[llvm] [NVPTX] Don't use stack memory when bitcasting to/from v2i8 (PR #113928)

[Justin Fargnoli via llvm-commits]

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@@ -551,6 +551,10 @@ NVPTXTargetLowering::NVPTXTargetLowering(const NVPTXTargetMachine &TM,
   setOperationAction(ISD::EXTRACT_VECTOR_ELT, MVT::v4i8, Custom);
   setOperationAction(ISD::INSERT_VECTOR_ELT, MVT::v4i8, Custom);
   setOperationAction(ISD::VECTOR_SHUFFLE, MVT::v4i8, Custom);
+
+  // Custom conversions to/from v2i8.
+  setOperationAction(ISD::BITCAST, MVT::v2i8, Custom);
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justinfargnoli wrote:

`Expand` doesn't work for this problem, right? 

https://github.com/llvm/llvm-project/pull/113928