9c5c872b3b
This adds support for all atomic operations that were unimplemented so far in the s390x back end: - atomic_rmw operations xchg, nand, smin, smax, umin, umax - $I8 and $I16 versions of atomic_rmw and atomic_cas - little endian versions of atomic_rmw and atomic_cas All of these have to be implemented by a compare-and-swap loop; and for the $I8 and $I16 versions the actual atomic instruction needs to operate on the surrounding aligned 32-bit word. Since we cannot emit new control flow during ISLE instruction selection, these compare-and-swap loops are emitted as a single meta-instruction to be expanded at emit time. However, since there is a large number of different versions of the loop required to implement all the above operations, I've implemented a facility to allow specifying the loop bodies from within ISLE after all, by creating a vector of MInst structures that will be emitted as part of the meta-instruction. There are still restrictions, in particular instructions that are part of the loop body may not modify any virtual register. But even so, this approach looks preferable to doing everything in emit.rs. A few instructions needed in those compare-and-swap loop bodies were added as well, in particular the RxSBG family of instructions as well as the LOAD REVERSED in-register byte-swap instructions. This patch also adds filetest runtests to verify the semantics of all operations, in particular the subword and little-endian variants (those are currently only executed on s390x).
This crate contains the core Cranelift code generator. It translates code from an intermediate representation into executable machine code.