compress arithmetic expressions further (#3529)

1 files changed, 83 insertions, 69 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 03c1f590..6d8c1f8f 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2437,9 +2437,10 @@ merge(Compressor.prototype, {
                 || this.operator == "=" && this.right.is_number(compressor);
         });
         def(AST_Binary, function(compressor) {
-            return binary[this.operator] || this.operator == "+"
-                && this.left.is_number(compressor)
-                && this.right.is_number(compressor);
+            if (binary[this.operator]) return true;
+            if (this.operator != "+") return false;
+            return (this.left.is_boolean(compressor) || this.left.is_number(compressor))
+                && (this.right.is_boolean(compressor) || this.right.is_number(compressor));
         });
         var fn = makePredicate([
             "charCodeAt",
@@ -5777,6 +5778,7 @@ merge(Compressor.prototype, {
             }
         }
         if (compressor.option("evaluate")) {
+            var associative = true;
             switch (self.operator) {
               case "&&":
                 var ll = fuzzy_eval(self.left);
@@ -5845,9 +5847,6 @@ merge(Compressor.prototype, {
                     }).optimize(compressor);
                 }
                 break;
-            }
-            var associative = true;
-            switch (self.operator) {
               case "+":
                 // "foo" + ("bar" + x) => "foobar" + x
                 if (self.left instanceof AST_Constant
@@ -5927,13 +5926,38 @@ merge(Compressor.prototype, {
                     });
                     break;
                 }
+              case "-":
+                // a - -b => a + b
+                if (self.right instanceof AST_UnaryPrefix
+                    && self.right.operator == "-"
+                    && self.left.is_number(compressor)) {
+                    self = make_node(AST_Binary, self, {
+                        operator: "+",
+                        left: self.left,
+                        right: self.right.expression
+                    });
+                    break;
+                }
               case "*":
+              case "/":
                 associative = compressor.option("unsafe_math");
+                // +a - b => a - b
+                // a - +b => a - b
+                if (self.operator != "+") {
+                    if (self.left instanceof AST_UnaryPrefix && self.left.operator == "+") {
+                        self.left = self.left.expression;
+                    }
+                    if (self.right instanceof AST_UnaryPrefix && self.right.operator == "+") {
+                        self.right = self.right.expression;
+                    }
+                }
               case "&":
               case "|":
               case "^":
                 // a + +b => +b + a
-                if (self.left.is_number(compressor)
+                if (self.operator != "-"
+                    && self.operator != "/"
+                    && self.left.is_number(compressor)
                     && self.right.is_number(compressor)
                     && reversible()
                     && !(self.left instanceof AST_Binary
@@ -5951,77 +5975,56 @@ merge(Compressor.prototype, {
                         self = best_of(compressor, self, reversed);
                     }
                 }
-                if (associative && self.is_number(compressor)) {
-                    // a + (b + c) => (a + b) + c
-                    if (self.right instanceof AST_Binary
-                        && self.right.operator == self.operator) {
-                        self = make_node(AST_Binary, self, {
+                if (!associative || !self.is_number(compressor)) break;
+                // a + (b + c) => (a + b) + c
+                if (self.right instanceof AST_Binary
+                    && self.right.operator != "%"
+                    && PRECEDENCE[self.right.operator] == PRECEDENCE[self.operator]) {
+                    self = make_node(AST_Binary, self, {
+                        operator: align(self.operator, self.right.operator),
+                        left: make_node(AST_Binary, self.left, {
                             operator: self.operator,
+                            left: self.left,
+                            right: self.right.left,
+                            start: self.left.start,
+                            end: self.right.left.end
+                        }),
+                        right: self.right.right
+                    });
+                }
+                // (2 * n) * 3 => 6 * n
+                // (n + 2) + 3 => n + 5
+                if (self.right instanceof AST_Constant
+                    && self.left instanceof AST_Binary
+                    && self.left.operator != "%"
+                    && PRECEDENCE[self.left.operator] == PRECEDENCE[self.operator]) {
+                    if (self.left.left instanceof AST_Constant) {
+                        self = make_node(AST_Binary, self, {
+                            operator: self.left.operator,
                             left: make_node(AST_Binary, self.left, {
                                 operator: self.operator,
-                                left: self.left,
-                                right: self.right.left,
-                                start: self.left.start,
-                                end: self.right.left.end
+                                left: self.left.left,
+                                right: self.right,
+                                start: self.left.left.start,
+                                end: self.right.end
                             }),
-                            right: self.right.right
+                            right: self.left.right
                         });
-                    }
-                    // (n + 2) + 3 => 5 + n
-                    // (2 * n) * 3 => 6 + n
-                    if (self.right instanceof AST_Constant
-                        && self.left instanceof AST_Binary
-                        && self.left.operator == self.operator) {
-                        if (self.left.left instanceof AST_Constant) {
-                            self = make_node(AST_Binary, self, {
-                                operator: self.operator,
-                                left: make_node(AST_Binary, self.left, {
-                                    operator: self.operator,
-                                    left: self.left.left,
-                                    right: self.right,
-                                    start: self.left.left.start,
-                                    end: self.right.end
-                                }),
-                                right: self.left.right
-                            });
-                        } else if (self.left.right instanceof AST_Constant) {
-                            self = make_node(AST_Binary, self, {
-                                operator: self.operator,
-                                left: make_node(AST_Binary, self.left, {
-                                    operator: self.operator,
-                                    left: self.left.right,
-                                    right: self.right,
-                                    start: self.left.right.start,
-                                    end: self.right.end
-                                }),
-                                right: self.left.left
-                            });
-                        }
-                    }
-                    // (a | 1) | (2 | d) => (3 | a) | b
-                    if (self.left instanceof AST_Binary
-                        && self.left.operator == self.operator
-                        && self.left.right instanceof AST_Constant
-                        && self.right instanceof AST_Binary
-                        && self.right.operator == self.operator
-                        && self.right.left instanceof AST_Constant) {
+                    } else if (self.left.right instanceof AST_Constant) {
                         self = make_node(AST_Binary, self, {
-                            operator: self.operator,
-                            left: make_node(AST_Binary, self.left, {
-                                operator: self.operator,
-                                left: make_node(AST_Binary, self.left.left, {
-                                    operator: self.operator,
-                                    left: self.left.right,
-                                    right: self.right.left,
-                                    start: self.left.right.start,
-                                    end: self.right.left.end
-                                }),
-                                right: self.left.left
-                            }),
-                            right: self.right.right
+                            operator: self.left.operator,
+                            left: self.left.left,
+                            right: make_node(AST_Binary, self.left, {
+                                operator: align(self.left.operator, self.operator),
+                                left: self.left.right,
+                                right: self.right,
+                                start: self.left.right.start,
+                                end: self.right.end
+                            })
                         });
                     }
                 }
+                break;
             }
         }
         if (compressor.option("unsafe")) {
@@ -6086,6 +6089,17 @@ merge(Compressor.prototype, {
         }
         return self;
 
+        function align(ref, op) {
+            switch (ref) {
+              case "-":
+                return op == "+" ? "-" : "+";
+              case "/":
+                return op == "*" ? "/" : "*";
+              default:
+                return op;
+            }
+        }
+
         function fuzzy_eval(node) {
             if (node.truthy) return true;
             if (node.falsy) return false;