[stdlib]String normalization functions (#21026)

[lancep]

5.0 cherry pick of #21026

[lancep]

@swift-ci please test

[lancep]

@swift-ci please benchmark

[swift-ci]

Build comment file:

Performance: -O

TEST	OLD	NEW	DELTA	RATIO
Regression
StringHashing_emoji	1231	1344	+9.2%	0.92x
StringHashing_nonBMPSlowestPrenormal	1593	1726	+8.3%	0.92x
Improvement
StringComparison_abnormal	8329	1188	-85.7%	7.01x
StringComparison_zalgo	97122	64048	-34.1%	1.52x
NormalizedIterator_ascii	141	126	-10.6%	1.12x
StringHashing_zalgo	4045	3642	-10.0%	1.11x
NormalizedIterator_zalgo	4067	3663	-9.9%	1.11x

Code size: -O

TEST	OLD	NEW	DELTA	RATIO
Regression
CSVParsing.o	30353	31425	+3.5%	0.97x
StringInterpolation.o	7371	7515	+2.0%	0.98x
RemoveWhere.o	23783	24135	+1.5%	0.99x

Performance: -Osize

TEST	OLD	NEW	DELTA	RATIO
Regression
CharIndexing_ascii_unicodeScalars_Backwards	5585	6138	+9.9%	0.91x
CharIndexing_tweet_unicodeScalars_Backwards	10967	12045	+9.8%	0.91x
NormalizedIterator_emoji	1299	1397	+7.5%	0.93x
Improvement
StringComparison_abnormal	8679	1155	-86.7%	7.51x
StringWalk	3848	1534	-60.1%	2.51x
StrComplexWalk	5547	3536	-36.3%	1.57x
StringComparison_zalgo	97678	64151	-34.3%	1.52x
CSVParsingAltIndices2	1475	1029	-30.2%	1.43x
NormalizedIterator_ascii	141	125	-11.3%	1.13x
NormalizedIterator_zalgo	4083	3662	-10.3%	1.11x
Hanoi	4024	3643	-9.5%	1.10x
StringHashing_abnormal	1640	1521	-7.3%	1.08x (?)
NormalizedIterator_abnormal	1634	1523	-6.8%	1.07x

Code size: -Osize

TEST	OLD	NEW	DELTA	RATIO
Regression
CSVParsing.o	30289	30817	+1.7%	0.98x
Hash.o	20399	20719	+1.6%	0.98x
RemoveWhere.o	23758	24110	+1.5%	0.99x
ReversedCollections.o	11706	11842	+1.2%	0.99x
Improvement
RangeAssignment.o	5101	5018	-1.6%	1.02x

Performance: -Onone

TEST	OLD	NEW	DELTA	RATIO
Improvement
StringComparison_abnormal	10088	2614	-74.1%	3.86x
StringComparison_zalgo	101474	67476	-33.5%	1.50x
StrComplexWalk	7952	6824	-14.2%	1.17x
StringHashing_zalgo	4274	3811	-10.8%	1.12x
NormalizedIterator_zalgo	4274	3822	-10.6%	1.12x
NormalizedIterator_abnormal	1952	1777	-9.0%	1.10x

Code size: -swiftlibs

TEST	OLD	NEW	DELTA	RATIO
Improvement
libswiftCore.dylib	3604480	3567616	-1.0%	1.01x

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

--------------

[lancep]

@swift-ci please test

[lancep]

@swift-ci please test

[lancep]

@swift-ci please test