From a7389541f332e652260b95494994aabf5a622bff Mon Sep 17 00:00:00 2001
From: whitequark <cz@m-labs.hk>
Date: Tue, 18 Dec 2018 15:06:02 +0000
Subject: [PATCH] hdl.ast, hdl.xfrm: various microoptimizations to speed up
 pysim.

---
 nmigen/hdl/ast.py  | 16 +++++++++-------
 nmigen/hdl/xfrm.py | 23 ++++++++++++-----------
 2 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/nmigen/hdl/ast.py b/nmigen/hdl/ast.py
index 0eb8275..b9a7d7a 100644
--- a/nmigen/hdl/ast.py
+++ b/nmigen/hdl/ast.py
@@ -980,7 +980,7 @@ class ValueKey:
         if isinstance(self.value, Const):
             return hash(self.value.value)
         elif isinstance(self.value, Signal):
-            return hash(id(self.value))
+            return hash(self.value.duid)
         elif isinstance(self.value, Operator):
             return hash((self.value.op, tuple(ValueKey(o) for o in self.value.operands)))
         elif isinstance(self.value, Slice):
@@ -998,15 +998,15 @@ class ValueKey:
                             .format(self.value))
 
     def __eq__(self, other):
-        if not isinstance(other, ValueKey):
+        if type(other) is not ValueKey:
             return False
-        if type(self.value) != type(other.value):
+        if type(self.value) is not type(other.value):
             return False
 
         if isinstance(self.value, Const):
             return self.value.value == other.value.value
         elif isinstance(self.value, Signal):
-            return id(self.value) == id(other.value)
+            return self.value is other.value
         elif isinstance(self.value, Operator):
             return (self.value.op == other.value.op and
                     len(self.value.operands) == len(other.value.operands) and
@@ -1066,7 +1066,7 @@ class ValueSet(_MappedKeySet):
 
 class SignalKey:
     def __init__(self, signal):
-        if not isinstance(signal, Signal):
+        if type(signal) is not Signal:
             raise TypeError("Object '{!r}' is not an nMigen signal")
         self.signal = signal
 
@@ -1074,10 +1074,12 @@ class SignalKey:
         return hash(self.signal.duid)
 
     def __eq__(self, other):
-        return isinstance(other, SignalKey) and self.signal.duid == other.signal.duid
+        if type(other) is not SignalKey:
+            return False
+        return self.signal is other.signal
 
     def __lt__(self, other):
-        if not isinstance(other, SignalKey):
+        if type(other) is not SignalKey:
             raise TypeError("Object '{!r}' cannot be compared to a SignalKey")
         return self.signal.duid < other.signal.duid
 
diff --git a/nmigen/hdl/xfrm.py b/nmigen/hdl/xfrm.py
index 36b0c98..a87a524 100644
--- a/nmigen/hdl/xfrm.py
+++ b/nmigen/hdl/xfrm.py
@@ -60,25 +60,25 @@ class AbstractValueTransformer(metaclass=ABCMeta):
         raise TypeError("Cannot transform value '{!r}'".format(value)) # :nocov:
 
     def on_value(self, value):
-        if isinstance(value, Const):
+        if type(value) is Const:
             new_value = self.on_Const(value)
-        elif isinstance(value, Signal):
+        elif type(value) is Signal:
             new_value = self.on_Signal(value)
-        elif isinstance(value, ClockSignal):
+        elif type(value) is ClockSignal:
             new_value = self.on_ClockSignal(value)
-        elif isinstance(value, ResetSignal):
+        elif type(value) is ResetSignal:
             new_value = self.on_ResetSignal(value)
-        elif isinstance(value, Operator):
+        elif type(value) is Operator:
             new_value = self.on_Operator(value)
-        elif isinstance(value, Slice):
+        elif type(value) is Slice:
             new_value = self.on_Slice(value)
-        elif isinstance(value, Part):
+        elif type(value) is Part:
             new_value = self.on_Part(value)
-        elif isinstance(value, Cat):
+        elif type(value) is Cat:
             new_value = self.on_Cat(value)
-        elif isinstance(value, Repl):
+        elif type(value) is Repl:
             new_value = self.on_Repl(value)
-        elif isinstance(value, ArrayProxy):
+        elif type(value) is ArrayProxy:
             new_value = self.on_ArrayProxy(value)
         else:
             new_value = self.on_unknown_value(value)
@@ -140,9 +140,10 @@ class AbstractStatementTransformer(metaclass=ABCMeta):
         raise TypeError("Cannot transform statement '{!r}'".format(stmt)) # :nocov:
 
     def on_statement(self, stmt):
-        if isinstance(stmt, Assign):
+        if type(stmt) is Assign:
             return self.on_Assign(stmt)
         elif isinstance(stmt, Switch):
+            # Uses `isinstance()` and not `type() is` because nmigen.compat requires it.
             return self.on_Switch(stmt)
         elif isinstance(stmt, Iterable):
             return self.on_statements(stmt)
-- 
2.30.2