Automated testing of a TCG frontend for Qemu

Implementing a new target architecture in Qemu involves creation of a dynamic binary translator TCG front-end for that architecture. Testing is necessary to verify correctness of that translator component. Currently, existing TCG front-end testing systems use an approach based on a comparison with an oracle. Such oracle have the same processor architecture. And an oracle may be a real processor, a high-fidelity emulator or another binary translator. Unfortunately, such oracles are not always available. This paper is devoted to testing a target architecture implementation in Qemu when the necessary oracle is not available. The main idea is following. There is observation, a program written in a high-level programming language is expected to execute equally regardless of processor architecture. In other words, one can use a real processor with a different architecture for comparison. In this paper, it is the processor of a developer AMD64 machine. The comparison objects are the term of a high-level programming language. I.e. tests are written in C. C language was chosen for this purpose, because, on the one hand, it is fairly close to the hardware, and, on the other, it has compilers for many processor architectures. The approach is implemented in CPU Testing Tool (c2t) which is part of QDT. Source code is available at https://github.com/ispras/qdt. The tool is implemented in Python programming language and supports testing of Qemu in both full system and user level emulation modes. c2t is suitable for testing TCG front-ends which are  generated by the automatic TCG front-end generation system or implemented in the classical way (manually).