SILOptimizer: always assume that inout arguments are not aliasing

[eeckstein]

We can do that now as we have exclusivity checking

[eeckstein]

@swift-ci test

[eeckstein]

@swift-ci benchmark

[swift-ci]

Performance: -O

Regression	OLD	NEW	DELTA	RATIO
Dictionary4	158	199	+25.9%	0.79x
SortIntPyramid	395	475	+20.3%	0.83x
Dictionary4OfObjects	198	229	+15.7%	0.86x
SortAdjacentIntPyramids	655	720	+9.9%	0.91x (?)
UTF8Decode_InitDecoding	115	124	+7.8%	0.93x (?)
Improvement	OLD	NEW	DELTA	RATIO
LessSubstringSubstring	28	21	-25.0%	1.33x
PrefixWhileArray	53	40	-24.5%	1.32x
EqualSubstringSubstring	27	21	-22.2%	1.29x
EqualSubstringString	27	21	-22.2%	1.29x
LessSubstringSubstringGenericComparable	27	21	-22.2%	1.29x
EqualStringSubstring	28	22	-21.4%	1.27x
EqualSubstringSubstringGenericEquatable	28	22	-21.4%	1.27x
ArrayAppendGenericStructs	670	590	-11.9%	1.14x (?)
StringComparison_longSharedPrefix	356	320	-10.1%	1.11x
DataSubscriptMedium	41	37	-9.8%	1.11x (?)

Code size: -O

Performance: -Osize

Regression	OLD	NEW	DELTA	RATIO
PrefixWhileCountableRangeLazy	13	26	+100.0%	0.50x
PrefixWhileAnyCollection	106	126	+18.9%	0.84x (?)
ObjectiveCBridgeStubDateAccess	130	152	+16.9%	0.86x
PrefixWhileAnySeqCRangeIterLazy	94	108	+14.9%	0.87x (?)
Improvement	OLD	NEW	DELTA	RATIO
PrefixWhileArray	53	40	-24.5%	1.32x
LessSubstringSubstring	27	21	-22.2%	1.29x
EqualSubstringString	27	21	-22.2%	1.29x (?)
LessSubstringSubstringGenericComparable	27	21	-22.2%	1.29x
EqualSubstringSubstring	28	22	-21.4%	1.27x
EqualStringSubstring	28	22	-21.4%	1.27x (?)
EqualSubstringSubstringGenericEquatable	28	22	-21.4%	1.27x
PrefixWhileAnyCollectionLazy	94	81	-13.8%	1.16x (?)
FlattenListLoop	3141	2730	-13.1%	1.15x (?)
StringComparison_longSharedPrefix	355	320	-9.9%	1.11x
Dictionary4	184	166	-9.8%	1.11x (?)
PrefixCountableRange	14	13	-7.1%	1.08x (?)

Code size: -Osize

Performance: -Onone

Regression	OLD	NEW	DELTA	RATIO
UTF8Decode_InitDecoding	135	146	+8.1%	0.92x (?)
Improvement	OLD	NEW	DELTA	RATIO
EqualSubstringSubstringGenericEquatable	31	25	-19.4%	1.24x (?)
LessSubstringSubstringGenericComparable	31	25	-19.4%	1.24x
EqualSubstringSubstring	32	26	-18.7%	1.23x (?)
LessSubstringSubstring	32	26	-18.7%	1.23x (?)
EqualStringSubstring	32	26	-18.7%	1.23x (?)
EqualSubstringString	32	26	-18.7%	1.23x

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

[atrick]

@eeckstein lgtm. I've had exactly this change on my working branch for a while now.