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introduce eager evaluation (#3587)
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@alexlamsl
alexlamsl committed Nov 15, 2019
1 parent dcfc4ac commit 552be61
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5 changes: 4 additions & 1 deletion README.md
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Expand Up @@ -631,7 +631,10 @@ If you're using the `X-SourceMap` header instead, you can just omit `sourceMap.u

- `drop_debugger` (default: `true`) -- remove `debugger;` statements

- `evaluate` (default: `true`) -- attempt to evaluate constant expressions
- `evaluate` (default: `true`) -- Evaluate expression for shorter constant
representation. Pass `"eager"` to always replace function calls whenever
possible, or a positive integer to specify an upper bound for each individual
evaluation in number of characters.

- `expression` (default: `false`) -- Pass `true` to preserve completion values
from terminal statements without `return`, e.g. in bookmarklets.
Expand Down
69 changes: 25 additions & 44 deletions lib/compress.js
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Expand Up @@ -96,6 +96,8 @@ function Compressor(options, false_by_default) {
unsafe_undefined: false,
unused : !false_by_default,
}, true);
var evaluate = this.options["evaluate"];
this.eval_threshold = /eager/.test(evaluate) ? 1 / 0 : +evaluate;
var global_defs = this.options["global_defs"];
if (typeof global_defs == "object") for (var key in global_defs) {
if (/^@/.test(key) && HOP(global_defs, key)) {
Expand Down Expand Up @@ -2676,22 +2678,21 @@ merge(Compressor.prototype, {
node.DEFMETHOD("_find_defs", func);
});

function best_of_expression(ast1, ast2) {
return ast1.print_to_string().length >
ast2.print_to_string().length
? ast2 : ast1;
function best_of_expression(ast1, ast2, threshold) {
var delta = ast2.print_to_string().length - ast1.print_to_string().length;
return delta < (threshold || 0) ? ast2 : ast1;
}

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

function best_of(compressor, ast1, ast2) {
return (first_in_statement(compressor) ? best_of_statement : best_of_expression)(ast1, ast2);
function best_of(compressor, ast1, ast2, threshold) {
return (first_in_statement(compressor) ? best_of_statement : best_of_expression)(ast1, ast2, threshold);
}

function convert_to_predicate(obj) {
Expand All @@ -2700,6 +2701,13 @@ merge(Compressor.prototype, {
});
}

function try_evaluate(compressor, node) {
var ev = node.evaluate(compressor);
if (ev === node) return node;
ev = make_node_from_constant(ev, node).optimize(compressor);
return best_of(compressor, node, ev, compressor.eval_threshold);
}

var object_fns = [
"constructor",
"toString",
Expand Down Expand Up @@ -5366,12 +5374,7 @@ merge(Compressor.prototype, {
&& is_iife_call(self)) {
return self.negate(compressor, true);
}
var ev = self.evaluate(compressor);
if (ev !== self) {
ev = make_node_from_constant(ev, self).optimize(compressor);
return best_of(compressor, ev, self);
}
return self;
return try_evaluate(compressor, self);

function return_value(stat) {
if (!stat) return make_node(AST_Undefined, self);
Expand Down Expand Up @@ -5702,15 +5705,8 @@ merge(Compressor.prototype, {
});
}
// avoids infinite recursion of numerals
if (self.operator != "-"
|| !(e instanceof AST_Number || e instanceof AST_Infinity)) {
var ev = self.evaluate(compressor);
if (ev !== self) {
ev = make_node_from_constant(ev, self).optimize(compressor);
return best_of(compressor, ev, self);
}
}
return self;
return self.operator == "-" && (e instanceof AST_Number || e instanceof AST_Infinity)
? self : try_evaluate(compressor, self);
});

AST_Binary.DEFMETHOD("lift_sequences", function(compressor) {
Expand Down Expand Up @@ -6274,12 +6270,7 @@ merge(Compressor.prototype, {
self.right = self.right.right;
return self.transform(compressor);
}
var ev = self.evaluate(compressor);
if (ev !== self) {
ev = make_node_from_constant(ev, self).optimize(compressor);
return best_of(compressor, ev, self);
}
return self;
return try_evaluate(compressor, self);

function align(ref, op) {
switch (ref) {
Expand Down Expand Up @@ -6448,11 +6439,11 @@ merge(Compressor.prototype, {
};
}
var name_length = def.name.length;
var overhead = 0;
if (compressor.option("unused") && !compressor.exposed(def)) {
overhead = (name_length + 2 + value_length) / (def.references.length - def.assignments);
name_length += (name_length + 2 + value_length) / (def.references.length - def.assignments);
}
def.should_replace = value_length <= name_length + overhead ? fn : false;
var delta = value_length - Math.floor(name_length);
def.should_replace = delta < compressor.eval_threshold ? fn : false;
} else {
def.should_replace = false;
}
Expand Down Expand Up @@ -7046,12 +7037,7 @@ merge(Compressor.prototype, {
});
}
}
var ev = self.evaluate(compressor);
if (ev !== self) {
ev = make_node_from_constant(ev, self).optimize(compressor);
return best_of(compressor, ev, self);
}
return self;
return try_evaluate(compressor, self);

