@@ -642,151 +642,134 @@ merge(Compressor.prototype, {
642 642
// and if it has exactly one reference then attempt to replace its reference
643 643
// in the statement with the var value and then erase the var definition.
644 644 645 -
var self = compressor.self();
646 -
var var_defs_removed = false;
645 +
var scope = compressor.find_parent(AST_Scope);
647 646
var toplevel = compressor.option("toplevel");
648 647
for (var stat_index = statements.length; --stat_index >= 0;) {
649 648
var stat = statements[stat_index];
650 -
if (stat instanceof AST_Definitions) continue;
651 - 652 -
// Process child blocks of statement if present.
653 -
[stat, stat.body, stat.alternative, stat.bcatch, stat.bfinally].forEach(function(node) {
654 -
node && node.body && collapse_single_use_vars(node.body, compressor);
655 -
});
656 649 657 -
// The variable definition must precede a statement.
658 -
if (stat_index <= 0) break;
659 -
var prev_stat_index = stat_index - 1;
660 -
var prev_stat = statements[prev_stat_index];
661 -
if (!(prev_stat instanceof AST_Definitions)) continue;
662 -
var var_defs = prev_stat.definitions;
663 -
if (var_defs == null) continue;
664 - 665 -
var var_names_seen = {};
650 +
var var_names_seen = Object.create(null);
666 651
var side_effects_encountered = false;
667 652
var lvalues_encountered = false;
668 -
var lvalues = {};
653 +
var lvalues = Object.create(null);
654 +
var prev_stat_index, var_defs, var_defs_index;
669 655 670 656
// Scan variable definitions from right to left.
671 -
for (var var_defs_index = var_defs.length; --var_defs_index >= 0;) {
672 - 673 -
// Obtain var declaration and var name with basic sanity check.
674 -
var var_decl = var_defs[var_defs_index];
675 -
if (var_decl.value == null) break;
676 -
var var_name = var_decl.name.name;
677 -
if (!var_name || !var_name.length) break;
678 - 679 -
// Bail if we've seen a var definition of same name before.
680 -
if (var_name in var_names_seen) break;
681 -
var_names_seen[var_name] = true;
682 - 683 -
// Only interested in cases with just one reference to the variable.
684 -
var def = self.find_variable && self.find_variable(var_name);
685 -
if (!def || !def.references || def.references.length !== 1
686 -
|| var_name == "arguments" || (!toplevel && def.global)) {
687 -
side_effects_encountered = true;
688 -
continue;
657 +
if (stat instanceof AST_Definitions) {
658 +
prev_stat_index = stat_index;
659 +
var_defs = stat.definitions;
660 +
for (var_defs_index = var_defs.length - 1; --var_defs_index >= 0;) {
661 +
if (collapse(var_defs[var_defs_index + 1])) break;
689 662
}
690 -
var ref = def.references[0];
691 - 692 -
// Don't replace ref if eval() or with statement in scope.
693 -
if (ref.scope.uses_eval || ref.scope.uses_with) break;
694 - 695 -
// Constant single use vars can be replaced in any scope.
696 -
if (var_decl.value.is_constant()) {
697 -
var ctt = new TreeTransformer(function(node) {
698 -
var parent = ctt.parent();
699 -
if (parent instanceof AST_IterationStatement
700 -
&& (parent.condition === node || parent.init === node)) {
701 -
return node;
702 -
}
703 -
if (node === ref)
704 -
return replace_var(node, parent, true);
705 -
});
706 -
stat.transform(ctt);
707 -
continue;
663 +
} else if (stat_index > 0) {
664 +
// The variable definition must precede a statement.
665 +
prev_stat_index = stat_index - 1;
666 +
var prev_stat = statements[prev_stat_index];
667 +
if (!(prev_stat instanceof AST_Definitions)) continue;
668 +
var_defs = prev_stat.definitions;
669 +
for (var_defs_index = var_defs.length; --var_defs_index >= 0;) {
670 +
if (collapse(stat)) break;
708 671
}
672 +
}
673 +
}
709 674 710 -
// Restrict var replacement to constants if side effects encountered.
711 -
if (side_effects_encountered |= lvalues_encountered) continue;
675 +
return statements;
712 676 713 -
var value_has_side_effects = var_decl.value.has_side_effects(compressor);
714 -
// Non-constant single use vars can only be replaced in same scope.
