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some speedup and more savings from unused vars that have side effects in initialization

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This commit is contained in:
Mihai Bazon
2012-09-26 16:43:14 +03:00
parent 78be8f5296
commit 15d58f5917
1 changed files with 78 additions and 54 deletions
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132
lib/compress.js
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@@ -75,12 +75,26 @@ merge(Compressor.prototype, {
AST_Node.warn.apply(AST_Node, arguments); AST_Node.warn.apply(AST_Node, arguments);
}, },
before: function(node, descend, in_list) { before: function(node, descend, in_list) {
if (node._squeezed) return node;
node = node.clone(); node = node.clone();
if (node instanceof AST_Scope) { if (node instanceof AST_Scope) {
node.drop_unused(this);
node = node.hoist_declarations(this); node = node.hoist_declarations(this);
} }
descend(node, this); descend(node, this);
node = node.optimize(this); node = node.optimize(this);
if (node instanceof AST_Scope) {
// dead code removal might leave further unused declarations.
// this'll usually save very few bytes, but the performance
// hit seems negligible so I'll just drop it here.
// no point to repeat warnings.
var save_warnings = this.options.warnings;
this.options.warnings = false;
node.drop_unused(this);
this.options.warnings = save_warnings;
}
node._squeezed = true;
return node; return node;
} }
}); });
@@ -89,7 +103,12 @@ merge(Compressor.prototype, {
function OPT(node, optimizer) { function OPT(node, optimizer) {
node.DEFMETHOD("optimize", function(compressor){ node.DEFMETHOD("optimize", function(compressor){
return optimizer(this, compressor); var self = this;
if (self._optimized) return self;
var opt = optimizer(self, compressor);
opt._optimized = true;
if (opt === self) return opt;
return opt.transform(compressor);
}); });
}; };
@@ -104,8 +123,10 @@ merge(Compressor.prototype, {
function make_node(ctor, orig, props) { function make_node(ctor, orig, props) {
if (!props) props = {}; if (!props) props = {};
if (!props.start) props.start = orig.start; if (orig) {
if (!props.end) props.end = orig.end; if (!props.start) props.start = orig.start;
if (!props.end) props.end = orig.end;
}
return new ctor(props); return new ctor(props);
}; };
@@ -173,9 +194,6 @@ merge(Compressor.prototype, {
// step. nevertheless, it's good to check. // step. nevertheless, it's good to check.
continue loop; continue loop;
case stat instanceof AST_If: case stat instanceof AST_If:
// compressor.warn("Current if: {code}", {
// code: stat.condition.print_to_string()
// });
if (stat.body instanceof AST_Return) { if (stat.body instanceof AST_Return) {
//--- //---
// pretty silly case, but: // pretty silly case, but:
@@ -186,7 +204,7 @@ merge(Compressor.prototype, {
CHANGED = true; CHANGED = true;
var cond = make_node(AST_SimpleStatement, stat.condition, { var cond = make_node(AST_SimpleStatement, stat.condition, {
body: stat.condition body: stat.condition
}).optimize(compressor); });
ret.unshift(cond); ret.unshift(cond);
continue loop; continue loop;
} }
@@ -323,7 +341,7 @@ merge(Compressor.prototype, {
} else { } else {
left = AST_Seq.cons(left, right); left = AST_Seq.cons(left, right);
} }
return left.optimize(compressor); return left.transform(compressor);
}; };
var ret = [], prev = null; var ret = [], prev = null;
statements.forEach(function(stat){ statements.forEach(function(stat){
@@ -478,7 +496,7 @@ merge(Compressor.prototype, {
case "string": case "string":
ast = make_node(AST_String, this, { ast = make_node(AST_String, this, {
value: val value: val
}); }).optimize(compressor);
break; break;
case "number": case "number":
ast = make_node(isNaN(val) ? AST_NaN : AST_Number, this, { ast = make_node(isNaN(val) ? AST_NaN : AST_Number, this, {
@@ -493,7 +511,7 @@ merge(Compressor.prototype, {
break; break;
default: default:
if (val === null) { if (val === null) {
ast = make_node(AST_Null, this); ast = make_node(AST_Null, this).optimize(compressor);
