[DNM] Disable jump threading through a potential loop header

[meg-gupta]

PR to test performance impact of disabling jump threading through a loop header to avoid irreducible loops.

[meg-gupta]

@swift-ci apple silicon benchmark

[meg-gupta]

------- Performance (arm64): -O -------

REGRESSION                                                 OLD        NEW         DELTA        RATIO    
ExclusivityGlobal                                          0.0        5.706       +570600.0%   **0.00x**
ArrayValueProp3                                            0.0        2.854       +285400.0%   **0.00x**
ArrayValueProp4                                            0.0        2.854       +285400.0%   **0.00x**
ArrayValueProp2                                            0.0        2.854       +285400.0%   **0.00x**
ArrayValueProp                                             0.0        2.853       +285300.0%   **0.00x**
UTF16Decode                                                89.731     384.833     +328.9%      **0.23x**
SubstringFromLongStringGeneric2                            17.124     47.087      +175.0%      **0.36x**
CreateObjects                                              8.557      19.972      +133.4%      **0.43x**
BitCount                                                   63.053     140.471     +122.8%      **0.45x**
SubstringFromLongString2                                   17.118     35.661      +108.3%      **0.48x**
DropFirstArray                                             17.963     35.188      +95.9%       **0.51x**
DropWhileSequence                                          17.759     30.104      +69.5%       **0.59x**
DropWhileAnySeqCntRange                                    17.759     29.493      +66.1%       **0.60x**
DropWhileAnySeqCRangeIter                                  17.759     29.492      +66.1%       **0.60x**
DropWhileAnySequence                                       18.429     30.409      +65.0%       **0.61x**
NaiveRRC.append.smallContiguousRepeated                    40.471     57.622      +42.4%       **0.70x**
ProtocolDispatch2                                          57.103     71.333      +24.9%       **0.80x**
PointerArithmetics                                         14268.75   17121.429   +20.0%       **0.83x**
MapReduceLazyCollectionShort                               19.969     22.826      +14.3%       **0.87x**
DictionaryBridgeToObjC_Bridge                              6.055      6.787       +12.1%       **0.89x (?)**
StringFromLongWholeSubstringGeneric                        3.138      3.423       +9.1%        **0.92x**
CharIndexing_punctuatedJapanese_unicodeScalars_Backwards   549.615    594.783     +8.2%        **0.92x**

IMPROVEMENT                                                OLD        NEW         DELTA        RATIO    
StringWithCString2                                         0.002      0.001       -33.3%       **1.50x**
UTF8Decode_InitDecoding                                    132.625    96.136      -27.5%       **1.38x**
UTF8Decode_InitFromCustom_contiguous                       131.706    96.13       -27.0%       **1.37x**
UTF8Decode_InitFromData                                    132.941    98.217      -26.1%       **1.35x**
UTF8Decode_InitFromBytes                                   137.625    102.19      -25.7%       **1.35x**
UTF8Decode_InitFromCustom_noncontiguous                    149.733    114.053     -23.8%       **1.31x**
DataCountSmall                                             14.265     11.413      -20.0%       **1.25x**
EqualSubstringSubstring                                    20.25      17.36       -14.3%       **1.17x**
LessSubstringSubstring                                     20.198     17.343      -14.1%       **1.16x**
EqualSubstringSubstringGenericEquatable                    20.198     17.352      -14.1%       **1.16x**
RawBuffer.copyContents                                     11.167     9.64        -13.7%       **1.16x (?)**
ArrayAppendGenericStructs                                  1088.889   948.125     -12.9%       **1.15x (?)**
ParseInt.UInt64.Hex                                        157.909    138.5       -12.3%       **1.14x (?)**
LessSubstringSubstringGenericComparable                    20.208     17.808      -11.9%       **1.13x**
EqualSubstringString                                       20.521     18.13       -11.7%       **1.13x**
SuffixArray                                                7.484      6.635       -11.3%       **1.13x (?)**
SuffixArrayLazy                                            7.484      6.635       -11.3%       **1.13x (?)**
EqualStringSubstring                                       20.282     18.232      -10.1%       **1.11x**
UTF16Decode.initFromCustom.cont                            250.714    229.75      -8.4%        **1.09x**
UTF16Decode.initFromCustom.noncont                         259.25     238.111     -8.2%        **1.09x**
ObserverUnappliedMethod                                    270.625    250.196     -7.5%        **1.08x (?)**

