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enhance pure_getters, reduce_vars & unused (#4863)
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@alexlamsl
alexlamsl committed Apr 23, 2021
1 parent f46209b commit 9b8deff
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Showing 6 changed files with 125 additions and 43 deletions.
76 changes: 40 additions & 36 deletions lib/compress.js
View file
Expand Up @@ -814,11 +814,12 @@ merge(Compressor.prototype, {
def(AST_Assign, function(tw, descend, compressor) {
var node = this;
var left = node.left;
var right = node.right;
var scan = left instanceof AST_Destructured || left instanceof AST_SymbolRef;
switch (node.operator) {
case "=":
if (left.equivalent_to(node.right) && !left.has_side_effects(compressor)) {
node.right.walk(tw);
if (left.equivalent_to(right) && !left.has_side_effects(compressor)) {
right.walk(tw);
walk_prop(left);
node.__drop = true;
return true;
Expand All @@ -838,7 +839,7 @@ merge(Compressor.prototype, {
walk_assign();
} else {
mark_assignment_to_arguments(left);
node.right.walk(tw);
right.walk(tw);
}
pop(tw);
return true;
Expand All @@ -855,7 +856,7 @@ merge(Compressor.prototype, {
return;
}
var safe = safe_to_read(tw, d);
node.right.walk(tw);
right.walk(tw);
if (safe && !left.in_arg && safe_to_assign(tw, d)) {
push_ref(d, left);
mark(tw, d);
Expand All @@ -864,7 +865,7 @@ merge(Compressor.prototype, {
return make_node(AST_Binary, node, {
operator: node.operator.slice(0, -1),
left: make_ref(left, fixed),
right: node.right
right: node.right,
});
};
left.fixed.assigns = !fixed || !fixed.assigns ? [] : fixed.assigns.slice();
Expand Down Expand Up @@ -899,7 +900,7 @@ merge(Compressor.prototype, {
}

