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

[Matt Arsenault via llvm-commits]

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@@ -826,6 +855,22 @@ ParseStatus XtensaAsmParser::parseDirective(AsmToken DirectiveID) {
   return ParseStatus::NoMatch;
 }
 
+// Verify Special Register
+bool XtensaAsmParser::checkRegister(MCRegister RegNo) {
+  bool Res = true;
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arsenm wrote:

This can be rewritten with a simpler expression without any conditional assign and break 

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