------- Code size: -O -------

REGRESSION                                     OLD     NEW     DELTA    RATIO  
DropWhile.o                                    10071   11675   +15.9%   **0.86x**
Exclusivity.o                                  2870    3282    +14.4%   **0.87x**
TypeFlood.o                                    543     611     +12.5%   **0.89x**
RomanNumbers.o                                 3267    3667    +12.2%   **0.89x**
DropFirst.o                                    9053    10039   +10.9%   **0.90x**
BitCount.o                                     1178    1290    +9.5%    **0.91x**
CreateObjects.o                                761     809     +6.3%    **0.94x**
DiffingMyers.o                                 5065    5357    +5.8%    **0.95x**
ProtocolDispatch2.o                            1170    1222    +4.4%    **0.96x**
ArrayLiteral.o                                 1248    1300    +4.2%    **0.96x**
ChainedFilterMap.o                             2443    2539    +3.9%    **0.96x**
DictionaryLiteralTest.o                        969     1005    +3.7%    **0.96x**
SevenBoom.o                                    1152    1192    +3.5%    **0.97x**
StringInterpolation.o                          5458    5626    +3.1%    **0.97x**
PrefixWhile.o                                  9753    10053   +3.1%    **0.97x**
ProtocolDispatch.o                             560     576     +2.9%    **0.97x**
CharacterLiteralsSmall.o                       894     918     +2.7%    **0.97x**
SubstringTest.o                                15511   15918   +2.6%    **0.97x**
CaptureProp.o                                  779     799     +2.6%    **0.97x**
RangeIteration.o                               1104    1132    +2.5%    **0.98x**
StringRepeating.o                              2846    2918    +2.5%    **0.98x**
MonteCarloPi.o                                 1142    1170    +2.5%    **0.98x**
NSDictionaryCastToSwift.o                      1158    1186    +2.4%    **0.98x**
BinaryFloatingPointProperties.o                3829    3921    +2.4%    **0.98x**
FloatingPointPrinting.o                        3368    3448    +2.4%    **0.98x**
Prefix.o                                       9486    9706    +2.3%    **0.98x**
DropLast.o                                     15576   15908   +2.1%    **0.98x**
ReduceInto.o                                   8669    8849    +2.1%    **0.98x**
DictionaryCopy.o                               7641    7797    +2.0%    **0.98x**
DictionaryBridgeToObjC.o                       3910    3986    +1.9%    **0.98x**
DictionaryRemove.o                             16204   16504   +1.9%    **0.98x**
AnyHashableWithAClass.o                        2431    2475    +1.8%    **0.98x**
XorLoop.o                                      1150    1170    +1.7%    **0.98x**
MapReduce.o                                    18881   19201   +1.7%    **0.98x**
StringComparison.o                             28352   28820   +1.7%    **0.98x**
LazyFilter.o                                   5401    5489    +1.6%    **0.98x**
DeadArray.o                                    1238    1258    +1.6%    **0.98x**
DictTest2.o                                    8443    8579    +1.6%    **0.98x**
LinkedList.o                                   1766    1794    +1.6%    **0.98x**
CString.o                                      5309    5393    +1.6%    **0.98x**
NaiveRangeReplaceableCollectionConformance.o   7182    7294    +1.6%    **0.98x**
NSErrorTest.o                                  1083    1099    +1.5%    **0.99x**
FlattenList.o                                  2730    2770    +1.5%    **0.99x**
IterateData.o                                  1395    1415    +1.4%    **0.99x**
StrToInt.o                                     5322    5398    +1.4%    **0.99x**
Histogram.o                                    2329    2361    +1.4%    **0.99x**
DictionarySwap.o                               14479   14675   +1.4%    **0.99x**
Ackermann.o                                    1198    1214    +1.3%    **0.99x**
CharacterProperties.o                          16764   16984   +1.3%    **0.99x**
ReversedCollections.o                          6584    6668    +1.3%    **0.99x**
Combos.o                                       3772    3820    +1.3%    **0.99x**
StrComplexWalk.o                               2202    2230    +1.3%    **0.99x**
StringWalk.o                                   27524   27872   +1.3%    **0.99x**
StringBuilder.o                                5727    5799    +1.3%    **0.99x**
DictTest3.o                                    12583   12735   +1.2%    **0.99x**
DataBenchmarks.o                               48897   49469   +1.2%    **0.99x**
NSStringConversion.o                           11350   11478   +1.1%    **0.99x**
UTF16Decode.o                                  14658   14822   +1.1%    **0.99x**
ArrayInClass.o                                 2615    2643    +1.1%    **0.99x**
DictionarySubscriptDefault.o                   15132   15292   +1.1%    **0.99x**

