CTFE eval_fn_call: use FnAbi to determine argument skipping and compatibility

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -260,7 +260,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
         args: &[OpTy<'tcx>],
         _ret: Option<(&PlaceTy<'tcx>, mir::BasicBlock)>,
         _unwind: StackPopUnwind, // unwinding is not supported in consts
-    ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> {
+    ) -> InterpResult<'tcx, Option<(&'mir mir::Body<'tcx>, ty::Instance<'tcx>)>> {
         debug!("find_mir_or_eval_fn: {:?}", instance);
 
         // Only check non-glue functions
@@ -283,7 +283,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
             }
         }
         // This is a const fn. Call it.
-        Ok(Some(ecx.load_mir(instance.def, None)?))
+        Ok(Some((ecx.load_mir(instance.def, None)?, instance)))
     }
 
     fn call_intrinsic(