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extend fuzzy RHS folding (#3006)

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- `a = []; if (1) x();` => `if (a = []) x();`
This commit is contained in:
Alex Lam S.L
2018-03-17 03:10:21 +08:00
committed by GitHub
parent 20ca0f5906
commit ccf0e2ef4f
3 changed files with 138 additions and 58 deletions
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114
lib/compress.js
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@@ -147,27 +147,6 @@ merge(Compressor.prototype, {
return true;
return false;
},
in_boolean_context: function() {
if (!this.option("booleans")) return false;
var self = this.self();
for (var i = 0, p; p = this.parent(i); i++) {
if (p instanceof AST_SimpleStatement
|| p instanceof AST_Conditional && p.condition === self
|| p instanceof AST_DWLoop && p.condition === self
|| p instanceof AST_For && p.condition === self
|| p instanceof AST_If && p.condition === self
|| p instanceof AST_UnaryPrefix && p.operator == "!" && p.expression === self) {
return true;
}
if (p instanceof AST_Binary && (p.operator == "&&" || p.operator == "||")
|| p instanceof AST_Conditional
|| p.tail_node() === self) {
self = p;
} else {
return false;
}
}
},
compress: function(node) {
if (this.option("expression")) {
node.process_expression(true);
@@ -980,7 +959,7 @@ merge(Compressor.prototype, {
var args;
var candidates = [];
var stat_index = statements.length;
var scanner = new TreeTransformer(function(node, descend) {
var scanner = new TreeTransformer(function(node) {
if (abort) return node;
// Skip nodes before `candidate` as quickly as possible
if (!hit) {
@@ -1019,7 +998,7 @@ merge(Compressor.prototype, {
if (can_replace
&& !(node instanceof AST_SymbolDeclaration)
&& (scan_lhs && (hit_lhs = lhs.equivalent_to(node))
|| scan_rhs && (hit_rhs = rhs.equivalent_to(node)))) {
|| scan_rhs && (hit_rhs = scan_rhs(node, this)))) {
if (stop_if_hit && (hit_rhs || !lhs_local || !replace_all)) {
abort = true;
return node;
@@ -1388,12 +1367,16 @@ merge(Compressor.prototype, {
}
function foldable(expr) {
if (expr.is_constant()) return true;
if (expr instanceof AST_Array) return false;
if (expr instanceof AST_Function) return false;
if (expr instanceof AST_Object) return false;
if (expr instanceof AST_RegExp) return false;
if (expr instanceof AST_Symbol) return true;
if (expr instanceof AST_SymbolRef) {
var value = expr.evaluate(compressor);
if (value === expr) return rhs_exact_match;
return rhs_fuzzy_match(value, rhs_exact_match);
}
if (expr instanceof AST_This) return rhs_exact_match;
if (expr.is_truthy()) return rhs_fuzzy_match(true, return_false);
if (expr.is_constant()) {
return rhs_fuzzy_match(expr.evaluate(compressor), rhs_exact_match);
}
if (!(lhs instanceof AST_SymbolRef)) return false;
if (expr.has_side_effects(compressor)) return false;
var circular;
@@ -1404,7 +1387,25 @@ merge(Compressor.prototype, {
circular = true;
}
}));
return !circular;
return !circular && rhs_exact_match;
}
function rhs_exact_match(node) {
return rhs.equivalent_to(node);
}
function rhs_fuzzy_match(value, fallback) {
return function(node, tw) {
if (tw.in_boolean_context()) {
if (value && node.is_truthy() && !node.has_side_effects(compressor)) {
return true;
}
if (node.is_constant()) {
return !node.evaluate(compressor) == !value;
}
}
return fallback(node);
};
}
function get_lvalues(expr) {
@@ -5089,7 +5090,7 @@ merge(Compressor.prototype, {
}
break;
}
if (self.operator == "+" && compressor.in_boolean_context()) {
if (compressor.option("booleans") && self.operator == "+" && compressor.in_boolean_context()) {
var ll = self.left.evaluate(compressor);
var rr = self.right.evaluate(compressor);
if (ll && typeof ll == "string") {
@@ -5154,7 +5155,7 @@ merge(Compressor.prototype, {
}
var rr = self.right.evaluate(compressor);
if (!rr) {
if (compressor.in_boolean_context()) {
if (compressor.option("booleans") && compressor.in_boolean_context()) {
compressor.warn("Boolean && always false [{file}:{line},{col}]", self.start);
return make_sequence(self, [
self.left,
@@ -5163,7 +5164,8 @@ merge(Compressor.prototype, {
} else self.falsy = true;
} else if (!(rr instanceof AST_Node)) {
var parent = compressor.parent();
if (parent.operator == "&&" && parent.left === compressor.self() || compressor.in_boolean_context()) {
if (parent.operator == "&&" && parent.left === compressor.self()
|| compressor.option("booleans") && compressor.in_boolean_context()) {
compressor.warn("Dropping side-effect-free && [{file}:{line},{col}]", self.start);
return self.left.optimize(compressor);
}
@@ -5190,12 +5192,13 @@ merge(Compressor.prototype, {
var rr = self.right.evaluate(compressor);
if (!rr) {
var parent = compressor.parent();
if (parent.operator == "||" && parent.left === compressor.self() || compressor.in_boolean_context()) {
if (parent.operator == "||" && parent.left === compressor.self()
|| compressor.option("booleans") && compressor.in_boolean_context()) {
compressor.warn("Dropping side-effect-free || [{file}:{line},{col}]", self.start);
return self.left.optimize(compressor);
}
} else if (!(rr instanceof AST_Node)) {
if (compressor.in_boolean_context()) {
if (compressor.option("booleans") && compressor.in_boolean_context()) {
compressor.warn("Boolean || always true [{file}:{line},{col}]", self.start);
return make_sequence(self, [
self.left,
@@ -5833,7 +5836,7 @@ merge(Compressor.prototype, {
right: alternative
}).optimize(compressor);
}
var in_bool = compressor.in_boolean_context();
var in_bool = compressor.option("booleans") && compressor.in_boolean_context();
if (is_true(self.consequent)) {
if (is_false(self.alternative)) {
// c ? true : false ---> !!c
@@ -5931,32 +5934,29 @@ merge(Compressor.prototype, {
});
OPT(AST_Boolean, function(self, compressor){
if (!compressor.option("booleans")) return self;
if (compressor.in_boolean_context()) return make_node(AST_Number, self, {
value: +self.value
});
if (compressor.option("booleans")) {
var p = compressor.parent();
if (p instanceof AST_Binary && (p.operator == "=="
|| p.operator == "!=")) {
compressor.warn("Non-strict equality against boolean: {operator} {value} [{file}:{line},{col}]", {
operator : p.operator,
value : self.value,
file : p.start.file,
line : p.start.line,
col : p.start.col,
});
return make_node(AST_Number, self, {
value: +self.value
});
}
return make_node(AST_UnaryPrefix, self, {
operator: "!",
expression: make_node(AST_Number, self, {
value: 1 - self.value
})
var p = compressor.parent();
if (p instanceof AST_Binary && (p.operator == "==" || p.operator == "!=")) {
compressor.warn("Non-strict equality against boolean: {operator} {value} [{file}:{line},{col}]", {
operator : p.operator,
value : self.value,
file : p.start.file,
line : p.start.line,
col : p.start.col,
});
return make_node(AST_Number, self, {
value: +self.value
});
}
return self;
return make_node(AST_UnaryPrefix, self, {
operator: "!",
expression: make_node(AST_Number, self, {
value: 1 - self.value
})
});
});
OPT(AST_Sub, function(self, compressor){