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clean up negate_iife
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- remove extra tree scanning phase for `negate_iife`
- `negate_iife` now only deals with the narrowest form, i.e. IIFE sitting directly under `AST_SimpleStatement`
- `booleans`, `conditionals` etc. will now take care the rest via more accurate accounting
- `a(); void b();` => `a(); b();`

fixes #1288
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@alexlamsl
alexlamsl committed Feb 1, 2017
1 parent 7f8d72d commit 1fd8caa
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Showing 5 changed files with 277 additions and 99 deletions.
142 changes: 68 additions & 74 deletions lib/compress.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -261,6 +261,15 @@ merge(Compressor.prototype, {
return x;
};

var readOnlyPrefix = makePredicate("! ~ + - void typeof");
function statement_to_expression(stat) {
if (stat.body instanceof AST_UnaryPrefix && readOnlyPrefix(stat.body.operator)) {
return stat.body.expression;
} else {
return stat.body;
}
}

function tighten_body(statements, compressor) {
var CHANGED, max_iter = 10;
do {
Expand All @@ -286,10 +295,6 @@ merge(Compressor.prototype, {
}
} while (CHANGED && max_iter-- > 0);

if (compressor.option("negate_iife")) {
negate_iifes(statements, compressor);
}

return statements;

function collapse_single_use_vars(statements, compressor) {
Expand Down Expand Up @@ -731,7 +736,7 @@ merge(Compressor.prototype, {
};
statements.forEach(function(stat){
if (stat instanceof AST_SimpleStatement && seqLength(seq) < compressor.sequences_limit) {
seq.push(stat.body);
seq.push(seq.length > 0 ? statement_to_expression(stat) : stat.body);
} else {
push_seq();
ret.push(stat);
Expand Down Expand Up @@ -780,7 +785,7 @@ merge(Compressor.prototype, {
stat.init = cons_seq(stat.init);
}
else if (!stat.init) {
stat.init = prev.body;
stat.init = statement_to_expression(prev);
ret.pop();
}
} catch(ex) {
Expand Down Expand Up @@ -837,50 +842,6 @@ merge(Compressor.prototype, {
}, []);
};

function negate_iifes(statements, compressor) {
function is_iife_call(node) {
if (node instanceof AST_Call) {
return node.expression instanceof AST_Function || is_iife_call(node.expression);
}
return false;
}

statements.forEach(function(stat){
if (stat instanceof AST_SimpleStatement) {
stat.body = (function transform(thing) {
return thing.transform(new TreeTransformer(function(node){
if (node instanceof AST_New) {
return node;
}
if (is_iife_call(node)) {
return make_node(AST_UnaryPrefix, node, {
operator: "!",
expression: node
});
}
else if (node instanceof AST_Call) {
node.expression = transform(node.expression);
}
else if (node instanceof AST_Seq) {
node.car = transform(node.car);
}
else if (node instanceof AST_Conditional) {
var expr = transform(node.condition);
if (expr !== node.condition) {
// it has been negated, reverse
node.condition = expr;
var tmp = node.consequent;
node.consequent = node.alternative;
node.alternative = tmp;
}
}
return node;
}));
})(stat.body);
}
});
};

};

function extract_functions_from_statement_array(statements) {
Expand Down Expand Up @@ -985,7 +946,15 @@ merge(Compressor.prototype, {
return ast1.print_to_string().length >
ast2.print_to_string().length
? ast2 : ast1;
};
}

function best_of_statement(ast1, ast2) {
return best_of(make_node(AST_SimpleStatement, ast1, {
body: ast1
}), make_node(AST_SimpleStatement, ast2, {
body: ast2
})).body;
}