function find_lambda() {
var i = 0, p;
Expand Down Expand Up @@ -7152,12 +7138,7 @@ merge(Compressor.prototype, {
}
var sub = self.flatten_object(self.property, compressor);
if (sub) return sub.optimize(compressor);
var ev = self.evaluate(compressor);
if (ev !== self) {
ev = make_node_from_constant(ev, self).optimize(compressor);
return best_of(compressor, ev, self);
}
return self;
return try_evaluate(compressor, self);
});

OPT(AST_Object, function(self, compressor) {
Expand Down
136 changes: 136 additions & 0 deletions test/compress/evaluate.js
View file
Expand Up @@ -1921,3 +1921,139 @@ conditional_function: {
}
expect_stdout: "42 42"
}

best_of_evaluate: {
options = {
evaluate: true,
reduce_vars: true,
toplevel: true,
unused: true,
}
input: {
function d(x, y) {
return x / y;
}
console.log(0 / 3, 1 / 64, 4 / 7, 7 / 7);
console.log(d(0, 3), d(1, 64), d(4, 7), d(7, 7));
}
expect: {
function d(x, y) {
return x / y;
}
console.log(0, 1 / 64, 4 / 7, 1);
console.log(0, .015625, d(4, 7), 1);
}
expect_stdout: [
"0 0.015625 0.5714285714285714 1",
"0 0.015625 0.5714285714285714 1",
]
}

eager_evaluate: {
options = {
evaluate: "eager",
reduce_vars: true,
toplevel: true,
unused: true,
}
input: {
function d(x, y) {
return x / y;
}
console.log(0 / 3, 1 / 64, 4 / 7, 7 / 7);
console.log(d(0, 3), d(1, 64), d(4, 7), d(7, 7));
}
expect: {
console.log(0, .015625, .5714285714285714, 1);
console.log(0, .015625, .5714285714285714, 1);
}
expect_stdout: [
"0 0.015625 0.5714285714285714 1",
"0 0.015625 0.5714285714285714 1",
]
}

threshold_evaluate_default: {
options = {
evaluate: true,
reduce_vars: true,
toplevel: true,
unused: true,
}
input: {
function b(x) {
return x + x + x;
}
console.log(b("1"), b(2), b(b(b("ABCDEFGHIJK"))));
}
expect: {
function b(x) {
return x + x + x;
}
console.log("111", 6, b(b(b("ABCDEFGHIJK"))));
}
expect_stdout: "111 6 ABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJK"
}

threshold_evaluate_30: {
options = {
evaluate: 30,
reduce_vars: true,
toplevel: true,
unused: true,
}
input: {
function b(x) {
return x + x + x;
}
console.log(b("1"), b(2), b(b(b("ABCDEFGHIJK"))));
}
expect: {
function b(x) {
return x + x + x;
}
console.log("111", 6, b(b("ABCDEFGHIJKABCDEFGHIJKABCDEFGHIJK")));
}
expect_stdout: "111 6 ABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJK"
}

threshold_evaluate_100: {
options = {
evaluate: 100,
reduce_vars: true,
toplevel: true,
unused: true,
}
input: {
function b(x) {
return x + x + x;
}
console.log(b("1"), b(2), b(b(b("ABCDEFGHIJK"))));
}
expect: {
function b(x) {
return x + x + x;
}
console.log("111", 6, b("ABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJK"));
}
expect_stdout: "111 6 ABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJK"
}

threshold_evaluate_999: {
options = {
evaluate: 999,
reduce_vars: true,
toplevel: true,
unused: true,
}
input: {
function b(x) {
return x + x + x;
}
console.log(b("1"), b(2), b(b(b("ABCDEFGHIJK"))));
}
expect: {
console.log("111", 6, "ABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJK");
}
expect_stdout: "111 6 ABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJKABCDEFGHIJK"
}
27 changes: 27 additions & 0 deletions test/compress/issue-1609.js
View file
Expand Up @@ -52,3 +52,30 @@ chained_evaluation_2: {
})();
}
}

chained_evaluation_3: {
options = {
collapse_vars: true,
evaluate: 10,
reduce_funcs: true,
reduce_vars: true,
unused: true,
}
input: {
(function() {
var a = "long piece of string";
(function() {
var b = a, c;
c = f(b);
c.bar = b;
})();
})();
}
expect: {
(function() {
(function() {
f("long piece of string").bar = "long piece of string";
})();
})();
}
}

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