a5c48fda8a
The checker was built to validate programs produced by the fuzzing testcase generator, which was built before regalloc2 supported special handling of moves. (In a pure-SSA world, move elision is not needed, because moves are not needed, and blockparams are the only way of tying together vregs.) Due to this, the checker works great for our independent regalloc2 fuzzing setup, but when used on regalloc inputs produced by Cranelift, cannot prove correctness. This PR extends the checker's analysis to properly handle "program moves", which are distinct from regalloc-inserted moves in that they are present in the original program and hence are semantically relevant. A program move edits all sets of symbolic vregs at all allocs, and where the source vreg appears, it inserts the dest vreg as well. (It also removes the dest vreg from all other sets, since the old value becomes stale, as is done for other defs.) Given this, and given some additional checking for moves to/from pinned vregs, the checker can now be used to fully validate Cranelift-sourced regalloc2 invocations.
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.