// methods to evaluate a constant expression
(function (def){
Expand Down Expand Up @@ -1205,7 +1174,17 @@ merge(Compressor.prototype, {
operator: "!",
expression: exp
});
};
}
function best(orig, alt, first_in_statement) {
var negated = basic_negation(orig);
if (first_in_statement) {
var stat = make_node(AST_SimpleStatement, alt, {
body: alt
});
return best_of(negated, stat) === stat ? alt : negated;
}
return best_of(negated, alt);
}
def(AST_Node, function(){
return basic_negation(this);
});
Expand All @@ -1225,13 +1204,13 @@ merge(Compressor.prototype, {
self.cdr = self.cdr.negate(compressor);
return self;
});
def(AST_Conditional, function(compressor){
def(AST_Conditional, function(compressor, first_in_statement){
var self = this.clone();
self.consequent = self.consequent.negate(compressor);
self.alternative = self.alternative.negate(compressor);
return best_of(basic_negation(this), self);
return best(this, self, first_in_statement);
});
def(AST_Binary, function(compressor){
def(AST_Binary, function(compressor, first_in_statement){
var self = this.clone(), op = this.operator;
if (compressor.option("unsafe_comps")) {
switch (op) {
Expand All @@ -1248,20 +1227,20 @@ merge(Compressor.prototype, {
case "!==": self.operator = "==="; return self;
case "&&":
self.operator = "||";
self.left = self.left.negate(compressor);
self.left = self.left.negate(compressor, first_in_statement);
self.right = self.right.negate(compressor);
return best_of(basic_negation(this), self);
return best(this, self, first_in_statement);
case "||":
self.operator = "&&";
self.left = self.left.negate(compressor);
self.left = self.left.negate(compressor, first_in_statement);
self.right = self.right.negate(compressor);
return best_of(basic_negation(this), self);
return best(this, self, first_in_statement);
}
return basic_negation(this);
});
})(function(node, func){
node.DEFMETHOD("negate", function(compressor){
return func.call(this, compressor);
node.DEFMETHOD("negate", function(compressor, first_in_statement){
return func.call(this, compressor, first_in_statement);
});
});

Expand Down Expand Up @@ -1890,8 +1869,8 @@ merge(Compressor.prototype, {
return make_node(AST_SimpleStatement, self, {
body: make_node(AST_Conditional, self, {
condition : self.condition,
consequent : self.body.body,
alternative : self.alternative.body
consequent : statement_to_expression(self.body),
alternative : statement_to_expression(self.alternative)
})
}).transform(compressor);
}
Expand All @@ -1907,14 +1886,14 @@ merge(Compressor.prototype, {
body: make_node(AST_Binary, self, {
operator : "||",
left : negated,
right : self.body.body
right : statement_to_expression(self.body)
})
}).transform(compressor);
return make_node(AST_SimpleStatement, self, {
body: make_node(AST_Binary, self, {
operator : "&&",
left : self.condition,
right : self.body.body
right : statement_to_expression(self.body)
})
}).transform(compressor);
}
Expand All @@ -1925,7 +1904,7 @@ merge(Compressor.prototype, {
body: make_node(AST_Binary, self, {
operator : "||",
left : self.condition,
right : self.alternative.body
right : statement_to_expression(self.alternative)
})
}).transform(compressor);
}
Expand Down Expand Up @@ -2292,7 +2271,19 @@ merge(Compressor.prototype, {
}
}
}
return self.evaluate(compressor)[0];
if (compressor.option("negate_iife")
&& compressor.parent() instanceof AST_SimpleStatement
&& is_iife_call(self)) {
return self.negate(compressor, true);
}
return self;

function is_iife_call(node) {
if (node instanceof AST_Call && !(node instanceof AST_New)) {
return node.expression instanceof AST_Function || is_iife_call(node.expression);
}
return false;
}
});

