Previously, GCInfoTrait relied on the non-trivial constructor of a
static object for registering a new GCInfo object. The generated code
is required to be thread-safe which is achieved by introducing guard
variables in the compiler.
The new version is similar to Blink in that it relies on zero
initialization of a trivially constructible atomic.
Compared to guard variables that are created per GCInfo registration,
the atomic creates less bloat (~20bytes/type) and also results in a
better fast path.
Minimum example: https://godbolt.org/z/qrdTf8
Bug: chromium:1056170
Change-Id: I95efbbf035b655d0440c9477f5391e310e2b71fa
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2764750
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73463}
d76064df4f