Cranelift JIT Code Generation & SIMD Vectorization

Why Cranelift Beats LLVM for JIT Workloads

While LLVM produces extraordinary peak optimizations for AOT compilation, its compilation throughput is slow (compiling hundreds of lines can take seconds). Cranelift (the code generator powering Wasmtime and Vitalis) generates optimized native machine code orders of magnitude faster, making it the premier choice for runtime JIT execution.

Generating Machine Code with cranelift-jit

use cranelift::prelude::*;
use cranelift_jit::{JITBuilder, JITModule};
use cranelift_module::{Module, Linkage};

pub fn build_native_jit_add() -> fn(i64, i64) -> i64 {
    let mut flag_builder = settings::builder();
    flag_builder.set("opt_level", "speed").unwrap();
    let isa = isa::lookup(target_lexicon::Triple::host()).unwrap().finish(settings::Flags::new(flag_builder)).unwrap();

    let builder = JITBuilder::with_isa(isa, cranelift_module::default_libcall_names());
    let mut module = JITModule::new(builder);
    let mut ctx = module.make_context();

    let mut sig = module.make_signature();
    sig.params.push(AbiParam::new(types::I64));
    sig.params.push(AbiParam::new(types::I64));
    sig.returns.push(AbiParam::new(types::I64));

    let func_id = module.declare_function("jit_add", Linkage::Export, &sig).unwrap();
    ctx.func.signature = sig;

    let mut builder_context = FunctionBuilderContext::new();
    let mut fb = FunctionBuilder::new(&mut ctx.func, &mut builder_context);
    let block = fb.create_block();
    fb.append_block_params_for_function_params(block);
    fb.switch_to_block(block);

    let p0 = fb.block_params(block)[0];
    let p1 = fb.block_params(block)[1];
    let sum = fb.ins().iadd(p0, p1);
    fb.ins().return_(&[sum]);
    fb.seal_all_blocks();
    fb.finalize();

    module.define_function(func_id, &mut ctx).unwrap();
    module.clear_context(&mut ctx);
    module.finalize_definitions().unwrap();

    let code_ptr = module.get_finalized_function(func_id);
    unsafe { std::mem::transmute(code_ptr) }
}