[clang] [CIR] Support __builtin_nondeterministic_value (PR #206149)

[Henrich Lauko via cfe-commits]

================
@@ -1636,8 +1636,13 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
         builder.createIsFPClass(loc, v, cir::FPClassTest(test)),
         convertType(e->getType())));
   }
-  case Builtin::BI__builtin_nondeterministic_value:
-    return errorBuiltinNYI(*this, e, builtinID);
+  case Builtin::BI__builtin_nondeterministic_value: {
+    mlir::Type ty = convertType(e->getArg(0)->getType());
+    mlir::Value result =
+        cir::ConstantOp::create(builder, loc, ty, cir::PoisonAttr::get(ty));
+    result = builder.createFreeze(loc, result);
----------------
xlauko wrote:

```suggestion
    result = cir::FreezeOp::create(builder, loc, value);
```

https://github.com/llvm/llvm-project/pull/206149