Disable fix_lifetime DCE. #36183

atrick · 2021-02-26T17:36:54Z

Unless the type is a trivial scalar. As a follow-up we could try to
prove that the referenced object is unique, but that seems more
natural for DeadObjectElimination.

This optimization was never correct because references may alias. See
rdar://36038096 ([SR-6608] DeadCodeElimination removes fix_lifetime
instructions.)

Fixes rdar://74759728 (The compiler/optimizer seems to be shortening
the lifetime too early)

atrick · 2021-02-26T17:37:03Z

@swift-ci smoke test

atrick · 2021-02-26T17:37:11Z

@swift-ci benchmark

eeckstein

lgtm

atrick · 2021-02-26T18:51:20Z

@swift-ci smoke test

atrick · 2021-02-26T18:51:32Z

@swift-ci benchmark

Unless the type is a trivial scalar. As a follow-up we could try to prove that the referenced object is unique, but that seems more natural for DeadObjectElimination. This optimization was never correct because references may alias. See rdar://36038096 ([SR-6608] DeadCodeElimination removes fix_lifetime instructions.) Fixes rdar://74759728 (The compiler/optimizer seems to be shortening the lifetime too early)

atrick · 2021-02-26T19:07:10Z

@swift-ci smoke test

atrick · 2021-02-26T19:07:18Z

@swift-ci benchmark

swift-ci · 2021-02-26T21:43:36Z

Performance: -O

Regression	OLD	NEW	DELTA	RATIO
HashTest	840	1140	+35.7%	0.74x
CSVParsingAlt2	1089	1287	+18.2%	0.85x (?)
UTF8Decode_InitFromCustom_noncontiguous_ascii	632	739	+16.9%	0.86x (?)
UTF8Decode_InitFromCustom_noncontiguous_ascii_as_ascii	713	813	+14.0%	0.88x (?)
UnicodeStringFromCodable	309	333	+7.8%	0.93x (?)
StringHasPrefixAscii	1320	1420	+7.6%	0.93x (?)

Improvement	OLD	NEW	DELTA	RATIO
EqualSubstringString	30	22	-26.7%	1.36x
LessSubstringSubstring	29	22	-24.1%	1.32x
EqualStringSubstring	29	22	-24.1%	1.32x
EqualSubstringSubstringGenericEquatable	29	22	-24.1%	1.32x
LessSubstringSubstringGenericComparable	29	22	-24.1%	1.32x
EqualSubstringSubstring	30	23	-23.3%	1.30x
FlattenListLoop	1340	1032	-23.0%	1.30x (?)
UTF8Decode_InitFromCustom_contiguous	165	130	-21.2%	1.27x
UTF8Decode_InitDecoding	158	129	-18.4%	1.22x
SortAdjacentIntPyramids	800	660	-17.5%	1.21x
CharIteration_punctuatedJapanese_unicodeScalars_Backwards	800	720	-10.0%	1.11x (?)
CharIndexing_punctuatedJapanese_unicodeScalars_Backwards	800	720	-10.0%	1.11x (?)
BucketSort	86	78	-9.3%	1.10x (?)
CharIteration_punctuatedJapanese_unicodeScalars	480	440	-8.3%	1.09x (?)
CharIteration_japanese_unicodeScalars_Backwards	5640	5200	-7.8%	1.08x (?)
CharIndexing_japanese_unicodeScalars_Backwards	5640	5200	-7.8%	1.08x (?)
CharIteration_punctuated_unicodeScalars	520	480	-7.7%	1.08x (?)
CharIteration_korean_unicodeScalars	2640	2440	-7.6%	1.08x (?)
CharIteration_chinese_unicodeScalars_Backwards	3320	3080	-7.2%	1.08x (?)
CharIndexing_chinese_unicodeScalars_Backwards	3320	3080	-7.2%	1.08x (?)
CharIteration_ascii_unicodeScalars	2320	2160	-6.9%	1.07x (?)
CharIteration_japanese_unicodeScalars	3560	3320	-6.7%	1.07x (?)

