Tag: x86

My internship: the experience and achievements

In this last post of the summer, which also marks the end of my summer internship, I would like to write a bit about my experience working for FlingOS™. Also, I would like to give you a summary of what has been achieved in the last nine weeks.

The experience

The internship has been a great experience. I have learnt a great deal about the x86 and MIPS32 processor architectures. Learning about these two very different designs alongside each other was truly valuable in recognising the merits of each approach and in learning about low-level development in general. Working on the IL to assembly conversion was fairly challenging but nevertheless fun. I also had a chance at writing and debugging substantial amounts of assembly code, which definitely worth the effort. Using Visual Studio and C# has given me a valuable experience in using the .NET framework as well. The internship provided me with skills I wouldn’t have learnt on my undergraduate course because most of the topics we covered during the summer are either not included or not discussed in such detail. So overall the experience with FlingOS™ has been a great addition to my studies. Although I was slightly intimidated by the amount of new information at the start, I think I managed to do well, with thanks to Ed for his patience and good teaching skills.

Achievements

During my internship, I helped to produce the resources for the upcoming tutorials, we achieved compiler support for MIPS and an extensive verification kernel has been created. The new kernel turned out to be very useful as we uncovered some errors from earlier implementations that caused problems in the compiler. The testing kernel, on which we have been working the last three weeks, has been a supreme success. It was great to see that the implementations worked as intended and also to detect a few corner-case bugs. To sum up, we not only have achieved what we have set out to do at the beginning but were also able to produce the verification kernel, which will definitely help future developments and improve the stability of FlingOS™.

Future plans

This week, my summer internship has come to an end, however, this does not mean farewell. Our plan is that I will continue to work for the project, during the coming academic year, as much as possible. I will also try and post here frequently to keep you up-to-date on what is happening here at FlingOS™, so you will definitely be seeing me around in the future.

Thank you for your interest in the project and thank you FlingOS™ for the great experience, it has been a great summer.

See you soon…

Roland

Cross-platform compiler verification kernel

The compiler verification framework I mentioned in last week’s post is currently under development and is due for completion by the end of next week. Of course, compiler testing never really reaches a completed state; new features can be added or old ones may require verification for a new use-case. So what I mean by completed is that by next week we will have included all the test cases we originally intended to include, which were decided upon after some thought and reasonably made assumptions. In the future, it is very likely that new test cases will be added to the framework. Our intended test cases will cover every expected (and many unexpected) use cases of the IL ops.

FlingOops™

The testing framework verifies the correctness of the compiler using behavioural testing, which essentially tests whether the IL to ASM conversions were correct. It is a behavioural testing framework because it tests the functionality of the compiler by testing the behaviour of the output and thus whether the compiler compiled correctly. It is also cross-architecture/cross-platform because it can be used for testing both the x86 and the MIPS architecture libraries (and any others we may add in the future).

The test kernel is called FlingOops™ and consists of a wrapper framework (with variations for different target architectures) and a long list of method calls, where each method contains a particular test relating to an operation as well as a message to the console stating whether the test case passed. Particular attention is paid to testing signed operations and the ones that require the handling of 64-bit values. To verify that signed and 64-bit values are calculated correctly, depending on the operation tested, we need to make sure that the carry- and borrow-bits are handled correctly as well as overflow happens as expected. There aren’t special carry and borrow flags on MIPS, so these have to be implemented by the compiler and therefore it is crucial to test the correctness of these implementations. The testing is going well and it is great to see that so far, all the test cases passed with the exception of a couple of small errors which were in the x86 target library. Thankfully these issues were fixed quickly as we were able draw from the knowledge and experience gained form working with MIPS viagra 100 mg 4 comprim. On the plus side, the detection of bugs in the x86 build demonstrated that our testing works!

For the last week

For the last week of my internship, our plan is to finalise the testing framework. I will post another article next week to confirm the completion of testing and to review my experience working for FlingOS™.

Thanks for reading! See you next week,
Roland