bcfc10c44e
When a liverange starts at a *late* point of an instruction, and it undergoes the fallback "split into all minimal pieces" transform, we end up creating one minimal bundle that starts at the *early* point of the instruction at the start of the original LR. This can create impossible-to-allocate situations where a fixed-constraint LR overlaps another constrained to the same register (e.g. at calls). We fix this by ensuring the minimal bundle is trimmed only to the half of the instruction that overlaps the original LR. This is analogous to the third fix in #74, but on the other end (start of LR rather than end of it).
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.