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Currently there are two serialization modes for bitstream Remarks: standalone and separate. The separate mode splits remark metadata (e.g. the string table) from actual remark data. The metadata is written into the object file by the AsmPrinter, while the remark data is stored in a separate remarks file. This means we can't use bitstream remarks with tools like opt that don't generate an object file. Also, it is confusing to post-process bitstream remarks files, because only the standalone files can be read by llvm-remarkutil. We always need to use dsymutil to convert the separate files to standalone files, which only works for MachO. It is not possible for clang/opt to directly emit bitstream remark files in standalone mode, because the string table can only be serialized after all remarks were emitted. Therefore, this change completely removes the separate serialization mode. Instead, the remark string table is now always written to the end of the remarks file. This requires us to tell the serializer when to finalize remark serialization. This automatically happens when the serializer goes out of scope. However, often the remark file goes out of scope before the serializer is destroyed. To diagnose this, I have added an assert to alert users that they need to explicitly call finalizeLLVMOptimizationRemarks. This change paves the way for further improvements to the remark infrastructure, including more tooling (e.g. #159784), size optimizations for bitstream remarks, and more. Pull Request: https://github.com/llvm/llvm-project/pull/156715
The LLVM/Offload Subproject
The Offload subproject aims at providing tooling, runtimes, and APIs that allow users to execute code on accelerators or other "co-processors" that may or may not match the architecture of their "host". In the long run, all kinds of targets are in scope of this effort, including but not limited to: CPUs, GPUs, FPGAs, AI/ML accelerators, distributed resources, etc.
For OpenMP offload users, the project is ready and fully usable. The final API design is still under development. More content will show up here and on our webpage soon. In the meantime, people are encouraged to participate in our meetings (see below) and check our development board as well as the discussions on Discourse.
Meetings
Every second Wednesday, 7:00 - 8:00am PT, starting Jan 24, 2024. Alternates with the OpenMP in LLVM meeting. invite.ics Meeting Minutes and Agenda