Bug 186724
| Summary: | [DFG] DFG fixup checkArray typically considers only one Structure | ||
|---|---|---|---|
| Product: | WebKit | Reporter: | Yusuke Suzuki <ysuzuki> |
| Component: | JavaScriptCore | Assignee: | Nobody <webkit-unassigned> |
| Status: | NEW | ||
| Severity: | Normal | CC: | fpizlo, keith_miller, mark.lam, saam, ysuzuki |
| Priority: | P2 | ||
| Version: | WebKit Nightly Build | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Bug Depends on: | 186193 | ||
| Bug Blocks: | |||
Yusuke Suzuki
The simple example is below.
function test()
{
var array = [0, 1, 2, 3];
for (var i = 0; i < 4; ++i) {
array[0] = array[0] + 1;
}
return array;
}
noInline(test);
for (var i = 0; i < 1e6; ++i)
test();
Our ArrayProfile takes only one array. So typically, `array[0]` op_put_by_val says "Yeah, the array seems ArrayWithInt32".
But actually, this should see both `CopyOnWriteArrayWithInt32` and `ArrayWithInt32`.
The above example first emit CheckStructure for ArrayWithInt32. Then it fails repeatedly, and the op_put_by_val emits
PutByVal(Check:Untyped:@26, Check:Untyped:@29, Check:Untyped:Kill:@47, MustGen|VarArgs, Generic+OriginalNonArray+OutOfBounds+AsIs+Write, R:World, W:Heap, Exits, ClobbersExit, bc#37, ExitValid)
It is bad. Ideally, we should emit ArrayifyToStructure for ArrayWithInt32 first.
| Attachments | ||
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| Add attachment proposed patch, testcase, etc. |
Yusuke Suzuki
I think this is the reason why Kraken crypto-aes and crypto-ccm cause regression right now.
Yusuke Suzuki
Keith, Saam do you have any idea to fix this?
One way fixing this is https://bugs.webkit.org/show_bug.cgi?id=186193.
Keith Miller
I think the simplest solution to this have ArrayProfile track if it has seen a CoW array. Then, if fixup sees original and maybe copy on write can can do an arrayify to structure. Thoughts?