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

[Matt Arsenault via llvm-commits]

================
@@ -9,16 +9,30 @@
 //===----------------------------------------------------------------------===//
 
 //===----------------------------------------------------------------------===//
-// Xtensa return value calling convention
+// Xtensa base calling convention
 //===----------------------------------------------------------------------===//
+// Xtensa return value
 def RetCC_Xtensa : CallingConv<[
   // First two return values go in a2, a3, a4, a5
   CCIfType<[i32], CCAssignToReg<[A2, A3, A4, A5]>>,
   CCIfType<[i64], CCAssignToRegWithShadow<[A2, A4], [A3, A5]>>
 ]>;
 
+// Callee-saved register lists
+def CSR_Xtensa : CalleeSavedRegs<(add A0, A12, A13, A14, A15)>;
+
 //===----------------------------------------------------------------------===//
-// Callee-saved register lists.
+// Xtensa windowed calling convention. Currently by default implemented
+// rotation window by 8 registers.
 //===----------------------------------------------------------------------===//
+// Xtensa return value for 8 registers window
+def RetCCW8_Xtensa : CallingConv<[
+  //First two return values go in a10, a11, a12, a13
+  CCIfType<[i32], CCAssignToReg<[A10, A11, A12, A13]>>,
+  CCIfType<[i64], CCAssignToRegWithShadow<[A10, A12], [A11, A13]>>
+]>;
 
-def CSR_Xtensa : CalleeSavedRegs<(add A0, A12, A13, A14, A15)>;
+// Callee-saved register lists for rotation window by 8 registers
+def CSRW8_Xtensa : CalleeSavedRegs<(add)> {
+  let OtherPreserved = (add A0, SP, A2, A3, A4, A5, A6, A7);
+}
----------------
arsenm wrote:

End of file whitespace error 

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