> >>+-- Those `rn` variables before and after `main_payload` are
> >>+-- required to generate enough register pressure (for GPR). Amount
> >>+-- of repeats is empirical.
> >>+-- Additional `test_f(...)` wrapper is needed for IR_VLOAD usage,
> >>+-- when `main_payload` is just `...`.
> >>+local function generate_payload(n_fillers, main_payload)
> >>+ local code_chunk = 'local function test_f(...)\n'
> >>+ code_chunk = code_chunk .. 'local r\n'
> >>+ for i = 1, n_fillers do
> >>+ code_chunk = code_chunk .. ('local rup%d\n'):format(i)
> >>+ end
> >>+ code_chunk = code_chunk .. 'for _ = 1, 4 do\n'
> >>+ for i = 1, n_fillers do
> >>+ code_chunk = code_chunk ..
> >>+ ('local r%d = ffi.cast("int", %d)\n'):format(i, i)
> >>+ end
> >>+ code_chunk = code_chunk .. 'r = ' .. main_payload .. '\n'
> >>+ for i = 1, n_fillers do
> >>+ code_chunk = code_chunk .. ('rup%d = r%d\n'):format(i, i)
> >>+ end
> >>+ code_chunk = code_chunk .. 'end\nend\n'
> >>+ code_chunk = code_chunk .. 'return test_f'
> >>+ local f, err = loadstring(code_chunk, 'test_function')
> >>+ assert(type(f) == 'function', err)
> >>+ f = f()
> >>+ assert(type(f) == 'function', 'returned generated value is not a function')
> >>+ return f
> >>+end
> >That section is really hard to read, is there any way to make it more
> >readable? I believe even slight reformatting might help.

I've add the additional empty lines to separate cycle's body
generation.
Does it help?