[llvm] [AMDGPU][MC] Implement fft and rotate modes for ds_swizzle_b32 (PR #108064)

[Jay Foad via llvm-commits]

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@@ -0,0 +1,131 @@
+// RUN: not llvm-mc -triple=amdgcn -mcpu=bonaire -show-encoding %s | FileCheck -check-prefix=GFX7 %s
+// RUN: not llvm-mc -triple=amdgcn -mcpu=tonga -show-encoding %s | FileCheck -check-prefix=GFX8 %s
+// RUN: not llvm-mc -triple=amdgcn -mcpu=gfx908 -show-encoding %s | FileCheck %s
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jayfoad wrote:

```suggestion
// RUN: not llvm-mc -triple=amdgcn -mcpu=gfx908 -show-encoding %s | FileCheck -check-prefix=GFX9 %s
```
Please also add some tests for disassembly of the ROTATE form.

https://github.com/llvm/llvm-project/pull/108064