Commit graph

6 commits

Author SHA1 Message Date
Andreas Kling
1d8ec677a3 LibJS/JIT: Add fast path for cached GetVariable accesses
We can now stay in machine code for environment variable read accesses
as long as they are cached and initialized.

20% speed-up on Octane/zlib.js :^)
2023-11-07 11:33:04 +01:00
Andreas Kling
640d48255b LibJS: Remove unhelpful environment lookup optimization for globals
This optimization was no longer helpful after the bug fix for missing
invalidation on global delete was introduced in 331f6a9e6, since we
now have to check bindings for presence in the global environment every
time anyway.

Since the bytecode VM now has fast GetGlobal in most cases, let's not
even worry about this and just remove the unhelpful "optimization".

In fact, removing this is actually an *optimization*, since we avoid
a redundant has_binding() check on every global variable access. :^)
2023-07-13 10:56:59 +02:00
Andreas Kling
0f1f925532 LibJS: Shrink Identifier's environment coordinate cache
This patch does two things:

- We now use u32 instead of size_t for the hops and index fields
  in EnvironmentCoordinate. This means we're limited to an environment
  nesting level and variable count of 4Gs respectively.

- Instead of wrapping it in an Optional, EnvironmentCoordinate now has
  a custom valid/invalid state using a magic marker value.

These two changes reduce the size of Identifier by 16 bytes. :^)
2022-11-22 21:13:35 +01:00
Andreas Kling
d7e5a2058d LibJS: Cache access to bindings in the global environment
This patch adds a special EnvironmentCoordinate::global_marker value
that signifies that a binding lookup ended up searching the global
environment. It doesn't matter if we find it there or not, the global
marker is always returned. This allows us to bypass other environments
on subsequent access, going directly to the global environment.
2022-11-11 12:22:01 +00:00
Ben Wiederhake
0a53cf2a07 LibJS: Add missing header in EnvironmentCoordinate.h 2021-10-20 09:20:18 +01:00
Andreas Kling
41a072bded LibJS: Fast non-local variable access :^)
This patch introduces the "environment coordinate" concept, which
encodes the distance from a variable access to the binding it ends up
resolving to.

EnvironmentCoordinate has two fields:

    - hops:  The number of hops up the lexical environment chain we have
             to make before getting to the resolved binding.

    - index: The index of the resolved binding within its declarative
             environment record.

Whenever a variable lookup resolves somewhere inside a declarative
environment, we now cache the coordinates and reuse them in subsequent
lookups. This is achieved via a coordinate cache in JS::Identifier.

Note that non-strict direct eval() breaks this optimization and so it
will not be performed if the resolved environment has been permanently
screwed by eval().

This makes variable access *significantly* faster. :^)
2021-10-07 11:53:18 +02:00