assigns = eq || !fixed.assigns ? [] : fixed.assigns.slice();
-            mark(tw, d, false);
+                sym.fixed.assigns.push(node);
-            node.right.walk(tw);
-            mark(tw, d, true);
-            if (eq) {
-                mark_escaped(tw, d, sym.scope, node, value, 0, 1);
-                set_assign(tw, d, node);
-            } else {
-                add_assign(tw, d, node);
             }
             return true;
         });
@@ -740,13 +738,13 @@ merge(Compressor.prototype, {
                 fn.argnames.forEach(function(arg, i) {
                     var d = arg.definition();
                     if (d.fixed === undefined && (!fn.uses_arguments || tw.has_directive("use strict"))) {
+                        tw.loop_ids[d.id] = tw.in_loop;
+                        mark(tw, d, true);
                         var value = iife.args[i];
                         d.fixed = function() {
                             var j = fn.argnames.indexOf(arg);
                             return (j < 0 ? value : iife.args[j]) || make_node(AST_Undefined, iife);
                         };
-                        tw.loop_ids[d.id] = tw.in_loop;
-                        mark(tw, d, true);
                     } else {
                         d.fixed = false;
                     }
@@ -787,7 +785,6 @@ merge(Compressor.prototype, {
             this.definition().fixed = false;
         });
         def(AST_SymbolRef, function(tw, descend, compressor) {
-            if (this.fixed) delete this.fixed;
             var d = this.definition();
             push_ref(d, this);
             if (d.references.length == 1
@@ -826,6 +823,7 @@ merge(Compressor.prototype, {
                 }
                 mark_escaped(tw, d, this.scope, this, value, 0, 1);
             }
+            this.fixed = d.fixed;
             var parent;
             if (d.fixed instanceof AST_Defun
                 && !((parent = tw.parent()) instanceof AST_Call && parent.expression === this)) {
@@ -864,12 +862,18 @@ merge(Compressor.prototype, {
                 mark_assignment_to_arguments(exp);
                 return;
             }
-            if (exp.fixed) delete exp.fixed;
             var d = exp.definition();
-            var safe = safe_to_assign(tw, d, true);
             d.assignments++;
+            var safe = safe_to_read(tw, d) && safe_to_assign(tw, d);
             var fixed = d.fixed;
-            if (!fixed) return;
+            if (safe) {
+                push_ref(d, exp);
+                mark(tw, d, true);
+            } else {
+                descend();
+            }
+            if (fixed !== false && d.fixed !== false) {
+                if (fixed == null) fixed = make_node(AST_Undefined, d.orig[0]);
                 d.fixed = function() {
                     var value = fixed instanceof AST_Node ? fixed : fixed();
                     return value && make_node(AST_Binary, node, {
@@ -883,32 +887,38 @@ merge(Compressor.prototype, {
                         })
                     });
                 };
-            exp.fixed = node instanceof AST_UnaryPrefix ? d.fixed : function() {
+                d.fixed.assigns = fixed.assigns ? fixed.assigns.slice() : [];
+                d.fixed.assigns.push(node);
+                if (node instanceof AST_UnaryPrefix) {
+                    exp.fixed = d.fixed;
+                } else {
+                    exp.fixed = function() {
                         var value = fixed instanceof AST_Node ? fixed : fixed();
                         return value && make_node(AST_UnaryPrefix, node, {
                             operator: "+",
                             expression: value
                         });
                     };
-            if (!safe) return;
+                    exp.fixed.assigns = fixed.assigns;
-            push_ref(d, exp);
+                }
-            mark(tw, d, true);
+            }
-            add_assign(tw, d, node);
             return true;
         });
         def(AST_VarDef, function(tw, descend) {
             var node = this;
             var d = node.name.definition();
             if (node.value) {
-                if (safe_to_assign(tw, d, node.value)) {
+                if (safe_to_assign(tw, d)) {
-                    d.fixed = function() {
-                        return node.value;
-                    };
