Optimization: Detect variable references discarded sooner

* The expression was already adding its usage indication,
  undo that such that next micro pass knows if it's used
  or not sooner. Otherwise it may not happen if that will
  have no other changes. And if it did, it will need even
  one more than necessary.

nuitka/nodes/ConditionalNodes.py

@@ -716,6 +716,7 @@ branches.""",
 Both branches have no effect, reduced to evaluate condition.""",
                 )
             else:
+                condition.undoComputeExpressionRaw(trace_collection)
                 self.finalize()
 
                 return (

nuitka/nodes/ExpressionBases.py

@@ -153,7 +153,7 @@ class ExpressionBase(NodeBase):
 
     @staticmethod
     def extractUnhashableNodeType():
-        """Return the value type that is not hashable, if isKnowtoBeHashable() returns False."""
+        """Return the value type that is not hashable, if isKnownToBeHashable() returns False."""
 
         # Not available by default.
         return None
@@ -182,6 +182,11 @@ class ExpressionBase(NodeBase):
             not overload this unless necessary.
         """
 
+    @staticmethod
+    def undoComputeExpressionRaw(trace_collection):
+        # Virtual method
+        pass
+
     def computeExpressionAttribute(self, lookup_node, attribute_name, trace_collection):
         # By default, an attribute lookup may change everything about the lookup
         # source.

nuitka/nodes/ExpressionBasesGenerated.py

@@ -34,7 +34,6 @@ spell-checker: ignore winmode zfill
 
 # Loop unrolling over child names, pylint: disable=too-many-branches
 
-
 from abc import abstractmethod
 
 from .ExpressionBases import ExpressionBase
@@ -62,6 +61,17 @@ class NoChildHavingFinalNoRaiseMixin(ExpressionBase):
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -141,6 +151,17 @@ class NoChildHavingFinalNoRaiseNameMixin(ExpressionBase):
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -259,6 +280,17 @@ class ChildHavingArgsTupleFinalNoRaiseMixin(ExpressionBase):
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -442,6 +474,17 @@ class ChildrenHavingArgsTupleNameOptionalObjOptionalFinalNoRaiseForRaiseMixin(
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -644,6 +687,17 @@ class ChildrenHavingArgsTupleNameOptionalPathOptionalFinalNoRaiseForRaiseMixin(
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -796,6 +850,17 @@ class ChildrenHavingCallableArgSentinelFinalMixin(ExpressionBase):
         trace_collection.onExceptionRaiseExit(BaseException)
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     def collectVariableAccesses(self, emit_variable):
         """Collect variable reads and writes of child nodes."""
 
@@ -877,6 +942,17 @@ class ChildHavingDistributionNameFinalChildrenMixin(ExpressionBase):
         # Then ask ourselves to work on it.
         return self.computeExpression(trace_collection)
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @abstractmethod
     def computeExpression(self, trace_collection):
         """Must be overloaded for non-final node."""
@@ -999,6 +1075,17 @@ class ChildHavingElementsTupleFinalNoRaiseMixin(ExpressionBase):
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -1112,6 +1199,17 @@ class ChildHavingExpressionAttributeNameMixin(ExpressionBase):
         # Then ask ourselves to work on it.
         return self.computeExpression(trace_collection)
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @abstractmethod
     def computeExpression(self, trace_collection):
         """Must be overloaded for non-final node."""
@@ -1244,6 +1342,17 @@ class ChildrenHavingExpressionNameRaiseWaitConstantNameMixin(ExpressionBase):
         # Then ask ourselves to work on it.
         return self.computeExpression(trace_collection)
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @abstractmethod
     def computeExpression(self, trace_collection):
         """Must be overloaded for non-final node."""
@@ -1373,6 +1482,17 @@ class ChildHavingInterpolationsTupleStrValuesMixin(ExpressionBase):
         # Then ask ourselves to work on it.
         return self.computeExpression(trace_collection)
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @abstractmethod
     def computeExpression(self, trace_collection):
         """Must be overloaded for non-final node."""
@@ -1498,6 +1618,17 @@ class ChildrenHavingLeftRightFinalNoRaiseMixin(ExpressionBase):
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -1599,6 +1730,17 @@ class ChildHavingListArgNoRaiseMixin(ExpressionBase):
         # Then ask ourselves to work on it.
         return self.computeExpression(trace_collection)
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -1732,6 +1874,17 @@ class ChildrenHavingListArgItemNoRaiseMixin(ExpressionBase):
         # Then ask ourselves to work on it.
         return self.computeExpression(trace_collection)
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -1866,6 +2019,17 @@ class ChildrenHavingListArgValueFinalNoRaiseMixin(ExpressionBase):
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -1987,6 +2151,17 @@ class ChildHavingPairsTupleFinalNoRaiseMixin(ExpressionBase):
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -2107,6 +2282,17 @@ class ChildHavingPromptOptionalFinalMixin(ExpressionBase):
         trace_collection.onExceptionRaiseExit(BaseException)
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     def collectVariableAccesses(self, emit_variable):
         """Collect variable reads and writes of child nodes."""
 
