of MontiumC that was envisioned at the outset of its development.
\subsection{Familiarizing with LLVM}
-This section says something about integrating in the LLVM community as well as
-getting acquainted with the code.
+Since during my internship I have been working mainly with LLVM (code), one of
+the first challenges was to get myself familiar with LLVM. There are two main
+aspects to this: Getting to know my way around the LLVM codebase and getting to
+know the LLVM community.
+
+Since LLVM has a pretty large amount of documentation, I spent most of my first
+weeks with reading tutorials and documents. Since there was already a (very
+preliminary) version of the clang-based frontend, I also had some code to play
+with.
+
+During this period, it was not completely clear what the frontend should
+be doing and what transformations should be written. To prevent circular
+dependencies in my tasks (I can't write any code before I know what needs to be
+written, but I can't really tell what's needed until I know how the code works,
+which I can't effectively learn without actively working with it, etc.) I
+started out with adapting the loop unrolling pass in LLVM to be better suited to
+the Montium architecture. Eventually, this code didn't turn out to be
+immediately useful (it's still not included currently), but it proved very
+insightful as to how the LLVM framework is built and what its possibilities are.
+
+Additionally, during my working with the code in this stage I also produced a
+number of patches for LLVM, containing bugfixes, some cleanup and documentation
+improvements. Since the best way to integrate with any open source project seems
+to be contributing code, I was giving commit access to the LLVM tree not long
+thereafter. This access has proved very useful during the rest of the
+internship, since it was now a a lot easier to make (simple) changes to the LLVM
+framework to better suit the needs of Recore.
+
+A major challenge during my internship was to find the balance between doing
+work specifically for Recore, and doing work that is useful for LLVM in general.
+Any tasks that are required by the Montium frontend and the LLVM changes they
+directly need are obvious. However, usually when making changes to the main LLVM
+code, just changing enough for Recore is not engough for LLVM. Since the LLVM
+code must work on any program, not just MontiumC programs, extra changes are
+required (see also parapgrah \ref{StayingGeneric}. This is also an issue of
+building up credit within the LLVM community: The more you contribute to LLVM,
+the more influence you have when things need changing.
+
+Lastly, this is also a matter of efficiency: If I have been working
+with a particular piece of code intensively, it is more efficient for me to fix
+a bug in that code than most others, even though the particular bug does not
+interfere with the MontiumC frontend. In the end, I think I managed to find a
+decent balance, though it might have been tipped slighly in favour of the LLVM
+project.
\subsection{Coding}
This section says something about the challenges encountered while actually
This section says something about working with colleagues in various ways.
\subsection{Staying generic}
-This section says something about the challenge of writing generic code:
-(changes to) transformations that are useful for both LLVM (ie on regular
-architectures) as well as for Recore (on the Montium).
+\label{StayingGeneric}
+The toughest challenge by far was to fit the features and changes required by
+Recore into code that is maintained by the LLVM project. The main problem here
+is clash of goals: The LLVM project aims for code that performs well on their
+supported architectures, while Recore aims for code that performs well (or more
+often, can compile at all) on the Montium architecture.
+
+In general, these problems mainly occur because MontiumC and in particular
+MontiumIR poses a number of constraints that are not present in other
+architectures. This means that some transformations present in LLVM will violate
+these constraints (which would result in better code on most other
+architectures) resulting in miscompiled or uncompilable code.
+
+In some cases, these extra constraints can be formulated in a generic way, such
+that the LLVM code can handle architectures with or without the constraint.
+In a lot of cases, however, the constraint is so Montium specific that changing
+LLVM to support it is not feasible. In a few cases, this meant that the backend
+was changed to support more features of the LLVM IR. In other cases, a
+Recore-specific pass was added to solve these problems. In a few more cases, the
+problems are still unresolved, effectively resulting in additional constraints
+on the MontiumC language.
\subsection{Pipelined scheduling}
I've also been involved for a bit with the instruction scheduling algorithm
projects / matthijs / projects / internship.git / blobdiff