Inconsistent and counterintuitive codegen behavior of `+` operator for `Vector512<T>` depending on the number and order of operands generated by compare instructions, unlike for `Vector256<T>`

### Description

When I was playing with the `Vector512<T>`, I found some inconsistent behavior of `+` operator for `Vector512<byte>`, depending on one or more arguments being generated by `Vector512.Equals` or not.

Both the `.NET 7` and `.NET 8 RC 1` are doing the right thing for `Vector256<byte>`:
```csharp
[MethodImpl(MethodImplOptions.AggressiveOptimization)]
private static Vector256<byte> Test1(Vector256<byte> ymm0, Vector256<byte> ymm1, Vector256<byte> ymm2, Vector256<byte> ymm3)
    => Avx2.BlendVariable(ymm0, ymm2, Vector256.Equals(ymm0, ymm1) + Vector256.Equals(ymm2, ymm3));
```
In `.NET 7`, it generates:
```asm
vzeroupper  
mov         rax,qword ptr [rsp+28h]  
vmovupd     ymm0,ymmword ptr [rdx]  
vmovupd     ymm1,ymmword ptr [r9]  
vpcmpeqb    ymm2,ymm0,ymmword ptr [r8]  
vpcmpeqb    ymm3,ymm1,ymmword ptr [rax]  
vpaddb      ymm2,ymm2,ymm3  
vpblendvb   ymm0,ymm0,ymm1,ymm2  
vmovupd     ymmword ptr [rcx],ymm0  
mov         rax,rcx  
vzeroupper  
ret  
```
In `.NET 8 RC 1`, it generates:
```asm
vzeroupper  
mov         rax,qword ptr [rsp+28h]  
vmovups     ymm0,ymmword ptr [rdx]  
vmovups     ymm1,ymmword ptr [r9]  
vpcmpeqb    ymm2,ymm0,ymmword ptr [r8]  
vpcmpeqb    ymm3,ymm1,ymmword ptr [rax]  
vpaddb      ymm2,ymm2,ymm3  
vpblendvb   ymm0,ymm0,ymm1,ymm2  
vmovups     ymmword ptr [rcx],ymm0  
mov         rax,rcx  
vzeroupper  
ret  
```

But when it comes to `Vector512<byte>`, it somehow goes wrong.
```csharp
[MethodImpl(MethodImplOptions.AggressiveOptimization)]
private static Vector512<byte> Test512Blend(Vector512<byte> zmm0, Vector512<byte> zmm1, Vector512<byte> zmm2, Vector512<byte> zmm3)
    => Avx512BW.BlendVariable(zmm0, zmm2, Vector512.Equals(zmm0, zmm1) + Vector512.Equals(zmm2, zmm3));
```
In `.NET 8 RC 1`, it generates:
```asm
vzeroupper  
mov         rax,qword ptr [rsp+28h]  
vmovups     zmm0,zmmword ptr [rdx]  
vmovups     zmm1,zmmword ptr [r9]  
vpcmpeqb    k1,zmm0,zmmword ptr [r8]  
vpcmpeqb    k2,zmm1,zmmword ptr [rax]  
kaddq       k1,k1,k2                 ; WRONG INSTRUCTION!
vpblendmb   zmm0{k1},zmm0,zmm1  
vmovups     zmmword ptr [rcx],zmm0  
mov         rax,rcx  
vzeroupper  
ret  
```
While what I expect it to generate looks like:
```asm
vzeroupper  
mov         rax,qword ptr [rsp+28h]  
vmovups     zmm0,zmmword ptr [rdx]  
vmovups     zmm1,zmmword ptr [r9]  
vpcmpeqb    k1,zmm0,zmmword ptr [r8]  
vpmovm2b    zmm2,k1  
vpcmpeqb    k1,zmm1,zmmword ptr [rax]  
vpmovm2b    zmm3,k1  
vpaddb      zmm2,zmm2,zmm3  
vpmovb2m    k1,zmm2  
vpblendmb   zmm0{k1},zmm0,zmm1  
vmovups     zmmword ptr [rcx],zmm0  
mov         rax,rcx  
vzeroupper  
ret  
```

