Skip to content

Commit

Permalink
improve handling of lexical scope (#4979)
Browse files Browse the repository at this point in the history
  • Loading branch information
@alexlamsl
alexlamsl committed May 29, 2021
1 parent 7fa1dea commit 260431f
Show file tree
Hide file tree
Showing 2 changed files with 44 additions and 45 deletions.
86 changes: 43 additions & 43 deletions lib/compress.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -449,6 +449,13 @@ merge(Compressor.prototype, {
});
}

function has_escaped(d, scope, node, parent) {
if (parent instanceof AST_Assign) return parent.operator == "=" && parent.right === node;
if (parent instanceof AST_Call) return parent.expression !== node || parent instanceof AST_New;
if (parent instanceof AST_Exit) return parent.value === node && scope.resolve() !== d.scope.resolve();
if (parent instanceof AST_VarDef) return parent.value === node;
}

var RE_POSITIVE_INTEGER = /^(0|[1-9][0-9]*)$/;
(function(def) {
def(AST_Node, noop);
Expand Down Expand Up @@ -594,7 +601,7 @@ merge(Compressor.prototype, {
var safe = tw.safe_ids[def.id];
if (!HOP(tw.safe_ids, def.id)) {
if (!safe) return false;
if (safe.read && def.scope !== tw.find_parent(AST_Scope)) return false;
if (safe.read && def.scope.resolve() !== tw.find_parent(AST_Scope)) return false;
safe.assign = safe.assign && safe.assign !== tw.safe_ids ? true : tw.safe_ids;
}
if (def.fixed != null && safe.read) {
Expand Down Expand Up @@ -630,13 +637,6 @@ merge(Compressor.prototype, {
return value.is_constant() || is_lambda(value) || value instanceof AST_ObjectIdentity;
}

function has_escaped(d, node, parent) {
if (parent instanceof AST_Assign) return parent.operator == "=" && parent.right === node;
if (parent instanceof AST_Call) return parent.expression !== node || parent instanceof AST_New;
if (parent instanceof AST_Exit) return parent.value === node && node.scope !== d.scope;
if (parent instanceof AST_VarDef) return parent.value === node;
}