@@ -2200,6 +2386,17 @@ class ChildHavingValueFinalNoRaiseMixin(ExpressionBase):
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @staticmethod
     def mayRaiseExceptionOperation():
         return False
@@ -2349,6 +2546,17 @@ class ChildrenHavingValueFormatSpecOptionalConversionStrValueMixin(ExpressionBas
         # Then ask ourselves to work on it.
         return self.computeExpression(trace_collection)
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
     @abstractmethod
     def computeExpression(self, trace_collection):
         """Must be overloaded for non-final node."""

nuitka/nodes/VariableRefNodes.py

@@ -557,6 +557,9 @@ Replaced read-only module attribute '__spec__' with module attribute reference."
 
         return self, None, None
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        self.variable_trace.removeUsage()
+
     def computeExpressionCall(self, call_node, call_args, call_kw, trace_collection):
         if self.variable_trace is not None:
             attribute_node = self.variable_trace.getAttributeNode()

nuitka/optimizations/ValueTraces.py

@@ -85,6 +85,9 @@ class ValueTraceBase(object):
     def addUsage(self):
         self.usage_count += 1
 
+    def removeUsage(self):
+        self.usage_count -= 1
+
     def addNameUsage(self):
         self.usage_count += 1
         self.name_usage_count += 1
@@ -92,10 +95,21 @@ class ValueTraceBase(object):
         if self.name_usage_count <= 2 and self.previous is not None:
             self.previous.addNameUsage()
 
+    def removeNameUsage(self):
+        self.usage_count -= 1
+        self.name_usage_count -= 1
+
+        if self.name_usage_count < 2 and self.previous is not None:
+            self.previous.removeNameUsage()
+
     def addMergeUsage(self):
         self.usage_count += 1
         self.merge_usage_count += 1
 
+    def removeMergeUsage(self):
+        self.usage_count -= 1
+        self.merge_usage_count -= 1
+
     def getUsageCount(self):
         return self.usage_count
 
@@ -283,14 +297,25 @@ class ValueTraceStartMixin(object):
     def addUsage(self):
         self.usage_count += 1
 
+    def removeUsage(self):
+        self.usage_count -= 1
+
     def addMergeUsage(self):
         self.usage_count += 1
         self.merge_usage_count += 1
 
+    def removeMergeUsage(self):
+        self.usage_count -= 1
+        self.merge_usage_count -= 1
+
     def addNameUsage(self):
         self.usage_count += 1
         self.name_usage_count += 1
 
+    def removeNameUsage(self):
+        self.usage_count -= 1
+        self.name_usage_count -= 1
+
     @staticmethod
     def getAttributeNode():
         return None
@@ -454,6 +479,12 @@ class ValueTraceUnknownBase(ValueTraceBase):
         if self.previous:
             self.previous.addUsage()
 
+    def removeUsage(self):
+        self.usage_count -= 1
+
+        if self.previous:
+            self.previous.removeUsage()
+
     def addMergeUsage(self):
         self.usage_count += 1
         self.merge_usage_count += 1
@@ -461,6 +492,13 @@ class ValueTraceUnknownBase(ValueTraceBase):
         if self.previous:
             self.previous.addMergeUsage()
 
+    def removeMergeUsage(self):
+        self.usage_count -= 1
+        self.merge_usage_count -= 1
+
+        if self.previous:
+            self.previous.removeMergeUsage()
+
     def compareValueTrace(self, other):
         # We are unknown, just need to know if the other one is, pylint: disable=no-self-use
         return other.isUnknownTrace()
@@ -542,6 +580,13 @@ class ValueTraceEscaped(ValueTraceUnknown):
         if self.usage_count <= 2:
             self.previous.addNameUsage()
 
+    def removeUsage(self):
+        self.usage_count -= 1
+
+        # The previous must be prevented from optimization if still used afterwards.
+        if self.usage_count < 2:
+            self.previous.removeNameUsage()
+
     def addMergeUsage(self):
         self.usage_count += 1
         if self.usage_count <= 2:
@@ -551,6 +596,15 @@ class ValueTraceEscaped(ValueTraceUnknown):
         if self.merge_usage_count <= 2:
             self.previous.addMergeUsage()
 
+    def removeMergeUsage(self):
+        self.usage_count -= 1
+        if self.usage_count < 2:
+            self.previous.removeNameUsage()
+
+        self.merge_usage_count -= 1
+        if self.merge_usage_count < 2:
+            self.previous.removeMergeUsage()
+
     def getTypeShape(self):
         return self.previous.getTypeShape()
 
@@ -766,6 +820,14 @@ class ValueTraceMergeBase(ValueTraceBase):
             for previous in self.previous:
                 previous.addNameUsage()
 
+    def removeNameUsage(self):
+        self.usage_count -= 1
+        self.name_usage_count -= 1
+
+        if self.name_usage_count < 2 and self.previous is not None:
+            for previous in self.previous:
+                previous.removeNameUsage()
+
     def addUsage(self):
         self.usage_count += 1
 
@@ -774,10 +836,22 @@ class ValueTraceMergeBase(ValueTraceBase):
             for trace in self.previous:
                 trace.addMergeUsage()
 
+    def removeUsage(self):
+        self.usage_count -= 1
+
+        # Only do it once.
+        if self.usage_count == 0:
+            for trace in self.previous:
+                trace.removeMergeUsage()
+
     def addMergeUsage(self):
         self.addUsage()
         self.merge_usage_count += 1
 
+    def removeMergeUsage(self):
+        self.removeUsage()
+        self.merge_usage_count -= 1
+
     def isUsingTrace(self):
         # Checking definite is enough, the merges, we shall see them as well.
         return self.usage_count

nuitka/tools/specialize/templates_python/ChildrenHavingMixin.py.j2

@@ -361,6 +361,17 @@ class {{mixin_name}}({{base_class}}):
         return self.computeExpression(trace_collection)
 {% endif %}
 
+    def undoComputeExpressionRaw(self, trace_collection):
+        for child in self.getVisitableNodes():
+            child.undoComputeExpressionRaw(trace_collection)
+
+        self.undoComputeExpression()
+
+    # For overload only
+    @staticmethod
+    def undoComputeExpression():
+        pass
+
 {% if raise_mode == "no_raise" %}
     @staticmethod
     def mayRaiseExceptionOperation():