[clang] [llvm] [NVPTX] Support __usAtomicCAS builtin (PR #99646)

[via llvm-commits]

================
@@ -871,7 +871,8 @@ NVPTXTargetLowering::NVPTXTargetLowering(const NVPTXTargetMachine &TM,
   // actions
   computeRegisterProperties(STI.getRegisterInfo());
 
-  setMinCmpXchgSizeInBits(32);
+  bool Allow16BitCAS = STI.getSmVersion() >= 70 && STI.getPTXVersion() >= 63;
+  setMinCmpXchgSizeInBits(Allow16BitCAS ? 16 : 32);
----------------
gonzalobg wrote:

Thank you, looks great!

https://github.com/llvm/llvm-project/pull/99646