function walk_assign() {
node.right.walk(tw);
right.walk(tw);
scan_declaration(tw, compressor, left, function() {
return node.right;
}, function(sym, fixed, walk) {
Expand All @@ -911,14 +912,14 @@ merge(Compressor.prototype, {
var d = sym.definition();
d.assignments++;
if (fixed
&& !is_modified(compressor, tw, node, node.right, 0)
&& !is_modified(compressor, tw, node, right, 0, is_immutable(right), recursive_ref(tw, d))
&& !sym.in_arg
&& safe_to_assign(tw, d)) {
push_ref(d, sym);
mark(tw, d);
if (d.single_use && left instanceof AST_Destructured) d.single_use = false;
tw.loop_ids[d.id] = tw.in_loop;
mark_escaped(tw, d, sym.scope, node, node.right, 0, 1);
mark_escaped(tw, d, sym.scope, node, right, 0, 1);
sym.fixed = d.fixed = fixed;
sym.fixed.assigns = [ node ];
} else {
Expand Down Expand Up @@ -3656,11 +3657,11 @@ merge(Compressor.prototype, {
// may_throw_on_access()
// returns true if this node may be null, undefined or contain `AST_Accessor`
(function(def) {
AST_Node.DEFMETHOD("may_throw_on_access", function(compressor) {
return !compressor.option("pure_getters") || this._dot_throw(compressor);
AST_Node.DEFMETHOD("may_throw_on_access", function(compressor, force) {
return !compressor.option("pure_getters") || this._dot_throw(compressor, force);
});
function is_strict(compressor) {
return /strict/.test(compressor.option("pure_getters"));
function is_strict(compressor, force) {
return force || /strict/.test(compressor.option("pure_getters"));
}
def(AST_Node, is_strict);
def(AST_Array, return_false);
Expand All @@ -3683,28 +3684,28 @@ merge(Compressor.prototype, {
return this.consequent._dot_throw(compressor) || this.alternative._dot_throw(compressor);
});
def(AST_Constant, return_false);
def(AST_Dot, function(compressor) {
if (!is_strict(compressor)) return false;
def(AST_Dot, function(compressor, force) {
if (!is_strict(compressor, force)) return false;
var exp = this.expression;
if (exp instanceof AST_SymbolRef) exp = exp.fixed_value();
return !(this.property == "prototype" && is_lambda(exp));
});
def(AST_Lambda, return_false);
def(AST_Null, return_true);
def(AST_Object, function(compressor) {
return is_strict(compressor) && !all(this.properties, function(prop) {
def(AST_Object, function(compressor, force) {
return is_strict(compressor, force) && !all(this.properties, function(prop) {
return prop instanceof AST_ObjectKeyVal;
});
});
def(AST_ObjectIdentity, function(compressor) {
return is_strict(compressor) && !this.scope.new;
def(AST_ObjectIdentity, function(compressor, force) {
return is_strict(compressor, force) && !this.scope.new;
});
def(AST_Sequence, function(compressor) {
return this.tail_node()._dot_throw(compressor);
});
def(AST_SymbolRef, function(compressor) {
def(AST_SymbolRef, function(compressor, force) {
if (this.is_undefined) return true;
if (!is_strict(compressor)) return false;
if (!is_strict(compressor, force)) return false;
if (is_undeclared_ref(this) && this.is_declared(compressor)) return false;
if (this.is_immutable()) return false;
var def = this.definition();
Expand Down Expand Up @@ -5817,11 +5818,10 @@ merge(Compressor.prototype, {
var assign_as_unused = /keep_assign/.test(compressor.option("unused")) ? return_false : function(node, props) {
var sym, nested = false;
if (node instanceof AST_Assign) {
if (node.write_only || node.operator == "=") sym = node.left;
if (node.write_only || node.operator == "=") sym = extract_reference(node.left, props);
} else if (node instanceof AST_Unary) {
if (node.write_only) sym = node.expression;
if (node.write_only) sym = extract_reference(node.expression, props);
}
if (/strict/.test(compressor.option("pure_getters"))) sym = extract_reference(sym, props);
if (!(sym instanceof AST_SymbolRef)) return;
var def = sym.definition();
if (export_defaults[def.id]) return;
Expand All @@ -5832,15 +5832,17 @@ merge(Compressor.prototype, {
function extract_reference(node, props) {
if (node instanceof AST_PropAccess) {
var expr = node.expression;
if (!expr.may_throw_on_access(compressor)) {
if (!expr.may_throw_on_access(compressor, true)) {
nested = true;
if (props && node instanceof AST_Sub) props.unshift(node.property);
return extract_reference(expr, props);
}
} else if (node instanceof AST_Assign && node.operator == "=") {
node.write_only = "p";
var ref = extract_reference(node.right);
if (props) props.assign = node;
return ref;
if (!props) return ref;
props.assign = node;
return ref instanceof AST_SymbolRef ? ref : node.left;
}
return node;
}
Expand Down Expand Up @@ -6125,6 +6127,10 @@ merge(Compressor.prototype, {
value = make_node(AST_Number, node, { value: 0 });
}
if (value) {
if (props.assign) {
var assign = props.assign.drop_side_effect_free(compressor);
if (assign) props.unshift(assign);
}
if (parent instanceof AST_Sequence && parent.tail_node() !== node) {
value = value.drop_side_effect_free(compressor);
}
Expand Down Expand Up @@ -6662,16 +6668,17 @@ merge(Compressor.prototype, {
}
}, true);
}))) {
if (props.assign) {
props.assign.write_only = true;
props.assign.walk(tw);
delete props.assign.write_only;
if (node.write_only === "p" && node.right.may_throw_on_access(compressor, true)) return;
var assign = props.assign;
if (assign) {
assign.write_only = true;
assign.walk(tw);
assign.write_only = "p";
}
props.forEach(function(prop) {
prop.walk(tw);
});
if (node instanceof AST_Assign) {
if (node.write_only === "p" && node.right.may_throw_on_access(compressor)) return;
var right = get_rhs(node);
if (init && node.write_only === true && node_def.scope === self && !right.has_side_effects(compressor)) {
initializations.add(node_def.id, right);
Expand Down Expand Up @@ -7312,11 +7319,8 @@ merge(Compressor.prototype, {
def(AST_Assign, function(compressor) {
var left = this.left;
if (left instanceof AST_PropAccess) {
var expr = left.expression;
if (expr instanceof AST_Assign && expr.operator == "=" && !expr.may_throw_on_access(compressor)) {
expr.write_only = "p";
}
if (compressor.has_directive("use strict") && expr.is_constant()) return this;
if (left.expression.may_throw_on_access(compressor, true)) return this;
if (compressor.has_directive("use strict") && left.expression.is_constant()) return this;
}
if (left.has_side_effects(compressor)) return this;
var right = this.right;
Expand Down
2 changes: 2 additions & 0 deletions test/compress/classes.js
View file
Expand Up @@ -1546,6 +1546,8 @@ drop_unused_self_reference: {
options = {
pure_getters: "strict",
reduce_vars: true,
sequences: true,
side_effects: true,
toplevel: true,
unused: true,
}
Expand Down
6 changes: 3 additions & 3 deletions test/compress/drop-unused.js
View file
Expand Up @@ -2371,6 +2371,7 @@ function_parameter_ie8: {
issue_3664: {
options = {
pure_getters: "strict",
side_effects: true,
unused: true,
}
input: {
Expand All @@ -2381,7 +2382,7 @@ issue_3664: {
}
expect: {
console.log(function() {
var b = ([ b && console.log("FAIL") ].p = 0, 0);
var b = (b && console.log("FAIL"), 0, 0);
return "PASS";
}());
}
Expand All @@ -2391,6 +2392,7 @@ issue_3664: {
issue_3673: {
options = {
pure_getters: "strict",
sequences: true,
side_effects: true,
toplevel: true,
unused: true,
Expand All @@ -2401,8 +2403,6 @@ issue_3673: {
console.log("PASS");
}
expect: {
var a;
(a = [ a ]).p = 42;
console.log("PASS");
}
expect_stdout: "PASS"
Expand Down
2 changes: 2 additions & 0 deletions test/compress/functions.js
View file
Expand Up @@ -6026,6 +6026,8 @@ drop_unused_self_reference: {
options = {
pure_getters: "strict",
reduce_vars: true,
sequences: true,
side_effects: true,
toplevel: true,
unused: true,
}
Expand Down
74 changes: 74 additions & 0 deletions test/compress/pure_getters.js
View file
Expand Up @@ -1564,3 +1564,77 @@ issue_4803: {
}
expect_stdout: "PASS"
}

