Overhaul filename handling for cross-compiler consistency

[Urgau]

This PR overhauls the way we handle filenames in the compiler and rmeta in order to achieve achieve cross-compiler consistency (ie. having the same path no matter if the filename was created in the current compiler session or is coming from rmeta).

This is required as some parts of the compiler rely on consistent paths for the soundness of generated code (see #148328).

In order to achieved consistency multiple steps are being taken by this PR:

• by making RealFileName immutable
• by only having SourceMap::to_real_filename create RealFileName
  • currently RealFileName can be created from any Path and are remapped afterwards, which creates consistency issue
• by also making RealFileName holds it's working directory, embeddable name and the remapped scopes
  • this removes the need for a Session, to know the current(!) scopes and cwd, which is invalid as they may not be equal to the scopes used when creating the filename

In order for SourceMap::to_real_filename to know which scopes to apply FilePathMapping now takes the current remapping scopes to apply, which makes FileNameDisplayPreference and company useless and are removed.

This PR is split-up in multiple commits (unfortunately not atomic), but should help review the changes.

Unblocks #147611
Fixes #148328

cc @RalfJung @oli-obk
r? @davidtwco

[rustbot]

Some changes occurred in coverage instrumentation.

cc @Zalathar

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.

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

The Miri subtree was changed

cc @rust-lang/miri

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

[rustbot]

Some changes occurred in src/tools/rustfmt

cc @rust-lang/rustfmt

[RalfJung]

@bors try
@rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 05b3365 (05b33656fd9ded2829b42521378e6fa37f788cc6, parent: ba86c0460b0233319e01fd789a42a7276eade805)

[rust-timer]

Finished benchmarking commit (05b3365): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.7%	[0.2%, 1.1%]	7
Regressions ❌ (secondary)	0.6%	[0.0%, 2.2%]	32
Improvements ✅ (primary)	-0.6%	[-1.6%, -0.2%]	12
Improvements ✅ (secondary)	-0.3%	[-0.7%, -0.2%]	4
All ❌✅ (primary)	-0.2%	[-1.6%, 1.1%]	19

Max RSS (memory usage)

Results (primary 0.7%, secondary 1.5%)

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

	mean	range	count
Regressions ❌ (primary)	0.7%	[0.7%, 0.7%]	1
Regressions ❌ (secondary)	3.2%	[2.3%, 6.1%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.8%	[-4.4%, -3.1%]	2
All ❌✅ (primary)	0.7%	[0.7%, 0.7%]	1

Cycles

Results (primary -2.6%, secondary -0.8%)

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)	4.0%	[4.0%, 4.0%]	1
Improvements ✅ (primary)	-2.6%	[-2.6%, -2.6%]	1
Improvements ✅ (secondary)	-2.4%	[-2.7%, -2.0%]	3
All ❌✅ (primary)	-2.6%	[-2.6%, -2.6%]	1

Binary size

Results (primary 0.1%, secondary 0.1%)

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

	mean	range	count
Regressions ❌ (primary)	0.1%	[0.0%, 0.3%]	96
Regressions ❌ (secondary)	0.1%	[0.0%, 0.4%]	54
Improvements ✅ (primary)	-0.0%	[-0.0%, -0.0%]	4
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	2
All ❌✅ (primary)	0.1%	[-0.0%, 0.3%]	100

Bootstrap: 470.7s -> 471.092s (0.08%)
Artifact size: 388.87 MiB -> 388.90 MiB (0.01%)

[Urgau]

Those perf results seems to be mostly noise.

Instruction count saw a lot of variability but is overall positive for primary, but more interestingly Max RSS, Cycles and Wall Time are within noise level.

The only metric that shows a really change is Binary size since we now encode more metadata. Before we encoded two PathBuf max, now we encode six PathBuf max (two * (name, working dir, embeddable name)).

We could potentially de-duplicate the encoding of the working directory but that seems like a lot of work for not much gain.