IMPROVEMENT                                    OLD     NEW     DELTA    RATIO  
NopDeinit.o                                    3517    2877    -18.2%   **1.22x**
ClassArrayGetter.o                             3130    3018    -3.6%    **1.04x**
CharacterLiteralsLarge.o                       630     614     -2.5%    **1.03x**
PopFrontGeneric.o                              1973    1929    -2.2%    **1.02x**
RangeReplaceableCollectionPlusDefault.o        7119    6963    -2.2%    **1.02x**
ByteSwap.o                                     1106    1082    -2.2%    **1.02x**
PopFront.o                                     2616    2560    -2.1%    **1.02x**
Integrate.o                                    1677    1649    -1.7%    **1.02x**
Hanoi.o                                        2144    2116    -1.3%    **1.01x**
Suffix.o                                       15542   15366   -1.1%    **1.01x**
Fibonacci.o                                    1126    1114    -1.1%    **1.01x**

####### Testing optimization level -Osize #######
------- Performance (arm64): -Osize -------

REGRESSION                                OLD        NEW        DELTA        RATIO    
ArrayValueProp3                           0.0        2.854      +285400.0%   **0.00x**
ArrayValueProp                            0.0        2.854      +285400.0%   **0.00x**
ArrayValueProp4                           0.0        2.854      +285400.0%   **0.00x**
ArrayValueProp2                           0.0        2.853      +285300.0%   **0.00x**
SubstringFromLongStringGeneric2           17.124     49.93      +191.6%      **0.34x**
CreateObjects                             8.557      22.825     +166.7%      **0.37x**
DropWhileSequence                         17.759     41.846     +135.6%      **0.42x**
SubstringFromLongString2                  18.543     38.519     +107.7%      **0.48x**
ExclusivityGlobal                         2.853      5.706      +100.0%      **0.50x**
BitCount                                  128.667    191.167    +48.6%       **0.67x**
NaiveRRC.append.smallContiguousRepeated   40.49      56.205     +38.8%       **0.72x**
ArrayAppendSequence                       324.444    440.556    +35.8%       **0.74x (?)**
ProtocolDispatch2                         57.103     71.406     +25.0%       **0.80x**
StringFromLongWholeSubstringGeneric       3.282      3.994      +21.7%       **0.82x**
DataCountSmall                            14.268     17.124     +20.0%       **0.83x**
DataCountMedium                           14.268     17.118     +20.0%       **0.83x**
StringFromLongWholeSubstring              1.854      2.14       +15.4%       **0.87x**
ProtocolDispatch                          199.727    228.3      +14.3%       **0.87x**
SuffixSequenceLazy                        84.074     96.043     +14.2%       **0.88x**
SuffixSequence                            84.192     96.083     +14.1%       **0.88x**
DataAppendDataSmallToLarge                5080.0     5717.808   +12.6%       **0.89x (?)**
DictionaryBridgeToObjC_Bridge             5.949      6.644      +11.7%       **0.90x**
Array.removeAll.keepingCapacity.Object    2.35       2.609      +11.0%       **0.90x (?)**
StrComplexWalk                            1936.667   2123.636   +9.7%        **0.91x**
NSStringConversion.Rebridge               41.528     45.14      +8.7%        **0.92x**
NSStringConversion                        160.786    174.462    +8.5%        **0.92x**
DataReplaceLarge                          5932.432   6397.143   +7.8%        **0.93x (?)**

