[DO NOT MERGE] Test jemalloc's sized deallocation path.

[nnethercote]

My local measurements showed that doing this was a slowdown. Let's see what happens on CI.

r? @ghost

[nnethercote]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit 424c6c9 with merge 110536592fcd2f4d09f5646b980dd6546bd9a81f...

[rust-log-analyzer]

The job mingw-check failed! Check out the build log: (web) (plain)

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

    Checking rustc-main v0.0.0 (/checkout/compiler/rustc)
error[E0432]: unresolved import `tikv_jemallocator`
  --> compiler/rustc/src/main.rs:29:5
   |
29 | use tikv_jemallocator::Jemalloc;
   |     ^^^^^^^^^^^^^^^^^ use of undeclared crate or module `tikv_jemallocator`
error: unused import: `GlobalAlloc`
  --> compiler/rustc/src/main.rs:28:18
   |
28 | use std::alloc::{GlobalAlloc, Layout};
28 | use std::alloc::{GlobalAlloc, Layout};
   |                  ^^^^^^^^^^^
   |
   = note: `-D unused-imports` implied by `-D warnings`
For more information about this error, try `rustc --explain E0432`.
error: could not compile `rustc-main` due to 2 previous errors
warning: build failed, waiting for other jobs to finish...
error: build failed

[bors]

☀️ Try build successful - checks-actions
Build commit: 110536592fcd2f4d09f5646b980dd6546bd9a81f (110536592fcd2f4d09f5646b980dd6546bd9a81f)

[rust-timer]

Queued 110536592fcd2f4d09f5646b980dd6546bd9a81f with parent 2b681ac, future comparison URL.

[rust-timer]

Finished benchmarking commit (110536592fcd2f4d09f5646b980dd6546bd9a81f): comparison url.

Summary: This change led to large relevant regressions 😿 in compiler performance.

• Large regression in instruction counts (up to 3.8% on incr-unchanged builds of deep-vector)

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR led to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression

[nnethercote]

Lots of performance regressions here, it matches closely what I saw locally, so that's a good confirmation that the sized deallocation is definitely not a win for rustc.