From 5e16516706fa6a9717be0ec39705c9ebd936440a Mon Sep 17 00:00:00 2001
From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Mon, 21 Mar 2016 23:52:52 +0100
Subject: [PATCH] gen: add missing sim files

---
 litex/gen/sim/core.py | 372 ++++++++++++++++++++++++++++++++++++++++++
 litex/gen/sim/vcd.py  |  85 ++++++++++
 2 files changed, 457 insertions(+)
 create mode 100644 litex/gen/sim/core.py
 create mode 100644 litex/gen/sim/vcd.py

diff --git a/litex/gen/sim/core.py b/litex/gen/sim/core.py
new file mode 100644
index 000000000..928e9a32b
--- /dev/null
+++ b/litex/gen/sim/core.py
@@ -0,0 +1,372 @@
+import operator
+import collections
+import inspect
+from functools import wraps
+
+from litex.gen.fhdl.structure import *
+from litex.gen.fhdl.structure import (_Value, _Statement,
+                                  _Operator, _Slice, _ArrayProxy,
+                                  _Assign, _Fragment)
+from litex.gen.fhdl.bitcontainer import value_bits_sign
+from litex.gen.fhdl.tools import (list_targets, list_signals,
+                              insert_resets, lower_specials)
+from litex.gen.fhdl.simplify import MemoryToArray
+from litex.gen.fhdl.specials import _MemoryLocation
+from litex.gen.sim.vcd import VCDWriter, DummyVCDWriter
+
+
+class ClockState:
+    def __init__(self, high, half_period, time_before_trans):
+        self.high = high
+        self.half_period = half_period
+        self.time_before_trans = time_before_trans
+
+
+class TimeManager:
+    def __init__(self, description):
+        self.clocks = collections.OrderedDict()
+
+        for k, period_phase in description.items():
+            if isinstance(period_phase, tuple):
+                period, phase = period_phase
+            else:
+                period = period_phase
+                phase = 0
+            half_period = period//2
+            if phase >= half_period:
+                phase -= half_period
+                high = True
+            else:
+                high = False
+            self.clocks[k] = ClockState(high, half_period, half_period - phase)
+    
+    def tick(self):
+        rising = set()
+        falling = set()
+        dt = min(cs.time_before_trans for cs in self.clocks.values())
+        for k, cs in self.clocks.items():
+            if cs.time_before_trans == dt:
+                cs.high = not cs.high
+                if cs.high:
+                    rising.add(k)
+                else:
+                    falling.add(k)
+            cs.time_before_trans -= dt
+            if not cs.time_before_trans:
+                cs.time_before_trans += cs.half_period
+        return dt, rising, falling
+
+
+str2op = {
+    "~": operator.invert,
+    "+": operator.add,
+    "-": operator.sub,
+    "*": operator.mul,
+    
+    ">>>": operator.rshift,
+    "<<<": operator.lshift,
+    
+    "&": operator.and_,
+    "^": operator.xor,
+    "|": operator.or_,
+    
+    "<": operator.lt,
+    "<=": operator.le,
+    "==": operator.eq,
+    "!=": operator.ne,
+    ">": operator.gt,
+    ">=": operator.ge,
+}
+
+
+def _truncate(value, nbits, signed):
+    value = value & (2**nbits - 1)
+    if signed and (value & 2**(nbits - 1)):
+        value -= 2**nbits
+    return value
+
+
+class Evaluator:
+    def __init__(self, clock_domains, replaced_memories):
+        self.clock_domains = clock_domains
+        self.replaced_memories = replaced_memories
+        self.signal_values = dict()
+        self.modifications = dict()
+
+    def commit(self):
+        r = set()
+        for k, v in self.modifications.items():
+            if k not in self.signal_values or self.signal_values[k] != v:
+                self.signal_values[k] = v
+                r.add(k)
+        self.modifications.clear()
+        return r
+
+    def eval(self, node, postcommit=False):
+        if isinstance(node, Constant):
+            return node.value
+        elif isinstance(node, Signal):
+            if postcommit:
+                try:
+                    return self.modifications[node]
+                except KeyError:
+                    pass
+            try:
+                return self.signal_values[node]
+            except KeyError:
+                return node.reset.value
+        elif isinstance(node, _Operator):
