[clang] [clang] Add __builtin_start_object_lifetime builtin. (PR #82776)

[Haojian Wu via cfe-commits]

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@@ -4386,6 +4386,7 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
 
     return RValue::get(nullptr);
   }
+  case Builtin::BI__builtin_start_object_lifetime:
   case Builtin::BI__builtin_launder: {
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hokein wrote:

I think the name is fine, we're in the CodeGen, and the BuiltinLaunder in `TypeRequiresBuiltinLaunder` means the LLVM IR `llvm.launder` [intrinsics](https://llvm.org/docs/LangRef.html#llvm-launder-invariant-group-intrinsic).

https://github.com/llvm/llvm-project/pull/82776