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

[Matt Arsenault via llvm-commits]

================
@@ -1503,8 +1503,21 @@ void AMDGPUInstPrinter::printSwizzle(const MCInst *MI, unsigned OpNo,
 
   O << " offset:";
 
-  if ((Imm & QUAD_PERM_ENC_MASK) == QUAD_PERM_ENC) {
+  // Rotate and FFT modes
+  if (Imm >= ROTATE_MODE_LO && AMDGPU::isGFX9Plus(STI)) {
+    if (Imm >= FFT_MODE_LO) {
+      O << "swizzle(" << IdSymbolic[ID_FFT] << "," << (Imm & FFT_SWIZZLE_MASK)
+        << ")";
+    } else if (Imm >= ROTATE_MODE_LO) {
+      O << "swizzle(" << IdSymbolic[ID_ROTATE] << ","
+        << ((Imm >> ROTATE_DIR_SHIFT) & ROTATE_DIR_MASK) << ","
+        << ((Imm >> ROTATE_SIZE_SHIFT) & ROTATE_SIZE_MASK) << ")";
----------------
arsenm wrote:

```suggestion
      O << "swizzle(" << IdSymbolic[ID_FFT] << ',' << (Imm & FFT_SWIZZLE_MASK)
        << ')';
    } else if (Imm >= ROTATE_MODE_LO) {
      O << "swizzle(" << IdSymbolic[ID_ROTATE] << ','
        << ((Imm >> ROTATE_DIR_SHIFT) & ROTATE_DIR_MASK) << ','
        << ((Imm >> ROTATE_SIZE_SHIFT) & ROTATE_SIZE_MASK) << ')';
```

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