OPT(AST_New, function(self, compressor){
Expand Down Expand Up @@ -2379,6 +2370,10 @@ merge(Compressor.prototype, {
// !!foo ==> foo, if we're in boolean context
return e.expression;
}
if (e instanceof AST_Binary) {
var statement = first_in_statement(compressor);
self = (statement ? best_of_statement : best_of)(self, e.negate(compressor, statement));
}
break;
case "typeof":
// typeof always returns a non-empty string, thus it's
Expand All @@ -2392,9 +2387,6 @@ merge(Compressor.prototype, {
}
return make_node(AST_True, self);
}
if (e instanceof AST_Binary && self.operator == "!") {
self = best_of(self, e.negate(compressor));
}
}
return self.evaluate(compressor)[0];
});
Expand Down Expand Up @@ -2570,11 +2562,12 @@ merge(Compressor.prototype, {
if (compressor.option("comparisons") && self.is_boolean()) {
if (!(compressor.parent() instanceof AST_Binary)
|| compressor.parent() instanceof AST_Assign) {
var statement = first_in_statement(compressor);
var negated = make_node(AST_UnaryPrefix, self, {
operator: "!",
expression: self.negate(compressor)
expression: self.negate(compressor, statement)
});
self = best_of(self, negated);
self = (statement ? best_of_statement : best_of)(self, negated);
}
if (compressor.option("unsafe_comps")) {
switch (self.operator) {
Expand Down Expand Up @@ -2773,8 +2766,9 @@ merge(Compressor.prototype, {
return maintain_this_binding(compressor.parent(), self, self.alternative);
}
}
var negated = cond[0].negate(compressor);
if (best_of(cond[0], negated) === negated) {
var statement = first_in_statement(compressor);
var negated = cond[0].negate(compressor, statement);
if ((statement ? best_of_statement : best_of)(cond[0], negated) === negated) {
self = make_node(AST_Conditional, self, {
condition: negated,
consequent: self.alternative,
Expand Down
25 changes: 0 additions & 25 deletions lib/output.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -425,7 +425,6 @@ function OutputStream(options) {
pos : function() { return current_pos },
push_node : function(node) { stack.push(node) },
pop_node : function() { return stack.pop() },
stack : function() { return stack },
parent : function(n) {
return stack[stack.length - 2 - (n || 0)];
}
Expand Down Expand Up @@ -1334,30 +1333,6 @@ function OutputStream(options) {
}
};

// return true if the node at the top of the stack (that means the
// innermost node in the current output) is lexically the first in
// a statement.
function first_in_statement(output) {
var a = output.stack(), i = a.length, node = a[--i], p = a[--i];
while (i > 0) {
if (p instanceof AST_Statement && p.body === node)
return true;
if ((p instanceof AST_Seq && p.car === node ) ||
(p instanceof AST_Call && p.expression === node && !(p instanceof AST_New) ) ||
(p instanceof AST_Dot && p.expression === node ) ||
(p instanceof AST_Sub && p.expression === node ) ||
(p instanceof AST_Conditional && p.condition === node ) ||
(p instanceof AST_Binary && p.left === node ) ||
(p instanceof AST_UnaryPostfix && p.expression === node ))
{
node = p;
p = a[--i];
} else {
return false;
}
}
};

// self should be AST_New. decide if we want to show parens or not.
function need_constructor_parens(self, output) {
// Always print parentheses with arguments
Expand Down
23 changes: 23 additions & 0 deletions lib/utils.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -320,3 +320,26 @@ Dictionary.fromObject = function(obj) {
function HOP(obj, prop) {
return Object.prototype.hasOwnProperty.call(obj, prop);
}

// return true if the node at the top of the stack (that means the
// innermost node in the current output) is lexically the first in
// a statement.
function first_in_statement(stack) {
var node = stack.parent(-1);
for (var i = 0, p; p = stack.parent(i); i++) {
if (p instanceof AST_Statement && p.body === node)
return true;
if ((p instanceof AST_Seq && p.car === node ) ||
(p instanceof AST_Call && p.expression === node && !(p instanceof AST_New) ) ||
(p instanceof AST_Dot && p.expression === node ) ||
(p instanceof AST_Sub && p.expression === node ) ||
(p instanceof AST_Conditional && p.condition === node ) ||
(p instanceof AST_Binary && p.left === node ) ||
(p instanceof AST_UnaryPostfix && p.expression === node ))
{
node = p;
} else {
return false;
}
}
}
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