std: move check for destroyed TLS variable

[joboet]

When accessing a TLS variable, the comparison that checks whether the variable is initialised can be inlined to the call site. The comparison that checks whether the variable has been destroyed is however performed in the #[cold] accessor function. Since all call-sites need to check whether the returned pointer is null, this split prevents these two checks from being merged into one. Thus moving the liveliness check into the inlineable accessor may yield more optimal codegen. This is especially true in the case where the variable does not need destruction and thus no null pointer will ever be returned, as the null-pointer check can now be optimised out.

[rustbot]

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[joboet]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[rust-log-analyzer]

The job tidy failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

finished building tool typos
error: `Uninitalized` should be `Uninitialized`
   ╭▸ library/std/src/sys/thread_local/native/lazy.rs:67:40
   │
67 │     /// * The state of `self` must be `Uninitalized`.
   ╰╴                                       ━━━━━━━━━━━━
rerun tidy with `--extra-checks=spellcheck --bless` to fix typos
tidy [extra_checks]: checks with external tool 'typos' failed
tidy [extra_checks]: FAIL
tidy: The following check failed: extra_checks
Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage1-tools-bin/rust-tidy /checkout /checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo /checkout/obj/build 4 /node/bin/npm --extra-checks=py,cpp,js,spellcheck` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1549:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:1280:29

Command has failed. Rerun with -v to see more details.
Bootstrap failed while executing `test src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck`
Build completed unsuccessfully in 0:02:33
  local time: Thu Oct 23 15:55:15 UTC 2025
  network time: Thu, 23 Oct 2025 15:55:15 GMT
##[error]Process completed with exit code 1.

[rust-bors]

☀️ Try build successful (CI)
Build commit: db38fd3 (db38fd3601bd22cc534c47281f839697adae4273, parent: 11d2046fe9962720558cb15f72541f7fd170dec9)

[rust-timer]

Queued db38fd3 with parent 11d2046, future comparison URL.
There is currently 1 preceding artifact in the queue.
It will probably take at least ~2.0 hours until the benchmark run finishes.