9733cb2227
* Clobbers: use a more efficient bitmask representation in API. Currently, the `Function` trait requires a `&[PReg]` for the clobber-list for a given instruction. In most cases where clobbers are used, the list may be long: e.g., ABIs specify a fixed set of registers that are clobbered and there may be ~half of all registers in this list. What's more, the list can't be shared for e.g. all calls of a given ABI, because actual return-values (defs) can't be clobbers. So we need to allocate space for long, sometimes-slightly-different lists; this is inefficient for the embedder and for us. It's much more efficient to use a bitmask to represent a set of physical registers. With current data structure bitpacking limitations, we can support at most 128 physical registers; this means we can use a `u128` bitmask. This also allows e.g. an embedder to start with a constant for a given ABI, and mask out bits for actual return-value registers on call instructions. This PR makes that change, for minor but positive performance impact. * Review comments.
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.