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- discard statements with no side effects (unsafe? could be)
- safer hoist_vars (needs some revamping of scope/mangling)
This commit is contained in:
Mihai Bazon
2012-09-11 13:15:55 +03:00
parent 1579c0fb97
commit da407d46c6
4 changed files with 110 additions and 31 deletions
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3
bin/uglifyjs2
View File

@@ -69,6 +69,7 @@ var output = UglifyJS.OutputStream({
files = files.map(do_file_1);
files = files.map(do_file_2);
UglifyJS.base54.sort();
files.forEach(do_file_3);
if (ARGS.v) {
sys.error("BASE54 digits: " + UglifyJS.base54.get());
@@ -124,7 +125,7 @@ function do_file_1(file) {
function do_file_2(ast) {
time_it("scope", function(){
//ast.figure_out_scope();
ast.figure_out_scope();
ast.compute_char_frequency();
});
return ast;

112
lib/compress.js
View File

@@ -64,8 +64,9 @@ function Compressor(options, false_by_default) {
evaluate : !false_by_default,
booleans : !false_by_default,
loops : !false_by_default,
unused_func : !false_by_default,
hoist_funs : !false_by_default,
//hoist_vars : !false_by_default, // XXX: turns out, this is really bad
hoist_vars : !false_by_default,
warnings : true
});
@@ -461,6 +462,36 @@ function Compressor(options, false_by_default) {
node.DEFMETHOD("negate", func);
});
// determine if expression has side effects
(function(def){
def(AST_Node, function(){ return true });
def(AST_EmptyStatement, function(){ return false });
def(AST_Constant, function(){ return false });
def(AST_This, function(){ return false });
def(AST_Function, function(){ return false });
def(AST_SimpleStatement, function(){
return this.body.has_side_effects();
});
def(AST_Binary, function(){
return this.left.has_side_effects()
|| this.right.has_side_effects ();
});
def(AST_Conditional, function(){
return this.condition.has_side_effects()
|| this.consequent.has_side_effects()
|| this.alternative.has_side_effects();
});
def(AST_Unary, function(){
return this.operator == "delete"
|| this.operator == "++"
|| this.operator == "--";
});
})(function(node, func){
node.DEFMETHOD("has_side_effects", func);
});
/* -----[ node squeezers ]----- */
SQUEEZE(AST_Debugger, function(self, compressor){
@@ -508,49 +539,55 @@ function Compressor(options, false_by_default) {
var self = this;
var hoisted = [];
var defuns = {};
var vars = {}, vars_found = 0;
var vars = {}, vars_found = 0, vardecl = [];
var tw = new TreeWalker(function(node){
if (node !== self) {
if (node instanceof AST_Defun && hoist_funs) {
if (node instanceof AST_Defun && hoist_funs && !node.hoisted) {
hoisted.push(node.clone());
node.hoisted = true;
defuns[node.name.name] = true;
}
if (node instanceof AST_Var && hoist_vars) {
if (node instanceof AST_Var && hoist_vars && !node.hoisted) {
node.definitions.forEach(function(def){
vars[def.name.name] = def;
++vars_found;
});
node.hoisted = true;
vardecl.push(node);
}
if (node instanceof AST_Scope)
return true;
}
});
self.walk(tw);
if (vars_found > 0) {
if (self instanceof AST_Lambda && !self.uses_arguments) {
for (var i in vars) if (HOP(vars, i)) {
var sym = vars[i].name;
if (!find_if(function(arg){ return arg.name == sym.name }, self.argnames)) {
self.argnames.push(sym);
}
}
} else {
var node = make_node(AST_Var, self, {
definitions: Object.keys(vars).map(function(name){
var def = vars[name].clone();
def.value = null;
return def;
})
});
hoisted.unshift(node);
}
if (vars_found > 0 && vardecl.length > 1) {
vardecl.forEach(function(v){ v.hoisted = true });
var node = make_node(AST_Var, self, {
definitions: Object.keys(vars).map(function(name){
var def = vars[name].clone();
def.value = null;
return def;
})
});
hoisted.unshift(node);
}
self.body = hoisted.concat(self.body);
}
});
SQUEEZE(AST_SimpleStatement, function(self, compressor){
self = self.clone();
self.body = self.body.squeeze(compressor);
return self.optimize(compressor);
});
AST_SimpleStatement.DEFMETHOD("optimize", function(compressor){
if (!this.body.has_side_effects()) {
AST_Node.warn("Dropping side-effect-free statement [{line},{col}]", this.start);
return make_node(AST_EmptyStatement, this);
}
return this;
});
SQUEEZE(AST_EmptyStatement, function(self, compressor){
return self;
});
@@ -790,9 +827,10 @@ function Compressor(options, false_by_default) {
AST_Definitions.DEFMETHOD("to_assignments", function(){
var assignments = this.definitions.reduce(function(a, def){
if (def.value) {
var name = make_node(AST_SymbolRef, def.name, def.name);
a.push(make_node(AST_Assign, def, {
operator : "=",
left : def.name,
left : name,
right : def.value
}));
}
@@ -842,7 +880,31 @@ function Compressor(options, false_by_default) {
self.argnames = do_list(self.argnames, compressor);
self.hoist_declarations(compressor);
self.body = tighten_body(self.body, compressor);
return self;
return self.optimize(compressor);
});
AST_Lambda.DEFMETHOD("optimize", function(compressor){
if (compressor.option("unused_func")) {
if (this.name && this.name.unreferenced()) {
this.name = null;
}
}
return this;
});
AST_Defun.DEFMETHOD("optimize", function(compressor){
if (compressor.option("unused_func")) {
if (this.name.unreferenced()
&& !(this.parent_scope instanceof AST_Toplevel)) {
AST_Node.warn("Dropping unused function {name} [{line},{col}]", {
name: this.name.name,
line: this.start.line,
col: this.start.col
});
return make_node(AST_EmptyStatement, this);
}
}
return this;
});
SQUEEZE(AST_Call, function(self, compressor){

