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improve collapse_vars (#3103)
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@alexlamsl
alexlamsl committed Apr 26, 2018
1 parent 69fc7ca commit 82a8b6f
Showing 1 changed file with 53 additions and 31 deletions.
84 changes: 53 additions & 31 deletions lib/compress.js
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Original file line number Diff line number Diff line change
Expand Up @@ -980,24 +980,12 @@ merge(Compressor.prototype, {
}
// Stop immediately if these node types are encountered
var parent = scanner.parent();
if (node instanceof AST_Assign && node.operator != "=" && lhs.equivalent_to(node.left)
|| node instanceof AST_Call && lhs instanceof AST_PropAccess && lhs.equivalent_to(node.expression)
|| node instanceof AST_Debugger
|| node instanceof AST_IterationStatement && !(node instanceof AST_For)
|| node instanceof AST_LoopControl
|| node instanceof AST_Try
|| node instanceof AST_With
|| parent instanceof AST_For && node !== parent.init
|| !replace_all
&& (node instanceof AST_SymbolRef && !node.is_declared(compressor))) {
if (should_stop(node, parent)) {
abort = true;
return node;
}
// Stop only if candidate is found within conditional branches
if (!stop_if_hit
&& (parent instanceof AST_Binary && lazy_op[parent.operator] && parent.left !== node
|| parent instanceof AST_Conditional && parent.condition !== node
|| parent instanceof AST_If && parent.condition !== node)) {
if (!stop_if_hit && in_conditional(node, parent)) {
stop_if_hit = parent;
}
// Replace variable with assignment when found
Expand Down Expand Up @@ -1047,20 +1035,7 @@ merge(Compressor.prototype, {
// These node types have child nodes that execute sequentially,
// but are otherwise not safe to scan into or beyond them.
var sym;
if (node instanceof AST_Call
|| node instanceof AST_Exit
&& (side_effects || lhs instanceof AST_PropAccess || may_modify(lhs))
|| node instanceof AST_PropAccess
&& (side_effects || node.expression.may_throw_on_access(compressor))
|| node instanceof AST_SymbolRef
&& (symbol_in_lvalues(node) || side_effects && may_modify(node))
|| node instanceof AST_This && symbol_in_lvalues(node)
|| node instanceof AST_VarDef && node.value
&& (node.name.name in lvalues || side_effects && may_modify(node.name))
|| (sym = is_lhs(node.left, node))
&& (sym instanceof AST_PropAccess || sym.name in lvalues)
|| may_throw
&& (in_try ? node.has_side_effects(compressor) : side_effects_external(node))) {
if (is_last_node(node, parent) || may_throw(node)) {
stop_after = node;
if (node instanceof AST_Scope) abort = true;
}
Expand Down Expand Up @@ -1119,7 +1094,9 @@ merge(Compressor.prototype, {
var lhs_local = is_lhs_local(lhs);
if (!side_effects) side_effects = value_has_side_effects(candidate);
var replace_all = replace_all_symbols();
var may_throw = candidate.may_throw(compressor);
var may_throw = candidate.may_throw(compressor) ? in_try ? function(node) {
return node.has_side_effects(compressor);
} : side_effects_external : return_false;
var funarg = candidate.name instanceof AST_SymbolFunarg;
var hit = funarg;
var abort = false, replaced = 0, can_replace = !args || !hit;
Expand Down Expand Up @@ -1171,6 +1148,51 @@ merge(Compressor.prototype, {
}
}

function should_stop(node, parent) {
if (node instanceof AST_Assign) return node.operator != "=" && lhs.equivalent_to(node.left);
if (node instanceof AST_Call) {
return lhs instanceof AST_PropAccess && lhs.equivalent_to(node.expression);
}
if (node instanceof AST_Debugger) return true;
if (node instanceof AST_IterationStatement) return !(node instanceof AST_For);
if (node instanceof AST_LoopControl) return true;
if (node instanceof AST_Try) return true;
if (node instanceof AST_With) return true;
if (parent instanceof AST_For) return node !== parent.init;
if (replace_all) return false;
return node instanceof AST_SymbolRef && !node.is_declared(compressor);
}

function in_conditional(node, parent) {
if (parent instanceof AST_Binary) return lazy_op[parent.operator] && parent.left !== node;
if (parent instanceof AST_Conditional) return parent.condition !== node;
return parent instanceof AST_If && parent.condition !== node;
}

function is_last_node(node, parent) {
if (node instanceof AST_Call) return true;
if (node instanceof AST_Exit) {
return side_effects || lhs instanceof AST_PropAccess || may_modify(lhs);
}
if (node instanceof AST_PropAccess) {
return side_effects || node.expression.may_throw_on_access(compressor);
}
if (node instanceof AST_SymbolRef) {
if (symbol_in_lvalues(node, parent)) {
return !parent || parent.operator != "=" || parent.left !== node;
}
return side_effects && may_modify(node);
}
if (node instanceof AST_This) return symbol_in_lvalues(node, parent);
if (node instanceof AST_VarDef) {
if (!node.value) return false;
return node.name.name in lvalues || side_effects && may_modify(node.name);
}
var sym = is_lhs(node.left, node);
if (sym && sym.name in lvalues) return true;
if (sym instanceof AST_PropAccess) return true;
}

function extract_args() {
var iife, fn = compressor.self();
if (fn instanceof AST_Function
Expand Down Expand Up @@ -1482,10 +1504,10 @@ merge(Compressor.prototype, {
return false;
}

function symbol_in_lvalues(sym) {
function symbol_in_lvalues(sym, parent) {
var lvalue = lvalues[sym.name];
if (!lvalue) return;
if (lvalue !== lhs) return true;
if (lvalue !== lhs) return !(parent instanceof AST_Call);
scan_rhs = false;
}

Expand Down

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