Add ILLink.Substitutions.xml files for System.Private.CoreLib.

[eerhardt]

Ported the settings from https://github.com/mono/mono/blob/eaa32d13659f0a6b6b5e62ddb49af68b1f9efb6c/sdks/wasm/src/linker-subs.xml and split them out as appropriate to reduce duplication across the different platform builds.

Contributes to #31785

The only API proposed in #31785 that I didn't cover was System.Runtime.InteropService.OSPlatform since there isn't a good way of supporting that in the linker, AFAIK.

For a "Hello, World" wasm app, System.Private.CoreLib.dll sizes go from:

Build	Size
master	1,534 KB
PR	1,475 KB
PR + Invariant Mode	1,456 KB

[ghost]

Tagging subscribers to this area: @ViktorHofer
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[joperezr]

FYI @layomia since you have a PR out changing this too.

[eerhardt]

Note that this work is blocked by the failing CI. The failure occurs when creating a Windows PDB for the portable PDB:

  System.Private.CoreLib -> F:\workspace\_work\1\s\artifacts\bin\coreclr\Windows_NT.x64.Checked\IL\System.Private.CoreLib.dll
  PDB0004: token 0x06001C30: Method containing local variables has no local signature
  PDB0004: token 0x06001C30: Method containing local variables has no local signature
  PDB0004: token 0x06001C31: Method containing local variables has no local signature
  PDB0004: token 0x06001C31: Method containing local variables has no local signature
  Error HRESULT E_FAIL has been returned from a call to a COM component.
F:\workspace\_work\1\s\.packages\microsoft.dotnet.arcade.sdk\5.0.0-beta.20280.1\tools\SymStore.targets(70,5): error MSB3073: The command ""F:\workspace\_work\1\s\.packages\microsoft.diasymreader.pdb2pdb\1.1.0-beta2-19575-01\tools\Pdb2Pdb.exe" "F:\workspace\_work\1\s\artifacts\bin\coreclr\Windows_NT.x64.Checked\IL\System.Private.CoreLib.dll" /out "F:\workspace\_work\1\s\artifacts\SymStore\Checked\System.Private.CoreLib\netcoreapp2.1\x64\System.Private.CoreLib.pdb" /srcsvrvar SRC_INDEX=public" exited with code 2. [F:\workspace\_work\1\s\src\coreclr\src\System.Private.CoreLib\System.Private.CoreLib.csproj]
##[error].packages\microsoft.dotnet.arcade.sdk\5.0.0-beta.20280.1\tools\SymStore.targets(70,5): error MSB3073: (NETCORE_ENGINEERING_TELEMETRY=Build) The command ""F:\workspace\_work\1\s\.packages\microsoft.diasymreader.pdb2pdb\1.1.0-beta2-19575-01\tools\Pdb2Pdb.exe" "F:\workspace\_work\1\s\artifacts\bin\coreclr\Windows_NT.x64.Checked\IL\System.Private.CoreLib.dll" /out "F:\workspace\_work\1\s\artifacts\SymStore\Checked\System.Private.CoreLib\netcoreapp2.1\x64\System.Private.CoreLib.pdb" /srcsvrvar SRC_INDEX=public" exited with code 2.

Debugging into Pdb2Pdb.exe, I see the first problem is that we are trimming away locals from this method:

runtime/src/libraries/System.Private.CoreLib/src/System/Numerics/BitOperations.cs

Lines 233 to 251 in bd6cbe3

	public static int PopCount(uint value)
	{
	if (Popcnt.IsSupported)
	{
	return (int)Popcnt.PopCount(value);
	}
	if (AdvSimd.Arm64.IsSupported)
	{
	// PopCount works on vector so convert input value to vector first.
	// Vector64.CreateScalar(uint) generates suboptimal code by storing and
	// loading the result to memory.
	// See https://github.com/dotnet/runtime/issues/35976 for details.
	// Hence use Vector64.Create(ulong) to create Vector64<ulong> and operate on that.
	Vector64<ulong> input = Vector64.Create((ulong)value);
	Vector64<byte> aggregated = AdvSimd.Arm64.AddAcross(AdvSimd.PopCount(input.AsByte()));
	return aggregated.ToScalar();
	}

The if (AdvSimd.Arm64.IsSupported) branch is getting trimmed, but it looks like the local variables are not getting removed from the portable .pdb. Here is the code after trimming:

        public static int PopCount(uint value)
        {
            if (Popcnt.IsSupported)
            {
                return (int)Popcnt.PopCount(value);
            }
            !AdvSimd.Arm64.IsSupported;
            return BitOperations.<PopCount>g__SoftwareFallback|9_0(value);
        }

@vitek-karas @marek-safar - I logged dotnet/linker#1260 for this.