Code size: -O

Regression	OLD	NEW	DELTA	RATIO
RangeOverlaps.o	6090	6626	+8.8%	0.92x
MonteCarloE.o	2801	2865	+2.3%	0.98x
BucketSort.o	8591	8751	+1.9%	0.98x
RangeAssignment.o	3313	3369	+1.7%	0.98x
RomanNumbers.o	6774	6870	+1.4%	0.99x
FlattenList.o	3898	3946	+1.2%	0.99x

Performance: -Osize

Regression	OLD	NEW	DELTA	RATIO
StringWalk	1360	3080	+126.5%	0.44x
ArrayAppendReserved	250	350	+40.0%	0.71x (?)
HashTest	890	1170	+31.5%	0.76x
Dictionary4	158	207	+31.0%	0.76x
CharIndexing_punctuatedJapanese_unicodeScalars	680	880	+29.4%	0.77x
CharIndexing_tweet_unicodeScalars	6280	7960	+26.8%	0.79x
CharIndexing_japanese_unicodeScalars	4960	6200	+25.0%	0.80x
ArrayAppendLazyMap	680	850	+25.0%	0.80x (?)
CharIndexing_chinese_unicodeScalars	3000	3720	+24.0%	0.81x
CharIndexing_punctuated_unicodeScalars	720	880	+22.2%	0.82x
CharIndexing_korean_unicodeScalars	3920	4760	+21.4%	0.82x
CharIndexing_ascii_unicodeScalars	3200	3880	+21.2%	0.82x
ArrayAppendLatin1Substring	19476	23580	+21.1%	0.83x (?)
ArrayAppendUTF16Substring	19080	23004	+20.6%	0.83x
ArrayAppendAsciiSubstring	19044	22896	+20.2%	0.83x
CharIndexing_utf16_unicodeScalars	4560	5440	+19.3%	0.84x
CSVParsingAlt2	1122	1331	+18.6%	0.84x
CharIteration_japanese_unicodeScalars	3600	4240	+17.8%	0.85x
CharIteration_punctuated_unicodeScalars	480	560	+16.7%	0.86x
CharIndexing_russian_unicodeScalars	3680	4160	+13.0%	0.88x (?)
SortIntPyramid	730	825	+13.0%	0.88x (?)
CharIteration_chinese_unicodeScalars	2120	2360	+11.3%	0.90x (?)
StringHasPrefixAscii	1170	1300	+11.1%	0.90x (?)
Dictionary4OfObjects	275	304	+10.5%	0.90x (?)
Breadcrumbs.UTF16ToIdxRange.longMixed	112	121	+8.0%	0.93x (?)

Improvement	OLD	NEW	DELTA	RATIO
ArrayPlusEqualSingleElementCollection	658	423	-35.7%	1.56x (?)
UTF8Decode_InitFromCustom_noncontiguous	368	256	-30.4%	1.44x
UTF8Decode_InitFromCustom_noncontiguous_ascii	879	632	-28.1%	1.39x
LessSubstringSubstring	30	22	-26.7%	1.36x
EqualStringSubstring	30	22	-26.7%	1.36x
EqualSubstringString	30	22	-26.7%	1.36x
ArrayAppendRepeatCol	680	500	-26.5%	1.36x
UTF8Decode_InitFromCustom_noncontiguous_ascii_as_ascii	961	711	-26.0%	1.35x
EqualSubstringSubstringGenericEquatable	29	22	-24.1%	1.32x
EqualSubstringSubstring	30	23	-23.3%	1.30x (?)
LessSubstringSubstringGenericComparable	30	23	-23.3%	1.30x
UTF8Decode_InitFromCustom_contiguous	165	131	-20.6%	1.26x
UTF8Decode_InitDecoding	163	130	-20.2%	1.25x
Data.init.Sequence.2049B.Count0.I	398	333	-16.3%	1.20x
Data.init.Sequence.2047B.Count0.I	381	320	-16.0%	1.19x (?)
CharIteration_korean_unicodeScalars_Backwards	4600	4160	-9.6%	1.11x (?)
CharacterLiteralsLarge	64	58	-9.4%	1.10x (?)
CharIteration_japanese_unicodeScalars_Backwards	6160	5600	-9.1%	1.10x (?)
CharIteration_punctuatedJapanese_unicodeScalars_Backwards	880	800	-9.1%	1.10x
DataSetCountMedium	220	200	-9.1%	1.10x (?)
Data.init.Sequence.64kB.Count0	181	165	-8.8%	1.10x (?)
Data.init.Sequence.64kB.Count0.I	182	167	-8.2%	1.09x (?)

