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improve compression of undefined, NaN & Infinitiy (#1748)

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- migrate transformation logic from `OutputStream` to `Compressor`
- always turn `undefined` into `void 0` (unless `unsafe`)
- always keep `NaN` except when avoiding local variable redefinition
- introduce `keep_infinity` to suppress `1/0` transform, except when avoiding local variable redefinition

supersedes #1723
fixes #1730
This commit is contained in:
Alex Lam S.L
2017-04-01 03:02:14 +08:00
committed by GitHub
parent 1ddc05725d
commit 257ddc3bdb
9 changed files with 170 additions and 56 deletions
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3
README.md
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@@ -443,6 +443,9 @@ to set `true`; it's effectively a shortcut for `foo=true`).
integer argument larger than 1 to further reduce code size in some cases.
Note: raising the number of passes will increase uglify compress time.
- `keep_infinity` -- default `false`. Pass `true` to prevent `Infinity` from
being compressed into `1/0`, which may cause performance issues on Chrome.
### The `unsafe` option
It enables some transformations that *might* break code logic in certain

75
lib/compress.js
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@@ -66,6 +66,7 @@ function Compressor(options, false_by_default) {
join_vars : !false_by_default,
keep_fargs : true,
keep_fnames : false,
keep_infinity : false,
loops : !false_by_default,
negate_iife : !false_by_default,
passes : 1,
@@ -215,7 +216,12 @@ merge(Compressor.prototype, {
}) : make_node(AST_EmptyStatement, node);
}
return make_node(AST_SimpleStatement, node, {
body: node.value || make_node(AST_Undefined, node)
body: node.value || make_node(AST_UnaryPrefix, node, {
operator: "void",
expression: make_node(AST_Number, node, {
value: 0
})
})
});
}
if (node instanceof AST_Lambda && node !== self) {
@@ -1123,8 +1129,12 @@ merge(Compressor.prototype, {
}));
};
function is_undefined(node) {
return node instanceof AST_Undefined || node.is_undefined;
function is_undefined(node, compressor) {
return node.is_undefined
|| node instanceof AST_Undefined
|| node instanceof AST_UnaryPrefix
&& node.operator == "void"
&& !node.expression.has_side_effects(compressor);
}
/* -----[ boolean/negation helpers ]----- */
@@ -1313,7 +1323,7 @@ merge(Compressor.prototype, {
return this;
}
});
var unaryPrefix = makePredicate("! ~ - +");
var unaryPrefix = makePredicate("! ~ - + void");
AST_Node.DEFMETHOD("is_constant", function(){
// Accomodate when compress option evaluate=false
// as well as the common constant expressions !0 and -1
@@ -2971,7 +2981,7 @@ merge(Compressor.prototype, {
}
}
}
if (is_undefined(self.cdr)) {
if (is_undefined(self.cdr, compressor)) {
return make_node(AST_UnaryPrefix, self, {
operator : "void",
expression : self.car
@@ -3010,7 +3020,7 @@ merge(Compressor.prototype, {
self.expression = e;
return self;
} else {
return make_node(AST_Undefined, self).transform(compressor);
return make_node(AST_Undefined, self).optimize(compressor);
}
}
if (compressor.option("booleans") && compressor.in_boolean_context()) {
@@ -3034,6 +3044,9 @@ merge(Compressor.prototype, {
})).optimize(compressor);
}
}
if (self.operator == "-" && e instanceof AST_Infinity) {
e = e.transform(compressor);
}
if (e instanceof AST_Binary
&& (self.operator == "+" || self.operator == "-")
&& (e.operator == "*" || e.operator == "/" || e.operator == "%")) {
@@ -3043,8 +3056,7 @@ merge(Compressor.prototype, {
}
// avoids infinite recursion of numerals
if (self.operator != "-"
|| !(self.expression instanceof AST_Number
|| self.expression instanceof AST_Infinity)) {
|| !(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);
@@ -3087,8 +3099,8 @@ merge(Compressor.prototype, {
OPT(AST_Binary, function(self, compressor){
function reversible() {
return self.left instanceof AST_Constant
|| self.right instanceof AST_Constant
return self.left.is_constant()
|| self.right.is_constant()
|| !self.left.has_side_effects(compressor)
&& !self.right.has_side_effects(compressor);
}
@@ -3101,8 +3113,8 @@ merge(Compressor.prototype, {
}
}
if (commutativeOperators(self.operator)) {
if (self.right instanceof AST_Constant
&& !(self.left instanceof AST_Constant)) {
if (self.right.is_constant()
&& !self.left.is_constant()) {
// if right is a constant, whatever side effects the
// left side might have could not influence the
// result. hence, force switch.
@@ -3464,9 +3476,9 @@ merge(Compressor.prototype, {
case "undefined":
return make_node(AST_Undefined, self).optimize(compressor);
case "NaN":
return make_node(AST_NaN, self);
return make_node(AST_NaN, self).optimize(compressor);
case "Infinity":
return make_node(AST_Infinity, self);
return make_node(AST_Infinity, self).optimize(compressor);
}
}
if (compressor.option("evaluate") && compressor.option("reduce_vars")) {
@@ -3508,7 +3520,38 @@ merge(Compressor.prototype, {
return ref;
}
}
return self;
return make_node(AST_UnaryPrefix, self, {
operator: "void",
expression: make_node(AST_Number, self, {
value: 0
})
});
});
OPT(AST_Infinity, function(self, compressor){
var retain = compressor.option("keep_infinity")
&& !compressor.find_parent(AST_Scope).find_variable("Infinity");
return retain ? self : make_node(AST_Binary, self, {
operator: "/",
left: make_node(AST_Number, self, {
value: 1
}),
right: make_node(AST_Number, self, {
value: 0
})
});
});
OPT(AST_NaN, function(self, compressor){
return compressor.find_parent(AST_Scope).find_variable("NaN") ? make_node(AST_Binary, self, {
operator: "/",
left: make_node(AST_Number, self, {
value: 0
}),
right: make_node(AST_Number, self, {
value: 0
})
}) : self;
});
var ASSIGN_OPS = [ '+', '-', '/', '*', '%', '>>', '<<', '>>>', '|', '^', '&' ];
@@ -3809,7 +3852,7 @@ merge(Compressor.prototype, {
OPT(AST_RegExp, literals_in_boolean_context);
OPT(AST_Return, function(self, compressor){
if (self.value && is_undefined(self.value)) {
if (self.value && is_undefined(self.value, compressor)) {
self.value = null;
}
return self;

