Add a size_hint function to Display

[Kobzol]

Just an experiment for perf, nothing to see here.

[Kobzol]

@bors try @rust-timer queue

[rust-bors]

💔 Test for d9d1a1f failed: CI. Failed job:

• try - dist-x86_64-linux-quick (web logs, enhanced plaintext logs)

[Kobzol]

@bors try @rust-timer queue

[rust-log-analyzer]

The job x86_64-gnu-gcc-core-tests failed! Check out the build log: (web) (plain enhanced) (plain)

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

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[rust-bors]

☀️ Try build successful (CI)
Build commit: b2da04e (b2da04e16117d7344a6cefa658b39405b8fe036e)
Base parent: 526c36b (526c36b4c477994b7905ec6a084d6150e49076f5)

[rust-timer]

Finished benchmarking commit (b2da04e): 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)	0.4%	[0.1%, 1.9%]	45
Regressions ❌ (secondary)	1.2%	[0.1%, 8.3%]	29
Improvements ✅ (primary)	-0.3%	[-3.2%, -0.1%]	24
Improvements ✅ (secondary)	-0.5%	[-1.5%, -0.1%]	30
All ❌✅ (primary)	0.1%	[-3.2%, 1.9%]	69

Max RSS (memory usage)

Results (primary 2.0%, secondary -5.7%)

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

	mean	range	count
Regressions ❌ (primary)	2.0%	[0.8%, 3.6%]	6
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-5.7%	[-8.3%, -4.2%]	3
All ❌✅ (primary)	2.0%	[0.8%, 3.6%]	6

Cycles

Results (primary -0.3%, secondary 4.1%)

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

	mean	range	count
Regressions ❌ (primary)	2.1%	[2.1%, 2.1%]	1
Regressions ❌ (secondary)	5.0%	[2.3%, 9.1%]	8
Improvements ✅ (primary)	-2.7%	[-2.7%, -2.7%]	1
Improvements ✅ (secondary)	-2.9%	[-2.9%, -2.9%]	1
All ❌✅ (primary)	-0.3%	[-2.7%, 2.1%]	2

Binary size

Results (primary 1.1%, secondary 1.0%)

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

	mean	range	count
Regressions ❌ (primary)	1.1%	[0.1%, 5.0%]	125
Regressions ❌ (secondary)	1.0%	[0.0%, 4.7%]	147
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.1%	[0.1%, 5.0%]	125

Bootstrap: 470.08s -> 466.848s (-0.69%)
Artifact size: 400.00 MiB -> 401.57 MiB (0.39%)