                     tw.loop_ids[d.id] = tw.in_loop;
                     mark(tw, d, false);
                     descend();
                     mark(tw, d, true);
-                    set_assign(tw, d, node);
+                    if (d.fixed !== false) {
+                        d.fixed = function() {
+                            return node.value;
+                        };
+                        d.fixed.assigns = [ node ];
+                    }
                     return true;
                 } else {
                     d.fixed = false;
@@ -933,8 +943,6 @@ merge(Compressor.prototype, {
             reset_flags(node);
             return node.reduce_vars(tw, descend, compressor);
         } : reset_flags);
-        // Assignment chains
-        tw.assigns = new Dictionary();
         // Flow control for visiting `AST_Defun`s
         tw.defun_ids = Object.create(null);
         tw.defun_visited = Object.create(null);
@@ -951,6 +959,7 @@ merge(Compressor.prototype, {
         function reset_flags(node) {
             node._squeezed = false;
             node._optimized = false;
+            delete node.fixed;
             if (node instanceof AST_Scope) delete node._var_names;
         }
     });
@@ -4222,7 +4231,7 @@ merge(Compressor.prototype, {
             })) return;
             return sym;
         };
-        var chained = Object.create(null);
+        var assign_in_use = Object.create(null);
         var in_use = [];
         var in_use_ids = Object.create(null); // avoid expensive linear scans of in_use
         var value_read = Object.create(null);
@@ -4235,7 +4244,7 @@ merge(Compressor.prototype, {
                 }
             });
         }
-        var assign_in_use = new Dictionary();
+        var assignments = new Dictionary();
         var var_defs_by_id = new Dictionary();
         var initializations = new Dictionary();
         // pass 1: find out which symbols are directly used in
@@ -4282,7 +4291,7 @@ merge(Compressor.prototype, {
                         } else {
                             initializations.add(node_def.id, def.value);
                         }
-                        match_assigns(node_def, def);
+                        assignments.add(node_def.id, def);
                     }
                 });
                 return true;
@@ -4300,6 +4309,33 @@ merge(Compressor.prototype, {
                 init.walk(tw);
             });
         }
+        Object.keys(assign_in_use).forEach(function(id) {
+            var assigns = assign_in_use[id];
+            if (!assigns) {
+                delete assign_in_use[id];
+                return;
+            }
+            assigns = assigns.reduce(function(in_use, assigns) {
+                assigns.forEach(function(assign) {
+                    push_uniq(in_use, assign);
+                });
+                return in_use;
+            }, []);
+            var in_use = (assignments.get(id) || []).filter(function(node) {
+                return find_if(node instanceof AST_Unary ? function(assign) {
+                    return assign === node;
+                } : function(assign) {
+                    if (assign === node) return true;
+                    if (assign instanceof AST_Unary) return false;
+                    return get_rvalue(assign) === get_rvalue(node);
+                }, assigns);
+            });
+            if (assigns.length == in_use.length) {
+                assign_in_use[id] = in_use;
+            } else {
+                delete assign_in_use[id];
+            }
+        });
         var drop_fn_name = compressor.option("keep_fnames") ? return_false : compressor.option("ie8") ? function(def) {
             return !compressor.exposed(def) && def.references.length == def.replaced;
         } : function(def) {
@@ -4487,7 +4523,7 @@ merge(Compressor.prototype, {
                             right: def.value
                         });
                         var index = indexOf_assign(sym, def);
-                        if (index >= 0) assign_in_use.get(sym.id)[index] = assign;
+                        if (index >= 0) assign_in_use[sym.id][index] = assign;
                         sym.eliminated++;
                         return assign.transform(tt);
                     }));
@@ -4605,30 +4641,20 @@ merge(Compressor.prototype, {
             };
         }
 
