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optimise binary operands with evaluate() (#1427)

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- remove call to evaluate() in is_constant() and let nested optimize() does its job instead
- reject RegExp in is_constant() and remove special case logic under collapse_vars
- operands to conditionals optimisation are now always evaluate()-ed
- throw error in constant_value() instead of returning undefined to catch possible bugs, similar to make_node_from_constant()
- optimise binary boolean operators under `evaluate` instead of `conditionals`
This commit is contained in:
Alex Lam S.L
2017-01-26 19:16:50 +08:00
committed by Richard van Velzen
parent 0d7d4918eb
commit 0610c020b1
4 changed files with 290 additions and 220 deletions
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119
lib/compress.js
View File

@@ -347,7 +347,7 @@ merge(Compressor.prototype, {
if (ref.scope.uses_eval || ref.scope.uses_with) break;
// Constant single use vars can be replaced in any scope.
if (!(var_decl.value instanceof AST_RegExp) && var_decl.value.is_constant(compressor)) {
if (var_decl.value.is_constant()) {
var ctt = new TreeTransformer(function(node) {
if (node === ref)
return replace_var(node, ctt.parent(), true);
@@ -1013,31 +1013,46 @@ merge(Compressor.prototype, {
}
return [ best_of(node, this), val ];
});
AST_Node.DEFMETHOD("is_constant", function(compressor){
var unaryPrefix = makePredicate("! ~ - +");
AST_Node.DEFMETHOD("is_constant", function(){
// Accomodate when compress option evaluate=false
// as well as the common constant expressions !0 and !1
return this instanceof AST_Constant
|| (this instanceof AST_UnaryPrefix && this.operator == "!"
&& this.expression instanceof AST_Constant)
|| this.evaluate(compressor).length > 1;
// as well as the common constant expressions !0 and -1
if (this instanceof AST_Constant) {
return !(this instanceof AST_RegExp);
} else {
return this instanceof AST_UnaryPrefix
&& this.expression instanceof AST_Constant
&& unaryPrefix(this.operator);
}
});
// Obtain the constant value of an expression already known to be constant.
// Result only valid iff this.is_constant(compressor) is true.
// Result only valid iff this.is_constant() is true.
AST_Node.DEFMETHOD("constant_value", function(compressor){
// Accomodate when option evaluate=false.
if (this instanceof AST_Constant) return this.value;
// Accomodate the common constant expressions !0 and !1 when option evaluate=false.
if (this instanceof AST_UnaryPrefix
&& this.operator == "!"
&& this.expression instanceof AST_Constant) {
return !this.expression.value;
if (this instanceof AST_Constant && !(this instanceof AST_RegExp)) {
return this.value;
}
var result = this.evaluate(compressor)
// Accomodate the common constant expressions !0 and -1 when option evaluate=false.
if (this instanceof AST_UnaryPrefix
&& this.expression instanceof AST_Constant) switch (this.operator) {
case "!":
return !this.expression.value;
case "~":
return ~this.expression.value;
case "-":
return -this.expression.value;
case "+":
return +this.expression.value;
default:
throw new Error(string_template("Cannot evaluate unary expression {value}", {
value: this.print_to_string()
}));
}
var result = this.evaluate(compressor);
if (result.length > 1) {
return result[1];
}
// should never be reached
return undefined;
throw new Error(string_template("Cannot evaluate constant [{file}:{line},{col}]", this.start));
});
def(AST_Statement, function(){
throw new Error(string_template("Cannot evaluate a statement [{file}:{line},{col}]", this.start));
