[Runtime] Use a #define for the value of swift_isaMask.

[mikeash]

This allows _swift_getClassOfAllocated to use a constant instead of loading from a global, and allows swift_isaMask to be computed without a static initializer. Debug builds verify that the #define matches the value from libobjc.

rdar://problem/22375602 rdar://problem/46385113

[mikeash]

@swift-ci please test

[Catfish-Man]

Looks great!

[Catfish-Man]

@swift-ci please smoke benchmark

[swift-ci]

Performance: -O

TEST	OLD	NEW	DELTA	RATIO
Regression
EqualStringSubstring	38	43	+13.2%	0.88x (?)
LessSubstringSubstring	39	44	+12.8%	0.89x
EqualSubstringSubstring	38	42	+10.5%	0.90x (?)
EqualSubstringSubstringGenericEquatable	38	42	+10.5%	0.90x
EqualSubstringString	39	43	+10.3%	0.91x (?)
LessSubstringSubstringGenericComparable	39	43	+10.3%	0.91x
Improvement
StringToDataMedium	3600	3300	-8.3%	1.09x (?)
FlattenListLoop	4336	3978	-8.3%	1.09x
RemoveWhereMoveInts	37	34	-8.1%	1.09x (?)
Array2D	7520	6912	-8.1%	1.09x (?)
RemoveWhereSwapInts	65	60	-7.7%	1.08x (?)
MapReduce	397	368	-7.3%	1.08x (?)
MapReduceAnyCollection	397	369	-7.1%	1.08x
FlattenListFlatMap	6529	6079	-6.9%	1.07x (?)

Performance: -Osize

TEST	OLD	NEW	DELTA	RATIO
Regression
LessSubstringSubstring	39	44	+12.8%	0.89x
EqualSubstringString	39	44	+12.8%	0.89x (?)
LessSubstringSubstringGenericComparable	39	44	+12.8%	0.89x
EqualSubstringSubstring	39	43	+10.3%	0.91x (?)
EqualStringSubstring	39	43	+10.3%	0.91x
EqualSubstringSubstringGenericEquatable	39	43	+10.3%	0.91x (?)
Improvement
FlattenListLoop	4433	4070	-8.2%	1.09x (?)
RemoveWhereMoveInts	37	34	-8.1%	1.09x (?)
Array2D	7520	6912	-8.1%	1.09x (?)
RemoveWhereSwapInts	67	62	-7.5%	1.08x (?)
MapReduce	433	404	-6.7%	1.07x (?)

Performance: -Onone

TEST	OLD	NEW	DELTA	RATIO
Regression
ArrayOfGenericPOD2	1065	1179	+10.7%	0.90x (?)
ArrayOfPOD	779	853	+9.5%	0.91x (?)
Improvement
ExclusivityIndependent	84	74	-11.9%	1.14x (?)
ObjectiveCBridgeStubFromNSDateRef	5080	4510	-11.2%	1.13x (?)
CharacterLiteralsLarge	608	568	-6.6%	1.07x (?)

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]

Those substring tests have been really inconclusive and noisy lately, I wonder if that's fixable

[swift-ci]

Build failed
Swift Test OS X Platform
Git Sha - 6ffec666ffde0cffbe11ae6284aed9e49bcba742

[mikeash]

@swift-ci please test

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - 6ffec666ffde0cffbe11ae6284aed9e49bcba742

[swift-ci]

Build failed
Swift Test OS X Platform
Git Sha - 6ffec666ffde0cffbe11ae6284aed9e49bcba742

[mikeash]

@swift-ci please smoke test