Refactor FnDecl and FnSig non-type fields into a new wrapper type

[teor2345]

Why this Refactor?

This PR is part of an initial cleanup for the arg splat experiment, but it's a useful refactor by itself.

It refactors the non-type fields of FnDecl, FnSig, and FnHeader into a new packed wrapper types, based on this comment in the splat experiment PR:
#153697 (comment)

It also refactors some common FnSig creation settings into their own methods. I did this instead of creating a struct with defaults.

Relationship to splat Experiment

I don't think we can use functional struct updates (..default()) to create FnDecl and FnSig, because we need the bit-packing for the splat experiment.

Bit-packing will avoid breaking "type is small" assertions for commonly used types when splat is added.
This PR packs these types:

• ExternAbi: enum + unwind variants (38) -> 6 bits
• ImplicitSelfKind: enum variants (5) -> 3 bits
• lifetime_elision_allowed, safety, c_variadic: bool -> 1 bit

Minor Changes

Fixes some typos, and applies rustfmt to clippy files that got skipped somehow.

[rustbot]

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

cc @rust-lang/rust-analyzer

HIR ty lowering was modified

cc @fmease

stdarch is developed in its own repository. If possible, consider making this change to rust-lang/stdarch instead.

cc @Amanieu, @folkertdev, @sayantn

This PR changes rustc_public

cc @oli-obk, @celinval, @ouz-a, @makai410

Some changes occurred in compiler/rustc_sanitizers

cc @rcvalle

The Miri subtree was changed

cc @rust-lang/miri

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

Some changes occurred in compiler/rustc_passes/src/check_attr.rs

cc @jdonszelmann, @JonathanBrouwer

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

[rustbot]

r? @mati865

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• Owners of files modified in this PR: compiler
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[teor2345]

This is ready for review now, but I have some questions for reviewers (or compiler experts) about the legacy name mangling hash.

I'd also like to check if this PR impacts perf, either positively or negatively. I don't think I have permissions, but let's try anyway:

@bors try @rust-timer queue

View changes since this review

[rust-bors]

@teor2345: 🔑 Insufficient privileges: not in try users

[nnethercote]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: d647df9 (d647df90c918d4747135501dba51b294ffa85de3, parent: e8e4541ff19649d95afab52fdde2c2eaa6829965)

[rust-timer]

Finished benchmarking commit (d647df9): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

@bors rollup=never
@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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.3%	[-0.7%, -0.1%]	45
Improvements ✅ (secondary)	-0.6%	[-1.4%, -0.2%]	68
All ❌✅ (primary)	-0.3%	[-0.7%, -0.1%]	45

Max RSS (memory usage)

Results (primary -1.8%, secondary 0.5%)

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)	3.1%	[0.9%, 5.3%]	2
Improvements ✅ (primary)	-1.8%	[-1.8%, -1.8%]	1
Improvements ✅ (secondary)	-4.6%	[-4.6%, -4.6%]	1
All ❌✅ (primary)	-1.8%	[-1.8%, -1.8%]	1

Cycles

Results (primary -2.0%, secondary -1.6%)

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)	8.0%	[2.8%, 13.2%]	2
Improvements ✅ (primary)	-2.0%	[-2.3%, -1.7%]	2
Improvements ✅ (secondary)	-3.2%	[-4.3%, -2.1%]	12
All ❌✅ (primary)	-2.0%	[-2.3%, -1.7%]	2

Binary size

Results (primary -0.1%, secondary -0.2%)

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)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.2%, -0.0%]	63
Improvements ✅ (secondary)	-0.2%	[-1.0%, -0.0%]	56
All ❌✅ (primary)	-0.1%	[-0.2%, -0.0%]	63

Bootstrap: 490.756s -> 487.632s (-0.64%)
Artifact size: 394.16 MiB -> 394.10 MiB (-0.01%)

[RalfJung]

position returns an index, this here returns a bool -- something does not check out.

View changes since the review

[teor2345]

Oops, that comment should have been on as_packed, it got left behind when I also needed a const equality check.

[teor2345]

Fixed in a70f37b (this PR)