enhance merge_vars (#4125)
This commit is contained in:
Alex Lam S.L
@@ -4322,7 +4322,7 @@ merge(Compressor.prototype, {
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AST_Scope.DEFMETHOD("merge_variables", function(compressor) {
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if (!compressor.option("merge_vars")) return;
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var self = this, segment = null;
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var self = this, segment = {};
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var first = [], last = [], index = 0;
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var declarations = new Dictionary();
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var references = Object.create(null);
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@@ -4331,9 +4331,9 @@ merge(Compressor.prototype, {
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if (node instanceof AST_Assign) {
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var sym = node.left;
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if (!(sym instanceof AST_SymbolRef)) return;
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if (node.operator != "=") mark(sym);
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if (node.operator != "=") mark(sym, true, false);
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node.right.walk(tw);
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mark(sym, true);
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mark(sym, false, true);
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return true;
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}
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if (node instanceof AST_Binary) {
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@@ -4357,6 +4357,7 @@ merge(Compressor.prototype, {
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if (node instanceof AST_For) {
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if (node.init) node.init.walk(tw);
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push();
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segment.block = node;
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if (node.condition) node.condition.walk(tw);
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node.body.walk(tw);
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if (node.step) node.step.walk(tw);
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@@ -4366,6 +4367,7 @@ merge(Compressor.prototype, {
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if (node instanceof AST_ForIn) {
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node.object.walk(tw);
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push();
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segment.block = node;
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node.init.walk(tw);
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node.body.walk(tw);
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pop();
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@@ -4385,12 +4387,14 @@ merge(Compressor.prototype, {
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}
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if (node instanceof AST_IterationStatement) {
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push();
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segment.block = node;
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descend();
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pop();
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return true;
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}
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if (node instanceof AST_LabeledStatement) {
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push();
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segment.block = node;
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node.body.walk(tw);
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pop();
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return true;
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@@ -4401,6 +4405,7 @@ merge(Compressor.prototype, {
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if (node.name) references[node.name.definition().id] = false;
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}
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push();
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segment.block = node;
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descend();
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pop();
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return true;
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@@ -4422,11 +4427,11 @@ merge(Compressor.prototype, {
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return true;
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}
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if (node instanceof AST_SymbolFunarg) {
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if (!node.__unused) mark(node, true);
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if (!node.__unused) mark(node, false, true);
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return true;
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}
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if (node instanceof AST_SymbolRef) {
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mark(node);
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mark(node, true, false);
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return true;
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}
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if (node instanceof AST_Try) {
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@@ -4446,13 +4451,13 @@ merge(Compressor.prototype, {
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if (!unary_arithmetic[node.operator]) return;
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var sym = node.expression;
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if (!(sym instanceof AST_SymbolRef)) return;
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mark(sym);
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mark(sym, true, true);
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return true;
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}
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if (node instanceof AST_VarDef) {
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if (node.value) {
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node.value.walk(tw);
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mark(node.name, true);
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mark(node.name, false, true);
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} else {
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var id = node.name.definition().id;
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if (!(id in references)) {
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@@ -4479,7 +4484,7 @@ merge(Compressor.prototype, {
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if (tail.index > head.index) continue;
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var id = tail.definition.id;
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if (!references[id]) continue;
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if (references[def.id].segment !== references[id].segment) {
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if (!mergeable()) {
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skipped.unshift(tail);
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continue;
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}
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@@ -4510,7 +4515,36 @@ merge(Compressor.prototype, {
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segment = Object.getPrototypeOf(segment);
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}
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function read(def) {
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function mark(sym, read, write) {
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var def = sym.definition();
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if (def.id in references) {
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var refs = references[def.id];
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if (!refs) return;
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if (write ? refs.start !== segment : refs.start.block !== segment.block) {
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return references[def.id] = false;
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}
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refs.push(sym);
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refs.end = segment;
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if (def.id in prev) {
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last[prev[def.id]] = null;
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} else if (!read) {
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return;
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}
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} else if (self.variables.get(def.name) !== def || compressor.exposed(def)) {
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return references[def.id] = false;
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} else {
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var refs = declarations.get(def.id) || [];
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refs.push(sym);
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references[def.id] = refs;
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if (!read) {
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refs.start = segment;
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return first.push({
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index: index++,
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definition: def,
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});
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}
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refs.start = self;
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}
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prev[def.id] = last.length;
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last.push({
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index: index++,
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@@ -4518,32 +4552,15 @@ merge(Compressor.prototype, {
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});
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}
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function mark(sym, write_only) {
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var def = sym.definition();
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if (def.id in references) {
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var refs = references[def.id];
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if (!refs) return;
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if (refs.segment !== segment) return references[def.id] = false;
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refs.push(sym);
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if (def.id in prev) last[prev[def.id]] = null;
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read(def);
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} else if (self.variables.get(def.name) !== def || compressor.exposed(def)) {
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references[def.id] = false;
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} else {
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var refs = declarations.get(def.id) || [];
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refs.push(sym);
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references[def.id] = refs;
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if (write_only) {
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refs.segment = segment;
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first.push({
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index: index++,
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definition: def,
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});
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} else {
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refs.segment = self;
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read(def);
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}
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}
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function must_visit(base, segment) {
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return base === segment || base.isPrototypeOf(segment);
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}
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function mergeable() {
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var head = references[def.id];
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var tail = references[id];
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if (head.start.block !== tail.start.block) return false;
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return must_visit(head.start, head.end) || must_visit(head.start, tail.start);
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}
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});
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