+184
-5
lines changedFilter options
+184
-5
lines changed Original file line number Diff line number Diff line change
@@ -348,6 +348,9 @@ to set `true`; it's effectively a shortcut for `foo=true`).
348 348
- `collapse_vars` -- default `false`. Collapse single-use `var` and `const`
349 349
definitions when possible.
350 350 351 +
- `reduce_vars` -- default `false`. Improve optimization on variables assigned
352 +
with and used as constant values.
353 + 351 354
- `warnings` -- display warnings when dropping unreachable code or unused
352 355
declarations etc.
353 356
@@ -67,6 +67,7 @@ function Compressor(options, false_by_default) {
67 67
if_return : !false_by_default,
68 68
join_vars : !false_by_default,
69 69
collapse_vars : false,
70 +
reduce_vars : false,
70 71
cascade : !false_by_default,
71 72
side_effects : !false_by_default,
72 73
pure_getters : false,
@@ -1107,7 +1108,7 @@ merge(Compressor.prototype, {
1107 1108
this._evaluating = true;
1108 1109
try {
1109 1110
var d = this.definition();
1110 -
if (d && d.constant && d.init) {
1111 +
if (d && (d.constant || compressor.option("reduce_vars") && !d.modified) && d.init) {
1111 1112
return ev(d.init, compressor);
1112 1113
}
1113 1114
} finally {
@@ -197,7 +197,8 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
197 197
}
198 198
if (node instanceof AST_SymbolRef) {
199 199
var name = node.name;
200 -
if (name == "eval" && tw.parent() instanceof AST_Call) {
200 +
var parent = tw.parent();
201 +
if (name == "eval" && parent instanceof AST_Call) {
201 202
for (var s = node.scope; s && !s.uses_eval; s = s.parent_scope) {
202 203
s.uses_eval = true;
203 204
}
@@ -213,12 +214,15 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
213 214
g.global = true;
214 215
globals.set(name, g);
215 216
}
216 -
node.thedef = g;
217 +
sym = g;
217 218
if (func && name == "arguments") {
218 219
func.uses_arguments = true;
219 220
}
220 -
} else {
221 -
node.thedef = sym;
221 +
}
222 +
node.thedef = sym;
223 +
if (parent instanceof AST_Unary && (parent.operator === '++' || parent.operator === '--')
224 +
|| parent instanceof AST_Assign && parent.left === node) {
225 +
sym.modified = true;
222 226
}
223 227
node.reference();
224 228
return true;
@@ -0,0 +1,171 @@
1 +
reduce_vars: {
2 +
options = {
3 +
conditionals : true,
4 +
evaluate : true,
5 +
global_defs : {
6 +
C : 0
7 +
},
8 +
reduce_vars : true,
9 +
unused : true
10 +
}
11 +
input: {
12 +
var A = 1;
13 +
(function f0() {
14 +
var a = 2;
15 +
console.log(a - 5);
16 +
console.log(A - 5);
17 +
})();
18 +
(function f1() {
19 +
var a = 2;
20 +
console.log(a - 5);
21 +
eval("console.log(a);");
22 +
})();
23 +
(function f2(eval) {
24 +
var a = 2;
25 +
console.log(a - 5);
26 +
eval("console.log(a);");
27 +
})(eval);
28 +
(function f3() {
29 +
var b = typeof C !== "undefined";
30 +
var c = 4;
31 +
if (b) {
32 +
return 'yes';
33 +
} else {
34 +
return 'no';
35 +
}
36 +
})();
37 +
console.log(A + 1);
38 +
}
39 +
expect: {
40 +
var A = 1;
41 +
(function() {
42 +
console.log(-3);
43 +
console.log(-4);
44 +
})();
45 +
(function f1() {
46 +
var a = 2;
47 +
console.log(-3);
48 +
eval("console.log(a);");
49 +
})();
50 +
(function f2(eval) {
51 +
var a = 2;
52 +
console.log(-3);
53 +
eval("console.log(a);");
54 +
})(eval);
55 +
(function() {
56 +
return "yes";
57 +
})();
58 +
console.log(2);
59 +
}
60 +
}
61 + 62 +
modified: {
63 +
options = {
64 +
conditionals : true,
65 +
evaluate : true,
66 +
reduce_vars : true,
67 +
unused : true
68 +
}
69 +
input: {
70 +
function f0() {
71 +
var a = 1, b = 2;
72 +
b++;
73 +
console.log(a + 1);
74 +
console.log(b + 1);
75 +
}
76 + 77 +
function f1() {
78 +
var a = 1, b = 2;
79 +
--b;
80 +
console.log(a + 1);
81 +
console.log(b + 1);
82 +
}
83 + 84 +
function f2() {
85 +
var a = 1, b = 2, c = 3;
86 +
b = c;
87 +
console.log(a + b);
88 +
console.log(b + c);
89 +
console.log(a + c);
90 +
console.log(a + b + c);
91 +
}
92 + 93 +
function f3() {
94 +
var a = 1, b = 2, c = 3;
95 +
b *= c;
96 +
console.log(a + b);
97 +
console.log(b + c);
98 +
console.log(a + c);
99 +
console.log(a + b + c);
100 +
}
101 + 102 +
function f4() {
103 +
var a = 1, b = 2, c = 3;
104 +
if (a) {
105 +
b = c;
106 +
} else {
107 +
c = b;
108 +
}
109 +
console.log(a + b);
110 +
console.log(b + c);
111 +
// TODO: as "modified" is determined in "figure_out_scope",
112 +
// even "passes" wouldn't improve this any further
113 +
console.log(a + c);
114 +
console.log(a + b + c);
115 +
}
116 + 117 +
function f5(a) {
118 +
B = a;
119 +
console.log(A ? 'yes' : 'no');
120 +
console.log(B ? 'yes' : 'no');
121 +
}
122 +
}
123 +
expect: {
124 +
function f0() {
125 +
var b = 2;
126 +
b++;
127 +
console.log(2);
128 +
console.log(b + 1);
129 +
}
130 + 131 +
function f1() {
132 +
var b = 2;
133 +
--b;
134 +
console.log(2);
135 +
console.log(b + 1);
136 +
}
137 + 138 +
function f2() {
139 +
var a = 1, b = 2, c = 3;
140 +
b = c;
141 +
console.log(a + b);
142 +
console.log(b + c);
143 +
console.log(4);
144 +
console.log(a + b + c);
145 +
}
146 + 147 +
function f3() {
148 +
var a = 1, b = 2, c = 3;
149 +
b *= c;
150 +
console.log(a + b);
151 +
console.log(b + c);
152 +
console.log(4);
153 +
console.log(a + b + c);
154 +
}
155 + 156 +
function f4() {
157 +
var a = 1, b = 2, c = 3;
158 +
b = c;
159 +
console.log(a + b);
160 +
console.log(b + c);
161 +
console.log(a + c);
162 +
console.log(a + b + c);
163 +
}
164 + 165 +
function f5(a) {
166 +
B = a;
167 +
console.log(A ? 'yes' : 'no');
168 +
console.log(B ? 'yes' : 'no');
169 +
}
170 +
}
171 +
}
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