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consolidate evaluate & reduce_vars (#1505)
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- improve marking efficiency
- apply smarter `const` replacement to `var`

fixes #1501
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@alexlamsl
alexlamsl authored Feb 25, 2017
1 parent 834f9f3 commit 16cd5d5
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Showing 5 changed files with 57 additions and 50 deletions.
81 changes: 45 additions & 36 deletions lib/compress.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -118,7 +118,7 @@ merge(Compressor.prototype, {
var passes = +this.options.passes || 1;
for (var pass = 0; pass < passes && pass < 3; ++pass) {
if (pass > 0 || this.option("reduce_vars"))
node.reset_opt_flags(this);
node.reset_opt_flags(this, true);
node = node.transform(this);
}
return node;
Expand Down Expand Up @@ -177,39 +177,45 @@ merge(Compressor.prototype, {
return this.print_to_string() == node.print_to_string();
});

AST_Node.DEFMETHOD("reset_opt_flags", function(compressor){
var reduce_vars = compressor.option("reduce_vars");
AST_Node.DEFMETHOD("reset_opt_flags", function(compressor, rescan){
var reduce_vars = rescan && compressor.option("reduce_vars");
var unsafe = compressor.option("unsafe");
var tw = new TreeWalker(function(node){
if (reduce_vars && node instanceof AST_Scope) {
node.variables.each(function(def) {
delete def.modified;
});
}
if (node instanceof AST_SymbolRef) {
var d = node.definition();
if (d.init) {
delete d.init._evaluated;
if (reduce_vars) {
if (node instanceof AST_Toplevel) node.globals.each(reset_def);
if (node instanceof AST_Scope) node.variables.each(reset_def);
if (node instanceof AST_SymbolRef) {
var d = node.definition();
d.references.push(node);
if (!d.modified && (d.orig.length > 1 || isModified(node, 0))) {
d.modified = true;
}
}
if (reduce_vars && (d.orig.length > 1 || isModified(node, 0))) {
d.modified = true;
if (node instanceof AST_Call && node.expression instanceof AST_Function) {
node.expression.argnames.forEach(function(arg, i) {
arg.definition().init = node.args[i] || make_node(AST_Undefined, node);
});
}
}
if (reduce_vars && node instanceof AST_Call && node.expression instanceof AST_Function) {
node.expression.argnames.forEach(function(arg, i) {
arg.definition().init = node.args[i] || make_node(AST_Undefined, node);
});
}
if (!(node instanceof AST_Directive || node instanceof AST_Constant)) {
node._squeezed = false;
node._optimized = false;
}
});
this.walk(tw);

function reset_def(def) {
def.modified = false;
def.references = [];
def.should_replace = undefined;
if (unsafe && def.init) {
def.init._evaluated = undefined;
}
}

function isModified(node, level) {
var parent = tw.parent(level);
if (parent instanceof AST_Unary && (parent.operator === "++" || parent.operator === "--")
|| parent instanceof AST_Assign && parent.left === node
if (isLHS(node, parent)
|| parent instanceof AST_Call && parent.expression === node) {
return true;
} else if (parent instanceof AST_PropAccess && parent.expression === node) {
Expand Down Expand Up @@ -1254,7 +1260,7 @@ merge(Compressor.prototype, {
var d = this.definition();
if (compressor.option("reduce_vars") && !d.modified && d.init) {
if (compressor.option("unsafe")) {
if (!HOP(d.init, '_evaluated')) {
if (d.init._evaluated === undefined) {
d.init._evaluated = ev(d.init, compressor);
}
return d.init._evaluated;
Expand Down Expand Up @@ -2403,9 +2409,6 @@ merge(Compressor.prototype, {
});

