b1a512dbf6
After going through the checker with @fitzgen, we discussed the dataflow analysis and @fitzgen noted that it would likely be more efficient to, for example, process an inner cycle of blocks in a loop nest and converge before returning to the outer loop. I had written a BFS-style workqueue loop to converge the dataflow analysis without much thought, with a FIFO workqueue. Any workqueue ordering will work and will converge to the same fixpoint (as long as we are operating on a lattice), but indeed some orderings will be more efficient, and a DFS-style (LIFO stack) workqueue will give us this property of converging inner loops first. In measurements, there doesn't seem to be much of a difference for small fuzz testcases, but this will likely matter more if/when we try to run the checker to validate register allocation on large functions.
regalloc2: another register allocator
This is a register allocator that started life as, and is about 50% still, a port of IonMonkey's backtracking register allocator to Rust. In many regards, it has been generalized, optimized, and improved since the initial port, and now supports both SSA and non-SSA use-cases.
In addition, it contains substantial amounts of testing infrastructure (fuzzing harnesses and checkers) that does not exist in the original IonMonkey allocator.
See the design overview for (much!) more detail on how the allocator works.
License
This crate is licensed under the Apache 2.0 License with LLVM
Exception. This license text can be found in the file LICENSE.
Parts of the code are derived from regalloc.rs: in particular,
src/checker.rs and src/domtree.rs. This crate has the same license
as regalloc.rs, so the license on these files does not differ.