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improve compression of undefined, NaN & Infinitiy (#1748)

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- migrate transformation logic from `OutputStream` to `Compressor`
- always turn `undefined` into `void 0` (unless `unsafe`)
- always keep `NaN` except when avoiding local variable redefinition
- introduce `keep_infinity` to suppress `1/0` transform, except when avoiding local variable redefinition

supersedes #1723
fixes #1730
This commit is contained in:
Alex Lam S.L
2017-04-01 03:02:14 +08:00
committed by GitHub
parent 1ddc05725d
commit 257ddc3bdb
9 changed files with 170 additions and 56 deletions
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28
lib/output.js
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@@ -586,21 +586,12 @@ function OutputStream(options) {
return first_in_statement(output);
});
PARENS([ AST_Unary, AST_Undefined ], function(output){
PARENS(AST_Unary, function(output){
var p = output.parent();
return p instanceof AST_PropAccess && p.expression === this
|| p instanceof AST_Call && p.expression === this;
});
PARENS([ AST_Infinity, AST_NaN ], function(output){
var p = output.parent();
return p instanceof AST_PropAccess && p.expression === this
|| p instanceof AST_Call && p.expression === this
|| p instanceof AST_Unary && p.operator != "+" && p.operator != "-"
|| p instanceof AST_Binary && p.right === this
&& (p.operator == "/" || p.operator == "%");
});
PARENS(AST_Seq, function(output){
var p = output.parent();
return p instanceof AST_Call // (foo, bar)() or foo(1, (2, 3), 4)
@@ -1258,24 +1249,7 @@ function OutputStream(options) {
var def = self.definition();
output.print_name(def ? def.mangled_name || def.name : self.name);
});
DEFPRINT(AST_Undefined, function(self, output){
output.print("void 0");
});
DEFPRINT(AST_Hole, noop);
DEFPRINT(AST_Infinity, function(self, output){
output.print("1");
output.space();
output.print("/");
output.space();
output.print("0");
});
DEFPRINT(AST_NaN, function(self, output){
output.print("0");
output.space();
output.print("/");
output.space();
output.print("0");
});
DEFPRINT(AST_This, function(self, output){
output.print("this");
});