Call Ruby method (FFI::Function) from LLVM

llvm_ruby_ffi_callback.rb

require 'ffi'
require 'llvm/core'
require 'llvm/analysis'
require 'llvm/execution_engine'

CALLBACK_TYPE = LLVM.Function([LLVM::Int], LLVM.Void)

mod = LLVM::Module.new("test.fprintf")

do_work = mod.functions.add("do_work", [CALLBACK_TYPE.pointer], LLVM.Void) do |fn, callback|
            callback.name = "callback"

            fn.basic_blocks.append.build do |builder|
              builder.call(callback, LLVM::Int(rand 1000))
              builder.ret_void
            end
          end

mod.verify!
mod.dump

# ; ModuleID = 'test.fprintf'
# 
# define void @do_work(void (i32)* %callback) {
#   call void %callback(i32 760)
#   ret void
# }
# LLVM callback: 760

# --- JIT
LLVM.init_jit

engine   = LLVM::JITCompiler.new(mod)
funptr   = engine.pointer_to_global(do_work)
ffi_fun  = FFI::Function.new(:void, [:pointer], funptr)
callback = FFI::Function.new(:void, [:int]) do |i|
  puts "LLVM callback: #{i}"
end

ffi_fun.call(callback)