litex/migen/fhdl/structure.py

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import builtins
from collections import defaultdict
from migen.fhdl import tracer
from migen.util.misc import flat_iteration
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class HUID:
__next_uid = 0
def __init__(self):
self.huid = HUID.__next_uid
HUID.__next_uid += 1
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def __hash__(self):
return self.huid
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class Value(HUID):
"""Base class for operands
Instances of `Value` or its subclasses can be operands to
arithmetic, comparison, bitwise, and logic operators.
They can be assigned (:meth:`eq`) or indexed/sliced (using the usual
Python indexing and slicing notation).
Values created from integers have the minimum bit width to necessary to
represent the integer.
"""
def __bool__(self):
raise NotImplementedError("For boolean operations between expressions: use '&'/'|' instead of 'and'/'or'")
def __invert__(self):
return _Operator("~", [self])
def __neg__(self):
return _Operator("-", [self])
def __add__(self, other):
return _Operator("+", [self, other])
def __radd__(self, other):
return _Operator("+", [other, self])
def __sub__(self, other):
return _Operator("-", [self, other])
def __rsub__(self, other):
return _Operator("-", [other, self])
def __mul__(self, other):
return _Operator("*", [self, other])
def __rmul__(self, other):
return _Operator("*", [other, self])
def __lshift__(self, other):
return _Operator("<<<", [self, other])
def __rlshift__(self, other):
return _Operator("<<<", [other, self])
def __rshift__(self, other):
return _Operator(">>>", [self, other])
def __rrshift__(self, other):
return _Operator(">>>", [other, self])
def __and__(self, other):
return _Operator("&", [self, other])
def __rand__(self, other):
return _Operator("&", [other, self])
def __xor__(self, other):
return _Operator("^", [self, other])
def __rxor__(self, other):
return _Operator("^", [other, self])
def __or__(self, other):
return _Operator("|", [self, other])
def __ror__(self, other):
return _Operator("|", [other, self])
def __lt__(self, other):
return _Operator("<", [self, other])
def __le__(self, other):
return _Operator("<=", [self, other])
def __eq__(self, other):
return _Operator("==", [self, other])
def __ne__(self, other):
return _Operator("!=", [self, other])
def __gt__(self, other):
return _Operator(">", [self, other])
def __ge__(self, other):
return _Operator(">=", [self, other])
def __getitem__(self, key):
from migen.fhdl.bitcontainer import flen
n = flen(self)
if isinstance(key, int):
if key >= n:
raise IndexError
if key < 0:
key += n
return _Slice(self, key, key+1)
elif isinstance(key, slice):
start, stop, step = key.indices(n)
if step != 1:
return Cat(self[i] for i in range(start, stop, step))
return _Slice(self, start, stop)
else:
raise TypeError
def eq(self, r):
"""Assignment
Parameters
----------
r : Value, in
Value to be assigned.
Returns
-------
_Assign
Assignment statement that can be used in combinatorial or
synchronous context.
"""
return _Assign(self, r)
def __hash__(self):
return HUID.__hash__(self)
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class _Operator(Value):
def __init__(self, op, operands):
Value.__init__(self)
self.op = op
self.operands = operands
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def Mux(sel, val1, val0):
"""Multiplex between two values
Parameters
----------
sel : Value(1), in
Selector.
val1 : Value(N), in
val0 : Value(N), in
Input values.
Returns
-------
Value(N), out
Output `Value`. If `sel` is asserted, the Mux returns
`val1`, else `val0`.
"""
return _Operator("m", [sel, val1, val0])
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class _Slice(Value):
def __init__(self, value, start, stop):
Value.__init__(self)
self.value = value
self.start = start
self.stop = stop
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class Cat(Value):
"""Concatenate values
Form a compound `Value` from several smaller ones by concatenation.
The first argument occupies the lower bits of the result.
The return value can be used on either side of an assignment, that
is, the concatenated value can be used as an argument on the RHS or
as a target on the LHS. If it is used on the LHS, it must solely
consist of `Signal` s, slices of `Signal` s, and other concatenations
meeting these properties. The bit length of the return value is the sum of
the bit lengths of the arguments::
flen(Cat(args)) == sum(flen(arg) for arg in args)
Parameters
----------
*args : Values or iterables of Values, inout
`Value` s to be concatenated.
Returns
-------
Cat, inout
Resulting `Value` obtained by concatentation.
"""
def __init__(self, *args):
Value.__init__(self)
self.l = list(flat_iteration(args))
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class Replicate(Value):
"""Replicate a value
An input value is replicated (repeated) several times
to be used on the RHS of assignments::
flen(Replicate(s, n)) == flen(s)*n
Parameters
----------
v : Value, in
Input value to be replicated.
n : int
Number of replications.
Returns
-------
Replicate, out
Replicated value.
"""
def __init__(self, v, n):
Value.__init__(self)
self.v = v
self.n = n
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class Signal(Value):
"""A `Value` that can change
The `Signal` object represents a value that is expected to change
in the circuit. It does exactly what Verilog's `wire` and
`reg` and VHDL's `signal` do.