IMPROVEMENT                               OLD        NEW        DELTA        RATIO    
SumUsingReduce                            860.0      294.25     -65.8%       **2.92x**
SumUsingReduceInto                        860.0      294.25     -65.8%       **2.92x**
UTF8Decode_InitDecoding                   131.813    96.304     -26.9%       **1.37x**
UTF8Decode_InitFromCustom_contiguous      131.765    96.625     -26.7%       **1.36x**
UTF8Decode_InitFromData                   132.294    97.304     -26.4%       **1.36x**
UTF8Decode_InitFromBytes                  137.75     101.952    -26.0%       **1.35x**
RawBuffer.copyContents                    12.29      9.538      -22.4%       **1.29x (?)**
CharacterLiteralsLarge                    48.511     39.942     -17.7%       **1.21x**
UTF8Decode_InitFromCustom_noncontiguous   228.2      190.167    -16.7%       **1.20x**
EqualSubstringString                      20.438     17.558     -14.1%       **1.16x**
EqualSubstringSubstringGenericEquatable   20.587     17.69      -14.1%       **1.16x**
EqualStringSubstring                      20.394     17.551     -13.9%       **1.16x**
SortIntPyramid                            515.0      443.696    -13.8%       **1.16x**
LessSubstringSubstringGenericComparable   20.531     17.69      -13.8%       **1.16x**
EqualSubstringSubstring                   20.5       17.688     -13.7%       **1.16x**
LessSubstringSubstring                    20.406     17.69      -13.3%       **1.15x**
SuffixArray                               7.484      6.635      -11.3%       **1.13x**
UTF16Decode.initFromCustom.noncont        285.286    258.375    -9.4%        **1.10x**
ParseInt.UInt64.Hex                       183.182    167.909    -8.3%        **1.09x (?)**
UTF16Decode.initFromCustom.cont           263.375    242.444    -7.9%        **1.09x**
SuffixArrayLazy                           7.195      6.635      -7.8%        **1.08x**
CharIteration_ascii_unicodeScalars        2520.0     2346.667   -6.9%        **1.07x**
CharIteration_tweet_unicodeScalars        4915.556   4580.0     -6.8%        **1.07x**

------- Code size: -Osize -------

REGRESSION                                     OLD     NEW     DELTA    RATIO  
StrToInt.o                                     5226    6638    +27.0%   **0.79x**
RomanNumbers.o                                 3211    3639    +13.3%   **0.88x**
TypeFlood.o                                    523     591     +13.0%   **0.88x**
DictionaryLiteralTest.o                        550     586     +6.5%    **0.94x**
CreateObjects.o                                737     785     +6.5%    **0.94x**
DropWhile.o                                    9635    10199   +5.9%    **0.94x**
ArrayLiteral.o                                 952     1004    +5.5%    **0.95x**
ProtocolDispatch2.o                            1134    1186    +4.6%    **0.96x**
CharacterLiteralsSmall.o                       806     842     +4.5%    **0.96x**
ReduceInto.o                                   5969    6189    +3.7%    **0.96x**
ChainedFilterMap.o                             2335    2415    +3.4%    **0.97x**
SevenBoom.o                                    1264    1304    +3.2%    **0.97x**
SubstringTest.o                                13087   13486   +3.0%    **0.97x**
ProtocolDispatch.o                             540     556     +3.0%    **0.97x**
MapReduce.o                                    14517   14929   +2.8%    **0.97x**
RangeIteration.o                               1076    1104    +2.6%    **0.97x**
DropLast.o                                     13070   13398   +2.5%    **0.98x**
NSDictionaryCastToSwift.o                      1122    1150    +2.5%    **0.98x**
PrefixWhile.o                                  9509    9737    +2.4%    **0.98x**
Histogram.o                                    1209    1237    +2.3%    **0.98x**
DropFirst.o                                    9671    9891    +2.3%    **0.98x**
BitCount.o                                     1070    1094    +2.2%    **0.98x**
Prefix.o                                       9964    10184   +2.2%    **0.98x**
StringInterpolation.o                          5146    5258    +2.2%    **0.98x**
DictionaryBridgeToObjC.o                       3150    3218    +2.2%    **0.98x**
StringRepeating.o                              2618    2674    +2.1%    **0.98x**
Exclusivity.o                                  2894    2954    +2.1%    **0.98x**
CaptureProp.o                                  791     807     +2.0%    **0.98x**
StringWalk.o                                   19576   19964   +2.0%    **0.98x**
XorLoop.o                                      1106    1126    +1.8%    **0.98x**
AnyHashableWithAClass.o                        2483    2527    +1.8%    **0.98x**
DictTest2.o                                    6218    6326    +1.7%    **0.98x**
FloatingPointPrinting.o                        2616    2660    +1.7%    **0.98x**
ArrayOfGenericRef.o                            6316    6420    +1.6%    **0.98x**
SortIntPyramids.o                              7048    7164    +1.6%    **0.98x**
LinkedList.o                                   1722    1750    +1.6%    **0.98x**
NaiveRangeReplaceableCollectionConformance.o   7110    7222    +1.6%    **0.98x**
IterateData.o                                  1295    1315    +1.5%    **0.98x**
StringComparison.o                             23192   23548   +1.5%    **0.98x**
DictionarySubscriptDefault.o                   9985    10137   +1.5%    **0.99x**
FlattenList.o                                  2638    2678    +1.5%    **0.99x**
MonteCarloPi.o                                 1074    1090    +1.5%    **0.99x**
Memset.o                                       1345    1365    +1.5%    **0.99x**
DictionaryCopy.o                               6457    6553    +1.5%    **0.99x**
CString.o                                      5137    5213    +1.5%    **0.99x**
DictionaryRemove.o                             13360   13556   +1.5%    **0.99x**
ArrayOfRef.o                                   5645    5725    +1.4%    **0.99x**
LazyFilter.o                                   5401    5477    +1.4%    **0.99x**
Ackermann.o                                    1158    1174    +1.4%    **0.99x**
CharacterProperties.o                          14564   14764   +1.4%    **0.99x**
CharacterLiteralsLarge.o                       586     594     +1.4%    **0.99x**
DiffingMyers.o                                 5275    5347    +1.4%    **0.99x**
DeadArray.o                                    1194    1210    +1.3%    **0.99x**
StringRemoveDupes.o                            2726    2762    +1.3%    **0.99x**
StrComplexWalk.o                               2134    2162    +1.3%    **0.99x**
BinaryFloatingPointProperties.o                3441    3485    +1.3%    **0.99x**
ReversedCollections.o                          5745    5817    +1.3%    **0.99x**
KeyPathPerformanceTests.o                      71433   72285   +1.2%    **0.99x**
DictionarySwap.o                               12495   12639   +1.2%    **0.99x**
Combos.o                                       3820    3864    +1.2%    **0.99x**
NSStringConversion.o                           9442    9546    +1.1%    **0.99x**
DictionaryOfAnyHashableStrings.o               4371    4419    +1.1%    **0.99x**
StringBuilder.o                                5166    5222    +1.1%    **0.99x**
DictionaryBridge.o                             2230    2254    +1.1%    **0.99x**
DataBenchmarks.o                               37889   38285   +1.0%    **0.99x**
ArrayInClass.o                                 2724    2752    +1.0%    **0.99x**