function value_in_use(node, parent) {
if (parent instanceof AST_Array) return true;
if (parent instanceof AST_Binary) return lazy_op[parent.operator];
Expand All @@ -648,11 +648,11 @@ merge(Compressor.prototype, {
function mark_escaped(tw, d, scope, node, value, level, depth) {
var parent = tw.parent(level);
if (value && value.is_constant()) return;
if (has_escaped(d, node, parent)) {
if (has_escaped(d, scope, node, parent)) {
d.escaped.push(parent);
if (depth > 1 && !(value && value.is_constant_expression(scope))) depth = 1;
if (!d.escaped.depth || d.escaped.depth > depth) d.escaped.depth = depth;
if (d.scope !== scope) d.escaped.cross_scope = true;
if (d.scope.resolve() !== scope.resolve()) d.escaped.cross_scope = true;
return;
} else if (value_in_use(node, parent)) {
mark_escaped(tw, d, scope, parent, parent, level + 1, depth);
Expand Down Expand Up @@ -1212,7 +1212,7 @@ merge(Compressor.prototype, {
var recursive = recursive_ref(tw, d);
if (recursive) recursive.enclosed.forEach(function(def) {
if (d === def) return;
if (def.scope === recursive) return;
if (def.scope.resolve() === recursive) return;
var assigns = def.fixed && def.fixed.assigns;
if (!assigns) return;
if (assigns[assigns.length - 1] instanceof AST_VarDef) return;
Expand Down Expand Up @@ -1607,11 +1607,12 @@ merge(Compressor.prototype, {
function safe_to_trim(stat) {
if (stat instanceof AST_LambdaDefinition) {
var def = stat.name.definition();
return def.scope === stat.name.scope || all(def.references, function(ref) {
var scope = ref.scope;
var scope = stat.name.scope;
return def.scope === scope || all(def.references, function(ref) {
var s = ref.scope;
do {
if (scope === stat.name.scope) return true;
} while (scope = scope.parent_scope);
if (s === scope) return true;
} while (s = s.parent_scope);
});
}
return !is_lexical_definition(stat);
Expand Down Expand Up @@ -2791,7 +2792,9 @@ merge(Compressor.prototype, {
if (!value) {
value = node;
var def = node.definition();
if (!def.undeclared && (def.assignments || !def.escaped || def.escaped.cross_scope)) {
if (!def.undeclared
&& (def.assignments || !def.escaped || def.escaped.cross_scope)
&& (has_escaped(def, node.scope, node, tw.parent()) || !same_scope(def))) {
well_defined = false;
}
}
Expand Down Expand Up @@ -2880,7 +2883,7 @@ merge(Compressor.prototype, {
function is_lhs_local(lhs) {
var sym = root_expr(lhs);
return sym instanceof AST_SymbolRef
&& sym.definition().scope === scope
&& sym.definition().scope.resolve() === scope
&& !(in_loop
&& (lvalues.has(sym.name) && lvalues.get(sym.name)[0] !== lhs
|| candidate instanceof AST_Unary
Expand Down Expand Up @@ -2921,7 +2924,7 @@ merge(Compressor.prototype, {
function may_modify(sym) {
var def = sym.definition();
if (def.orig.length == 1 && def.orig[0] instanceof AST_SymbolDefun) return false;
if (def.scope !== scope) return true;
if (def.scope.resolve() !== scope) return true;
if (modify_toplevel && compressor.exposed(def)) return true;
return !all(def.references, function(ref) {
return ref.scope.resolve() === scope;
Expand All @@ -2935,7 +2938,7 @@ merge(Compressor.prototype, {
if (lhs) {
if (node instanceof AST_Dot) return side_effects_external(node.expression, true);
if (node instanceof AST_Sub) return side_effects_external(node.expression, true);
if (node instanceof AST_SymbolRef) return node.definition().scope !== scope;
if (node instanceof AST_SymbolRef) return node.definition().scope.resolve() !== scope;
}
return false;
}
Expand Down Expand Up @@ -3818,7 +3821,7 @@ merge(Compressor.prototype, {
});
});
def(AST_ObjectIdentity, function(compressor, force) {
return is_strict(compressor, force) && !this.scope.new;
return is_strict(compressor, force) && !this.scope.resolve().new;
});
def(AST_Sequence, function(compressor) {
return this.tail_node()._dot_throw(compressor);
Expand Down Expand Up @@ -5021,7 +5024,7 @@ merge(Compressor.prototype, {
if (!(lhs instanceof AST_PropAccess)) return true;
var node = lhs.expression;
return !(node instanceof AST_ObjectIdentity)
|| !node.scope.new
|| !node.scope.resolve().new
|| lhs instanceof AST_Sub && lhs.property.has_side_effects(compressor)
|| this.right.has_side_effects(compressor);
});
Expand Down Expand Up @@ -6773,7 +6776,7 @@ merge(Compressor.prototype, {
}

