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enhance conditionals #3243

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merged 1 commit into from
Aug 29, 2018
Merged

enhance conditionals #3243

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57 changes: 33 additions & 24 deletions lib/compress.js
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Original file line number Diff line number Diff line change
Expand Up @@ -6047,20 +6047,22 @@ merge(Compressor.prototype, {
// |
// v
// exp = foo ? something : something_else;
if (consequent instanceof AST_Assign
&& alternative instanceof AST_Assign
&& consequent.operator == alternative.operator
&& consequent.left.equivalent_to(alternative.left)
&& (!self.condition.has_side_effects(compressor)
|| consequent.operator == "="
&& !consequent.left.has_side_effects(compressor))) {
var seq_tail = consequent.tail_node();
var alt_tail = alternative.tail_node();
if (seq_tail instanceof AST_Assign
&& alt_tail instanceof AST_Assign
&& seq_tail.operator == alt_tail.operator
&& seq_tail.left.equivalent_to(alt_tail.left)
&& (!condition.has_side_effects(compressor)
|| seq_tail.operator == "="
&& !seq_tail.left.has_side_effects(compressor))) {
return make_node(AST_Assign, self, {
operator: consequent.operator,
left: consequent.left,
operator: seq_tail.operator,
left: seq_tail.left,
right: make_node(AST_Conditional, self, {
condition: self.condition,
consequent: consequent.right,
alternative: alternative.right
condition: condition,
consequent: pop_lhs(consequent),
alternative: pop_lhs(alternative)
})
});
}
Expand All @@ -6071,12 +6073,12 @@ merge(Compressor.prototype, {
&& consequent.args.length > 0
&& consequent.args.length == alternative.args.length
&& consequent.expression.equivalent_to(alternative.expression)
&& !self.condition.has_side_effects(compressor)
&& !condition.has_side_effects(compressor)
&& !consequent.expression.has_side_effects(compressor)
&& typeof (arg_index = single_arg_diff()) == "number") {
var node = consequent.clone();
node.args[arg_index] = make_node(AST_Conditional, self, {
condition: self.condition,
condition: condition,
consequent: consequent.args[arg_index],
alternative: alternative.args[arg_index]
});
Expand All @@ -6087,7 +6089,7 @@ merge(Compressor.prototype, {
&& consequent.alternative.equivalent_to(alternative)) {
return make_node(AST_Conditional, self, {
condition: make_node(AST_Binary, self, {
left: self.condition,
left: condition,
operator: "&&",
right: consequent.condition
}),
Expand All @@ -6098,7 +6100,7 @@ merge(Compressor.prototype, {
// x ? y : y --> x, y
if (consequent.equivalent_to(alternative)) {
return make_sequence(self, [
self.condition,
condition,
consequent
]).optimize(compressor);
}
Expand All @@ -6107,7 +6109,7 @@ merge(Compressor.prototype, {
&& consequent.tail_node().equivalent_to(alternative.tail_node())) {
return make_sequence(self, [
make_node(AST_Conditional, self, {
condition: self.condition,
condition: condition,
consequent: pop_seq(consequent),
alternative: pop_seq(alternative)
}),
Expand All @@ -6122,7 +6124,7 @@ merge(Compressor.prototype, {
operator: "||",
left: make_node(AST_Binary, self, {
operator: "&&",
left: self.condition,
left: condition,
right: consequent.left
}),
right: alternative
Expand All @@ -6132,40 +6134,40 @@ merge(Compressor.prototype, {
if (is_true(self.consequent)) {
if (is_false(self.alternative)) {
// c ? true : false ---> !!c
return booleanize(self.condition);
return booleanize(condition);
}
// c ? true : x ---> !!c || x
return make_node(AST_Binary, self, {
operator: "||",
left: booleanize(self.condition),
left: booleanize(condition),
right: self.alternative
});
}
if (is_false(self.consequent)) {
if (is_true(self.alternative)) {
// c ? false : true ---> !c
return booleanize(self.condition.negate(compressor));
return booleanize(condition.negate(compressor));
}
// c ? false : x ---> !c && x
return make_node(AST_Binary, self, {
operator: "&&",
left: booleanize(self.condition.negate(compressor)),
left: booleanize(condition.negate(compressor)),
right: self.alternative
});
}
if (is_true(self.alternative)) {
// c ? x : true ---> !c || x
return make_node(AST_Binary, self, {
operator: "||",
left: booleanize(self.condition.negate(compressor)),
left: booleanize(condition.negate(compressor)),
right: self.consequent
});
}
if (is_false(self.alternative)) {
// c ? x : false ---> !!c && x
return make_node(AST_Binary, self, {
operator: "&&",
left: booleanize(self.condition),
left: booleanize(condition),
right: self.consequent
});
}
Expand Down Expand Up @@ -6217,6 +6219,13 @@ merge(Compressor.prototype, {
}
}

function pop_lhs(node) {
if (!(node instanceof AST_Sequence)) return node.right;
var exprs = node.expressions.slice();
exprs.push(exprs.pop().right);
return make_sequence(node, exprs);
}

function pop_seq(node) {
if (!(node instanceof AST_Sequence)) return make_node(AST_Number, node, {
value: 0
Expand Down
72 changes: 72 additions & 0 deletions test/compress/conditionals.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1292,3 +1292,75 @@ to_and_or: {
}
expect_stdout: true
}

cond_seq_assign_1: {
options = {
conditionals: true,
sequences: true,
}
input: {
function f(a) {
var t;
if (a) {
t = "foo";
t = "bar";
} else {
console.log(t);
t = 42;
}
console.log(t);
}
f(f);
f();
}
expect: {
function f(a) {
var t;
t = a ? (t = "foo", "bar") : (console.log(t), 42),
console.log(t);
}
f(f),
f();
}
expect_stdout: [
"bar",
"undefined",
"42",
]
}

cond_seq_assign_2: {
options = {
conditionals: true,
sequences: true,
}
input: {
function f(a) {
var t;
if (a) {
t = "foo";
a = "bar";
} else {
console.log(t);
t = 42;
}
console.log(t);
}
f(f);
f();
}
expect: {
function f(a) {
var t;
a ? (t = "foo", a = "bar") : (console.log(t), t = 42),
console.log(t);
}
f(f),
f();
}
expect_stdout: [
"foo",
"undefined",
"42",
]
}