And even weirder, if I add `Vector512<byte>.Zero` in advance of adding second operand, like:
```csharp
[MethodImpl(MethodImplOptions.AggressiveOptimization)]
private static Vector512<byte> Test512Blend3(Vector512<byte> zmm0, Vector512<byte> zmm1, Vector512<byte> zmm2, Vector512<byte> zmm3)
    => Avx512BW.BlendVariable(zmm0, zmm2, Vector512.Equals(zmm0, zmm1) + Vector512<byte>.Zero + Vector512.Equals(zmm2, zmm3));
```
It generates what I expect it to generate from `Test512Blend`:
```asm
vzeroupper  
mov         rax,qword ptr [rsp+28h]  
vmovups     zmm0,zmmword ptr [rdx]  
vmovups     zmm1,zmmword ptr [r9]  
vpcmpeqb    k1,zmm0,zmmword ptr [r8]  
vpmovm2b    zmm2,k1  
vpcmpeqb    k1,zmm1,zmmword ptr [rax]  
vpmovm2b    zmm3,k1  
vpaddb      zmm2,zmm2,zmm3  
vpmovb2m    k1,zmm2  
vpblendmb   zmm0{k1},zmm0,zmm1  
vmovups     zmmword ptr [rcx],zmm0  
mov         rax,rcx  
vzeroupper  
ret  
```
Adding the `Vector512<T>.Zero` MUST NOT alter the result of the whole integer `+` operation.

### Reproduction Steps

1. Obtain a JIT assembly for the codes below with `.NET 8 RC 1`:
```csharp
[MethodImpl(MethodImplOptions.AggressiveOptimization)]
private static Vector256<byte> Test1(Vector256<byte> ymm0, Vector256<byte> ymm1, Vector256<byte> ymm2, Vector256<byte> ymm3)
    => Avx2.BlendVariable(ymm0, ymm2, Vector256.Equals(ymm0, ymm1) + Vector256.Equals(ymm2, ymm3));
```

```csharp
[MethodImpl(MethodImplOptions.AggressiveOptimization)]
private static Vector512<byte> Test512Blend(Vector512<byte> zmm0, Vector512<byte> zmm1, Vector512<byte> zmm2, Vector512<byte> zmm3)
    => Avx512BW.BlendVariable(zmm0, zmm2, Vector512.Equals(zmm0, zmm1) + Vector512.Equals(zmm2, zmm3));
```

```csharp
[MethodImpl(MethodImplOptions.AggressiveOptimization)]
private static Vector512<byte> Test512Blend3(Vector512<byte> zmm0, Vector512<byte> zmm1, Vector512<byte> zmm2, Vector512<byte> zmm3)
    => Avx512BW.BlendVariable(zmm0, zmm2, Vector512.Equals(zmm0, zmm1) + Vector512<byte>.Zero + Vector512.Equals(zmm2, zmm3));
```

### Expected behavior

The code:
```csharp
[MethodImpl(MethodImplOptions.AggressiveOptimization)]
private static Vector512<byte> Test512Blend(Vector512<byte> zmm0, Vector512<byte> zmm1, Vector512<byte> zmm2, Vector512<byte> zmm3)
    => Avx512BW.BlendVariable(zmm0, zmm2, Vector512.Equals(zmm0, zmm1) + Vector512.Equals(zmm2, zmm3));
```
and
```csharp
[MethodImpl(MethodImplOptions.AggressiveOptimization)]
private static Vector512<byte> Test512Blend3(Vector512<byte> zmm0, Vector512<byte> zmm1, Vector512<byte> zmm2, Vector512<byte> zmm3)
    => Avx512BW.BlendVariable(zmm0, zmm2, Vector512.Equals(zmm0, zmm1) + Vector512<byte>.Zero + Vector512.Equals(zmm2, zmm3));
```
For both functions, it should generate something like:
```asm
vzeroupper  
mov         rax,qword ptr [rsp+28h]  
vmovups     zmm0,zmmword ptr [rdx]  
vmovups     zmm1,zmmword ptr [r9]  
vpcmpeqb    k1,zmm0,zmmword ptr [r8]  
vpmovm2b    zmm2,k1  
vpcmpeqb    k1,zmm1,zmmword ptr [rax]  
vpmovm2b    zmm3,k1  
vpaddb      zmm2,zmm2,zmm3  
vpmovb2m    k1,zmm2  
vpblendmb   zmm0{k1},zmm0,zmm1  
vmovups     zmmword ptr [rcx],zmm0  
mov         rax,rcx  
vzeroupper  
ret  
```