@@ -2419,6 +2434,16 @@ merge(Compressor.prototype, {
var commutativeOperators = makePredicate("== === != !== * & | ^");
OPT(AST_Binary, function(self, compressor){
var lhs = self.left.evaluate(compressor);
var rhs = self.right.evaluate(compressor);
if (lhs.length > 1 && lhs[0].is_constant() !== self.left.is_constant()
|| rhs.length > 1 && rhs[0].is_constant() !== self.right.is_constant()) {
return make_node(AST_Binary, self, {
operator: self.operator,
left: lhs[0],
right: rhs[0]
}).optimize(compressor);
}
function reverse(op, force) {
if (force || !(self.left.has_side_effects(compressor) || self.right.has_side_effects(compressor))) {
if (op) self.operator = op;
@@ -2491,32 +2516,6 @@ merge(Compressor.prototype, {
}
break;
}
if (compressor.option("conditionals")) {
if (self.operator == "&&") {
var ll = self.left.evaluate(compressor);
if (ll.length > 1) {
if (ll[1]) {
compressor.warn("Condition left of && always true [{file}:{line},{col}]", self.start);
return maintain_this_binding(compressor.parent(), self, self.right.evaluate(compressor)[0]);
} else {
compressor.warn("Condition left of && always false [{file}:{line},{col}]", self.start);
return maintain_this_binding(compressor.parent(), self, ll[0]);
}
}
}
else if (self.operator == "||") {
var ll = self.left.evaluate(compressor);
if (ll.length > 1) {
if (ll[1]) {
compressor.warn("Condition left of || always true [{file}:{line},{col}]", self.start);
return maintain_this_binding(compressor.parent(), self, ll[0]);
} else {
compressor.warn("Condition left of || always false [{file}:{line},{col}]", self.start);
return maintain_this_binding(compressor.parent(), self, self.right.evaluate(compressor)[0]);
}
}
}
}
if (compressor.option("booleans") && compressor.in_boolean_context()) switch (self.operator) {
case "&&":
var ll = self.left.evaluate(compressor);
@@ -2590,6 +2589,30 @@ merge(Compressor.prototype, {
return self.left;
}
if (compressor.option("evaluate")) {
switch (self.operator) {
case "&&":
if (self.left.is_constant()) {
if (self.left.constant_value(compressor)) {
compressor.warn("Condition left of && always true [{file}:{line},{col}]", self.start);
return maintain_this_binding(compressor.parent(), self, self.right);
} else {
compressor.warn("Condition left of && always false [{file}:{line},{col}]", self.start);
return maintain_this_binding(compressor.parent(), self, self.left);
}
}
break;
case "||":
if (self.left.is_constant()) {
if (self.left.constant_value(compressor)) {
compressor.warn("Condition left of || always true [{file}:{line},{col}]", self.start);
return maintain_this_binding(compressor.parent(), self, self.left);
} else {
compressor.warn("Condition left of || always false [{file}:{line},{col}]", self.start);
return maintain_this_binding(compressor.parent(), self, self.right);
}
}
break;
}
if (self.operator == "+") {
if (self.left instanceof AST_Constant
&& self.right instanceof AST_Binary
@@ -2816,14 +2839,14 @@ merge(Compressor.prototype, {
});
}
// y?1:1 --> 1
if (consequent.is_constant(compressor)
&& alternative.is_constant(compressor)
if (consequent.is_constant()
&& alternative.is_constant()
&& consequent.equivalent_to(alternative)) {
var consequent_value = consequent.constant_value(compressor);
var consequent_value = consequent.evaluate(compressor)[0];
if (self.condition.has_side_effects(compressor)) {
return AST_Seq.from_array([self.condition, make_node_from_constant(compressor, consequent_value, self)]);
return AST_Seq.from_array([self.condition, consequent_value]);
} else {
return make_node_from_constant(compressor, consequent_value, self);
return consequent_value;
}
}

