Add benchmarks for creating Strings from ASCII

[Catfish-Man]

No description provided.

[Catfish-Man]

@swift-ci please smoke benchmark

[swift-ci]

Performance: -O

Regression	OLD	NEW	DELTA	RATIO
ArrayAppendOptionals	1350	2480	+83.7%	0.54x (?)
Breadcrumbs.IdxToUTF16Range.longASCII	34	38	+11.8%	0.89x
Improvement	OLD	NEW	DELTA	RATIO
Breadcrumbs.UTF16ToIdxRange.longASCII	32	28	-12.5%	1.14x
ObjectiveCBridgeStubFromNSDateRef	4210	3800	-9.7%	1.11x (?)
Added	MIN	MAX	MEAN	MAX_RSS
UTF8Decode_InitDecoding_ascii_as_ascii	154655	155776	155255	—
UTF8Decode_InitFromBytes_ascii_as_ascii	493	493	493	—
UTF8Decode_InitFromData_ascii_as_ascii	742	743	743	—

Code size: -O

Regression	OLD	NEW	DELTA	RATIO
UTF8Decode.o	11695	13400	+14.6%	0.87x

Performance: -Osize

Added	MIN	MAX	MEAN	MAX_RSS
UTF8Decode_InitDecoding_ascii_as_ascii	155004	157434	155858	—
UTF8Decode_InitFromBytes_ascii_as_ascii	643	645	644	—
UTF8Decode_InitFromData_ascii_as_ascii	817	829	822	—

Code size: -Osize

Regression	OLD	NEW	DELTA	RATIO
UTF8Decode.o	10391	11824	+13.8%	0.88x

Performance: -Onone

Added	MIN	MAX	MEAN	MAX_RSS
UTF8Decode_InitDecoding_ascii_as_ascii	156050	156692	156424	—
UTF8Decode_InitFromBytes_ascii_as_ascii	572	572	572	—
UTF8Decode_InitFromData_ascii_as_ascii	837	841	839	—

Code size: -swiftlibs

✅	Benchmark Check Report
⛔️🔤	UTF8Decode_InitFromData_ascii_as_ascii name doesn`t conform to benchmark naming convention. See http://bit.ly/BenchmarkNaming
⛔️🔤	UTF8Decode_InitDecoding_ascii_as_ascii name doesn`t conform to benchmark naming convention. See http://bit.ly/BenchmarkNaming
⛔️⏱	UTF8Decode_InitDecoding_ascii_as_ascii execution took at least 154614 μs. Decrease the workload of UTF8Decode_InitDecoding_ascii_as_ascii by a factor of 256 (1000), to be less than 1000 μs.
⛔️🔤	UTF8Decode_InitFromBytes_ascii_as_ascii name doesn`t conform to benchmark naming convention. See http://bit.ly/BenchmarkNaming

How to read the data

The tables contain differences in performance which are larger than 8% and differences in code size which are larger than 1%.

If you see any unexpected regressions, you should consider fixing the
regressions before you merge the PR.

Noise: Sometimes the performance results (not code size!) contain false
alarms. Unexpected regressions which are marked with '(?)' are probably noise.
If you see regressions which you cannot explain you can try to run the
benchmarks again. If regressions still show up, please consult with the
performance team (@eeckstein).

Hardware Overview

  Model Name: Mac Pro
  Model Identifier: MacPro6,1
  Processor Name: 12-Core Intel Xeon E5
  Processor Speed: 2.7 GHz
  Number of Processors: 1
  Total Number of Cores: 12
  L2 Cache (per Core): 256 KB
  L3 Cache: 30 MB
  Memory: 64 GB

[Catfish-Man]

@swift-ci please smoke test

[lorentey]

This looks good to me. I had two comments, but given the existing benchmarks, it may be best to ignore them. (Local consistency may be more valuable than global in this case.)

[lorentey]

input stays constant over the duration of the for statement, so I wonder if a sufficiently clever optimizer would be able to move some of its processing outside the loop.

It may be worth passing input through identity. (Then again, the other benchmarks don't do this, and we should stay consistent if we want to be able to compare results,)

[lorentey]

Hm, the names aren't great here. Shouldn't we call this ASCIIDecode.initFromData?

The existing benchmarks have set an unfortunate pattern, but perhaps it's worth breaking it.

[Catfish-Man]

I felt keeping the prefix the same was worthwhile for being able to do something like "run all the benchmarks for X". The name does really suck though.