[clang] [CIR] Implement __builtin_return_address and __builtin_frame_address (PR #153698)

[Andy Kaylor via cfe-commits]

================
@@ -312,6 +312,20 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
   case Builtin::BI__builtin_rotateright64:
     return emitRotate(e, /*isRotateLeft=*/false);
 
+  case Builtin::BI__builtin_return_address:
+  case Builtin::BI__builtin_frame_address: {
+    mlir::Location loc = getLoc(e->getExprLoc());
+    mlir::Attribute levelAttr = ConstantEmitter(*this).emitAbstract(
+        e->getArg(0), e->getArg(0)->getType());
+    uint64_t level = mlir::cast<cir::IntAttr>(levelAttr).getUInt();
+    if (builtinID == Builtin::BI__builtin_return_address) {
+      return RValue::get(builder.create<cir::ReturnAddrOp>(
----------------
andykaylor wrote:

```suggestion
      return RValue::get(cir::ReturnAddrOp::create(builder,
```

https://github.com/llvm/llvm-project/pull/153698