Runtime: [Proposal] Expose cpuid

Created on 12 Aug 2020 · 3Comments · Source: dotnet/runtime

Background and Motivation

For some specific scenarios it's important to know the CPU Vendor / CPUID. The .NET Runtime itself also checks the CPUID already:
https://github.com/dotnet/runtime/blob/96f178d32b7ba62485917ac46ef1edcfd3c2d10d/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/X86Base.cs#L71-L81
https://github.com/dotnet/runtime/blob/96f178d32b7ba62485917ac46ef1edcfd3c2d10d/src/tests/JIT/HardwareIntrinsics/X86/X86Base/CpuId.cs#L27-L32

Because of that, it would be a small afford to expose this information. Specific scenarios where it matters:

Dealing with hardware intrinsic code, the performance can be different whether the CPU is intel or amd.
Disassembling and assembling / patching code via detours it is absolutely necessary to know if the CPU supports a vendor specific instruction set or not
AOT (future, i.e. patching its own code)

There might be other scenarios. When I searched for a way I found a couple of StackOverflow discussion about this.

The current "official" pure C# way for retrieving the CPUID is via using ManagementClass. The downside of this method is that its slow and only works on Windows ~~(and is because of that not supported in .NET Core, as far as I know)~~ //edit: Turns out its supported via nuget package, still limited to Windows only. So I'm proposing the expose a property which uses the same existing internal way of retrieving the cpuid as shown above.

Proposed API

I'm not quite sure where such a property fits into, so I've put them into Intrinsics namespace, if you have a better idea please feel free to let me know so I can edit it.

namespace System.Runtime.Intrinsics.X86
{
+    public static class CpuInfo
+    {
+        public enum CpuVendor 
+        {
+            AMD,
+            Intel
+            Unknown
+        }
+
+        public CpuVendor Id { }
+    }
}