break; break;
} }
throw new Error(string_template("Can't handle constant of type: {type}", { throw new Error(string_template("Can't handle constant of type: {type}", {
@@ -838,19 +856,43 @@ merge(Compressor.prototype, {
col : def.name.start.col col : def.name.start.col
}; };
if (def.value && def.value.has_side_effects()) { if (def.value && def.value.has_side_effects()) {
def._unused_side_effects = true;
compressor.warn("Side effects in initialization of unused variable {name} [{file}:{line},{col}]", w); compressor.warn("Side effects in initialization of unused variable {name} [{file}:{line},{col}]", w);
return true; return true;
} }
compressor.warn("Dropping unused variable {name} [{file}:{line},{col}]", w); compressor.warn("Dropping unused variable {name} [{file}:{line},{col}]", w);
return false; return false;
}); });
if (def.length == 0) { var side_effects = [];
def = mergeSort(def, function(a, b){
if (!a.value && b.value) return -1;
if (!b.value && a.value) return 1;
return 0;
});
while (def.length > 0 && def[def.length - 1]._unused_side_effects) {
side_effects.unshift(def.pop().value);
}
if (side_effects.length > 0) {
side_effects = make_node(AST_BlockStatement, node, {
body: side_effects.map(function(ss){
return make_node(AST_SimpleStatement, ss, { body: ss });
})
});
} else {
side_effects = null;
}
if (def.length == 0 && !side_effects) {
return make_node(AST_EmptyStatement, node); return make_node(AST_EmptyStatement, node);
} }
if (def.length != node.definitions.length) { if (def.length == 0) {
node.definitions = def; return side_effects;
return node;
} }
node.definitions = def;
if (side_effects) {
side_effects.body.unshift(node);
node = side_effects;
}
return node;
} }
if (node instanceof AST_Scope && node !== self) if (node instanceof AST_Scope && node !== self)
return node; return node;
@@ -864,7 +906,6 @@ merge(Compressor.prototype, {
var hoist_funs = compressor.option("hoist_funs"); var hoist_funs = compressor.option("hoist_funs");
var hoist_vars = compressor.option("hoist_vars"); var hoist_vars = compressor.option("hoist_vars");
var self = this; var self = this;
self.drop_unused(compressor);
if (hoist_funs || hoist_vars) { if (hoist_funs || hoist_vars) {
var dirs = []; var dirs = [];
var hoisted = []; var hoisted = [];
@@ -949,7 +990,7 @@ merge(Compressor.prototype, {
if (compressor.option("dead_code")) { if (compressor.option("dead_code")) {
var a = []; var a = [];
extract_declarations_from_unreachable_code(compressor, self.body, a); extract_declarations_from_unreachable_code(compressor, self.body, a);
return make_node(AST_BlockStatement, self, { body: a }).optimize(compressor); return make_node(AST_BlockStatement, self, { body: a });
} }
} else { } else {
return self.body; return self.body;
@@ -958,21 +999,6 @@ merge(Compressor.prototype, {
return self; return self;
}); });
// while(cond){ ... } ==> for(;cond;){ ... }
//
// not helpful, it seems (output is a bit bigger after gzip)
//
// OPT(AST_While, function(self, compressor){
// var self = AST_DWLoop.prototype.optimize.call(self, compressor);
// if (self instanceof AST_While) {
// self = make_node(AST_For, self, {
// condition: self.condition,
// body: self.body
// }).optimize(compressor);
// }
// return self;
// });
OPT(AST_For, function(self, compressor){ OPT(AST_For, function(self, compressor){
var cond = self.condition; var cond = self.condition;
if (cond) { if (cond) {
@@ -1030,13 +1056,13 @@ merge(Compressor.prototype, {
} }
} }
if (is_empty(self.alternative)) self.alternative = null; if (is_empty(self.alternative)) self.alternative = null;
var negated = self.condition.negate(compressor).optimize(compressor); var negated = self.condition.negate(compressor);
var negated_is_best = best_of(self.condition, negated) === negated; var negated_is_best = best_of(self.condition, negated) === negated;
if (self.alternative && negated_is_best) { if (self.alternative && negated_is_best) {
negated_is_best = false; // because we already do the switch here. negated_is_best = false; // because we already do the switch here.