28
lib/output.js
View File

@@ -586,21 +586,12 @@ function OutputStream(options) {
return first_in_statement(output);
});
PARENS([ AST_Unary, AST_Undefined ], function(output){
PARENS(AST_Unary, function(output){
var p = output.parent();
return p instanceof AST_PropAccess && p.expression === this
|| p instanceof AST_Call && p.expression === this;
});
PARENS([ AST_Infinity, AST_NaN ], function(output){
var p = output.parent();
return p instanceof AST_PropAccess && p.expression === this
|| p instanceof AST_Call && p.expression === this
|| p instanceof AST_Unary && p.operator != "+" && p.operator != "-"
|| p instanceof AST_Binary && p.right === this
&& (p.operator == "/" || p.operator == "%");
});
PARENS(AST_Seq, function(output){
var p = output.parent();
return p instanceof AST_Call // (foo, bar)() or foo(1, (2, 3), 4)
@@ -1258,24 +1249,7 @@ function OutputStream(options) {
var def = self.definition();
output.print_name(def ? def.mangled_name || def.name : self.name);
});
DEFPRINT(AST_Undefined, function(self, output){
output.print("void 0");
});
DEFPRINT(AST_Hole, noop);
DEFPRINT(AST_Infinity, function(self, output){
output.print("1");
output.space();
output.print("/");
output.space();
output.print("0");
});
DEFPRINT(AST_NaN, function(self, output){
output.print("0");
output.space();
output.print("/");
output.space();
output.print("0");
});
DEFPRINT(AST_This, function(self, output){
output.print("this");
});

8
test/compress/conditionals.js
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@@ -840,8 +840,8 @@ equality_conditionals_false: {
f(0, true, 0),
f(1, 2, 3),
f(1, null, 3),
f(0/0),
f(0/0, "foo");
f(NaN),
f(NaN, "foo");
}
expect_stdout: true
}
@@ -888,8 +888,8 @@ equality_conditionals_true: {
f(0, true, 0),
f(1, 2, 3),
f(1, null, 3),
f(0/0),
f(0/0, "foo");
f(NaN),
f(NaN, "foo");
}
expect_stdout: true
}

