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#873 Fix conditionals optimizations with default compress options

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This commit is contained in:
kzc
2015-11-24 13:27:50 -05:00
parent 15b5f70338
commit 774bda13cd
2 changed files with 256 additions and 20 deletions
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66
lib/compress.js
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@@ -726,6 +726,32 @@ merge(Compressor.prototype, {
return [ this ];
}
});
AST_Node.DEFMETHOD("is_constant", function(compressor){
// Accomodate when compress option evaluate=false
// as well as the common constant expressions !0 and !1
return this instanceof AST_Constant
|| (this instanceof AST_UnaryPrefix && this.operator == "!"
&& this.expression instanceof AST_Constant)
|| this.evaluate(compressor).length > 1;
});
// Obtain the constant value of an expression already known to be constant.
// Result only valid iff this.is_constant(compressor) is true.
AST_Node.DEFMETHOD("constant_value", function(compressor){
// Accomodate when option evaluate=false.
if (this instanceof AST_Constant) return this.value;
// Accomodate the common constant expressions !0 and !1 when option evaluate=false.
if (this instanceof AST_UnaryPrefix
&& this.operator == "!"
&& this.expression instanceof AST_Constant) {
return !this.expression.value;
}
var result = this.evaluate(compressor)
if (result.length > 1) {
return result[1];
}
// should never be reached
return undefined;
});
def(AST_Statement, function(){
throw new Error(string_template("Cannot evaluate a statement [{file}:{line},{col}]", this.start));
});
@@ -2427,32 +2453,48 @@ merge(Compressor.prototype, {
alternative: alternative
});
}
// x=y?1:1 --> x=1
if (consequent instanceof AST_Constant
&& alternative instanceof AST_Constant
// y?1:1 --> 1
if (consequent.is_constant(compressor)
&& alternative.is_constant(compressor)
&& consequent.equivalent_to(alternative)) {
var consequent_value = consequent.constant_value();
if (self.condition.has_side_effects(compressor)) {
return AST_Seq.from_array([self.condition, make_node_from_constant(compressor, consequent.value, self)]);
return AST_Seq.from_array([self.condition, make_node_from_constant(compressor, consequent_value, self)]);
} else {
return make_node_from_constant(compressor, consequent.value, self);
return make_node_from_constant(compressor, consequent_value, self);
}
}
// x=y?true:false --> x=!!y
if (consequent instanceof AST_True
&& alternative instanceof AST_False) {
// y?true:false --> !!y
if (is_true(consequent) && is_false(alternative)) {
self.condition = self.condition.negate(compressor);
return make_node(AST_UnaryPrefix, self.condition, {
operator: "!",
expression: self.condition
});
}
// x=y?false:true --> x=!y
if (consequent instanceof AST_False
&& alternative instanceof AST_True) {
// y?false:true --> !y
if (is_false(consequent) && is_true(alternative)) {
return self.condition.negate(compressor)
}
return self;
// AST_True or !0
function is_true(node) {
return node instanceof AST_True
|| (node instanceof AST_UnaryPrefix
&& node.operator == "!"
&& node.expression instanceof AST_Constant
&& !node.expression.value);
}
// AST_False or !1
function is_false(node) {
return node instanceof AST_False
|| (node instanceof AST_UnaryPrefix
&& node.operator == "!"
&& node.expression instanceof AST_Constant
&& !!node.expression.value);
}
});
OPT(AST_Boolean, function(self, compressor){