[llvm] [Xtensa] Implement vararg support. (PR #117126)

[Sergei Barannikov via llvm-commits]

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@@ -133,6 +134,14 @@ XtensaTargetLowering::XtensaTargetLowering(const TargetMachine &TM,
   setOperationAction(ISD::STACKSAVE, MVT::Other, Custom);
   setOperationAction(ISD::STACKRESTORE, MVT::Other, Custom);
 
+  // VASTART and VACOPY need to deal with the Xtensa-specific varargs
+  // structure, but VAEND is a no-op.
+  setOperationAction(ISD::VASTART, MVT::Other, Custom);
+  // we use special va_list structure so we have to customize this
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s-barannikov wrote:

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https://github.com/llvm/llvm-project/pull/117126