[llvm] [Xtensa] Implement Windowed Register Option. (PR #121118)

[Fangrui Song via llvm-commits]

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@@ -73,17 +74,22 @@ static DecodeStatus DecodeARRegisterClass(MCInst &Inst, uint64_t RegNo,
   return MCDisassembler::Success;
 }
 
-static const unsigned SRDecoderTable[] = {Xtensa::SAR, 3};
+static const unsigned SRDecoderTable[] = {
+    Xtensa::SAR, 3, Xtensa::WINDOWBASE, 72, Xtensa::WINDOWSTART, 73};
 
 static DecodeStatus DecodeSRRegisterClass(MCInst &Inst, uint64_t RegNo,
                                           uint64_t Address,
-                                          const void *Decoder) {
+                                          const MCDisassembler *Decoder) {
   if (RegNo > 255)
     return MCDisassembler::Fail;
 
   for (unsigned i = 0; i < std::size(SRDecoderTable); i += 2) {
     if (SRDecoderTable[i + 1] == RegNo) {
       unsigned Reg = SRDecoderTable[i];
+
+      if (!checkRegister(Reg, Decoder->getSubtargetInfo().getFeatureBits()))
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MaskRay wrote:

XtensaDisassembler cannot use functions defined in XtensaCodeGen (Xtensa/CMakeFiles.txt). 

After #123969   , you can place checkRegister in MCTargetDesc/

https://github.com/llvm/llvm-project/pull/121118