Status: Accepted
Owner: ----
CC: [email protected], [email protected]
Labels: Type-Bug Priority-Medium
New issue 3842 by [email protected]: 5x regression in the performance of
dispatch table pattern
https://code.google.com/p/v8/issues/detail?id=3842
Dispatch table is something like this
handlers[obj.type](obj)
A reproduction worth a thousand words (test.js attached):
# V8 ToT
$ out/ia32.release/d8 test.js
354
# V8 3.14.5.9
$ node test.js
74
I didn't dig to deep into this but I think whatever is patched into keyed
load doesn't probe megamorphic cache anymore. From the profile it looks
like it constantly misses.
Such patterns are often used to write tree visitors. I suspect this is the
reason for escodegen regression reported against io.js:
https://github.com/iojs/io.js/issues/472 (escodegen benchmark regresses by
50%).
Attachments:
test.js 618 bytes
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