[PyCDE] Simple transforms on channels (#7330)

Add 'transform' method to ChannelSignals to enable simple data
manipulations without worrying about signaling.

frontends/PyCDE/src/pycde/signals.py

@@ -13,7 +13,7 @@ from .circt import ir
 
 from contextvars import ContextVar
 from functools import singledispatchmethod
-from typing import Dict, List, Optional, Tuple, Union
+from typing import Callable, Dict, List, Optional, Tuple, Union
 import re
 import numpy as np
 
@@ -736,6 +736,20 @@ class ChannelSignal(Signal):
             stages=stages,
         ), self.type)
 
+  def transform(self, transform: Callable[[Signal], Signal]) -> ChannelSignal:
+    """Transform the data in the channel using the provided function. Said
+    function must be combinational so it is intended for wire and simple type
+    transformations."""
+
+    from .constructs import Wire
+    from .types import Bits, Channel
+    ready_wire = Wire(Bits(1))
+    data, valid = self.unwrap(ready_wire)
+    data = transform(data)
+    ret_chan, ready = Channel(data.type).wrap(data, valid)
+    ready_wire.assign(ready)
+    return ret_chan
+
 
 class BundleSignal(Signal):
   """Signal for types.Bundle."""

frontends/PyCDE/test/test_esi.py

@@ -184,6 +184,21 @@ class RecvBundleTest(Module):
     self.s1_out = to_channels['req']
 
 
+# CHECK-LABEL:  hw.module @ChannelTransform(in %s1_in : !esi.channel<i32>, out s2_out : !esi.channel<i8>) attributes {output_file = #hw.output_file<"ChannelTransform.sv", includeReplicatedOps>} {
+# CHECK-NEXT:     %rawOutput, %valid = esi.unwrap.vr %s1_in, %ready : i32
+# CHECK-NEXT:     [[R0:%.+]] = comb.extract %rawOutput from 0 : (i32) -> i8
+# CHECK-NEXT:     %chanOutput, %ready = esi.wrap.vr [[R0]], %valid : i8
+# CHECK-NEXT:     hw.output %chanOutput : !esi.channel<i8>
+@unittestmodule()
+class ChannelTransform(Module):
+  s1_in = InputChannel(Bits(32))
+  s2_out = OutputChannel(Bits(8))
+
+  @generator
+  def build(self):
+    self.s2_out = self.s1_in.transform(lambda x: x[0:8])
+
+
 # CHECK-LABEL:  hw.module @MMIOReq()
 # CHECK-NEXT:     %c0_i64 = hw.constant 0 : i64
 # CHECK-NEXT:     %false = hw.constant false