-        function match_assigns(def, node) {
+        function track_assigns(def, node) {
-            if (!def.fixed) return;
+            if (def.scope !== self) return false;
-            if (!def.assigns) return;
+            if (!def.fixed || !node.fixed) assign_in_use[def.id] = false;
-            if (find_if(node instanceof AST_Unary ? function(assign) {
+            return assign_in_use[def.id] !== false;
-                return assign === node;
-            } : function(assign) {
-                if (assign === node) return true;
-                if (assign instanceof AST_Unary) return false;
-                return get_rvalue(assign) === get_rvalue(node);
-            }, def.assigns)) {
-                assign_in_use.add(def.id, node);
         }
+
+        function add_assigns(def, node) {
+            if (!assign_in_use[def.id]) assign_in_use[def.id] = [];
+            if (node.fixed.assigns) push_uniq(assign_in_use[def.id], node.fixed.assigns);
         }
 
         function indexOf_assign(def, node) {
-            if (!def.fixed) return;
+            var nodes = assign_in_use[def.id];
-            if (!def.assigns) return;
+            return nodes && nodes.indexOf(node);
-            var assigns = assign_in_use.get(def.id);
-            if (!assigns) return;
-            if (assigns.length != def.assigns.length) return;
-            var index = assigns.indexOf(node);
-            if (index >= 0 || !chained[def.id] || node.assigns && all(node.assigns, function(assign) {
-                return assign.write_only || assign.operator == "=" || assign instanceof AST_VarDef;
-            })) return index;
         }
 
         function verify_safe_usage(def, read, modified) {
@@ -4653,14 +4679,12 @@ merge(Compressor.prototype, {
 
         function scan_ref_scoped(node, descend, init) {
             if (node instanceof AST_Assign && node.left instanceof AST_SymbolRef) {
-                var node_def = node.left.definition();
+                var def = node.left.definition();
-                if (node.operator != "=") chained[node_def.id] = true;
+                if (def.scope === self) assignments.add(def.id, node);
-                match_assigns(node_def, node);
             }
             if (node instanceof AST_Unary && node.expression instanceof AST_SymbolRef) {
-                var node_def = node.expression.definition();
+                var def = node.expression.definition();
-                chained[node_def.id] = true;
+                if (def.scope === self) assignments.add(def.id, node);
-                match_assigns(node_def, node);
             }
             var node_def, props = [], sym = assign_as_unused(node, props);
             if (sym && self.variables.get(sym.name) === (node_def = sym.definition())) {
@@ -4686,6 +4710,7 @@ merge(Compressor.prototype, {
                         }
                     }
                 }
+                track_assigns(node_def, sym);
                 return true;
             }
             if (node instanceof AST_SymbolRef) {
@@ -4694,6 +4719,7 @@ merge(Compressor.prototype, {
                     in_use_ids[node_def.id] = true;
                     in_use.push(node_def);
                 }
+                if (track_assigns(node_def, node)) add_assigns(node_def, node);
                 return true;
             }
             if (node instanceof AST_Scope) {
@@ -7641,7 +7667,8 @@ merge(Compressor.prototype, {
                 def.replaced++;
                 return value;
             }
-            if (fixed && def.should_replace === undefined) {
+            var local = self.fixed !== def.fixed;
+            if (fixed && (local || def.should_replace !== false)) {
                 var init;
                 if (fixed instanceof AST_This) {
                     if (!(def.orig[0] instanceof AST_SymbolFunarg) && same_scope(def)) {
@@ -7659,19 +7686,10 @@ merge(Compressor.prototype, {
                     }
                 }
                 if (init) {
+                    if (!local && def.should_replace === undefined) {
                         var value_length = init.optimize(compressor).print_to_string().length;
-                    var fn;
+                        if (!has_symbol_ref(fixed)) {
-                    if (has_symbol_ref(fixed)) {
-                        fn = function() {
-                            var result = init.optimize(compressor);
-                            return result === init ? result.clone(true) : result;
-                        };
-                    } else {
                             value_length = Math.min(value_length, fixed.print_to_string().length);
-                        fn = function() {
-                            var result = best_of_expression(init.optimize(compressor), fixed);
-                            return result === init || result === fixed ? result.clone(true) : result;
-                        };
                         }
                         var name_length = def.name.length;
                         if (compressor.option("unused") && !compressor.exposed(def)) {
@@ -7679,17 +7697,23 @@ merge(Compressor.prototype, {
                             name_length += (name_length + 2 + value_length) / (referenced - def.assignments);
                         }
                         var delta = value_length - Math.floor(name_length);
-                    def.should_replace = delta < compressor.eval_threshold ? fn : false;
+                        def.should_replace = delta < compressor.eval_threshold;
+                    }
+                    if (local || def.should_replace) {
+                        var value;
+                        if (has_symbol_ref(fixed)) {
+                            value = init.optimize(compressor);
+                            if (value === init) value = value.clone(true);
                         } else {
-                    def.should_replace = false;
+                            value = best_of_expression(init.optimize(compressor), fixed);
+                            if (value === init || value === fixed) value = value.clone(true);
                         }
-            }
-            if (def.should_replace) {
-                var value = def.should_replace();
                         def.replaced++;
                         return value;
                     }
                 }
+            }
+        }
         return self;
 
