[llvm] Xtensa] Implement windowed call ABI. (PR #130001)

[Matt Arsenault via llvm-commits]

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@@ -70,6 +70,8 @@ class XtensaSubtarget : public XtensaGenSubtargetInfo {
 
   bool hasBoolean() const { return HasBoolean; }
 
+  bool isWinABI() const { return hasWindowed(); }
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arsenm wrote:

Maybe should expand this to be windowed to avoid casual observers confusing this with windows 

https://github.com/llvm/llvm-project/pull/130001