16
lib/scope.js
View File

@@ -50,7 +50,8 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
// times on the same tree.
// pass 1: setup scope chaining and handle definitions
var scope = this.parent_scope;
var self = this;
var scope = self.parent_scope = null;
var labels = {};
var tw = new TreeWalker(function(node, descend){
if (node instanceof AST_Scope) {
@@ -110,7 +111,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
node.reference(sym);
}
});
this.walk(tw);
self.walk(tw);
// pass 2: find back references and eval
var func = null;
@@ -137,7 +138,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
}
}
});
this.walk(tw);
self.walk(tw);
});
AST_Scope.DEFMETHOD("init_scope_vars", function(){
@@ -364,6 +365,14 @@ AST_Toplevel.DEFMETHOD("compute_char_frequency", function(){
var tw = new TreeWalker(function(node){
if (node instanceof AST_Constant)
base54.consider(node.print_to_string());
else if (node instanceof AST_Return)
base54.consider("return");
else if (node instanceof AST_Throw)
base54.consider("throw");
else if (node instanceof AST_Continue)
base54.consider("continue");
else if (node instanceof AST_Break)
base54.consider("break");
else if (node instanceof AST_Debugger)
base54.consider("debugger");
else if (node instanceof AST_Directive)
@@ -420,7 +429,6 @@ AST_Toplevel.DEFMETHOD("compute_char_frequency", function(){
base54.consider(node.property);
});
this.walk(tw);
base54.sort();
});
var base54 = (function() {

10
tmp/test-node.js
View File

@@ -10,5 +10,13 @@ var code = fs.readFileSync(filename, "utf8");
var ast = UglifyJS.parse(code);
ast.figure_out_scope();
ast = ast.squeeze(UglifyJS.Compressor());
ast.compute_char_frequency();
console.log(UglifyJS.base54.get().join(","));
UglifyJS.base54.sort();
ast.figure_out_scope();
ast.mangle_names();
sys.error(UglifyJS.base54.get());
sys.print(ast.print_to_string({ beautify: true }));