715 -
if (ref.scope !== self) {
716 -
side_effects_encountered |= value_has_side_effects;
717 -
continue;
718 -
}
677 +
function collapse(stat) {
678 +
var var_decl = var_defs[var_defs_index];
679 +
// `drop_unused()` shuffles variables without values to the top,
680 +
// so we can terminate upon first sighting as an optimization.
681 +
if (var_decl.value == null) return true;
682 +
var var_name = var_decl.name.name;
683 + 684 +
// Bail if we've seen a var definition of same name before.
685 +
if (var_name in var_names_seen) return true;
686 +
var_names_seen[var_name] = true;
687 + 688 +
// Only interested in non-constant values.
689 +
if (var_decl.value.is_constant()) return;
690 + 691 +
// Only interested in cases with just one reference to the variable.
692 +
var def = var_decl.name.definition();
693 +
if (def.references.length !== 1
694 +
|| var_name == "arguments" || (!toplevel && def.global)) {
695 +
side_effects_encountered = true;
696 +
return;
697 +
}
698 +
var ref = def.references[0];
699 + 700 +
// Don't replace ref if eval() or with statement in scope.
701 +
if (ref.scope.uses_eval || ref.scope.uses_with) return true;
702 + 703 +
// Restrict var replacement to constants if side effects encountered.
704 +
if (side_effects_encountered |= lvalues_encountered) return;
719 705 720 -
// Detect lvalues in var value.
721 -
var tw = new TreeWalker(function(node){
722 -
if (node instanceof AST_SymbolRef && is_lvalue(node, tw.parent())) {
723 -
lvalues[node.name] = lvalues_encountered = true;
706 +
var value_has_side_effects = var_decl.value.has_side_effects(compressor);
707 +
// Non-constant single use vars can only be replaced in same scope.
708 +
if (ref.scope !== scope) {
709 +
side_effects_encountered |= value_has_side_effects;
710 +
return;
711 +
}
712 + 713 +
// Detect lvalues in var value.
714 +
var tw = new TreeWalker(function(node){
715 +
if (node instanceof AST_SymbolRef && is_lvalue(node, tw.parent())) {
716 +
lvalues[node.name] = lvalues_encountered = true;
717 +
}
718 +
});
719 +
var_decl.value.walk(tw);
720 + 721 +
// Replace the non-constant single use var in statement if side effect free.
722 +
var unwind = false;
723 +
var tt = new TreeTransformer(
724 +
function preorder(node) {
725 +
if (unwind || node instanceof AST_Scope && node !== scope) return node;
726 +
var parent = tt.parent();
727 +
if (node instanceof AST_Try
728 +
|| node instanceof AST_With
729 +
|| node instanceof AST_Case
730 +
|| node instanceof AST_IterationStatement
731 +
|| (parent instanceof AST_If && node !== parent.condition)
732 +
|| (parent instanceof AST_Conditional && node !== parent.condition)
733 +
|| (node instanceof AST_SymbolRef
734 +
&& value_has_side_effects
735 +
&& !are_references_in_scope(node.definition(), scope))
736 +
|| (parent instanceof AST_Binary
737 +
&& (parent.operator == "&&" || parent.operator == "||")
738 +
&& node === parent.right)
739 +
|| (parent instanceof AST_Switch && node !== parent.expression)) {
740 +
return side_effects_encountered = unwind = true, node;
724 741
}
725 -
});
726 -
var_decl.value.walk(tw);
727 - 728 -
// Replace the non-constant single use var in statement if side effect free.