Code size: -Osize

Regression	OLD	NEW	DELTA	RATIO
ArraySetElement.o	1148	1260	+9.8%	0.91x
Sim2DArray.o	1200	1312	+9.3%	0.91x
COWArrayGuaranteedParameterOverhead.o	1219	1331	+9.2%	0.92x
Join.o	1441	1567	+8.7%	0.92x
MonteCarloE.o	2657	2826	+6.4%	0.94x
StackPromo.o	1952	2076	+6.4%	0.94x
Memset.o	1787	1899	+6.3%	0.94x
BinaryFloatingPointProperties.o	4796	5091	+6.2%	0.94x
Array2D.o	2494	2643	+6.0%	0.94x
RangeAssignment.o	3065	3225	+5.2%	0.95x
ArraySubscript.o	2297	2409	+4.9%	0.95x
Prims.o	10477	10963	+4.6%	0.96x
PrimsSplit.o	10529	11015	+4.6%	0.96x
ObserverClosure.o	2499	2613	+4.6%	0.96x
ObserverPartiallyAppliedMethod.o	2548	2662	+4.5%	0.96x
FlattenList.o	3633	3793	+4.4%	0.96x
PopFrontGeneric.o	2599	2711	+4.3%	0.96x
Hanoi.o	2926	3052	+4.3%	0.96x
ObserverForwarderStruct.o	2924	3048	+4.2%	0.96x
SortArrayInClass.o	2666	2778	+4.2%	0.96x
RC4.o	2933	3054	+4.1%	0.96x
BucketSort.o	8019	8336	+4.0%	0.96x
ReversedCollections.o	7164	7441	+3.9%	0.96x
RemoveWhere.o	12943	13419	+3.7%	0.96x
ProtocolConformance.o	3590	3714	+3.5%	0.97x
PopFront.o	3317	3429	+3.4%	0.97x
RandomShuffle.o	3330	3442	+3.4%	0.97x
DiffingMyers.o	6286	6477	+3.0%	0.97x
RangeOverlaps.o	5437	5602	+3.0%	0.97x
Walsh.o	4035	4147	+2.8%	0.97x
Combos.o	5817	5976	+2.7%	0.97x
ArrayInClass.o	4232	4344	+2.6%	0.97x
ArrayAppend.o	21573	22137	+2.6%	0.97x
ObserverUnappliedMethod.o	5032	5156	+2.5%	0.98x
RangeReplaceableCollectionPlusDefault.o	4589	4701	+2.4%	0.98x
DictionaryOfAnyHashableStrings.o	5260	5386	+2.4%	0.98x
StringEdits.o	9638	9834	+2.0%	0.98x
RomanNumbers.o	5128	5216	+1.7%	0.98x
IndexPathTest.o	7206	7318	+1.6%	0.98x
FindStringNaive.o	7868	7989	+1.5%	0.98x
PrimsNonStrongRef.o	82845	84101	+1.5%	0.99x
Hash.o	18185	18449	+1.5%	0.99x
DictionaryGroup.o	10154	10299	+1.4%	0.99x
ArrayOfGenericRef.o	8056	8170	+1.4%	0.99x
Queue.o	11827	11993	+1.4%	0.99x
ArrayOfRef.o	8306	8422	+1.4%	0.99x
Breadcrumbs.o	35707	36204	+1.4%	0.99x
ReduceInto.o	8075	8187	+1.4%	0.99x
Mirror.o	9756	9882	+1.3%	0.99x
Phonebook.o	9004	9114	+1.2%	0.99x
ObjectiveCBridgingStubs.o	13630	13796	+1.2%	0.99x
CSVParsing.o	51646	52214	+1.1%	0.99x
SortIntPyramids.o	8826	8922	+1.1%	0.99x
StringRemoveDupes.o	3706	3746	+1.1%	0.99x

Performance: -Onone

Regression	OLD	NEW	DELTA	RATIO
UTF8Decode_InitDecoding_ascii_as_ascii	209	233	+11.5%	0.90x (?)

Improvement	OLD	NEW	DELTA	RATIO
UTF8Decode_InitFromCustom_contiguous	180	142	-21.1%	1.27x
UTF8Decode_InitDecoding	177	140	-20.9%	1.26x
LessSubstringSubstringGenericComparable	59	50	-15.3%	1.18x (?)
EqualSubstringSubstringGenericEquatable	58	50	-13.8%	1.16x (?)
LessSubstringSubstring	60	52	-13.3%	1.15x (?)
EqualSubstringString	60	52	-13.3%	1.15x (?)
EqualStringSubstring	61	53	-13.1%	1.15x (?)
EqualSubstringSubstring	59	53	-10.2%	1.11x (?)

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: 6-Core 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 requested a review from eeckstein February 26, 2021 17:36

eeckstein approved these changes Feb 26, 2021

View reviewed changes

atrick force-pushed the fix-dce-fixlifetime branch from 9329465 to f470b29 Compare February 26, 2021 19:06

atrick merged commit ecc7127 into swiftlang:main Feb 26, 2021

atrick deleted the fix-dce-fixlifetime branch February 26, 2021 22:37

atrick mentioned this pull request Feb 26, 2021

[SR-6608] DeadCodeElimination removes fix_lifetime instructions. #49158

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Disable fix_lifetime DCE. #36183

Disable fix_lifetime DCE. #36183

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Performance: -O

Code size: -O

Performance: -Osize

Code size: -Osize

Performance: -Onone

Code size: -swiftlibs

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