+            operands = [self.eval(o, postcommit) for o in node.operands]
+            if node.op == "-":
+                if len(operands) == 1:
+                    return -operands[0]
+                else:
+                    return operands[0] - operands[1]
+            elif node.op == "m":
+                return operands[1] if operands[0] else operands[2]
+            else:
+                return str2op[node.op](*operands)
+        elif isinstance(node, _Slice):
+            v = self.eval(node.value, postcommit)
+            idx = range(node.start, node.stop)
+            return sum(((v >> i) & 1) << j for j, i in enumerate(idx))
+        elif isinstance(node, Cat):
+            shift = 0
+            r = 0
+            for element in node.l:
+                nbits = len(element)
+                # make value always positive
+                r |= (self.eval(element, postcommit) & (2**nbits-1)) << shift
+                shift += nbits
+            return r
+        elif isinstance(node, Replicate):
+            nbits = len(node.v)
+            v = self.eval(node.v, postcommit) & (2**nbits - 1)
+            return sum(v << i*nbits for i in range(node.n))
+        elif isinstance(node, _ArrayProxy):
+            return self.eval(node.choices[self.eval(node.key, postcommit)],
+                             postcommit)
+        elif isinstance(node, _MemoryLocation):
+            array = self.replaced_memories[node.memory]
+            return self.eval(array[self.eval(node.index, postcommit)], postcommit)
+        elif isinstance(node, ClockSignal):
+            return self.eval(self.clock_domains[node.cd].clk, postcommit)
+        elif isinstance(node, ResetSignal):
+            rst = self.clock_domains[node.cd].rst
+            if rst is None:
+                if node.allow_reset_less:
+                    return 0
+                else:
+                    raise ValueError("Attempted to get reset signal of resetless"
+                                     " domain '{}'".format(node.cd))
+            else:
+                return self.eval(rst, postcommit)
+        else:
+            raise NotImplementedError(node)
+
+    def assign(self, node, value):
+        if isinstance(node, Signal):
+            assert not node.variable
+            self.modifications[node] = _truncate(value,
+                                                 node.nbits, node.signed)
+        elif isinstance(node, Cat):
+            for element in node.l:
+                nbits = len(element)
+                self.assign(element, value & (2**nbits-1))
+                value >>= nbits
+        elif isinstance(node, _Slice):
+            full_value = self.eval(node.value, True)
+            # clear bits assigned to by the slice
+            full_value &= ~((2**node.stop-1) - (2**node.start-1))
+            # set them to the new value
+            value &= 2**(node.stop - node.start)-1
+            full_value |= value << node.start
+            self.assign(node.value, full_value)
+        elif isinstance(node, _ArrayProxy):
+            self.assign(node.choices[self.eval(node.key)], value)
+        elif isinstance(node, _MemoryLocation):
+            array = self.replaced_memories[node.memory]
+            self.assign(array[self.eval(node.index)], value)
+        else:
+            raise NotImplementedError(node)
+
+    def execute(self, statements):
+        for s in statements:
+            if isinstance(s, _Assign):
+                self.assign(s.l, self.eval(s.r))
+            elif isinstance(s, If):
+                if self.eval(s.cond) & (2**len(s.cond) - 1):
+                    self.execute(s.t)
+                else:
+                    self.execute(s.f)
+            elif isinstance(s, Case):
+                nbits, signed = value_bits_sign(s.test)
+                test = _truncate(self.eval(s.test), nbits, signed)
+                found = False
+                for k, v in s.cases.items():
+                    if isinstance(k, Constant) and k.value == test:
+                        self.execute(v)
+                        found = True
+                        break
+                if not found and "default" in s.cases:
+                    self.execute(s.cases["default"])
+            elif isinstance(s, collections.Iterable):
+                self.execute(s)
