[perf] System.Tests.Perf.** and System.Perf.** performance regressions in Mono AOT x64 microbenchmarks from Preview 5 to Preview 7

[kotlarmilos]

Description

The following performance regressions occurred between the Preview 4 snapshot (May 2nd, 2023) and Preview 7 snapshot (July 19th, 2023).

The configuration used for the benchmarks is Mono AOT with LLVM on x64 ubuntu 18.04.

Name	Baseline Value	Compare Value	% Difference
System.Tests.Perf_Uri.CtorIdnHostPathAndQuery(input: https://contoso.com/path/with?key=value#fragment)	888.36	992.32	11.7
System.Tests.Perf_Uri.Ctor(input: https://contoso.com)	286.02	347.22	21.4
System.Tests.Perf_UInt32.ParseSpan(value: 12345)	40.52	42.6	5.13
System.Tests.Perf_UInt16.TryParse(value: 0)	29.02	32.44	11.78
System.Tests.Perf_String.Substring_Int(s: dzsdzsDDZSDZSDZSddsz, i: 0)	2.22	2.39	7.66
System.Tests.Perf_String.Split(s: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z, arr: [' '], options: None)	771.45	1034.74	34.13
System.Tests.Perf_String.Replace_String(text: This is a very nice sentence. This is another very nice sentence., oldValue: a, newValue: )	208.84	315.4	51.02
System.Tests.Perf_String.Replace_Char(text: This is a very nice sentence, oldChar: 'z', newChar: 'y')	28.82	47.39	64.43
System.Tests.Perf_String.IndexOfAny	115.42	136.59	18.34
System.Tests.Perf_String.CtorCharCount(size: 10)	25.82	28.31	9.64
System.Tests.Perf_String.CtorCharCount(size: 1)	21.53	23.2	7.76
System.Tests.Perf_Single.Parse(value: 12345)	112.2	175.82	56.7
System.Tests.Perf_SByte.Parse(value: -128)	41.35	45.24	9.41
System.Tests.Perf_Random.NextSingle	13.88	14.61	5.26
System.Tests.Perf_Int64.TryParseSpan(value: 12345)	41.94	46.03	9.75
System.Tests.Perf_Int32.TryParse(value: 2147483647)	55.94	65.38	16.88
System.Tests.Perf_Int32.TryParse(value: 12345)	41.25	47.36	14.81
System.Tests.Perf_Int32.Parse(value: 2147483647)	58.57	67.48	15.21
System.Tests.Perf_Int16.TryParse(value: 32767)	46.11	55.15	19.61
System.Tests.Perf_Environment.SetEnvironmentVariable	149.69	204.17	36.4
System.Tests.Perf_Enum.HasFlag	0.08	0.28	250
System.Tests.Perf_Enum.Compare	2.97	3.47	16.84
System.Tests.Perf_Double.Parse(value: 1.7976931348623157e+308)	221.62	274.76	23.98
System.Tests.Perf_Double.Parse(value: -1.7976931348623157e+308)	224.55	283.09	26.07
System.Tests.Perf_Char.Char_ToLower(c: '你', cultureName: zh-Hans)	85.97	91.74	6.71
System.Tests.Perf_Boolean.ToString(value: True)	0.21	0.35	66.67
System.Perf_Convert.ToBase64CharArray(binaryDataSize: 1024, formattingOptions: None)	1836.06	7554.54	311.45

[kotlarmilos]

@vargaz @stephentoub Do you have any changes in mind between May 2nd, 2023 and July 19th, 2023 that may have caused the regressions?

[stephentoub]

Purely given all the calls involving "Parse", I'd speculate #86875

[kotlarmilos]

Thanks! Let's check it out :)