NEW 186193
[JSC] NewArrayBuffer should have non-CoW mode 
https://bugs.webkit.org/show_bug.cgi?id=186193
Summary [JSC] NewArrayBuffer should have non-CoW mode
Yusuke Suzuki
Reported 2018-06-01 06:33:10 PDT
In some program, array created by new_array_buffer is not immutable (I think Kraken/crypto-aes and SixSpeed spread-literal.es5 are). But ArrayifyToStructure's array copying is really slow compared to non CoW array creation in NewArrayBuffer. I think we should have non-CoW mode for NewArrayBuffer / new_array_buffer. ArrayAllocationProfile should carefully profile the use of resulted array, and tell us whether using CoW mode is profitable.
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Saam Barati
Comment 1 2018-06-01 08:55:24 PDT
Why is arrayify to structure slow?
Keith Miller
Comment 2 2018-06-01 14:10:27 PDT
It seems like if this is a problem the fix is to make Arrayification faster. Since the total amount of work duplicating the butterfly should be the same either way, I don't see any obvious reason to eagerly copy.
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