A `Signal` can be indexed to access a subset of its bits. Negative
indices (`signal[-1]`) and the extended Python slicing notation
(`signal[start:stop:step]`) are supported.
The indeces 0 and -1 are the least and most significant bits
respectively.
Parameters
----------
bits_sign : int or tuple
Either an integer `bits` or a tuple `(bits, signed)`
specifying the number of bits in this `Signal` and whether it is
signed (can represent negative values). `signed` defaults to
`False`.
name : str or None
Name hint for this signal. If `None` (default) the name is
inferred from the variable name this `Signal` is assigned to.
Name collisions are automatically resolved by prepending
names of objects that contain this `Signal` and by
appending integer sequences.
variable : bool
Deprecated.
reset : int
Reset (synchronous) or default (combinatorial) value.
When this `Signal` is assigned to in synchronous context and the
corresponding clock domain is reset, the `Signal` assumes the
given value. When this `Signal` is unassigned in combinatorial
context (due to conditional assignments not being taken),
the `Signal` assumes its `reset` value. Defaults to 0.
name_override : str or None
Do not use the inferred name but the given one.
min : int or None
max : int or None
If `bits_sign` is `None`, the signal bit width and signedness are
determined by the integer range given by `min` (inclusive,
defaults to 0) and `max` (exclusive, defaults to 2).
related : Signal or None
"""
def __init__(self, bits_sign=None, name=None, variable=False, reset=0, name_override=None, min=None, max=None, related=None):
from migen.fhdl.bitcontainer import bits_for
Value.__init__(self)
# determine number of bits and signedness
if bits_sign is None:
if min is None:
min = 0
if max is None:
max = 2
max -= 1 # make both bounds inclusive
assert(min < max)
self.signed = min < 0 or max < 0
self.nbits = builtins.max(bits_for(min, self.signed), bits_for(max, self.signed))
else:
assert(min is None and max is None)
if isinstance(bits_sign, tuple):
self.nbits, self.signed = bits_sign
else:
self.nbits, self.signed = bits_sign, False
if not isinstance(self.nbits, int) or self.nbits <= 0:
raise ValueError("Signal width must be a strictly positive integer")
self.variable = variable # deprecated
self.reset = reset
self.name_override = name_override
self.backtrace = tracer.trace_back(name)
self.related = related
def __repr__(self):
return "<Signal " + (self.backtrace[-1][0] or "anonymous") + " at " + hex(id(self)) + ">"
@classmethod
def like(cls, other, **kwargs):
"""Create Signal based on another.
Parameters
----------
other : Value
Object to base this Signal on.
See `migen.fhdl.bitcontainer.value_bits_sign`() for details.
"""
from migen.fhdl.bitcontainer import value_bits_sign
return cls(bits_sign=value_bits_sign(other), **kwargs)
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class ClockSignal(Value):
"""Clock signal for a given clock domain
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`ClockSignal` s for a given clock domain can be retrieved multiple
times. They all ultimately refer to the same signal.
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Parameters
----------
cd : str
Clock domain to obtain a clock signal for. Defaults to `"sys"`.
"""
def __init__(self, cd="sys"):
Value.__init__(self)
self.cd = cd
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class ResetSignal(Value):
"""Reset signal for a given clock domain
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`ResetSignal` s for a given clock domain can be retrieved multiple
times. They all ultimately refer to the same signal.
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Parameters
----------
cd : str
Clock domain to obtain a reset signal for. Defaults to `"sys"`.
"""
def __init__(self, cd="sys"):
Value.__init__(self)
self.cd = cd
# statements
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class _Assign:
def __init__(self, l, r):
self.l = l
self.r = r
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class If:
"""Conditional execution of statements
Parameters
----------
cond : Value(1), in
Condition
*t : Statements
Statements to execute if `cond` is asserted.
Examples
--------
>>> a = Signal()
>>> b = Signal()
>>> c = Signal()
>>> d = Signal()
>>> If(a,
... b.eq(1)
... ).Elif(c,
... b.eq(0)
... ).Else(
... b.eq(d)
... )
"""
def __init__(self, cond, *t):
self.cond = cond
self.t = list(t)
self.f = []
def Else(self, *f):
"""Add an `else` conditional block
Parameters
----------
*f : Statements
Statements to execute if all previous conditions fail.
"""
_insert_else(self, list(f))
return self
def Elif(self, cond, *t):
"""Add an `else if` conditional block
Parameters
----------
cond : Value(1), in
Condition
*t : Statements
Statements to execute if previous conditions fail and `cond`
is asserted.
"""
_insert_else(self, [If(cond, *t)])
return self
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def _insert_else(obj, clause):
o = obj
while o.f:
assert(len(o.f) == 1)
assert(isinstance(o.f[0], If))
o = o.f[0]
o.f = clause
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class Case:
"""Case/Switch statement
Parameters
----------
test : Value, in
Selector value used to decide which block to execute
cases : dict
Dictionary of cases. The keys are numeric constants to compare
with `test`. The values are statements to be executed the
corresponding key matches `test`. The dictionary may contain a
string key `"default"` to mark a fall-through case that is
executed if no other key matches.
