Linus Groh 8074bdc049 LibJS: Skip declarative env in block statement without lexical decls ...

The idea here is simple: If the block statement doesn't contain any
lexical declarations, we don't need to allocate, initialize and
eventually garbage collect a new declarative environment.
This even makes lookups across nested blocks slightly faster as we don't
have to traverse a chain of empty environments anymore - instead, the
execution context just stores the outermost non-empty one.

This doesn't speed up test-js considerably, but has a noticeable effect
on test262 and real-world web content :^)

2021-10-05 14:52:53 +02:00

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