nested_property_assignments_1: {
options = {
pure_getters: "strict",
reduce_vars: true,
sequences: true,
side_effects: true,
toplevel: true,
unused: true,
}
input: {
var f;
((f = function() {
console.log("FAIL");
}).p = f).q = console.log("PASS");
}
expect: {
console.log("PASS");
}
expect_stdout: "PASS"
}

nested_property_assignments_2: {
options = {
pure_getters: "strict",
unused: true,
}
input: {
var o = {};
(function() {
var a;
(o.p = a = {}).q = "PASS";
})();
console.log(o.p.q);
}
expect: {
var o = {};
(function() {
(o.p = {}).q = "PASS";
})();
console.log(o.p.q);
}
expect_stdout: "PASS"
}

nested_property_assignments_3: {
options = {
collapse_vars: true,
pure_getters: true,
side_effects: true,
unused: true,
}
input: {
var o = { p: {} };
(function(a) {
console && a;
if (console) {
a = a.p;
a.q = a;
}
})(o);
console.log(o.p.q === o.p ? "PASS" : "FAIL");
}
expect: {
var o = { p: {} };
(function(a) {
console;
if (console)
(a = a.p).q = a;
})(o);
console.log(o.p.q === o.p ? "PASS" : "FAIL");
}
expect_stdout: "PASS"
}
8 changes: 4 additions & 4 deletions test/ufuzz/index.js
View file
Expand Up @@ -445,9 +445,9 @@ function addTrailingComma(list) {

function createParams(was_async, was_generator, noDuplicate) {
var save_async = async;
if (was_async) async = true;
if (!async) async = was_async;
var save_generator = generator;
if (was_generator) generator = true;
if (!generator) generator = was_generator;
var len = unique_vars.length;
var params = [];
for (var n = rng(4); --n >= 0;) {
Expand Down Expand Up @@ -569,9 +569,9 @@ function createAssignmentPairs(recurmax, stmtDepth, canThrow, nameLenBefore, was
function createName() {
unique_vars.push("a", "b", "c", "undefined", "NaN", "Infinity");
var save_async = async;
if (was_async) async = true;
if (!async) async = was_async;
var save_generator = generator;
if (was_generator) generator = true;
if (!generator) generator = was_generator;
var name = createVarName(MANDATORY);
generator = save_generator;
async = save_async;
Expand Down

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