After that, Pdb2Pdb is trying to work on this method:

runtime/src/libraries/System.Private.CoreLib/src/System/Globalization/CharUnicodeInfo.cs

Lines 231 to 248 in bd6cbe3

	private static double GetNumericValueNoBoundsCheck(uint codePoint)
	{
	nuint offset = GetNumericGraphemeTableOffsetNoBoundsChecks(codePoint);
	ref byte refToValue = ref Unsafe.AddByteOffset(ref MemoryMarshal.GetReference(NumericValues), offset * 8 /* sizeof(double) */);
	// 'refToValue' points to a little-endian 64-bit double.
	if (BitConverter.IsLittleEndian)
	{
	return Unsafe.ReadUnaligned<double>(ref refToValue);
	}
	else
	{
	ulong temp = Unsafe.ReadUnaligned<ulong>(ref refToValue);
	temp = BinaryPrimitives.ReverseEndianness(temp);
	return Unsafe.As<ulong, double>(ref temp);
	}
	}

But it is throwing a COMException when calling OpenScope:

>	Microsoft.DiaSymReader.Native.amd64.dll!SymWriter::OpenScope(unsigned int,unsigned int *)	Unknown
 	[Managed to Native Transition]	
 	Microsoft.DiaSymReader.dll!Microsoft.DiaSymReader.SymUnmanagedWriterImpl.OpenScope(int startOffset) Line 261	C#
 	Microsoft.DiaSymReader.Converter.dll!Microsoft.DiaSymReader.Tools.PdbConverterPortableToWindows.Convert.__OpenScope|6_6(int startOffset, int endOffset, ref Microsoft.DiaSymReader.Tools.PdbConverterPortableToWindows.<>c__DisplayClass6_0 value, ref Microsoft.DiaSymReader.Tools.PdbConverterPortableToWindows.<>c__DisplayClass6_1 value) Line 295	C#
 	Microsoft.DiaSymReader.Converter.dll!Microsoft.DiaSymReader.Tools.PdbConverterPortableToWindows.Convert(System.Reflection.PortableExecutable.PEReader peReader, System.Reflection.Metadata.MetadataReader pdbReader, Microsoft.DiaSymReader.SymUnmanagedWriter pdbWriter, Microsoft.DiaSymReader.Tools.PortablePdbConversionOptions options) Line 322	C#
 	Microsoft.DiaSymReader.Converter.dll!Microsoft.DiaSymReader.Tools.PdbConverter.ConvertPortableToWindows(System.Reflection.PortableExecutable.PEReader peReader, System.Reflection.Metadata.MetadataReader pdbReader, Microsoft.DiaSymReader.SymUnmanagedWriter pdbWriter, Microsoft.DiaSymReader.Tools.PortablePdbConversionOptions options) Line 189	C#
 	Microsoft.DiaSymReader.Converter.dll!Microsoft.DiaSymReader.Tools.PdbConverter.ConvertPortableToWindows(System.Reflection.PortableExecutable.PEReader peReader, System.Reflection.Metadata.MetadataReader pdbReader, System.IO.Stream targetPdbStream, Microsoft.DiaSymReader.Tools.PortablePdbConversionOptions options) Line 171	C#
 	Pdb2Pdb.exe!Microsoft.DiaSymReader.Tools.Pdb2Pdb.Convert(Microsoft.DiaSymReader.Tools.Pdb2Pdb.Args args) Line 268	C#
 	Pdb2Pdb.exe!Microsoft.DiaSymReader.Tools.Pdb2Pdb.Main(string[] args) Line 59	C#

From doing a little debugging, it appears that the top scope is getting closed in Microsoft.DiaSymReader.Native.amd64.dll, and the native code is returning E_FAIL when trying to open the scope again. It seems that Pdb2Pdb is getting in some invalid state right before this.

I've opened dotnet/symreader-converter#174 for the Pdb2Pdb crash, which is blocking clean CI.

[eerhardt]

I've removed the $(Platform)s that aren't wasm for now, until dotnet/linker#1260 is addressed. This should allow this change to move forward.