Examples
--------
>>> a = Signal()
>>> b = Signal()
>>> Case(a, {
... 0: b.eq(1),
... 1: b.eq(0),
... "default": b.eq(0),
... })
"""
def __init__(self, test, cases):
self.test = test
self.cases = cases
def makedefault(self, key=None):
"""Mark a key as the default case
Deletes/Substitutes any previously existing default case.
Parameters
----------
key : int or None
Key to use as default case if no other key matches.
By default, the largest key is the default key.
"""
if key is None:
for choice in self.cases.keys():
if key is None or choice > key:
key = choice
self.cases["default"] = self.cases[key]
del self.cases[key]
return self
# arrays
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class _ArrayProxy(Value):
def __init__(self, choices, key):
self.choices = choices
self.key = key
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def __getattr__(self, attr):
return _ArrayProxy([getattr(choice, attr) for choice in self.choices],
self.key)
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def __getitem__(self, key):
return _ArrayProxy([choice.__getitem__(key) for choice in self.choices],
self.key)
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class Array(list):
"""Addressable multiplexer
An array is created from an iterable of values and indexed using the
usual Python simple indexing notation (no negative indices or
slices). It can be indexed by numeric constants, `Value` s, or
`Signal` s.
The result of indexing the array is a proxy for the entry at the
given index that can be used on either RHS or LHS of assignments.
An array can be indexed multiple times.
Multidimensional arrays are supported by packing inner arrays into
outer arrays.
Parameters
----------
values : iterable of ints, Values, Signals
Entries of the array. Each entry can be a numeric constant, a
`Signal` or a `Record`.
Examples
--------
>>> a = Array(range(10))
>>> b = Signal(max=10)
>>> c = Signal(max=10)
>>> b.eq(a[9 - c])
"""
def __getitem__(self, key):
if isinstance(key, Value):
return _ArrayProxy(self, key)
else:
return list.__getitem__(self, key)
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class ClockDomain:
"""Synchronous domain
Parameters
----------
name : str or None
Domain name. If None (the default) the name is inferred from the
variable name this `ClockDomain` is assigned to (stripping any
`"cd_"` prefix).
reset_less : bool
The domain does not use a reset signal. Registers within this
domain are still all initialized to their reset state once, e.g.
through Verilog `"initial"` statements.
Attributes
----------
clk : Signal, inout
The clock for this domain. Can be driven or used to drive other
signals (preferably in combinatorial context).
rst : Signal or None, inout
Reset signal for this domain. Can be driven or used to drive.
"""
def __init__(self, name=None, reset_less=False):
self.name = tracer.get_obj_var_name(name)
if self.name is None:
raise ValueError("Cannot extract clock domain name from code, need to specify.")
if self.name.startswith("cd_"):
self.name = self.name[3:]
if self.name[0].isdigit():
raise ValueError("Clock domain name cannot start with a number.")
self.clk = Signal(name_override=self.name + "_clk")
if reset_less:
self.rst = None
else:
self.rst = Signal(name_override=self.name + "_rst")
def rename(self, new_name):
"""Rename the clock domain
Parameters
----------
new_name : str
New name
"""
self.name = new_name
self.clk.name_override = new_name + "_clk"
if self.rst is not None:
self.rst.name_override = new_name + "_rst"
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class _ClockDomainList(list):
def __getitem__(self, key):
if isinstance(key, str):
for cd in self:
if cd.name == key:
return cd
raise KeyError(key)
else:
return list.__getitem__(self, key)
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(SPECIAL_INPUT, SPECIAL_OUTPUT, SPECIAL_INOUT) = range(3)
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class StopSimulation(Exception):
pass
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class _Fragment:
def __init__(self, comb=None, sync=None, specials=None, clock_domains=None, sim=None):
if comb is None: comb = []
if sync is None: sync = dict()
if specials is None: specials = set()
if clock_domains is None: clock_domains = _ClockDomainList()
if sim is None: sim = []
self.comb = comb
self.sync = sync
self.specials = specials
self.clock_domains = _ClockDomainList(clock_domains)
self.sim = sim
def __add__(self, other):
newsync = defaultdict(list)
for k, v in self.sync.items():
newsync[k] = v[:]
for k, v in other.sync.items():
newsync[k].extend(v)
return _Fragment(self.comb + other.comb, newsync,
self.specials | other.specials,
self.clock_domains + other.clock_domains,
self.sim + other.sim)
def __iadd__(self, other):
newsync = defaultdict(list)
for k, v in self.sync.items():
newsync[k] = v[:]
for k, v in other.sync.items():
newsync[k].extend(v)
self.comb += other.comb
self.sync = newsync
self.specials |= other.specials
self.clock_domains += other.clock_domains
self.sim += other.sim
return self