[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

[Artem Belevich via cfe-commits]

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@@ -104,6 +104,7 @@ std::string SDNode::getOperationName(const SelectionDAG *G) const {
   case ISD::ATOMIC_STORE:               return "AtomicStore";
   case ISD::PCMARKER:                   return "PCMarker";
   case ISD::READCYCLECOUNTER:           return "ReadCycleCounter";
+  case ISD::READSTEADYCOUNTER:             return "ReadFixedTimer";
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Artem-B wrote:

Should it be "ReadSteadyCounter" ? 

Also, whitespace/alignment looks off.

https://github.com/llvm/llvm-project/pull/81331