[NativeAOT] Not using ICU on Windows by default

[adamsitnik]

I've identified multiple globalization benchmarks that are few times slower compared to .NET, but only on Windows.

Examples:

Details

System.Globalization.Tests.StringSearch.IndexOf_Word_NotFound(Options: (en-US, IgnoreNonSpace, False))

Result	Base	Diff	Ratio	Alloc Delta	Operating System	Bit	Processor Name	Modality
Slower	574.96	6346.39	0.09	+0	Windows 10	Arm64	Microsoft SQ1 3.0 GHz
Slower	512.44	3951.29	0.13	+0	Windows 10	X64	Intel Xeon CPU E5-1650 v4 3.60GHz
Slower	343.58	3359.13	0.10	+0	Windows 11	X64	AMD Ryzen Threadripper PRO 3945WX 12-Cores
Same	397.41	422.80	0.94	+0	ubuntu 18.04	X64	Intel Xeon CPU E5-1650 v4 3.60GHz
Slower	419.87	486.70	0.86	+0	macOS Monterey 12.2.1	X64	Intel Core i7-5557U CPU 3.10GHz (Broadwell)

System.Globalization.Tests.StringEquality.Compare_Same(Count: 1024, Options: (pl-PL, None))

Result	Base	Diff	Ratio	Alloc Delta	Operating System	Bit	Processor Name	Modality
Slower	1069.98	30836.45	0.03	+0	Windows 10	Arm64	Microsoft SQ1 3.0 GHz
Slower	579.14	21694.46	0.03	+0	Windows 10	X64	Intel Xeon CPU E5-1650 v4 3.60GHz
Slower	736.95	17273.03	0.04	+0	Windows 11	X64	AMD Ryzen Threadripper PRO 3945WX 12-Cores
Same	611.26	612.26	1.00	+0	ubuntu 18.04	X64	Intel Xeon CPU E5-1650 v4 3.60GHz
Same	506.27	510.46	0.99	+0	macOS Monterey 12.2.1	X64	Intel Core i7-5557U CPU 3.10GHz (Broadwell)

System.Globalization.Tests.StringSearch.LastIndexOf_Word_NotFound(Options: (en-US, IgnoreNonSpace, False))

Result	Base	Diff	Ratio	Alloc Delta	Operating System	Bit	Processor Name	Modality
Slower	575.01	4697.19	0.12	+0	Windows 10	Arm64	Microsoft SQ1 3.0 GHz
Slower	510.31	3140.84	0.16	+0	Windows 10	X64	Intel Xeon CPU E5-1650 v4 3.60GHz	several?
Slower	340.57	2604.90	0.13	+0	Windows 11	X64	AMD Ryzen Threadripper PRO 3945WX 12-Cores
Same	386.28	420.00	0.92	+0	ubuntu 18.04	X64	Intel Xeon CPU E5-1650 v4 3.60GHz
Slower	419.22	487.40	0.86	+0	macOS Monterey 12.2.1	X64	Intel Core i7-5557U CPU 3.10GHz (Broadwell)

Repro:

git clone https://github.com/dotnet/performance.git
cd performance
py .\scripts\benchmarks_ci.py -f net7.0 --filter System.Globalization.Tests.StringEquality.Compare_Same --bdn-arguments "--runtimes net7.0 nativeaot7.0"

BenchmarkDotNet=v0.13.1.1786-nightly, OS=Windows 10 (10.0.18363.2158/1909/November2019Update/19H2)
Intel Xeon CPU E5-1650 v4 3.60GHz, 1 CPU, 12 logical and 6 physical cores
.NET SDK=7.0.100-preview.5.22254.18
 [Host] : .NET 7.0.0 (7.0.22.25401), X64 RyuJIT
 Job-IDREEK : .NET 7.0.0 (7.0.22.25401), X64 RyuJIT
 Job-JQUIIN : .NET 7.0.0-preview.5.22254.9, X64 NativeAOT

Method	Runtime	Options	Mean	Ratio
Compare_Same	.NET 7.0	(, IgnoreCase)	580.84 ns	1.00
Compare_Same	NativeAOT 7.0	(, IgnoreCase)	1,083.74 ns	1.87
Compare_Same	.NET 7.0	(, None)	568.35 ns	1.00
Compare_Same	NativeAOT 7.0	(, None)	1,078.19 ns	1.90
Compare_Same	.NET 7.0	(en-US, IgnoreCase)	568.98 ns	1.00
Compare_Same	NativeAOT 7.0	(en-US, IgnoreCase)	1,077.04 ns	1.89
Compare_Same	.NET 7.0	(en-US, IgnoreNonSpace)	575.34 ns	1.00
Compare_Same	NativeAOT 7.0	(en-US, IgnoreNonSpace)	1,689.38 ns	2.94
Compare_Same	.NET 7.0	(en-US, IgnoreSymbols)	564.08 ns	1.00
Compare_Same	NativeAOT 7.0	(en-US, IgnoreSymbols)	1,692.27 ns	3.00
Compare_Same	.NET 7.0	(en-US, None)	676.68 ns	1.00
Compare_Same	NativeAOT 7.0	(en-US, None)	1,082.27 ns	1.64
Compare_Same	.NET 7.0	(en-US, Ordinal)	67.74 ns	1.00
Compare_Same	NativeAOT 7.0	(en-US, Ordinal)	69.86 ns	1.03
Compare_Same	.NET 7.0	(en-US, OrdinalIgnoreCase)	829.30 ns	1.00
Compare_Same	NativeAOT 7.0	(en-US, OrdinalIgnoreCase)	826.63 ns	1.00
Compare_Same	.NET 7.0	(pl-PL, None)	590.16 ns	1.00
Compare_Same	NativeAOT 7.0	(pl-PL, None)	21,787.90 ns	36.71

It seems that for some reason, on Windows NativeAOT is not using ICU:

cc @jkotas @MichalStrehovsky @tarekgh

[MichalStrehovsky]

It's this TODO:

runtime/src/libraries/System.Private.CoreLib/src/System/Globalization/GlobalizationMode.Windows.cs

Line 9 in 6ca8c9b

// CORERT-TODO: Enable Icu on Windows