[DRAFT] Cleanups related to RefDecodable

[Zalathar]

(For now this is a draft to measure perf.)

[Zalathar]

@bors try @rust-timer queue

[rust-log-analyzer]

The job pr-check-2 failed! Check out the build log: (web) (plain enhanced) (plain)

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

    Checking rustc_symbol_mangling v0.0.0 (/checkout/compiler/rustc_symbol_mangling)
warning: unresolved link to `impl_decodable_via_ref_decodable_for_local_type`
  --> compiler/rustc_middle/src/ty/codec/ref_decodable.rs:21:29
   |
21 | /// by a trait bound; see [`impl_decodable_via_ref_decodable_for_local_type`] for details.
   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no item named `impl_decodable_via_ref_decodable_for_local_type` in scope
   |
   = note: `macro_rules` named `impl_decodable_via_ref_decodable_for_local_type` exists in this crate, but it is not in scope at this link's location
   = note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default

[rust-bors]

☀️ Try build successful (CI)
Build commit: 91fa19a (91fa19a8b0f36ffcd6920c9f080e9a0c52a09950)
Base parent: 71238e2 (71238e21fc55e73ab3aad8c9f79fed7a47a179e1)

[rust-timer]

Finished benchmarking commit (91fa19a): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

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

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.2%, 0.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.3%, -0.2%]	4
All ❌✅ (primary)	0.2%	[0.2%, 0.2%]	1

Max RSS (memory usage)

Results (primary 2.7%, secondary 3.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.7%	[2.6%, 2.7%]	2
Regressions ❌ (secondary)	3.2%	[2.6%, 3.7%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.7%	[2.6%, 2.7%]	2

Cycles

Results (secondary 12.3%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	29.5%	[29.5%, 29.5%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.8%	[-4.8%, -4.8%]	1
All ❌✅ (primary)	-	-	0

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 475.37s -> 485.156s (2.06%)
Artifact size: 403.37 MiB -> 403.54 MiB (0.04%)