Remove a retain release pair in foreign string hashing

[Catfish-Man]

Fixes rdar://problem/52157564

[Catfish-Man]

@swift-ci please benchmark

[swift-ci]

Performance: -O

Regression	OLD	NEW	DELTA	RATIO
ObjectiveCBridgeStubFromNSString	456	501	+9.9%	0.91x (?)
Improvement	OLD	NEW	DELTA	RATIO
StringEnumRawValueInitialization	540	380	-29.6%	1.42x
SuffixArrayLazy	5	4	-20.0%	1.25x (?)
Calculator	152	134	-11.8%	1.13x (?)
Chars2	3350	3000	-10.4%	1.12x (?)
FlattenListFlatMap	4719	4251	-9.9%	1.11x (?)
UTF8Decode_InitDecoding	123	111	-9.8%	1.11x (?)
StringComparison_ascii	373	337	-9.7%	1.11x
OpenClose	61	56	-8.2%	1.09x (?)

Code size: -O

Performance: -Osize

Regression	OLD	NEW	DELTA	RATIO
ArrayAppendGenericStructs	590	1520	+157.6%	0.39x (?)
Improvement	OLD	NEW	DELTA	RATIO
StringEnumRawValueInitialization	540	400	-25.9%	1.35x
Calculator	153	133	-13.1%	1.15x
Chars2	3500	3150	-10.0%	1.11x (?)
UTF8Decode_InitDecoding	122	112	-8.2%	1.09x (?)
OpenClose	63	58	-7.9%	1.09x (?)
DropWhileSequence	14	13	-7.1%	1.08x (?)
FlattenListLoop	2272	2123	-6.6%	1.07x (?)

Code size: -Osize

Performance: -Onone

Regression	OLD	NEW	DELTA	RATIO
ArrayOfPOD	658	726	+10.3%	0.91x (?)

Code size: -swiftlibs

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 mini
  Model Identifier: Macmini8,1
  Processor Name: Intel Core i7
  Processor Speed: 3.2 GHz
  Number of Processors: 1
  Total Number of Cores: 6
  L2 Cache (per Core): 256 KB
  L3 Cache: 12 MB
  Memory: 64 GB

[Catfish-Man]

@swift-ci please smoke benchmark

[Catfish-Man]

wrong command >.<

[Catfish-Man]

@swift-ci please smoke test

[swift-ci]

Performance: -O

Regression	OLD	NEW	DELTA	RATIO
DataAppendDataSmallToSmall	4080	4580	+12.3%	0.89x (?)
StringBuilderWithLongSubstring	1310	1410	+7.6%	0.93x (?)
Improvement	OLD	NEW	DELTA	RATIO
StringEnumRawValueInitialization	840	620	-26.2%	1.35x

Code size: -O

Performance: -Osize

Regression	OLD	NEW	DELTA	RATIO
InsertCharacterEndIndexNonASCII	57	62	+8.8%	0.92x (?)
Improvement	OLD	NEW	DELTA	RATIO
StringEnumRawValueInitialization	840	620	-26.2%	1.35x
Breadcrumbs.IdxToUTF16Range.longMixed	406	378	-6.9%	1.07x (?)

Code size: -Osize

Performance: -Onone

Improvement	OLD	NEW	DELTA	RATIO
ObjectiveCBridgeStubFromNSDateRef	4550	4140	-9.0%	1.10x (?)

Code size: -swiftlibs

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

[milseman]

LGTM, good find