IMPROVEMENT                                    OLD     NEW     DELTA    RATIO  
NopDeinit.o                                    3265    2817    -13.7%   **1.16x**
PopFront.o                                     2420    2340    -3.3%    **1.03x**
ClassArrayGetter.o                             3006    2930    -2.5%    **1.03x**
RangeReplaceableCollectionPlusDefault.o        6771    6611    -2.4%    **1.02x**
PopFrontGeneric.o                              1917    1873    -2.3%    **1.02x**
ByteSwap.o                                     1070    1046    -2.2%    **1.02x**
Suffix.o                                       13056   12796   -2.0%    **1.02x**
Fibonacci.o                                    1086    1074    -1.1%    **1.01x**

####### Testing optimization level -Onone #######
  

------- Performance (arm64): -Onone -------

REGRESSION                                OLD        NEW        DELTA    RATIO    
DictionarySwapAt                          918.5      1038.857   +13.1%   **0.88x**
ChaCha                                    9407.0     10319.0    +9.7%    **0.91x**
Set.isStrictSuperset.Seq.Int100           1070.5     1167.0     +9.0%    **0.92x (?)**
DataReplaceLarge                          6020.0     6550.0     +8.8%    **0.92x (?)**
CharacterRecognizer.mixed                 12.192     13.193     +8.2%    **0.92x**

IMPROVEMENT                               OLD        NEW        DELTA    RATIO    
ArrayAppendGenericStructs                 1149.091   728.571    -36.6%   **1.58x (?)**
UTF8Decode_InitFromData                   133.071    97.263     -26.9%   **1.37x**
UTF8Decode_InitFromCustom_contiguous      135.588    100.5      -25.9%   **1.35x**
UTF8Decode_InitDecoding                   134.429    99.75      -25.8%   **1.35x**
UTF8Decode_InitFromBytes                  138.0      102.455    -25.8%   **1.35x**
EqualSubstringSubstringGenericEquatable   22.93      19.542     -14.8%   **1.17x**
EqualSubstringString                      24.413     20.888     -14.4%   **1.17x**
LessSubstringSubstringGenericComparable   22.756     19.542     -14.1%   **1.16x**
EqualStringSubstring                      24.055     20.726     -13.8%   **1.16x**
LessSubstringSubstring                    23.613     20.413     -13.6%   **1.16x**
EqualSubstringSubstring                   22.988     20.267     -11.8%   **1.13x**
RawBufferCopyBytes                        11.0       10.277     -6.6%    **1.07x (?)**

[meg-gupta]

This was an experiment to record performance regressions by disabling this optimization which can create irreducible loops.