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LibJS: Stop converting between Object <-> IteratorRecord all the time

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This patch makes IteratorRecord an Object. Although it's not exposed to
author code, this does allow us to store it in a VM register.

Now that we can store it in a VM register, we don't need to convert it
back and forth between IteratorRecord and Object when accessing it from
bytecode.

The big win here is avoiding 3 [[Get]] accesses on every iteration step
of for..of loops. There are also a bunch of smaller efficiencies gained.

20% speed-up on this microbenchmark:

    function go(a) {
        for (const p of a) {
        }
    }
    const a = [];
    a.length = 1_000_000;
    go(a);
This commit is contained in:
Andreas Kling 2023-12-07 10:44:41 +01:00
parent 4966c083df
commit 4699c81fc1
23 changed files with 226 additions and 144 deletions
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8
Userland/Libraries/LibJS/Runtime/PromiseConstructor.cpp
View file

@ -333,7 +333,7 @@ JS_DEFINE_NATIVE_FUNCTION(PromiseConstructor::all)
// 8. If result is an abrupt completion, then
if (result.is_error()) {
// a. If iteratorRecord.[[Done]] is false, set result to Completion(IteratorClose(iteratorRecord, result)).
if (!iterator_record.done)
if (!iterator_record->done)
result = iterator_close(vm, iterator_record, result.release_error());
// b. IfAbruptRejectPromise(result, promiseCapability).
@ -367,7 +367,7 @@ JS_DEFINE_NATIVE_FUNCTION(PromiseConstructor::all_settled)
// 8. If result is an abrupt completion, then
if (result.is_error()) {
// a. If iteratorRecord.[[Done]] is false, set result to Completion(IteratorClose(iteratorRecord, result)).
if (!iterator_record.done)
if (!iterator_record->done)
result = iterator_close(vm, iterator_record, result.release_error());
// b. IfAbruptRejectPromise(result, promiseCapability).
@ -401,7 +401,7 @@ JS_DEFINE_NATIVE_FUNCTION(PromiseConstructor::any)
// 8. If result is an abrupt completion, then
if (result.is_error()) {
// a. If iteratorRecord.[[Done]] is false, set result to Completion(IteratorClose(iteratorRecord, result)).
if (!iterator_record.done)
if (!iterator_record->done)
result = iterator_close(vm, iterator_record, result.release_error());
// b. IfAbruptRejectPromise(result, promiseCapability).
@ -435,7 +435,7 @@ JS_DEFINE_NATIVE_FUNCTION(PromiseConstructor::race)
// 8. If result is an abrupt completion, then
if (result.is_error()) {
// a. If iteratorRecord.[[Done]] is false, set result to Completion(IteratorClose(iteratorRecord, result)).
if (!iterator_record.done)
if (!iterator_record->done)
result = iterator_close(vm, iterator_record, result.release_error());
// b. IfAbruptRejectPromise(result, promiseCapability).