litex/migen/transform/unroll.py

from itertools import repeat

from migen.fhdl.structure import *
from migen.fhdl.structure import _Operator, _Slice, _Assign, _ArrayProxy
from migen.fhdl.tools import list_targets

# y <= y + a + b
#
# unroll_sync(sync, {b: [b1, b2], c: [c1, c2], y: [y1, y2]})
#
# ==>
#
# v_y1 = y2 + a1 + b1
# v_y2 = v_y1 + a2 + b2
# y1 <= v_y1
# y2 <= v_y2

(_UNDETERMINED, _IN, _OUT) = range(3)

# TODO: arrays

def _replace_if_in(d, s):
	try:
		return d[s]
	except KeyError:
		return s

def _replace(node, rin, rout, mode=_UNDETERMINED):
	if isinstance(node, Constant):
		return node
	elif isinstance(node, Signal):
		if mode == _IN:
			return _replace_if_in(rin, node)
		elif mode == _OUT:
			return _replace_if_in(rout, node)
		else:
			raise ValueError
	elif isinstance(node, _Operator):
		rop = [_replace(op, rin, rout, mode) for op in node.operands]
		return _Operator(node.op, rop)
	elif isinstance(node, _Slice):
		return _Slice(_replace(node.value, rin, rout, mode), node.start, node.stop)
	elif isinstance(node, Cat):
		rcomp = [_replace(comp, rin, rout, mode) for comp in node.l]
		return Cat(*rcomp)
	elif isinstance(node, Replicate):
		return Replicate(_replace(node.v, rin, rout, mode), node.n)
	elif isinstance(node, _Assign):
		return _Assign(_replace(node.l, rin, rout, _OUT), _replace(node.r, rin, rout, _IN))
	elif isinstance(node, list):
		return [_replace(s, rin, rout) for s in node]
	elif isinstance(node, If):
		r = If(_replace(node.cond, rin, rout, _IN))
		r.t = _replace(node.t, rin, rout)
		r.f = _replace(node.f, rin, rout)
		return r
	elif isinstance(node, Case):
		r = Case(_replace(case.test, rin, rout, _IN))
		r.cases = [(c[0], _replace(c[1], rin, rout)) for c in node.cases]
		r.default = _replace(node.default, rin, rout)
		return r
	else:
		raise TypeError

def _list_step_dicts(d):
	assert(d)
	iterdict = dict((k, iter(v)) for k, v in d.items())
	r = []
	try:
		while True:
			r.append(dict([(k, next(i)) for k, i in iterdict.items()]))
	except StopIteration:
		pass
	return r

def _classify_repl(statements, replacements):
	targets = list_targets(statements)
	inputs = {}
	outputs = {}
	for k, v in replacements.items():
		if k in targets:
			outputs[k] = v
		else:
			inputs[k] = v
	return inputs, outputs

def _variable_for(s, n):
	sn = s.backtrace[-1][0]
	if isinstance(sn, str):
		name = "v" + str(n) + "_" + sn
	else:
		name = "v"
	return Signal(s.bv, name=name, variable=True)

def unroll_sync(statements, replacements):
	if isinstance(statements, list):
		sl = statements
	else:
		sl = statements(0)
	inputs, outputs = _classify_repl(sl, replacements)
	assert(inputs or outputs)
	if inputs:
		sd_in = _list_step_dicts(inputs)
	else:
		sd_in = repeat({})
	if outputs:
		sd_out = _list_step_dicts(outputs)
		io_var_dict = sd_out[-1].copy()
	else:
		sd_out = repeat({})
		io_var_dict = {}

	r = []
	for n, (di, do) in enumerate(zip(sd_in, sd_out)):
		do_var = dict((k, _variable_for(v, n)) for k, v in do.items())
		
		# initialize variables
		for k, v in io_var_dict.items():
			if k.variable:
				r.append(do_var[k].eq(io_var_dict[k]))
				io_var_dict[k] = do_var[k]
			
		
		# replace signals with intermediate variables and copy statements
		io_var_dict.update(di)
		if n: # done for n = 0 at the beginning of function
			if isinstance(statements, list):
				sl = statements
			else:
				sl = statements(n)
		r += _replace(sl, io_var_dict, do_var)
		
		# assign to output signals
		r += [v.eq(do_var[k]) for k, v in do.items()]
		
		# prepare the next i+o dictionary
		io_var_dict = do_var.copy()
	
	return r