183
test/compress/conditionals.js
View File

@@ -635,166 +635,6 @@ ternary_boolean_alternative: {
}
}
conditional_and: {
options = {
conditionals: true,
evaluate : true
};
input: {
var a;
// compress these
a = true && condition;
a = 1 && console.log("a");
a = 2 * 3 && 2 * condition;
a = 5 == 5 && condition + 3;
a = "string" && 4 - condition;
a = 5 + "" && condition / 5;
a = -4.5 && 6 << condition;
a = 6 && 7;
a = false && condition;
a = NaN && console.log("b");
a = 0 && console.log("c");
a = undefined && 2 * condition;
a = null && condition + 3;
a = 2 * 3 - 6 && 4 - condition;
a = 10 == 7 && condition / 5;
a = !"string" && 6 % condition;
a = 0 && 7;
// don't compress these
a = condition && true;
a = console.log("a") && 2;
a = 4 - condition && "string";
a = 6 << condition && -4.5;
a = condition && false;
a = console.log("b") && NaN;
a = console.log("c") && 0;
a = 2 * condition && undefined;
a = condition + 3 && null;
}
expect: {
var a;
a = condition;
a = console.log("a");
a = 2 * condition;
a = condition + 3;
a = 4 - condition;
a = condition / 5;
a = 6 << condition;
a = 7;
a = false;
a = NaN;
a = 0;
a = void 0;
a = null;
a = 0;
a = false;
a = false;
a = 0;
a = condition && true;
a = console.log("a") && 2;
a = 4 - condition && "string";
a = 6 << condition && -4.5;
a = condition && false;
a = console.log("b") && NaN;
a = console.log("c") && 0;
a = 2 * condition && void 0;
a = condition + 3 && null;
}
}
conditional_or: {
options = {
conditionals: true,
evaluate : true
};
input: {
var a;
// compress these
a = true || condition;
a = 1 || console.log("a");
a = 2 * 3 || 2 * condition;
a = 5 == 5 || condition + 3;
a = "string" || 4 - condition;
a = 5 + "" || condition / 5;
a = -4.5 || 6 << condition;
a = 6 || 7;
a = false || condition;
a = 0 || console.log("b");
a = NaN || console.log("c");
a = undefined || 2 * condition;
a = null || condition + 3;
a = 2 * 3 - 6 || 4 - condition;
a = 10 == 7 || condition / 5;
a = !"string" || 6 % condition;
a = null || 7;
a = console.log(undefined && condition || null);
a = console.log(undefined || condition && null);
// don't compress these
a = condition || true;
a = console.log("a") || 2;
a = 4 - condition || "string";
a = 6 << condition || -4.5;
a = condition || false;
a = console.log("b") || NaN;
a = console.log("c") || 0;
a = 2 * condition || undefined;
a = condition + 3 || null;
}
expect: {
var a;
a = true;
a = 1;
a = 6;
a = true;
a = "string";
a = "5";
a = -4.5;
a = 6;
a = condition;
a = console.log("b");
a = console.log("c");
a = 2 * condition;
a = condition + 3;
a = 4 - condition;
a = condition / 5;
a = 6 % condition;
a = 7;
a = console.log(null);
a = console.log(condition && null);
a = condition || true;
a = console.log("a") || 2;
a = 4 - condition || "string";
a = 6 << condition || -4.5;
a = condition || false;
a = console.log("b") || NaN;
a = console.log("c") || 0;
a = 2 * condition || void 0;
a = condition + 3 || null;
}
}
trivial_boolean_ternary_expressions : {
options = {
conditionals: true,
@@ -906,3 +746,26 @@ issue_1154: {
function g6() { return g(), "number"; }
}
}
no_evaluate: {
options = {
conditionals: true,
evaluate : false
}
input: {
function f(b) {
a = b ? !0 : !0;
a = b ? ~1 : ~1;
a = b ? -2 : -2;
a = b ? +3 : +3;
}
}
expect: {
function f(b) {
a = !0;
a = ~1;
a = -2;
a = +3;
}
}
}

