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more sequence optimizations (lift some sequences above binary/unary expressions so that we can avoid parens)

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This commit is contained in:
Mihai Bazon
2012-10-22 11:49:58 +03:00
parent 41be8632d3
commit 30faaf13ed
4 changed files with 102 additions and 1 deletions
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49
lib/compress.js
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@@ -1380,6 +1380,10 @@ merge(Compressor.prototype, {
});
OPT(AST_Seq, function(self, compressor){
if (!compressor.option("side_effects"))
return self;
if (!self.car.has_side_effects())
return self.cdr;
if (compressor.option("cascade")) {
if (self.car instanceof AST_Assign
&& !self.car.left.has_side_effects()
@@ -1395,7 +1399,26 @@ merge(Compressor.prototype, {
return self;
});
AST_Unary.DEFMETHOD("lift_sequences", function(compressor){
if (compressor.option("sequences")) {
if (this.expression instanceof AST_Seq) {
var seq = this.expression;
var x = seq.to_array();
this.expression = x.pop();
x.push(this);
seq = AST_Seq.from_array(x).transform(compressor);
return seq;
}
}
return this;
});
OPT(AST_UnaryPostfix, function(self, compressor){
return self.lift_sequences(compressor);
});
OPT(AST_UnaryPrefix, function(self, compressor){
self = self.lift_sequences(compressor);
var e = self.expression;
if (compressor.option("booleans") && compressor.in_boolean_context()) {
switch (self.operator) {
@@ -1418,7 +1441,32 @@ merge(Compressor.prototype, {
return self.evaluate(compressor)[0];
});
AST_Binary.DEFMETHOD("lift_sequences", function(compressor){
if (compressor.option("sequences")) {
if (this.left instanceof AST_Seq) {
var seq = this.left;
var x = seq.to_array();
this.left = x.pop();
x.push(this);
seq = AST_Seq.from_array(x).transform(compressor);
return seq;
}
if (this.right instanceof AST_Seq
&& !(this.operator == "||" || this.operator == "&&")
&& !this.left.has_side_effects()) {
var seq = this.right;
var x = seq.to_array();
this.right = x.pop();
x.push(this);
seq = AST_Seq.from_array(x).transform(compressor);
return seq;
}
}
return this;
});
OPT(AST_Binary, function(self, compressor){
self = self.lift_sequences(compressor);
if (compressor.option("comparisons")) switch (self.operator) {
case "===":
case "!==":
@@ -1557,6 +1605,7 @@ merge(Compressor.prototype, {
var ASSIGN_OPS = [ '+', '-', '/', '*', '%', '>>', '<<', '>>>', '|', '^', '&' ];
OPT(AST_Assign, function(self, compressor){
self = self.lift_sequences(compressor);
if (self.operator == "="
&& self.left instanceof AST_SymbolRef
&& self.right instanceof AST_Binary