function track_assigns(def, node) {
if (def.scope !== self) return false;
if (def.scope.resolve() !== self) return false;
if (!def.fixed || !node.fixed) assign_in_use[def.id] = false;
return assign_in_use[def.id] !== false;
}
Expand Down Expand Up @@ -6833,14 +6836,15 @@ merge(Compressor.prototype, {
function scan_ref_scoped(node, descend, init) {
if (node instanceof AST_Assign && node.left instanceof AST_SymbolRef) {
var def = node.left.definition();
if (def.scope === self) assignments.add(def.id, node);
if (def.scope.resolve() === self) assignments.add(def.id, node);
}
if (node instanceof AST_Unary && node.expression instanceof AST_SymbolRef) {
var def = node.expression.definition();
if (def.scope === self) assignments.add(def.id, node);
if (def.scope.resolve() === self) assignments.add(def.id, node);
}
var node_def, props = [], sym = assign_as_unused(node, props);
if (sym && self.variables.get(sym.name) === (node_def = sym.definition())
if (sym && ((node_def = sym.definition()).scope.resolve() === self
|| self.variables.get(sym.name) === node_def)
&& !(is_arguments(node_def) && !all(self.argnames, function(argname) {
return !argname.match_symbol(function(node) {
if (node instanceof AST_SymbolFunarg) {
Expand All @@ -6861,7 +6865,7 @@ merge(Compressor.prototype, {
});
if (node instanceof AST_Assign) {
var right = get_rhs(node), shared = false;
if (init && node.write_only === true && node_def.scope === self && !right.has_side_effects(compressor)) {
if (init && node.write_only === true && !right.has_side_effects(compressor)) {
initializations.add(node_def.id, right);
} else {
right.walk(tw);
Expand Down Expand Up @@ -6892,7 +6896,7 @@ merge(Compressor.prototype, {
var sym = get_init_symbol(node);
if (!sym) return;
var def = sym.definition();
if (def.scope !== self) {
if (def.scope.resolve() !== self) {
var d = find_variable(sym.name);
if (d === def || d && d.redefined() === def) return;
}
Expand Down Expand Up @@ -7324,33 +7328,32 @@ merge(Compressor.prototype, {
if (node instanceof AST_Assign) {
if (node.operator != "=") return;
if (!node.write_only) return;
if (node.left.scope !== self) return;
if (!can_hoist(node.left, node.right, 1)) return;
descend(node, this);
var defs = new Dictionary();
var assignments = [];
var decls = [];
node.right.properties.forEach(function(prop) {
var decl = make_sym(node.left, prop.key);
var decl = make_sym(AST_SymbolVar, node.left, prop.key);
decls.push(make_node(AST_VarDef, node, {
name: decl,
value: null
value: null,
}));
var sym = make_node(AST_SymbolRef, node, {
name: decl.name,
scope: self,
thedef: decl.definition()
thedef: decl.definition(),
});
sym.reference();
assignments.push(make_node(AST_Assign, node, {
operator: "=",
left: sym,
right: prop.value
right: prop.value,
}));
});
defs_by_id[node.left.definition().id] = defs;
self.body.splice(self.body.indexOf(this.stack[1]) + 1, 0, make_node(AST_Var, node, {
definitions: decls
definitions: decls,
}));
return make_sequence(node, assignments);
}
Expand All @@ -7362,16 +7365,16 @@ merge(Compressor.prototype, {
var var_defs = [];
node.value.properties.forEach(function(prop) {
var_defs.push(make_node(AST_VarDef, node, {
name: make_sym(node.name, prop.key),
value: prop.value
name: make_sym(node.name.CTOR, node.name, prop.key),
value: prop.value,
}));
});
defs_by_id[node.name.definition().id] = defs;
return List.splice(var_defs);
}

function make_sym(sym, key) {
var new_var = self.make_var(AST_SymbolVar, sym, sym.name + "_" + key);
function make_sym(type, sym, key) {
var new_var = self.make_var(type, sym, sym.name + "_" + key);
defs.set(key, new_var.definition());
return new_var;
}
Expand All @@ -7386,7 +7389,7 @@ merge(Compressor.prototype, {
var sym = make_node(AST_SymbolRef, node, {
name: def.name,
scope: node.expression.scope,
thedef: def
thedef: def,
});
sym.reference();
return sym;
Expand All @@ -7401,9 +7404,7 @@ merge(Compressor.prototype, {
if (!(sym instanceof AST_SymbolRef)) return;
if (!(sym.definition().id in defs_by_id)) return;
var opt = node.clone();
opt[prop] = make_node(AST_Object, sym, {
properties: []
});
opt[prop] = make_node(AST_Object, sym, { properties: [] });
return opt;
}
}));
Expand All @@ -7423,8 +7424,7 @@ merge(Compressor.prototype, {
&& all(right.properties, can_hoist_property)
&& all(def.references, function(ref) {
return ref.fixed_value() === right;
})
&& can_drop_symbol(sym);
});
}
});

Expand Down
3 changes: 1 addition & 2 deletions test/compress/sequences.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -727,8 +727,7 @@ side_effects_cascade_1: {
}
expect: {
function f(a, b) {
(a -= 42) < 0 && (a = 0),
b.a = a;
b.a = a = (a -= 42) < 0 ? 0 : a;
}
var m = {}, n = {};
f(13, m),
Expand Down

0 comments on commit 260431f

Please sign in to comment.