184
test/compress/evaluate.js
View File

@@ -1,3 +1,187 @@
and: {
options = {
evaluate: true
}
input: {
var a;
// compress these
a = true && condition;
a = 1 && console.log("a");
a = 2 * 3 && 2 * condition;
a = 5 == 5 && condition + 3;
a = "string" && 4 - condition;
a = 5 + "" && condition / 5;
a = -4.5 && 6 << condition;
a = 6 && 7;
a = false && condition;
a = NaN && console.log("b");
a = 0 && console.log("c");
a = undefined && 2 * condition;
a = null && condition + 3;
a = 2 * 3 - 6 && 4 - condition;
a = 10 == 7 && condition / 5;
a = !"string" && 6 % condition;
a = 0 && 7;
// don't compress these
a = condition && true;
a = console.log("a") && 2;
a = 4 - condition && "string";
a = 6 << condition && -4.5;
a = condition && false;
a = console.log("b") && NaN;
a = console.log("c") && 0;
a = 2 * condition && undefined;
a = condition + 3 && null;
}
expect: {
var a;
a = condition;
a = console.log("a");
a = 2 * condition;
a = condition + 3;
a = 4 - condition;
a = condition / 5;
a = 6 << condition;
a = 7;
a = false;
a = NaN;
a = 0;
a = void 0;
a = null;
a = 0;
a = false;
a = false;
a = 0;
a = condition && true;
a = console.log("a") && 2;
a = 4 - condition && "string";
a = 6 << condition && -4.5;
a = condition && false;
a = console.log("b") && NaN;
a = console.log("c") && 0;
a = 2 * condition && void 0;
a = condition + 3 && null;
}
}
or: {
options = {
evaluate: true
}
input: {
var a;
// compress these
a = true || condition;
a = 1 || console.log("a");
a = 2 * 3 || 2 * condition;
a = 5 == 5 || condition + 3;
a = "string" || 4 - condition;
a = 5 + "" || condition / 5;
a = -4.5 || 6 << condition;
a = 6 || 7;
a = false || condition;
a = 0 || console.log("b");
a = NaN || console.log("c");
a = undefined || 2 * condition;
a = null || condition + 3;
a = 2 * 3 - 6 || 4 - condition;
a = 10 == 7 || condition / 5;
a = !"string" || 6 % condition;
a = null || 7;
a = console.log(undefined && condition || null);
a = console.log(undefined || condition && null);
// don't compress these
a = condition || true;
a = console.log("a") || 2;
a = 4 - condition || "string";
a = 6 << condition || -4.5;
a = condition || false;
a = console.log("b") || NaN;
a = console.log("c") || 0;
a = 2 * condition || undefined;
a = condition + 3 || null;
}
expect: {
var a;
a = true;
a = 1;
a = 6;
a = true;
a = "string";
a = "5";
a = -4.5;
a = 6;
a = condition;
a = console.log("b");
a = console.log("c");
a = 2 * condition;
a = condition + 3;
a = 4 - condition;
a = condition / 5;
a = 6 % condition;
a = 7;
a = console.log(null);
a = console.log(condition && null);
a = condition || true;
a = console.log("a") || 2;
a = 4 - condition || "string";
a = 6 << condition || -4.5;
a = condition || false;
a = console.log("b") || NaN;
a = console.log("c") || 0;
a = 2 * condition || void 0;
a = condition + 3 || null;
}
}
unary_prefix: {
options = {
evaluate: true
}
input: {
a = !0 && b;
a = !0 || b;
a = ~1 && b;
a = ~1 || b;
a = -2 && b;
a = -2 || b;
a = +3 && b;
a = +3 || b;
}
expect: {
a = b;
a = !0;
a = b;
a = -2;
a = b;
a = -2;
a = b;
a = 3;
}
}
negative_zero: {
options = { evaluate: true }
input: {

24
test/compress/reduce_vars.js
View File

@@ -136,30 +136,30 @@ modified: {
}
function f2() {
var a = 1, b = 2, c = 3;
var b = 2, c = 3;
b = c;
console.log(a + b);
console.log(b + c);
console.log(1 + b);
console.log(b + 3);
console.log(4);
console.log(a + b + c);
console.log(1 + b + 3);
}
function f3() {
var a = 1, b = 2, c = 3;
var b = 2, c = 3;
b *= c;
console.log(a + b);
console.log(b + c);
console.log(1 + b);
console.log(b + 3);
console.log(4);
console.log(a + b + c);
console.log(1 + b + 3);
}
function f4() {
var a = 1, b = 2, c = 3;
var b = 2, c = 3;
b = c;
console.log(a + b);
console.log(1 + b);
console.log(b + c);
console.log(a + c);
console.log(a + b + c);
console.log(1 + c);
console.log(1 + b + c);
}
function f5(a) {