GlobalISel is the planned successor to the SelectionDAG instruction selection framework, currently used by the AArch64 target by default at the -O0 optimization level, and with partial implementations in several other backends. It also has downstream users in the Apple GPU compiler. The long term goals for the project are to replace the block-based selection strategy of SelectionDAG with a more efficient framework that can also do function-wide analysis and optimization. The design of GlobalISel has evolved over its lifetime and continues to do so. The aim of this BoF is to bring together developers and other parties interested in the state and future progress of GlobalISel, and to discuss some issues that would benefit from community feedback. We will first give a short update on progress within the past year. Possible discussion topics include:
• The current design of GISel’s pipeline, with particular focus on how well the architecture will scale as the focus on optimisation increases. • For new backends, how is the experience in bringing up a GlobalISel based code generator? For existing backends, are there any impediments to continuing development? • Does using GlobalISel mean that double the work is necessary with more maintenance costs? How can this be mitigated? • Are there additional features that developers would like to see in the framework? What SelectionDAG annoyances should we take particular care to avoid or improve upon?