OPT(AST_Call, function(self, compressor){
self.args = self.args.map(function(arg) {
return arg.evaluate(compressor)[0];
});
if (compressor.option("unsafe")) {
var exp = self.expression;
if (exp instanceof AST_SymbolRef && exp.undeclared()) {
Expand Down Expand Up @@ -3025,18 +3028,24 @@ merge(Compressor.prototype, {
return make_node(AST_Infinity, self).transform(compressor);
}
}
if (compressor.option("evaluate")
&& compressor.option("reduce_vars")
&& !isLHS(self, compressor.parent())) {
if (compressor.option("evaluate") && compressor.option("reduce_vars")) {
var d = self.definition();
if (d.constant && !d.modified && d.init && d.init.is_constant(compressor)) {
var original_as_string = self.print_to_string();
var const_node = make_node_from_constant(compressor, d.init.constant_value(compressor), self);
var const_node_as_string = const_node.print_to_string();
var per_const_overhead = d.global || !d.references.length ? 0
: (d.name.length + 2 + const_node_as_string.length) / d.references.length;
if (const_node_as_string.length <= original_as_string.length + per_const_overhead)
return const_node;
if (!d.modified && d.init) {
if (d.should_replace === undefined) {
var init = d.init.evaluate(compressor);
if (init.length > 1) {
var value = init[0].print_to_string().length;
var name = d.name.length;
var freq = d.references.length;
var overhead = d.global || !freq ? 0 : (name + 2 + value) / freq;
d.should_replace = value <= name + overhead ? init[0] : false;
} else {
d.should_replace = false;
}
}
if (d.should_replace) {
return d.should_replace;
}
}
}
return self;
Expand Down
2 changes: 0 additions & 2 deletions lib/scope.js
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,6 @@ function SymbolDef(scope, index, orig) {
this.global = false;
this.mangled_name = null;
this.undeclared = false;
this.constant = false;
this.index = index;
this.id = SymbolDef.next_id++;
};
Expand Down Expand Up @@ -156,7 +155,6 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
else if (node instanceof AST_SymbolVar
|| node instanceof AST_SymbolConst) {
var def = defun.def_variable(node);
def.constant = node instanceof AST_SymbolConst;
def.init = tw.parent().value;
}
else if (node instanceof AST_SymbolCatch) {
Expand Down
2 changes: 1 addition & 1 deletion test/compress/evaluate.js
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Original file line number Diff line number Diff line change
Expand Up @@ -615,7 +615,7 @@ call_args: {
const a = 1;
console.log(1);
+function(a) {
return a;
return 1;
}(1);
}
}
Expand Down
16 changes: 8 additions & 8 deletions test/compress/reduce_vars.js
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Original file line number Diff line number Diff line change
Expand Up @@ -134,17 +134,17 @@ modified: {
}

function f2() {
var b = 2, c = 3;
b = c;
var b = 2;
b = 3;
console.log(1 + b);
console.log(b + 3);
console.log(4);
console.log(1 + b + 3);
}

function f3() {
var b = 2, c = 3;
b *= c;
var b = 2;
b *= 3;
console.log(1 + b);
console.log(b + 3);
console.log(4);
Expand Down Expand Up @@ -236,7 +236,7 @@ unsafe_evaluate_object: {
function f0(){
var a = 1;
var b = {};
b[a] = 2;
b[1] = 2;
console.log(4);
}

Expand Down Expand Up @@ -280,7 +280,7 @@ unsafe_evaluate_array: {
function f0(){
var a = 1;
var b = [];
b[a] = 2;
b[1] = 2;
console.log(4);
}

Expand Down Expand Up @@ -373,8 +373,8 @@ passes: {
}
expect: {
function f() {
var b = 2, c = 3;
b = c;
var b = 2;
b = 3;
console.log(1 + b);
console.log(b + 3);
console.log(4);
Expand Down
6 changes: 3 additions & 3 deletions test/mocha/comment_before_constant.js
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ describe("comment before constant", function() {
it("Should test comment before constant is retained and output after mangle.", function() {
var result = Uglify.minify(js, {
fromString: true,
compress: { collapse_vars: false },
compress: { collapse_vars: false, reduce_vars: false },
mangle: {},
output: { comments: true },
});
Expand All @@ -17,9 +17,9 @@ describe("comment before constant", function() {
it("Should test code works when comments disabled.", function() {
var result = Uglify.minify(js, {
fromString: true,
compress: { collapse_vars: false },
compress: { collapse_vars: false, reduce_vars: false },
mangle: {},
output: {},
output: { comments: false },
});
assert.strictEqual(result.code, 'function f(){var n=!1;return n}');
});
Expand Down

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