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enhance if_return (#5518)

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This commit is contained in:
Alex Lam S.L
2022-06-23 17:52:22 +01:00
committed by GitHub
parent 933ca9ddd8
commit 9f57920566
4 changed files with 187 additions and 4 deletions
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42
lib/compress.js
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@@ -3391,6 +3391,7 @@ Compressor.prototype.compress = function(node) {
var changed = false;
var parent = compressor.parent();
var self = compressor.self();
var exit, exit_defs, merge_exit;
var in_iife = in_lambda && parent && parent.TYPE == "Call" && parent.expression === self;
var chain_if_returns = in_lambda && compressor.option("conditionals") && compressor.option("sequences");
var multiple_if_returns = has_multiple_if_returns(statements);
@@ -3446,6 +3447,7 @@ Compressor.prototype.compress = function(node) {
stat.condition = cond;
statements[j] = stat.body;
stat.body = next;
if (next === exit) exit = null;
statements[i] = stat;
statements[i] = stat.transform(compressor);
continue;
@@ -3489,6 +3491,7 @@ Compressor.prototype.compress = function(node) {
changed = true;
stat = stat.clone();
stat.alternative = next;
if (next === exit) exit = null;
statements.splice(i, 1, stat.transform(compressor));
statements.splice(j, 1);
continue;
@@ -3532,6 +3535,11 @@ Compressor.prototype.compress = function(node) {
continue;
}
}
if (stat instanceof AST_Exit) {
exit = stat;
exit_defs = null;
}
}
return changed;
@@ -3553,7 +3561,25 @@ Compressor.prototype.compress = function(node) {
}
function can_drop_abort(ab) {
if (ab instanceof AST_Return) return in_lambda && is_undefined(ab.value);
if (ab instanceof AST_Exit) {
if (exit && exit.equivalent_to(ab)) {
if (!exit_defs) {
exit_defs = new Dictionary();
exit.walk(new TreeWalker(function(node) {
if (node instanceof AST_SymbolRef) exit_defs.set(node.name, node.definition());
}));
}
var abort = false;
ab.walk(new TreeWalker(function(node) {
if (abort) return true;
if (node instanceof AST_SymbolRef && exit_defs.get(node.name) !== node.definition()) {
return abort = true;
}
}));
if (!abort) return merge_exit = true;
}
return in_lambda && ab instanceof AST_Return && is_undefined(ab.value);
}
if (!(ab instanceof AST_LoopControl)) return false;
var lct = compressor.loopcontrol_target(ab);
if (ab instanceof AST_Continue) return match_target(loop_body(lct));
@@ -3562,6 +3588,7 @@ Compressor.prototype.compress = function(node) {
}
function can_merge_flow(ab) {
merge_exit = false;
if (!can_drop_abort(ab)) return false;
for (var j = statements.length; --j > i;) {
var stat = statements[j];
@@ -3581,7 +3608,16 @@ Compressor.prototype.compress = function(node) {
function extract_functions() {
var defuns = [];
var lexical = false;
var tail = statements.splice(i + 1).filter(function(stat) {
var start = i + 1;
var end;
if (merge_exit) {
end = statements.lastIndexOf(exit);
if (end < 0) end = statements.length;
} else {
end = statements.length;
exit = null;
}
var tail = statements.splice(start, end - start).filter(function(stat) {
if (stat instanceof AST_LambdaDefinition) {
defuns.push(stat);
return false;
@@ -3600,7 +3636,7 @@ Compressor.prototype.compress = function(node) {
block = last.body;
}
block.pop();
if (ab.value) block.push(make_node(AST_SimpleStatement, ab.value, { body: ab.value }));
if (!merge_exit && ab.value) block.push(make_node(AST_SimpleStatement, ab.value, { body: ab.value }));
return body;
}