729 -
var unwind = false;
730 -
var tt = new TreeTransformer(
731 -
function preorder(node) {
732 -
if (unwind) return node;
733 -
var parent = tt.parent();
734 -
if (node instanceof AST_Lambda
735 -
|| node instanceof AST_Try
736 -
|| node instanceof AST_With
737 -
|| node instanceof AST_Case
738 -
|| node instanceof AST_IterationStatement
739 -
|| (parent instanceof AST_If && node !== parent.condition)
740 -
|| (parent instanceof AST_Conditional && node !== parent.condition)
741 -
|| (node instanceof AST_SymbolRef
742 -
&& value_has_side_effects
743 -
&& !are_references_in_scope(node.definition(), self))
744 -
|| (parent instanceof AST_Binary
745 -
&& (parent.operator == "&&" || parent.operator == "||")
746 -
&& node === parent.right)
747 -
|| (parent instanceof AST_Switch && node !== parent.expression)) {
748 -
return side_effects_encountered = unwind = true, node;
749 -
}
750 -
function are_references_in_scope(def, scope) {
751 -
if (def.orig.length === 1
752 -
&& def.orig[0] instanceof AST_SymbolDefun) return true;
753 -
if (def.scope !== scope) return false;
754 -
var refs = def.references;
755 -
for (var i = 0, len = refs.length; i < len; i++) {
756 -
if (refs[i].scope !== scope) return false;
757 -
}
758 -
return true;
759 -
}
760 -
},
761 -
function postorder(node) {
762 -
if (unwind) return node;
763 -
if (node === ref)
764 -
return unwind = true, replace_var(node, tt.parent(), false);
765 -
if (side_effects_encountered |= node.has_side_effects(compressor))
766 -
return unwind = true, node;
767 -
if (lvalues_encountered && node instanceof AST_SymbolRef && node.name in lvalues) {
768 -
side_effects_encountered = true;
769 -
return unwind = true, node;
742 +
function are_references_in_scope(def, scope) {
743 +
if (def.orig.length === 1
744 +
&& def.orig[0] instanceof AST_SymbolDefun) return true;
745 +
if (def.scope !== scope) return false;
746 +
var refs = def.references;
747 +
for (var i = 0, len = refs.length; i < len; i++) {
748 +
if (refs[i].scope !== scope) return false;
770 749
}
750 +
return true;
771 751
}
772 -
);
773 -
stat.transform(tt);
774 -
}
775 -
}
776 - 777 -
// Remove extraneous empty statments in block after removing var definitions.
778 -
// Leave at least one statement in `statements`.
779 -
if (var_defs_removed) for (var i = statements.length; --i >= 0;) {
780 -
if (statements.length > 1 && statements[i] instanceof AST_EmptyStatement)
781 -
statements.splice(i, 1);
752 +
},
753 +
function postorder(node) {
754 +
if (unwind) return node;
755 +
if (node === ref)
756 +
return unwind = true, replace_var(var_decl, node, tt.parent(), false);
757 +
if (side_effects_encountered |= node.has_side_effects(compressor))
758 +
return unwind = true, node;
759 +
if (lvalues_encountered && node instanceof AST_SymbolRef && node.name in lvalues) {
760 +
side_effects_encountered = true;
761 +
return unwind = true, node;
762 +
}
763 +
}
764 +
);
765 +
stat.transform(tt);
782 766
}
783 767 784 -
return statements;
785 - 786 768
function is_lvalue(node, parent) {
787 769
return node instanceof AST_SymbolRef && is_lhs(node, parent);
788 770
}
789 -
function replace_var(node, parent, is_constant) {
771 + 772 +
function replace_var(var_decl, node, parent, is_constant) {
790 773
if (is_lvalue(node, parent)) return node;
791 774 792 775
// Remove var definition and return its value to the TreeTransformer to replace.
@@ -795,14 +778,19 @@ merge(Compressor.prototype, {
795 778 796 779
var_defs.splice(var_defs_index, 1);
797 780
if (var_defs.length === 0) {
798 -
statements[prev_stat_index] = make_node(AST_EmptyStatement, self);
799 -
var_defs_removed = true;
781 +
statements.splice(prev_stat_index, 1);
782 +
stat_index--;
800 783
}
801 784
// Further optimize statement after substitution.
802 785
stat.reset_opt_flags(compressor);
803 786 804 -
compressor.info("Collapsing " + (is_constant ? "constant" : "variable") +
805 -
" " + var_name + " [{file}:{line},{col}]", node.start);
787 +
compressor.info("Collapsing {type} {name} [{file}:{line},{col}]", {
788 +
type: is_constant ? "constant" : "variable",
789 +
name: var_decl.name.name,
790 +
file: node.start.file,
791 +
line: node.start.line,
792 +
col: node.start.col
793 +
});
806 794
CHANGED = true;
807 795
return value;
808 796
}
@@ -1746,6 +1734,7 @@ merge(Compressor.prototype, {
1746 1734
def(AST_SymbolRef, function(compressor){
1747 1735
return this.undeclared();
1748 1736
});
1737 +
def(AST_SymbolDeclaration, return_false);
1749 1738
def(AST_Object, function(compressor){
1750 1739
return any(this.properties, compressor);
1751 1740
});
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