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

[Matt Arsenault via llvm-commits]

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@@ -8141,6 +8143,54 @@ AMDGPUAsmParser::parseSwizzleBitmaskPerm(int64_t &Imm) {
   return true;
 }
 
+bool AMDGPUAsmParser::parseSwizzleFFT(int64_t &Imm) {
+  using namespace llvm::AMDGPU::Swizzle;
+
+  if (!AMDGPU::isGFX9Plus(getSTI())) {
+    Error(getLoc(), "FFT mode swizzle not supported on this GPU");
+    return false;
+  }
+
+  int64_t Swizzle;
+  SMLoc Loc;
+  if (!parseSwizzleOperand(Swizzle, 0, FFT_SWIZZLE_MAX,
+                           "FFT swizzle must be in the interval [0," +
+                               Twine(FFT_SWIZZLE_MAX).str() + Twine(']').str(),
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arsenm wrote:

parseSwizzleOperand should use Twine instead of StringRef for ErrMsg, and then you don't need the .str 

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