8
test/compress/evaluate.js
View File

@@ -52,7 +52,7 @@ and: {
a = 7;
a = false;
a = 0/0;
a = NaN;
a = 0;
a = void 0;
a = null;
@@ -67,7 +67,7 @@ and: {
a = 6 << condition && -4.5;
a = condition && false;
a = console.log("b") && 0/0;
a = console.log("b") && NaN;
a = console.log("c") && 0;
a = 2 * condition && void 0;
a = condition + 3 && null;
@@ -149,7 +149,7 @@ or: {
a = 6 << condition || -4.5;
a = condition || false;
a = console.log("b") || 0/0;
a = console.log("b") || NaN;
a = console.log("c") || 0;
a = 2 * condition || void 0;
a = condition + 3 || null;
@@ -533,7 +533,7 @@ unsafe_array: {
[1, 2, 3, a][0] + 1,
2,
3,
0/0,
NaN,
"1,21",
5,
(void 0)[1] + 1

68
test/compress/issue-1105.js
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@@ -193,6 +193,7 @@ assorted_Infinity_NaN_undefined_in_with_scope: {
cascade: true,
side_effects: true,
sequences: false,
keep_infinity: false,
}
input: {
var f = console.log;
@@ -224,10 +225,73 @@ assorted_Infinity_NaN_undefined_in_with_scope: {
};
if (o) {
f(void 0, void 0);
f(0/0, 0/0);
f(NaN, NaN);
f(1/0, 1/0);
f(-1/0, -1/0);
f(0/0, 0/0);
f(NaN, NaN);
}
with (o) {
f(undefined, void 0);
f(NaN, 0/0);
f(Infinity, 1/0);
f(-Infinity, -1/0);
f(9 + undefined, 9 + void 0);
}
}
expect_stdout: true
}
assorted_Infinity_NaN_undefined_in_with_scope_keep_infinity: {
options = {
unused: true,
evaluate: true,
dead_code: true,
conditionals: true,
comparisons: true,
booleans: true,
hoist_funs: true,
keep_fargs: true,
if_return: true,
join_vars: true,
cascade: true,
side_effects: true,
sequences: false,
keep_infinity: true,
}
input: {
var f = console.log;
var o = {
undefined : 3,
NaN : 4,
Infinity : 5,
};
if (o) {
f(undefined, void 0);
f(NaN, 0/0);
f(Infinity, 1/0);
f(-Infinity, -(1/0));
f(2 + 7 + undefined, 2 + 7 + void 0);
}
with (o) {
f(undefined, void 0);
f(NaN, 0/0);
f(Infinity, 1/0);
f(-Infinity, -(1/0));
f(2 + 7 + undefined, 2 + 7 + void 0);
}
}
expect: {
var f = console.log, o = {
undefined : 3,
NaN : 4,
Infinity : 5
};
if (o) {
f(void 0, void 0);
f(NaN, NaN);
f(Infinity, 1/0);
f(-Infinity, -1/0);
f(NaN, NaN);
}
with (o) {
f(undefined, void 0);

32
test/compress/issue-597.js
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@@ -6,7 +6,7 @@ NaN_and_Infinity_must_have_parens: {
}
expect: {
(1/0).toString();
(0/0).toString();
NaN.toString();
}
}
@@ -24,6 +24,36 @@ NaN_and_Infinity_should_not_be_replaced_when_they_are_redefined: {
}
}
NaN_and_Infinity_must_have_parens_evaluate: {
options = {
evaluate: true,
}
input: {
(123456789 / 0).toString();
(+"foo").toString();
}
expect: {
(1/0).toString();
NaN.toString();
}
}
NaN_and_Infinity_should_not_be_replaced_when_they_are_redefined_evaluate: {
options = {
evaluate: true,
}
input: {
var Infinity, NaN;
(123456789 / 0).toString();
(+"foo").toString();
}
expect: {
var Infinity, NaN;
(1/0).toString();
(0/0).toString();
}
}
beautify_off_1: {
options = {
evaluate: true,

2
test/compress/numbers.js
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@@ -186,7 +186,7 @@ unary_binary_parenthesis: {
});
}
expect: {
var v = [ 0, 1, 0/0, 1/0, null, void 0, true, false, "", "foo", /foo/ ];
var v = [ 0, 1, NaN, 1/0, null, void 0, true, false, "", "foo", /foo/ ];
v.forEach(function(x) {
v.forEach(function(y) {
console.log(

2
test/compress/properties.js
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@@ -77,7 +77,7 @@ sub_properties: {
a[3.14] = 3;
a.if = 4;
a["foo bar"] = 5;
a[0/0] = 6;
a[NaN] = 6;
a[null] = 7;
a[void 0] = 8;
}