18ee645ebe
* Allow hoisting `vconst` instructions out of loops Staring at some SIMD code and what LLVM and v8 both generate it appears that a common technique for SIMD-loops is to hoist constants outside of loops since they're nontrivial to rematerialize unlike integer constants. This commit updates the `loop_hoist_level` calculation with egraphs to have a nonzero default for instructions that have no arguments (e.g. consts) which enables hoisting these instructions out of loops. Note, though, that for now I've listed the maximum as hoisting outside of one loop, but not all of them. While theoretically vconsts could move up to the top of the function I'd be worried about their impact on register pressure and having to save/restore around calls or similar, so hopefully if the hot part of a program is a single loop then hoisting out of one loop is a reasonable-enough heuristic for now. Locally on x64 with a benchmark that just encodes binary to hex this saw a 15% performance improvement taking hex encoding from ~6G/s to ~6.7G/s. * Test vconst is only hoisted one loop out
This crate contains the core Cranelift code generator. It translates code from an intermediate representation into executable machine code.