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improve compression of loop conditions (#2543)

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This commit is contained in:
Alex Lam S.L
2017-12-01 05:52:33 +08:00
committed by GitHub
parent 172079a47f
commit b762f2d6f4
6 changed files with 64 additions and 46 deletions
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97
lib/compress.js
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@@ -3020,34 +3020,40 @@ merge(Compressor.prototype, {
return self;
});
OPT(AST_DWLoop, function(self, compressor){
OPT(AST_While, function(self, compressor){
return compressor.option("loops") ? make_node(AST_For, self, self).optimize(compressor) : self;
});
OPT(AST_Do, function(self, compressor){
if (!compressor.option("loops")) return self;
var cond = self.condition.evaluate(compressor);
if (cond !== self.condition) {
if (cond) {
return make_node(AST_For, self, {
body: self.body
});
}
if (compressor.option("dead_code") && self instanceof AST_While) {
var a = [];
extract_declarations_from_unreachable_code(compressor, self.body, a);
return make_node(AST_BlockStatement, self, { body: a }).optimize(compressor);
}
if (self instanceof AST_Do) {
var has_loop_control = false;
var tw = new TreeWalker(function(node) {
if (node instanceof AST_Scope || has_loop_control) return true;
if (node instanceof AST_LoopControl && tw.loopcontrol_target(node) === self)
return has_loop_control = true;
});
var parent = compressor.parent();
(parent instanceof AST_LabeledStatement ? parent : self).walk(tw);
if (!has_loop_control) return self.body;
}
}
if (self instanceof AST_While) {
return make_node(AST_For, self, self).optimize(compressor);
var cond = self.condition.tail_node().evaluate(compressor);
if (!(cond instanceof AST_Node)) {
if (cond) return make_node(AST_For, self, {
body: make_node(AST_BlockStatement, self.body, {
body: [
self.body,
make_node(AST_SimpleStatement, self.condition, {
body: self.condition
})
]
})
}).optimize(compressor);
var has_loop_control = false;
var tw = new TreeWalker(function(node) {
if (node instanceof AST_Scope || has_loop_control) return true;
if (node instanceof AST_LoopControl && tw.loopcontrol_target(node) === self)
return has_loop_control = true;
});
var parent = compressor.parent();
(parent instanceof AST_LabeledStatement ? parent : self).walk(tw);
if (!has_loop_control) return make_node(AST_BlockStatement, self.body, {
body: [
self.body,
make_node(AST_SimpleStatement, self.condition, {
body: self.condition
})
]
}).optimize(compressor);
}
return self;
});
@@ -3101,22 +3107,31 @@ merge(Compressor.prototype, {
if (!compressor.option("loops")) return self;
if (self.condition) {
var cond = self.condition.evaluate(compressor);
if (compressor.option("dead_code") && !cond) {
var a = [];
if (self.init instanceof AST_Statement) {
a.push(self.init);
if (!(cond instanceof AST_Node)) {
if (cond) self.condition = null;
else if (!compressor.option("dead_code")) {
var orig = self.condition;
self.condition = make_node_from_constant(cond, self.condition);
self.condition = best_of_expression(self.condition.transform(compressor), orig);
}
else if (self.init) {
a.push(make_node(AST_SimpleStatement, self.init, {
body: self.init
}));
}
extract_declarations_from_unreachable_code(compressor, self.body, a);
return make_node(AST_BlockStatement, self, { body: a }).optimize(compressor);
}
if (cond !== self.condition) {
cond = make_node_from_constant(cond, self.condition).transform(compressor);
self.condition = best_of_expression(cond, self.condition);
if (compressor.option("dead_code")) {
if (cond instanceof AST_Node) cond = self.condition.tail_node().evaluate(compressor);
if (!cond) {
var body = [];
extract_declarations_from_unreachable_code(compressor, self.body, body);
body.push(make_node(AST_SimpleStatement, self.condition, {
body: self.condition
}));
if (self.init instanceof AST_Statement) {
body.push(self.init);
} else if (self.init) {
body.push(make_node(AST_SimpleStatement, self.init, {
body: self.init
}));
}
return make_node(AST_BlockStatement, self, { body: body }).optimize(compressor);
}
}
}
if_break_in_loop(self, compressor);