bd3dcd313d
The relaxed-simd proposal for WebAssembly adds a fused-multiply-add operation for `v128` types so I was poking around at Cranelift's existing support for its `fma` instruction. I was also poking around at the x86_64 ISA's offerings for the FMA operation and ended up with this PR that improves the lowering of the `fma` instruction on the x64 backend in a number of ways: * A libcall-based fallback is now provided for `f32x4` and `f64x2` types in preparation for eventual support of the relaxed-simd proposal. These encodings are horribly slow, but it's expected that if FMA semantics must be guaranteed then it's the best that can be done without the `fma` feature. Otherwise it'll be up to producers (e.g. Wasmtime embedders) whether wasm-level FMA operations should be FMA or multiply-then-add. * In addition to the existing `vfmadd213*` instructions opcodes were added for `vfmadd132*`. The `132` variant is selected based on which argument can have a sinkable load. * Any argument in the `fma` CLIF instruction can now have a `sinkable_load` and it'll generate a single FMA instruction. * All `vfnmadd*` opcodes were added as well. These are pattern-matched where one of the arguments to the CLIF instruction is an `fneg`. I opted to not add a new CLIF instruction here since it seemed like pattern matching was easy enough but I'm also not intimately familiar with the semantics here so if that's the preferred approach I can do that too.
This crate contains the core Cranelift code generator. It translates code from an intermediate representation into executable machine code.