• dataflow_branch

Convert passes to use the new dataflow framework

A new dataflow framework is being developed by Kenneth Zadeck, Daniel Berlin, and others. The plan is to merge this framework for GCC 4.3. Once it is merged into the trunk, there will be a number of opportunities to use the new framework in existing passes that use the old dataflow framework (which lives in flow.c) or some ad-hoc pass specific dataflow engine.

There are a few general cleanups that have to be done, such as replacing the uses of reg_n_info (that is, REG_N_SETS and friends) and getting rid of reg_scan. Some of this work may even be completed on the dataflow branch before it is merged into the trunk.

Projects for much bigger cleanups will have to be done after the merge. Most of these cleanups are complete re-implementation of existing passes. The dataflow branch should be merged before the start of the Google Summer of Code 2007 projects, so these bigger cleanups can perhaps be done as Summer of Code projects.

The following list of projects is probably not complete. You can discuss these projects or your own ideas on the GCC mailing lists and on the #gcc IRC channel.

• Convert the lower-subreg pass to the new dataflow infrastructure
• Convert regrename pass to new dataflow infrastructure
• Investigate and document the transformations that the regmove pass can do, and re-implement it using the dataflow infrastructure
• Re-implement the constant/copy propagation and jump bypassing passes in gcse.c using the dataflow infrastructure
• Re-implement the mode-switching pass with the new dataflow solver (using block-based LCM)