### Actual behavior

For the code:
```csharp
[MethodImpl(MethodImplOptions.AggressiveOptimization)]
private static Vector512<byte> Test512Blend(Vector512<byte> zmm0, Vector512<byte> zmm1, Vector512<byte> zmm2, Vector512<byte> zmm3)
    => Avx512BW.BlendVariable(zmm0, zmm2, Vector512.Equals(zmm0, zmm1) + Vector512.Equals(zmm2, zmm3));
```
It instead generates something like:
```asm
vzeroupper  
mov         rax,qword ptr [rsp+28h]  
vmovups     zmm0,zmmword ptr [rdx]  
vmovups     zmm1,zmmword ptr [r9]  
vpcmpeqb    k1,zmm0,zmmword ptr [r8]  
vpcmpeqb    k2,zmm1,zmmword ptr [rax]  
kaddq       k1,k1,k2  
vpblendmb   zmm0{k1},zmm0,zmm1  
vmovups     zmmword ptr [rcx],zmm0  
mov         rax,rcx  
vzeroupper  
ret  
```

### Regression?

Unknown

### Known Workarounds

By adding `Vector512<T>.Zero` in advance of adding second operand, like:
```csharp
[MethodImpl(MethodImplOptions.AggressiveOptimization)]
private static Vector512<byte> Test512Blend3(Vector512<byte> zmm0, Vector512<byte> zmm1, Vector512<byte> zmm2, Vector512<byte> zmm3)
    => Avx512BW.BlendVariable(zmm0, zmm2, Vector512.Equals(zmm0, zmm1) + Vector512<byte>.Zero + Vector512.Equals(zmm2, zmm3));
```
It generates:
```asm
vzeroupper  
mov         rax,qword ptr [rsp+28h]  
vmovups     zmm0,zmmword ptr [rdx]  
vmovups     zmm1,zmmword ptr [r9]  
vpcmpeqb    k1,zmm0,zmmword ptr [r8]  
vpmovm2b    zmm2,k1  
vpcmpeqb    k1,zmm1,zmmword ptr [rax]  
vpmovm2b    zmm3,k1  
vpaddb      zmm2,zmm2,zmm3  
vpmovb2m    k1,zmm2  
vpblendmb   zmm0{k1},zmm0,zmm1  
vmovups     zmmword ptr [rcx],zmm0  
mov         rax,rcx  
vzeroupper  
ret  
```

### Configuration

- .NET version: `8.0.100-rc.1.23455.8`
- PC: Custom built PC
  - OS: Windows 11 Home 22H2 (22621.2283)
  - CPU: Intel(R) Xeon(R) w5-2455X   3.19 GHz
  - RAM: 32 GB DDR5 ECC RDIMM
  - Graphics: NVIDIA GeForce GTX1060(6 GB)
  - Storage: 
    - OS(C:) : WD_BLACK SN770 1TB PCIe 4.0 NVMe M.2 SSD
    - DATA (D:) : Western Digital WDC WD10EZEX-22MFCA0 1000.2 GB 7200RPM SATA HDD
    - WORKSPACE (E:) : Seagate ST1000DM003-1ER162 1000.2 GB 7200RPM SATA HDD

<details>
<summary>
Visual Studio 2022 installation
</summary>

Microsoft Visual Studio Community 2022
Version 17.8.0 Preview 2.0
VisualStudio.17.Preview/17.8.0-pre.2.0+34112.27
Microsoft .NET Framework
Version 4.8.09032

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C# ツール   4.8.0-2.23429.7+44555193fd1135b5d53a2099f76fec91e0d1ebde
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NuGet パッケージ マネージャー   6.8.0
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Razor (ASP.NET Core)   17.8.2.2345506+ade90399d42c1a7bf92191b1c067816c0ae1c311
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SonarLint for Visual Studio   7.3.0.77872
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Xamarin.Android SDK   13.2.1.2 (d17-5/a8a26c7)
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    Mono: d9a6e87
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    SQLite: xamarin/sqlite/3.40.1@68c69d8
    Xamarin.Android Tools: xamarin/xamarin-android-tools/d17-5@ca1552d


Xamarin.iOS and Xamarin.Mac SDK   16.4.0.16 (b5972410d)
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Inconsistent and counterintuitive codegen behavior of `+` operator for `Vector512<T>` depending on the number and order of operands generated by compare instructions, unlike for `Vector256<T>` #92261

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Inconsistent and counterintuitive codegen behavior of + operator for Vector512<T> depending on the number and order of operands generated by compare instructions, unlike for Vector256<T> #92261

Description

Description

Reproduction Steps

Expected behavior

Actual behavior

Regression?

Known Workarounds

Configuration

Other information

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions

Inconsistent and counterintuitive codegen behavior of `+` operator for `Vector512<T>` depending on the number and order of operands generated by compare instructions, unlike for `Vector256<T>` #92261