[PyCDE] ESI pure module entry (#4635)

Teach PyCDE about ESI pure modules.

frontends/PyCDE/src/esi.py

@@ -2,8 +2,9 @@
 #  See https://llvm.org/LICENSE.txt for license information.
 #  SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-from .common import Input, Output, InputChannel, OutputChannel, _PyProxy
-from .module import Generator, Module, ModuleLikeBuilderBase
+from .common import (Input, Output, InputChannel, OutputChannel, Clock,
+                     _PyProxy, PortError)
+from .module import Generator, Module, ModuleLikeBuilderBase, PortProxyBase
 from .signals import ChannelSignal, Signal, _FromCirctValue
 from .system import System
 from .types import Channel, Type, types, _FromCirctType
@@ -452,3 +453,66 @@ def _import_ram_decl(sys: "System", ram_op: raw_esi.RandomAccessMemoryDeclOp):
   ram.symbol = ir.StringAttr.get(sym)
   install(ram_op)
   return ram
+
+
+class PureModuleBuilder(ModuleLikeBuilderBase):
+  """Defines how an ESI `PureModule` gets built."""
+
+  @property
+  def circt_mod(self):
+    from .system import System
+    sys: System = System.current()
+    ret = sys._op_cache.get_circt_mod(self)
+    if ret is None:
+      return sys._create_circt_mod(self)
+    return ret
+
+  def create_op(self, sys: System, symbol):
+    """Callback for creating a ESIPureModule op."""
+    return raw_esi.ESIPureModuleOp(symbol, loc=self.loc, ip=sys._get_ip())
+
+  def scan_cls(self):
+    """Scan the class for input/output ports and generators. (Most `ModuleLike`
+    will use these.) Store the results for later use."""
+
+    generators = {}
+    for attr_name, attr in self.cls_dct.items():
+      if attr_name.startswith("_"):
+        continue
+
+      if isinstance(attr, (Clock, Input, Output)):
+        raise PortError("ESI pure modules cannot have ports")
+      elif isinstance(attr, Generator):
+        generators[attr_name] = attr
+
+    self.generators = generators
+
+  def create_port_proxy(self):
+    """Since pure ESI modules don't have any ports, this function is pretty
+    boring."""
+    proxy_attrs = {}
+    return type(self.modcls.__name__ + "Ports", (PortProxyBase,), proxy_attrs)
+
+  def add_external_port_accessors(self):
+    """Since we don't have ports, do nothing."""
+    pass
+
+  def generate(self):
+    """Fill in (generate) this module. Only supports a single generator
+    currently."""
+    if len(self.generators) != 1:
+      raise ValueError("Must have exactly one generator.")
+    g: Generator = list(self.generators.values())[0]
+
+    entry_block = self.circt_mod.add_entry_block()
+    ports = self.generator_port_proxy(None, self)
+    with self.GeneratorCtxt(self, ports, entry_block, g.loc):
+      g.gen_func(ports)
+
+
+class PureModule(Module):
+  """A pure ESI module has no ports and contains only instances of modules with
+  only ESI ports and connections between said instances. Use ESI services for
+  external communication."""
+
+  BuilderType = PureModuleBuilder

frontends/PyCDE/src/module.py

@@ -123,7 +123,8 @@ class PortProxyBase:
 
   def __init__(self, block_args, builder):
     self._block_args = block_args
-    self._output_values = [None] * len(builder.outputs)
+    if builder.outputs is not None:
+      self._output_values = [None] * len(builder.outputs)
     self._builder = builder
 
   def _get_input(self, idx):
@@ -314,7 +315,7 @@ class ModuleLikeBuilderBase(_PyProxy):
       self.loc = loc
       self.clk = None
       self.ports = ports
-      if len(builder.clocks) == 1:
+      if builder.clocks is not None and len(builder.clocks) == 1:
         # Enter clock block implicitly if only one clock given.
         clk_port = list(builder.clocks)[0]
         self.clk = ClockSignal(ports._block_args[clk_port], ClockType())

frontends/PyCDE/test/test_esi.py

@@ -94,6 +94,17 @@ class LoopbackInOutTop(Module):
     loopback.assign(data_chan)
 
 
+# CHECK-LABEL:  esi.pure_module @LoopbackInOutPure {
+# CHECK:          [[r0:%.+]] = esi.service.req.to_client <@HostComms::@from_host>(["loopback_in"]) : !esi.channel<i16>
+# CHECK:          esi.service.req.to_server [[r0]] -> <@HostComms::@to_host>(["loopback"]) : !esi.channel<i16>
+@unittestmodule(print=True)
+class LoopbackInOutPure(esi.PureModule):
+
+  @generator
+  def construct(self):
+    HostComms.to_host(HostComms.from_host("loopback_in", types.i16), "loopback")
+
+
 class MultiplexerService(esi.ServiceImplementation):
   clk = Clock()
   rst = Input(types.i1)

lib/Bindings/Python/dialects/_esi_ops_ext.py

@@ -33,3 +33,12 @@ class RandomAccessMemoryDeclOp:
   @property
   def innerType(self):
     return ir.TypeAttr(self.attributes["innerType"])
+
+
+class ESIPureModuleOp:
+
+  def add_entry_block(self):
+    if len(self.body.blocks) > 0:
+      raise IndexError('The module already has an entry block')
+    self.body.blocks.append()
+    return self.body.blocks[0]