+            else:
+                raise NotImplementedError
+
+
+# TODO: instances via Iverilog/VPI
+class Simulator:
+    def __init__(self, fragment_or_module, generators, clocks={"sys": 10}, vcd_name=None):
+        if isinstance(fragment_or_module, _Fragment):
+            self.fragment = fragment_or_module
+        else:
+            self.fragment = fragment_or_module.get_fragment()
+
+        mta = MemoryToArray()
+        mta.transform_fragment(None, self.fragment)
+
+        fs, lowered = lower_specials(overrides={}, specials=self.fragment.specials)
+        self.fragment += fs
+        self.fragment.specials -= lowered
+        if self.fragment.specials:
+            raise ValueError("Could not lower all specials", self.fragment.specials)
+
+        if not isinstance(generators, dict):
+            generators = {"sys": generators}
+        self.generators = dict()
+        self.passive_generators = set()
+        for k, v in generators.items():
+            if (isinstance(v, collections.Iterable)
+                    and not inspect.isgenerator(v)):
+                self.generators[k] = list(v)
+            else:
+                self.generators[k] = [v]
+
+        clocks = collections.OrderedDict(sorted(clocks.items(),
+                                                key=operator.itemgetter(0)))
+        self.time = TimeManager(clocks)
+        for clock in clocks.keys():
+            if clock not in self.fragment.clock_domains:
+                cd = ClockDomain(name=clock, reset_less=True)
+                cd.clk.reset = C(self.time.clocks[clock].high)
+                self.fragment.clock_domains.append(cd)
+
+        insert_resets(self.fragment)
+        # comb signals return to their reset value if nothing assigns them
+        self.fragment.comb[0:0] = [s.eq(s.reset)
+                                   for s in list_targets(self.fragment.comb)]
+        self.evaluator = Evaluator(self.fragment.clock_domains,
+                                   mta.replacements)
+
+        if vcd_name is None:
+            self.vcd = DummyVCDWriter()
+        else:
+            self.vcd = VCDWriter(vcd_name)
+
+            signals = list_signals(self.fragment)
+            for cd in self.fragment.clock_domains:
+                signals.add(cd.clk)
+                if cd.rst is not None:
+                    signals.add(cd.rst)
+            for memory_array in mta.replacements.values():
+                signals |= set(memory_array)
+            for signal in sorted(signals, key=lambda x: x.duid):
+                self.vcd.set(signal, signal.reset.value)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, type, value, traceback):
+        self.close()
+
+    def close(self):
+        self.vcd.close()
+
+    def _commit_and_comb_propagate(self):
+        # TODO: optimize
+        all_modified = set()
+        modified = self.evaluator.commit()
+        all_modified |= modified
+        while modified:
+            self.evaluator.execute(self.fragment.comb)
+            modified = self.evaluator.commit()
+            all_modified |= modified
+        for signal in all_modified:
+            self.vcd.set(signal, self.evaluator.signal_values[signal])
+
+    def _evalexec_nested_lists(self, x):
+        if isinstance(x, list):
+            return [self._evalexec_nested_lists(e) for e in x]
+        elif isinstance(x, _Value):
+            return self.evaluator.eval(x)
+        elif isinstance(x, _Statement):
+            self.evaluator.execute([x])
+            return None
+        else:
+            raise ValueError
+
+    def _process_generators(self, cd):
+        exhausted = []
+        for generator in self.generators[cd]:
+            reply = None
+            while True:
+                try:
+                    request = generator.send(reply)
+                    if request is None:
+                        break  # next cycle
+                    elif isinstance(request, str):
+                        if request == "passive":
+                            self.passive_generators.add(generator)
+                        elif request == "active":
+                            self.passive_generators.discard(generator)
+                        else:
+                            raise ValueError("Unknown simulator command: '{}'"