         function same_scope(def) {

test/compress/collapse_vars.js

@@ -3001,8 +3001,6 @@ issue_2298: {
     expect: {
         !function() {
             (function() {
-                var a = undefined;
-                var undefined = a++;
                 try {
                     !function(b) {
                         (void 0)[1] = "foo";
@@ -3836,20 +3834,19 @@ issue_2436_3: {
         }(o));
     }
     expect: {
-        var o = {
-            a: 1,
-            b: 2,
-        };
         console.log(function(c) {
-            o = {
+            ({
                 a: 3,
                 b: 4,
-            };
+            });
             return {
                 x: c.a,
                 y: c.b,
             };
-        }(o));
+        }({
+            a: 1,
+            b: 2,
+        }));
     }
     expect_stdout: true
 }
@@ -4071,16 +4068,15 @@ issue_2436_10: {
         }(o).join(" "));
     }
     expect: {
-        var o = {
-            a: 1,
-            b: 2,
-        };
         function f(n) {
-            o = { b: 3 };
+            ({ b: 3 });
             return n;
         }
         console.log([
-            (c = o).a,
+            (c = {
+                a: 1,
+                b: 2,
+            }).a,
             f(c.b),
             c.b,
         ].join(" "));

test/compress/drop-unused.js

@@ -1729,7 +1729,7 @@ chained_3: {
     }
     expect: {
         console.log(function(a, b) {
-            var c = b;
+            var c = 2;
             b++;
             return c;
         }(0, 2));
@@ -2557,7 +2557,7 @@ issue_3899: {
         console.log(typeof a);
     }
     expect: {
-        ++a;
+        0;
         var a = function() {
             return 2;
         };
@@ -2565,3 +2565,63 @@ issue_3899: {
     }
     expect_stdout: "function"
 }
+
+cross_scope_assign_chain: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a, b = 0;
+        (function() {
+            a = b;
+            a++;
+            while (b++);
+        })();
+        console.log(a ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a, b = 0;
+        (function() {
+            a = b;
+            a++;
+            while (b++);
+        })();
+        console.log(a ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+}
+
+assign_if_assign_read: {
+    options = {
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function(a) {
+            var b;
+            do {
+                b = "FAIL";
+                if (Array.isArray(a)) {
+                    b = a[0];
+                    console.log(b);
+                }
+            } while (!console);
+        })([ "PASS" ]);
+    }
+    expect: {
+        (function(a) {
+            var b;
+            do {
+                "FAIL";
+                if (Array.isArray(a)) {
+                    b = a[0];
+                    console.log(b);
+                }
+            } while (!console);
+        })([ "PASS" ]);
+    }
+    expect_stdout: "PASS"
+}

test/compress/evaluate.js

@@ -2412,9 +2412,9 @@ issue_3887: {
     expect: {
         (function(b) {
             try {
-                b-- && console.log("PASS");
+                1, console.log("PASS");
             } catch (a_2) {}
-        })(1);
+        })();
     }
     expect_stdout: "PASS"
 }
@@ -2478,10 +2478,10 @@ issue_3920: {
         console.log(a);
     }
     expect: {
-        var a = function(b) {
+        (function(b) {
-            return (b[b = 0] = 0) >= (b ? 0 : 1);
+            "foo"[0] = 0;
-        }("foo");
+        })();
-        console.log(a);
+        console.log(false);
     }
     expect_stdout: "false"
 }

test/compress/functions.js

@@ -2336,6 +2336,7 @@ issue_3274: {
         inline: true,
         join_vars: true,
         loops: true,
+        passes: 2,
         reduce_vars: true,
         unused: true,
     }

