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enhance collapse_vars (#3896)

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This commit is contained in:
Alex Lam S.L
2020-05-14 00:52:42 +01:00
committed by GitHub
parent fe2f1965d6
commit 938368ba21
2 changed files with 39 additions and 6 deletions
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10
lib/compress.js
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@@ -1350,7 +1350,7 @@ merge(Compressor.prototype, {
var lhs = get_lhs(candidate);
var side_effects = lhs && lhs.has_side_effects(compressor);
var scan_lhs = lhs && !side_effects && !is_lhs_read_only(lhs, compressor);
var scan_rhs = foldable(get_rhs(candidate));
var scan_rhs = foldable(candidate);
if (!scan_lhs && !scan_rhs) continue;
var modify_toplevel = false;
// Locate symbols which may execute code outside of scanning range
@@ -1841,10 +1841,6 @@ merge(Compressor.prototype, {
}
}
function get_rhs(expr) {
return candidate instanceof AST_Assign && candidate.operator == "=" && candidate.right;
}
function invariant(expr) {
if (expr instanceof AST_Array) return false;
if (expr instanceof AST_Binary && lazy_op[expr.operator]) {
@@ -1859,7 +1855,9 @@ merge(Compressor.prototype, {
}
function foldable(expr) {
if (!expr) return false;
while (expr instanceof AST_Assign && expr.operator == "=") {
expr = expr.right;
}
if (expr instanceof AST_SymbolRef) {
var value = expr.evaluate(compressor);
if (value === expr) return rhs_exact_match;