+                                             .format(request))
+                    else:
+                        reply = self._evalexec_nested_lists(request)
+                except StopIteration:
+                    exhausted.append(generator)
+                    break
+        for generator in exhausted:
+            self.generators[cd].remove(generator)
+
+    def _continue_simulation(self):
+        for cd_generators in self.generators.values():
+            if set(cd_generators) - self.passive_generators:
+                return True
+        return False
+
+    def run(self):
+        self.evaluator.execute(self.fragment.comb)
+        self._commit_and_comb_propagate()
+
+        while True:
+            dt, rising, falling = self.time.tick()
+            self.vcd.delay(dt)
+            for cd in rising:
+                self.evaluator.assign(self.fragment.clock_domains[cd].clk, 1)
+                if cd in self.fragment.sync:
+                    self.evaluator.execute(self.fragment.sync[cd])
+                if cd in self.generators:
+                    self._process_generators(cd)
+            for cd in falling:
+                self.evaluator.assign(self.fragment.clock_domains[cd].clk, 0)
+            self._commit_and_comb_propagate()
+
+            if not self._continue_simulation():
+                break
+
+
+def run_simulation(*args, **kwargs):
+    with Simulator(*args, **kwargs) as s:
+        s.run()
+
+
+def passive(generator):
+    @wraps(generator)
+    def wrapper(*args, **kwargs):
+        yield "passive"
+        yield from generator(*args, **kwargs)
+    return wrapper
diff --git a/litex/gen/sim/vcd.py b/litex/gen/sim/vcd.py
new file mode 100644
index 000000000..85482f51f
--- /dev/null
+++ b/litex/gen/sim/vcd.py
@@ -0,0 +1,85 @@
+from itertools import count
+import tempfile
+import os
+from collections import OrderedDict
+import shutil
+
+from litex.gen.fhdl.namer import build_namespace
+
+
+def vcd_codes():
+    codechars = [chr(i) for i in range(33, 127)]
+    for n in count():
+        q, r = divmod(n, len(codechars))
+        code = codechars[r]
+        while q > 0:
+            q, r = divmod(q, len(codechars))
+            code = codechars[r] + code
+        yield code
+
+
+class VCDWriter:
+    def __init__(self, filename):
+        self.filename = filename
+        self.buffer_file = tempfile.TemporaryFile(
+            dir=os.path.dirname(filename), mode="w+")
+        self.codegen = vcd_codes()
+        self.codes = OrderedDict()
+        self.signal_values = dict()
+        self.t = 0
+
+    def _write_value(self, f, signal, value):
+        l = len(signal)
+        if value < 0:
+            value += 2**l
+        if l > 1:
+            fmtstr = "b{:0" + str(l) + "b} {}\n"
+        else:
+            fmtstr = "{}{}\n"
+        try:
+            code = self.codes[signal]
+        except KeyError:
+            code = next(self.codegen)
+            self.codes[signal] = code
+        f.write(fmtstr.format(value, code))
+
+    def set(self, signal, value):
+        if (signal not in self.signal_values
+                or self.signal_values[signal] != value):
+            self._write_value(self.buffer_file, signal, value)
+            self.signal_values[signal] = value
+
+    def delay(self, delay):
+        self.t += delay
+        self.buffer_file.write("#{}\n".format(self.t))
+
+    def close(self):
+        out = open(self.filename, "w")
+        try:
+            ns = build_namespace(self.codes.keys())
+            for signal, code in self.codes.items():
+                name = ns.get_name(signal)
+                out.write("$var wire {len} {code} {name} $end\n"
+                          .format(name=name, code=code, len=len(signal)))
+            out.write("$dumpvars\n")
+            for signal in self.codes.keys():
+                self._write_value(out, signal, signal.reset.value)
+            out.write("$end\n")
+            out.write("#0\n")
+
+            self.buffer_file.seek(0)
+            shutil.copyfileobj(self.buffer_file, out)
+            self.buffer_file.close()
+        finally:
+            out.close()
+
+
+class DummyVCDWriter:
+    def set(self, signal, value):
+        pass
+
+    def delay(self, delay):
+        pass
+
+    def close(self):
+        pass