test/compress/keep_fargs.js

@@ -306,8 +306,6 @@ issue_2298: {
     expect: {
         !function() {
             (function() {
-                var a = undefined;
-                var undefined = a++;
                 try {
                     !function() {
                         (void 0)[1] = "foo";

test/compress/reduce_vars.js

@@ -905,7 +905,7 @@ use_before_var: {
     }
     expect: {
         function f(){
-            console.log(t);
+            console.log(void 0);
             var t = 1;
         }
     }
@@ -981,12 +981,12 @@ inner_var_for_1: {
     expect: {
         function f() {
             var a = 1;
-            x(1, b, d);
+            x(1, void 0, d);
-            for (var b = 2, c = 3; x(1, b, 3, d); x(1, b, 3, d)) {
+            for (var b = 2, c = 3; x(1, 2, 3, d); x(1, 2, 3, d)) {
                 var d = 4, e = 5;
-                x(1, b, 3, d, e);
+                x(1, 2, 3, d, e);
             }
-            x(1, b, 3, d, e);
+            x(1, 2, 3, d, e);
         }
     }
 }
@@ -1521,9 +1521,7 @@ func_inline: {
     expect: {
         function f() {
             console.log(1 + h());
-            var h = function() {
+            var h;
-                return 2;
-            };
         }
     }
 }
@@ -2372,8 +2370,7 @@ delay_def: {
             return;
         }
         function g() {
-            return a;
+            return;
-            var a = 1;
         }
         console.log(f(), g());
     }
@@ -2395,7 +2392,7 @@ delay_def_lhs: {
     expect: {
         console.log(function() {
             long_name++;
-            return long_name;
+            return NaN;
             var long_name;
         }());
     }
@@ -2651,11 +2648,9 @@ var_assign_5: {
     }
     expect: {
         !function() {
-            var a;
             !function(b) {
-                a = 2,
+                console.log(2, void 0);
-                console.log(a, b);
+            }();
-            }(a);
         }();
     }
     expect_stdout: "2 undefined"
@@ -4725,7 +4720,7 @@ escape_conditional: {
         function bar() {}
         (function() {
             var thing = baz();
-            if (thing !== (thing = baz()))
+            if (thing !== baz())
                 console.log("FAIL");
             else
                 console.log("PASS");
@@ -4763,7 +4758,7 @@ escape_sequence: {
         function bar() {}
         (function() {
             var thing = baz();
-            if (thing !== (thing = baz()))
+            if (thing !== baz())
                 console.log("FAIL");
             else
                 console.log("PASS");
@@ -4808,7 +4803,7 @@ escape_throw: {
         function foo() {}
         (function() {
             var thing = baz();
-            if (thing !== (thing = baz()))
+            if (thing !== baz())
                 console.log("FAIL");
             else
                 console.log("PASS");
@@ -4845,7 +4840,7 @@ escape_local_conditional: {
         }
         (function() {
             var thing = baz();
-            if (thing !== (thing = baz()))
+            if (thing !== baz())
                 console.log("PASS");
             else
                 console.log("FAIL");
@@ -4882,7 +4877,7 @@ escape_local_sequence: {
         }
         (function() {
             var thing = baz();
-            if (thing !== (thing = baz()))
+            if (thing !== baz())
                 console.log("PASS");
             else
                 console.log("FAIL");
@@ -4926,7 +4921,7 @@ escape_local_throw: {
         }
         (function() {
             var thing = baz();
-            if (thing !== (thing = baz()))
+            if (thing !== baz())
                 console.log("PASS");
             else
                 console.log("FAIL");
@@ -4980,11 +4975,7 @@ inverted_var: {
         console.log(1, 2, 3, 4, 5, function c() {
             c = 6;
             return c;
-        }(), 7, function() {
+        }(), 7, 8);
-            c = 8;
-            return c;
-            var c = "foo";
-        }());
     }
     expect_stdout: true
 }
@@ -5180,9 +5171,7 @@ defun_var_3: {
         var a = 42, b;
     }
     expect: {
-        function a() {}
+        console.log("function", "function");
-        console.log(typeof a, "function");
-        var a = 42;
     }
     expect_stdout: "function function"
 }