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enhance side_effects & unused (#4711)

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This commit is contained in:
Alex Lam S.L
2021-03-02 04:55:09 +08:00
committed by GitHub
parent bd73720061
commit 68b2dadc58
3 changed files with 96 additions and 15 deletions
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35
lib/compress.js
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@@ -420,12 +420,14 @@ merge(Compressor.prototype, {
} while (sym = sym.parent_scope);
}
function can_drop_symbol(ref, keep_lambda) {
function can_drop_symbol(ref, compressor, keep_lambda) {
var def = ref.definition();
if (ref.in_arg && is_funarg(def)) return false;
return all(def.orig, function(sym) {
return !(sym instanceof AST_SymbolConst || sym instanceof AST_SymbolLet
|| keep_lambda && sym instanceof AST_SymbolLambda);
if (sym instanceof AST_SymbolConst || sym instanceof AST_SymbolLet) {
return compressor && can_varify(compressor, sym);
}
return !(keep_lambda && sym instanceof AST_SymbolLambda);
});
}
@@ -599,6 +601,7 @@ merge(Compressor.prototype, {
function is_immutable(value) {
if (!value) return false;
return value.is_constant()
|| value instanceof AST_Class
|| value instanceof AST_Lambda
|| value instanceof AST_ObjectIdentity;
}
@@ -3585,6 +3588,7 @@ merge(Compressor.prototype, {
return false;
}
});
def(AST_Class, return_false);
def(AST_Conditional, function(compressor) {
return this.consequent._dot_throw(compressor) || this.alternative._dot_throw(compressor);
});
@@ -3593,7 +3597,7 @@ merge(Compressor.prototype, {
if (!is_strict(compressor)) return false;
var exp = this.expression;
if (exp instanceof AST_SymbolRef) exp = exp.fixed_value();
return !(exp instanceof AST_Lambda && this.property == "prototype");
return !(this.property == "prototype" && (exp instanceof AST_Class || exp instanceof AST_Lambda));
});
def(AST_Lambda, return_false);
def(AST_Null, return_true);
@@ -4869,7 +4873,7 @@ merge(Compressor.prototype, {
});
def(AST_SymbolDeclaration, return_false);
def(AST_SymbolRef, function(compressor) {
return !this.is_declared(compressor) || !can_drop_symbol(this);
return !this.is_declared(compressor) || !can_drop_symbol(this, compressor);
});
def(AST_Template, function(compressor) {
return this.tag && !is_raw_tag(compressor, this.tag) || any(this.expressions, compressor);
@@ -5698,7 +5702,7 @@ merge(Compressor.prototype, {
var def = sym.definition();
if (export_defaults[def.id]) return;
if (compressor.exposed(def)) return;
if (!can_drop_symbol(sym, nested)) return;
if (!can_drop_symbol(sym, compressor, nested)) return;
return sym;
};
var assign_in_use = Object.create(null);
@@ -7418,7 +7422,7 @@ merge(Compressor.prototype, {
return make_sequence(this, [ expression, property ]);
});
def(AST_SymbolRef, function(compressor) {
return this.is_declared(compressor) && can_drop_symbol(this) ? null : this;
return this.is_declared(compressor) && can_drop_symbol(this, compressor) ? null : this;
});
def(AST_Template, function(compressor, first_in_statement) {
if (this.tag && !is_raw_tag(compressor, this.tag)) return this;
@@ -7432,7 +7436,9 @@ merge(Compressor.prototype, {
this.write_only = !exp.has_side_effects(compressor);
return this;
}
if (this.operator == "typeof" && exp instanceof AST_SymbolRef && can_drop_symbol(exp)) return null;
if (this.operator == "typeof" && exp instanceof AST_SymbolRef && can_drop_symbol(exp, compressor)) {
return null;
}
var node = exp.drop_side_effect_free(compressor, first_in_statement);
if (first_in_statement && node && is_iife_call(node)) {
if (node === exp && this.operator == "!") return this;
@@ -8237,13 +8243,16 @@ merge(Compressor.prototype, {
});
}
function can_varify(compressor, sym) {
if (!sym.fixed_value()) return false;
var def = sym.definition();
return is_safe_lexical(def) && !may_overlap(compressor, def);
}
function varify(self, compressor) {
return compressor.option("varify") && all(self.definitions, function(defn) {
return !defn.name.match_symbol(function(node) {
if (node instanceof AST_SymbolDeclaration) {
var def = node.definition();
return !node.fixed_value() || !is_safe_lexical(def) || may_overlap(compressor, def);
}
if (node instanceof AST_SymbolDeclaration) return !can_varify(compressor, node);
}, true);
}) ? to_var(self) : self;
}
@@ -9370,7 +9379,7 @@ merge(Compressor.prototype, {
// always true in booleans
AST_Node.warn("Boolean expression always true [{file}:{line},{col}]", self.start);
var exprs = [ make_node(AST_True, self) ];
if (!(exp instanceof AST_SymbolRef && can_drop_symbol(exp))) exprs.unshift(exp);
if (!(exp instanceof AST_SymbolRef && can_drop_symbol(exp, compressor))) exprs.unshift(exp);
return make_sequence(self, exprs).optimize(compressor);
}
}