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de-duplicate trailing cases only

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avoid all potential side-effects
This commit is contained in:
alexlamsl 2017-03-26 16:29:26 +08:00
parent 4291ecc77c
commit 74d2f03dc6
2 changed files with 7 additions and 13 deletions
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18
lib/compress.js
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@ -2515,7 +2515,7 @@ merge(Compressor.prototype, {
self.expression = best_of_expression(expression, self.expression);
}
if (compressor.option("dead_code")) {
var blocks = Object.create(null);
var prev_block;
var decl = [];
var body = [];
var default_branch;
@ -2544,22 +2544,16 @@ merge(Compressor.prototype, {
}
var case_side_effects = branch instanceof AST_Case && branch.expression.has_side_effects(compressor);
if (aborts(branch)) {
var key = make_node(AST_BlockStatement, branch, branch).print_to_string();
var block;
if (!fallthrough && (block = blocks[key])) {
var insert = body.indexOf(block) + 1;
if (insert == body.length || !case_side_effects) {
block.body = [];
body.splice(insert, 0, branch);
} else body.push(branch);
} else body.push(branch);
var block = make_node(AST_BlockStatement, branch, branch).print_to_string();
if (!fallthrough && prev_block === block) body[body.length - 1].body = [];
body.push(branch);
prev_block = block;
fallthrough = false;
} else {
body.push(branch);
prev_block = null;
fallthrough = true;
}
if (case_side_effects) blocks = Object.create(null);
if (!fallthrough) blocks[key] = branch;
}
for (; i < len && fallthrough; i++) {
branch = self.body[i];

2
test/compress/switch.js
View File

@ -542,11 +542,11 @@ issue_1680_2: {
var a = 100, b = 10;
switch (b) {
case a--:
case a:
break;
case b:
var c;
break;
case a:
case a--:
}
console.log(a, b);