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enhance conditionals (#3643)

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This commit is contained in:
Alex Lam S.L
2019-12-22 04:29:32 +00:00
committed by GitHub
parent 519a00bd8a
commit 75aa6ef848
5 changed files with 120 additions and 33 deletions
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72
lib/compress.js
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@@ -7005,25 +7005,42 @@ merge(Compressor.prototype, {
});
}
}
// x ? y(a) : y(b) --> y(x ? a : b)
var arg_index;
// x ? y : y --> x, y
if (consequent.equivalent_to(alternative)) return make_sequence(self, [
condition,
consequent
]).optimize(compressor);
if (consequent instanceof AST_Call
&& alternative.TYPE === consequent.TYPE
&& consequent.args.length > 0
&& consequent.args.length == alternative.args.length
&& consequent.expression.equivalent_to(alternative.expression)
&& !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: condition,
consequent: consequent.args[arg_index],
alternative: alternative.args[arg_index]
});
return node;
&& consequent.args.length == alternative.args.length) {
var arg_index = arg_diff();
// x ? y(a) : z(a) --> (x ? y : z)(a)
if (arg_index == -1
&& !(consequent.expression instanceof AST_PropAccess)
&& !(alternative.expression instanceof AST_PropAccess)) {
var node = consequent.clone();
node.expression = make_node(AST_Conditional, self, {
condition: condition,
consequent: consequent.expression,
alternative: alternative.expression
});
return node;
}
// x ? y(a) : y(b) --> y(x ? a : b)
if (arg_index >= 0
&& consequent.expression.equivalent_to(alternative.expression)
&& !condition.has_side_effects(compressor)
&& !consequent.expression.has_side_effects(compressor)) {
var node = consequent.clone();
node.args[arg_index] = make_node(AST_Conditional, self, {
condition: condition,
consequent: consequent.args[arg_index],
alternative: alternative.args[arg_index]
});
return node;
}
}
// x?y?z:a:a --> x&&y?z:a
// x ? (y ? a : b) : b --> x && y ? a : b
if (consequent instanceof AST_Conditional
&& consequent.alternative.equivalent_to(alternative)) {
return make_node(AST_Conditional, self, {
@@ -7036,12 +7053,18 @@ merge(Compressor.prototype, {
alternative: alternative
});
}
// x ? y : y --> x, y
if (consequent.equivalent_to(alternative)) {
return make_sequence(self, [
condition,
consequent
]).optimize(compressor);
// x ? a : (y ? a : b)--> x || y ? a : b
if (alternative instanceof AST_Conditional
&& consequent.equivalent_to(alternative.consequent)) {
return make_node(AST_Conditional, self, {
condition: make_node(AST_Binary, self, {
left: condition,
operator: "||",
right: alternative.condition
}),
consequent: consequent,
alternative: alternative.alternative
});
}
// x ? (y, w) : (z, w) --> x ? y : z, w
if ((consequent instanceof AST_Sequence || alternative instanceof AST_Sequence)
@@ -7145,17 +7168,18 @@ merge(Compressor.prototype, {
&& node.expression.getValue());
}
function single_arg_diff() {
function arg_diff() {
var a = consequent.args;
var b = alternative.args;
for (var i = 0, len = a.length; i < len; i++) {
if (!a[i].equivalent_to(b[i])) {
for (var j = i + 1; j < len; j++) {
if (!a[j].equivalent_to(b[j])) return;
if (!a[j].equivalent_to(b[j])) return -2;
}
return i;
}
}
return -1;
}
function can_shift_lhs_of_tail(node) {