Azat Khuzhin 61dc1da395 Fix possible tcache corruption on fiber migration (under --enable-experimental-fiber-safe-tls) ...

Under LTO `&tsd_tls` is hoisted out of the inlined malloc/free and
survives swapcontext in a callee-saved register: a fiber resumed on
another OS thread races on the old thread's tcache.

Fix it by taking the address in a noinline volatile-asm barrier accessor.

It is done under option (--enable-experimental-fiber-safe-tls), because
it make the fastpath slower, on a microbench (that is very heavy depends
on the most optimal case) the overhead is 35%, but this is unlikely the
real world scenario.

Anyway here are some numbers for microbench.c compiled with LTO:

type    |vanilla (ns)|`--enable-experimental-fiber-safe-tls` (ns)|optimized (ns) [1]
--------|------------|-------------------------------------------|------------------
malloc  |6.51        |8.77 **(+34%)**                            |6.79 (4%)
mallocx |8.48        |10.62 **(25%)**                            |8.76 (3%)
free    |6.46        |8.68 **(34%)**                             |6.76 (5%)
dallocx |8.190       |10.97 **(33%)**                            |8.74 (7%)

  [1]: https://github.com/jemalloc/jemalloc/pull/2944

This patch also adds a separate lane for CI with LTO

2026-09-01 22:10:15 -04:00

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Fix possible tcache corruption on fiber migration (under --enable-experimental-fiber-safe-tls)

2026-09-01 22:10:15 -04:00