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compress numeric expressions
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- `unsafe_math` for unsafe associative operations

fixes mishoo#412
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@alexlamsl
alexlamsl committed Mar 1, 2017
1 parent fb2b6c7 commit 771748d
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Showing 2 changed files with 219 additions and 4 deletions.
117 changes: 113 additions & 4 deletions lib/compress.js
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,7 @@ function Compressor(options, false_by_default) {
drop_debugger : !false_by_default,
unsafe : false,
unsafe_comps : false,
unsafe_math : false,
unsafe_proto : false,
conditionals : !false_by_default,
comparisons : !false_by_default,
Expand Down Expand Up @@ -967,6 +968,34 @@ merge(Compressor.prototype, {
node.DEFMETHOD("is_boolean", func);
});

// methods to determine if an expression has a numeric result type
(function (def){
def(AST_Node, return_false);
def(AST_Number, return_true);
var unary = makePredicate("+ - ~ ++ --");
def(AST_Unary, function(){
return unary(this.operator);
});
var binary = makePredicate("- * / % & | ^ << >> >>>");
def(AST_Binary, function(compressor){
return binary(this.operator) || this.operator == "+"
&& this.left.is_number(compressor)
&& this.right.is_number(compressor);
});
var assign = makePredicate("-= *= /= %= &= |= ^= <<= >>= >>>=");
def(AST_Assign, function(compressor){
return assign(this.operator) || this.right.is_number(compressor);
});
def(AST_Seq, function(compressor){
return this.cdr.is_number(compressor);
});
def(AST_Conditional, function(compressor){
return this.consequent.is_number(compressor) && this.alternative.is_number(compressor);
});
})(function(node, func){
node.DEFMETHOD("is_number", func);
});

// methods to determine if an expression has a string result type
(function (def){
def(AST_Node, return_false);
Expand Down Expand Up @@ -2826,6 +2855,7 @@ merge(Compressor.prototype, {
case "===":
case "!==":
if ((self.left.is_string(compressor) && self.right.is_string(compressor)) ||
(self.left.is_number(compressor) && self.right.is_number(compressor)) ||
(self.left.is_boolean() && self.right.is_boolean())) {
self.operator = self.operator.substr(0, 2);
}
Expand Down Expand Up @@ -2948,22 +2978,25 @@ merge(Compressor.prototype, {
}
break;
}
if (self.operator == "+") {
switch (self.operator) {
case "+":
// "foo" + ("bar" + x) => "foobar" + x
if (self.left instanceof AST_Constant
&& self.right instanceof AST_Binary
&& self.right.operator == "+"
&& self.right.left instanceof AST_Constant
&& self.right.is_string(compressor)) {
self = make_node(AST_Binary, self, {
operator: "+",
left: make_node(AST_String, null, {
left: make_node(AST_String, self.left, {
value: "" + self.left.getValue() + self.right.left.getValue(),
start: self.left.start,
end: self.right.left.end
}),
right: self.right.right
});
}
// (x + "foo") + "bar" => x + "foobar"
if (self.right instanceof AST_Constant
&& self.left instanceof AST_Binary
&& self.left.operator == "+"
Expand All @@ -2972,13 +3005,14 @@ merge(Compressor.prototype, {
self = make_node(AST_Binary, self, {
operator: "+",
left: self.left.left,
right: make_node(AST_String, null, {
right: make_node(AST_String, self.right, {
value: "" + self.left.right.getValue() + self.right.getValue(),
start: self.left.right.start,
end: self.right.end
})
});
}
// (x + "foo") + ("bar" + y) => (x + "foobar") + y
if (self.left instanceof AST_Binary
&& self.left.operator == "+"
&& self.left.is_string(compressor)
Expand All @@ -2992,7 +3026,7 @@ merge(Compressor.prototype, {
left: make_node(AST_Binary, self.left, {
operator: "+",
left: self.left.left,
right: make_node(AST_String, null, {
right: make_node(AST_String, self.left.right, {
value: "" + self.left.right.getValue() + self.right.left.getValue(),
start: self.left.right.start,
end: self.right.left.end
Expand All @@ -3001,6 +3035,81 @@ merge(Compressor.prototype, {
right: self.right.right
});
}
case "*":
case "&":
case "|":
case "^":
if (compressor.option("unsafe_math") && 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, {
operator: self.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
});
}
// (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) {
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
});
}
}
}
}
// x && (y && z) ==> x && y && z
Expand Down
106 changes: 106 additions & 0 deletions test/compress/numbers.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -17,3 +17,109 @@ hex_numbers_in_parentheses_for_prototype_functions: {
}
expect_exact: "-2;(-2).toFixed(0);2;2..toFixed(0);.2;.2.toFixed(0);2e-8;2e-8.toFixed(0);0xde0b6b3a7640080;(0xde0b6b3a7640080).toFixed(0);"
}

comparisons: {
options = {
comparisons: true,
}
input: {
console.log(
~x === 42,
x % n === 42
);
}
expect: {
console.log(
42 == ~x,
x % n == 42
);
}
}

evaluate_1: {
options = {
evaluate: true,
unsafe_math: false,
}
input: {
console.log(
x + 1 + 2,
x * 1 * 2,
+x + 1 + 2,
1 + x + 2 + 3,
1 | x | 2 | 3,
1 + x-- + 2 + 3,
1 + (x*y + 2) + 3,
1 + (2 + x + 3),
1 & (2 & x & 3),
1 + (2 + (x |= 0) + 3)
);
}
expect: {
console.log(
x + 1 + 2,
1 * x * 2,
+x + 1 + 2,
1 + x + 2 + 3,
1 | x | 2 | 3,
1 + x-- + 2 + 3,
1 + (x*y + 2) + 3,
1 + (2 + x + 3),
1 & (2 & x & 3),
1 + (2 + (x |= 0) + 3)
);
}
}

evaluate_2: {
options = {
evaluate: true,
unsafe_math: true,
}
input: {
console.log(
x + 1 + 2,
x * 1 * 2,
+x + 1 + 2,
1 + x + 2 + 3,
1 | x | 2 | 3,
1 + x-- + 2 + 3,
1 + (x*y + 2) + 3,
1 + (2 + x + 3),
1 & (2 & x & 3),
1 + (2 + (x |= 0) + 3)
);
}
expect: {
console.log(
x + 1 + 2,
2 * x,
3 + +x,
1 + x + 2 + 3,
3 | x,
6 + x--,
6 + x*y,
1 + (2 + x + 3),
0 & x,
6 + (x |= 0)
);
}
}

evaluate_3: {
options = {
evaluate: true,
unsafe: true,
unsafe_math: true,
}
input: {
console.log(
1 + Number(x) + 2
);
}
expect: {
console.log(
3 + +x
);
}
}

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