self.condition = negated; self.condition = negated;
var tmp = self.body; var tmp = self.body;
self.body = self.alternative || new AST_EmptyStatement(); self.body = self.alternative || make_node(AST_EmptyStatement);
self.alternative = tmp; self.alternative = tmp;
} }
if (is_empty(self.body) && is_empty(self.alternative)) { if (is_empty(self.body) && is_empty(self.alternative)) {
@@ -1051,7 +1077,7 @@ merge(Compressor.prototype, {
condition : self.condition, condition : self.condition,
consequent : self.body.body, consequent : self.body.body,
alternative : self.alternative.body alternative : self.alternative.body
}).optimize(compressor) })
}); });
} }
if (is_empty(self.alternative) && self.body instanceof AST_SimpleStatement) { if (is_empty(self.alternative) && self.body instanceof AST_SimpleStatement) {
@@ -1060,14 +1086,14 @@ merge(Compressor.prototype, {
operator : "||", operator : "||",
left : negated, left : negated,
right : self.body.body right : self.body.body
}).optimize(compressor) })
}); });
return make_node(AST_SimpleStatement, self, { return make_node(AST_SimpleStatement, self, {
body: make_node(AST_Binary, self, { body: make_node(AST_Binary, self, {
operator : "&&", operator : "&&",
left : self.condition, left : self.condition,
right : self.body.body right : self.body.body
}).optimize(compressor) })
}); });
} }
if (self.body instanceof AST_EmptyStatement if (self.body instanceof AST_EmptyStatement
@@ -1078,7 +1104,7 @@ merge(Compressor.prototype, {
operator : "||", operator : "||",
left : self.condition, left : self.condition,
right : self.alternative.body right : self.alternative.body
}).optimize(compressor) })
}); });
} }
if (self.body instanceof AST_Exit if (self.body instanceof AST_Exit
@@ -1089,7 +1115,7 @@ merge(Compressor.prototype, {
condition : self.condition, condition : self.condition,
consequent : self.body.value, consequent : self.body.value,
alternative : self.alternative.value || make_node(AST_Undefined, self).optimize(compressor) alternative : self.alternative.value || make_node(AST_Undefined, self).optimize(compressor)
}).optimize(compressor) })
}); });
} }
if (self.body instanceof AST_If if (self.body instanceof AST_If
@@ -1099,7 +1125,7 @@ merge(Compressor.prototype, {
operator: "&&", operator: "&&",
left: self.condition, left: self.condition,
right: self.body.condition right: self.body.condition
}).optimize(compressor); });
self.body = self.body.body; self.body = self.body.body;
} }
if (aborts(self.body)) { if (aborts(self.body)) {
@@ -1108,17 +1134,17 @@ merge(Compressor.prototype, {
self.alternative = null; self.alternative = null;
return make_node(AST_BlockStatement, self, { return make_node(AST_BlockStatement, self, {
body: [ self, alt ] body: [ self, alt ]
}).optimize(compressor); });
} }
} }
if (aborts(self.alternative)) { if (aborts(self.alternative)) {
var body = self.body; var body = self.body;
self.body = self.alternative; self.body = self.alternative;
self.condition = negated_is_best ? negated : self.condition.negate(compressor).optimize(compressor); self.condition = negated_is_best ? negated : self.condition.negate(compressor);
self.alternative = null; self.alternative = null;
return make_node(AST_BlockStatement, self, { return make_node(AST_BlockStatement, self, {
body: [ self, body ] body: [ self, body ]
}).optimize(compressor); });
} }
return self; return self;
}); });
@@ -1199,14 +1225,14 @@ merge(Compressor.prototype, {
if (self.args.length != 1) { if (self.args.length != 1) {
return make_node(AST_Array, self, { return make_node(AST_Array, self, {
elements: self.args elements: self.args
}).optimize(compressor); });
} }
break; break;
case "Object": case "Object":
if (self.args.length == 0) { if (self.args.length == 0) {
return make_node(AST_Object, self, { return make_node(AST_Object, self, {
properties: [] properties: []
}).optimize(compressor); });
} }
break; break;
case "String": case "String":
@@ -1238,7 +1264,7 @@ merge(Compressor.prototype, {
case "Function": case "Function":
case "Error": case "Error":
case "Array": case "Array":
