Adding documentation for CA1516 - Use cross-platform intrinsics

docs/fundamentals/code-analysis/quality-rules/ca1516.md

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+---
+title: "CA1516: Use cross-platform intrinsics"
+description: "Learn about code analyzer rule CA1516 - Use cross-platform intrinsics"
+ms.date: 07/09/2025
+ms.topic: reference
+f1_keywords:
+ - CA1516
+ - UseCrossPlatformIntrinsicsAnalyzer
+helpviewer_keywords:
+ - CA1516
+author: TannerGooding
+dev_langs:
+ - CSharp
+---
+
+# CA1516: Use cross-platform intrinsics
+
+| Property                            | Value                                          |
+|-------------------------------------|------------------------------------------------|
+| **Rule ID**                         | CA1516                                         |
+| **Title**                           | Use cross-platform intrinsics                  |
+| **Category**                        | [Maintainability](maintainability-warnings.md) |
+| **Fix is breaking or non-breaking** | Non-breaking                                   |
+| **Enabled by default in .NET 9**    | No                                             |
+
+## Cause
+
+A platform or architecture specific intrinsic is used when a cross-platform equivalent exists.
+
+## Rule description
+
+This rule detects usage of platform-specific intrinsics that can be replaced with an equivalent cross-platform intrinsic instead.
+
+## How to fix violations
+
+Apply the fixer that switches the code to use the equivalent cross-platform intrinsic.
+
+## Example
+
+The following code snippet shows three similar violations of CA1516:
+
+```csharp
+using System;
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.Arm;
+using System.Runtime.Intrinsics.Wasm;
+using System.Runtime.Intrinsics.X86;
+
+class C
+{
+    Vector128<byte> M1(Vector128<byte> x, Vector128<byte> y) => AdvSimd.Add(x, y);
+    Vector128<byte> M2(Vector128<byte> x, Vector128<byte> y) => Sse2.Add(x, y);
+    Vector128<byte> M3(Vector128<byte> x, Vector128<byte> y) => PackedSimd.Add(x, y);
+}
+```
+
+The following code snippet fixes the violation and would be applied by the fixer:
+
+```csharp
+using System;
+using System.Runtime.Intrinsics;
+
+class C
+{
+    Vector128<byte> M1(Vector128<byte> x, Vector128<byte> y) => x + y;
+    Vector128<byte> M2(Vector128<byte> x, Vector128<byte> y) => x + y;
+    Vector128<byte> M3(Vector128<byte> x, Vector128<byte> y) => x + y;
+}
+```
+
+Once the fix has been applied, it becomes more obvious that the three methods could be simplified to be a single method that works on all platforms.
+
+## When to suppress warnings
+
+It's safe to suppress a violation of this rule if you're not concerned about the maintainability of your code.
+
+## Suppress a warning
+
+If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.
+
+```csharp
+#pragma warning disable CA1516
+// The code that's violating the rule is on this line.
+#pragma warning restore CA1516
+```
+
+To disable the rule for a file, folder, or project, set its severity to `none` in the [configuration file](../configuration-files.md).
+
+```ini
+[*.{cs,vb}]
+dotnet_diagnostic.CA1516.severity = none
+```
+
+For more information, see [How to suppress code analysis warnings](../suppress-warnings.md).
+
+## Configure code to analyze
+
+You can configure which _output assembly kinds_ to apply this rule to. For example, to only apply this rule to code that produces a console application or a dynamically linked library (that is, not a UI app), add the following key-value pair to an *.editorconfig* file in your project:
+
+```ini
+dotnet_code_quality.CA1516.output_kind = ConsoleApplication, DynamicallyLinkedLibrary
+```
+
+For more information, see [output_kind](../code-quality-rule-options.md#output_kind).