Deterministic encoding of DefPathHashMap

[aerooneqq]

Just for perf for now.
r? @petrochenkov

[petrochenkov]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: df2b5a2 (df2b5a2f0e02a8844635d39578b4c1b338a8c0d0)
Base parent: c999cef (c999cef531ea9059e189e82fe0e82c5daf249bc9)

[rust-timer]

Finished benchmarking commit (df2b5a2): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

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.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@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)	0.5%	[0.1%, 0.8%]	8
Regressions ❌ (secondary)	0.4%	[0.1%, 0.9%]	33
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.4%	[-0.9%, -0.3%]	9
All ❌✅ (primary)	0.5%	[0.1%, 0.8%]	8

Max RSS (memory usage)

Results (primary 3.1%, secondary 4.7%)

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

	mean	range	count
Regressions ❌ (primary)	3.1%	[0.7%, 12.2%]	195
Regressions ❌ (secondary)	4.8%	[0.5%, 12.7%]	307
Improvements ✅ (primary)	-0.8%	[-0.8%, -0.8%]	1
Improvements ✅ (secondary)	-3.1%	[-3.1%, -3.1%]	1
All ❌✅ (primary)	3.1%	[-0.8%, 12.2%]	196

Cycles

Results (primary 10.3%, secondary 4.2%)

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

	mean	range	count
Regressions ❌ (primary)	10.3%	[2.8%, 17.3%]	4
Regressions ❌ (secondary)	4.4%	[2.0%, 10.2%]	36
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.1%	[-3.1%, -3.1%]	1
All ❌✅ (primary)	10.3%	[2.8%, 17.3%]	4

Binary size

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

Bootstrap: 500.132s -> 496.691s (-0.69%)
Artifact size: 406.81 MiB -> 409.64 MiB (0.70%)