return make_node(AST_Call, self, self).optimize(compressor); return make_node(AST_Call, self, self);
} }
} }
} }
@@ -1247,8 +1273,6 @@ merge(Compressor.prototype, {
OPT(AST_Seq, function(self, compressor){ OPT(AST_Seq, function(self, compressor){
if (compressor.option("cascade")) { if (compressor.option("cascade")) {
if (self.cdr instanceof AST_Seq)
self.cdr = self.cdr.optimize(compressor);
if (self.car instanceof AST_Assign if (self.car instanceof AST_Assign
&& !self.car.left.has_side_effects() && !self.car.left.has_side_effects()
&& self.car.left.equivalent_to(self.cdr)) { && self.car.left.equivalent_to(self.cdr)) {
@@ -1277,7 +1301,7 @@ merge(Compressor.prototype, {
// typeof always returns a non-empty string, thus it's // typeof always returns a non-empty string, thus it's
// always true in booleans // always true in booleans
compressor.warn("Boolean expression always true [{file}:{line},{col}]", self.start); compressor.warn("Boolean expression always true [{file}:{line},{col}]", self.start);
return make_node(AST_True, self).optimize(compressor); return make_node(AST_True, self);
} }
} }
if (e instanceof AST_Binary) { if (e instanceof AST_Binary) {
@@ -1327,7 +1351,7 @@ merge(Compressor.prototype, {
var rr = self.right.evaluate(compressor), right = rr[0]; var rr = self.right.evaluate(compressor), right = rr[0];
if ((ll.length > 1 && !ll[1]) || (rr.length > 1 && !rr[1])) { if ((ll.length > 1 && !ll[1]) || (rr.length > 1 && !rr[1])) {
compressor.warn("Boolean && always false [{file}:{line},{col}]", self.start); compressor.warn("Boolean && always false [{file}:{line},{col}]", self.start);
return make_node(AST_False, self).optimize(compressor); return make_node(AST_False, self);
} }
if (ll.length > 1 && ll[1]) { if (ll.length > 1 && ll[1]) {
return rr[0]; return rr[0];
@@ -1341,7 +1365,7 @@ merge(Compressor.prototype, {
var rr = self.right.evaluate(compressor), right = rr[0]; var rr = self.right.evaluate(compressor), right = rr[0];
if ((ll.length > 1 && ll[1]) || (rr.length > 1 && rr[1])) { if ((ll.length > 1 && ll[1]) || (rr.length > 1 && rr[1])) {
compressor.warn("Boolean || always true [{file}:{line},{col}]", self.start); compressor.warn("Boolean || always true [{file}:{line},{col}]", self.start);
return make_node(AST_True, self).optimize(compressor); return make_node(AST_True, self);
} }
if (ll.length > 1 && !ll[1]) { if (ll.length > 1 && !ll[1]) {
return rr[0]; return rr[0];
@@ -1356,7 +1380,7 @@ merge(Compressor.prototype, {
if ((ll.length > 1 && ll[0] instanceof AST_String && ll[1]) || if ((ll.length > 1 && ll[0] instanceof AST_String && ll[1]) ||
(rr.length > 1 && rr[0] instanceof AST_String && rr[1])) { (rr.length > 1 && rr[0] instanceof AST_String && rr[1])) {
compressor.warn("+ in boolean context always true [{file}:{line},{col}]", self.start); compressor.warn("+ in boolean context always true [{file}:{line},{col}]", self.start);
return make_node(AST_True, self).optimize(compressor); return make_node(AST_True, self);
} }
break; break;
} }
@@ -1390,9 +1414,9 @@ merge(Compressor.prototype, {
OPT(AST_SymbolRef, function(self, compressor){ OPT(AST_SymbolRef, function(self, compressor){
if (self.undeclared()) switch (self.name) { if (self.undeclared()) switch (self.name) {
case "undefined": case "undefined":
return make_node(AST_Undefined, self).optimize(compressor); return make_node(AST_Undefined, self);
case "NaN": case "NaN":
return make_node(AST_NaN, self).optimize(compressor); return make_node(AST_NaN, self);
} }
return self; return self;
}); });
@@ -1433,7 +1457,7 @@ merge(Compressor.prototype, {
if (self.condition instanceof AST_Seq) { if (self.condition instanceof AST_Seq) {
var car = self.condition.car; var car = self.condition.car;
self.condition = self.condition.cdr; self.condition = self.condition.cdr;
return AST_Seq.cons(car, self.optimize(compressor)).optimize(compressor); return AST_Seq.cons(car, self);
} }
var cond = self.condition.evaluate(compressor); var cond = self.condition.evaluate(compressor);
if (cond.length > 1) { if (cond.length > 1) {