[itertools] Implement itertools.cycle with a polyfill (#159102)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/159102
Approved by: https://github.com/guilhermeleobas, https://github.com/zou3519
ghstack dependencies: #158774

torch/_dynamo/variables/iter.py

@@ -17,7 +17,7 @@ handling of iterator operations during code transformation and optimization.
 
 import itertools
 import sys
-from typing import Optional, TYPE_CHECKING, Union
+from typing import TYPE_CHECKING, Union
 
 from .. import graph_break_hints, polyfills, variables
 from ..bytecode_transformation import create_call_function, create_instruction
@@ -180,10 +180,6 @@ class ItertoolsVariable(VariableTracker):
             return variables.CountIteratorVariable(
                 *args, mutation_type=ValueMutationNew()
             )
-        elif self.value is itertools.cycle:
-            return variables.CycleIteratorVariable(
-                *args, mutation_type=ValueMutationNew()
-            )
         else:
             return super().call_function(tx, args, kwargs)
 
@@ -308,54 +304,6 @@ class CountIteratorVariable(IteratorVariable):
         codegen.extend_output(create_call_function(2, False))
 
 
-class CycleIteratorVariable(IteratorVariable):
-    def __init__(
-        self,
-        iterator: IteratorVariable,
-        saved: Optional[list[VariableTracker]] = None,
-        saved_index: int = 0,
-        item: Optional[VariableTracker] = None,
-        **kwargs,
-    ) -> None:
-        if saved is None:
-            saved = []
-        super().__init__(**kwargs)
-        self.iterator = iterator
-        self.saved = saved
-        self.saved_index = saved_index
-        self.item = item
-
-    def next_variable(self, tx):
-        assert self.is_mutable()
-
-        if self.iterator is not None:
-            try:
-                new_item = self.iterator.next_variable(tx)
-                if len(self.saved) > MAX_ITERATOR_LIMIT:
-                    unimplemented_v2(
-                        gb_type="input iterator to itertools.cycle has too many items",
-                        context=f"next({self})",
-                        explanation=f"Has reached internal Dynamo max iterator limit: {MAX_ITERATOR_LIMIT}",
-                        hints=[],
-                    )
-                tx.output.side_effects.mutation(self)
-                self.saved.append(new_item)
-                self.item = new_item
-                if self.item is None:
-                    return self.next_variable(tx)
-                return self.item
-            except ObservedUserStopIteration:
-                handle_observed_exception(tx)
-                self.iterator = None
-                return self.next_variable(tx)
-        elif len(self.saved) > 0:
-            tx.output.side_effects.mutation(self)
-            self.saved_index = (self.saved_index + 1) % len(self.saved)
-            return self.item
-        else:
-            raise_observed_exception(StopIteration, tx)
-
-
 class ZipVariable(IteratorVariable):
     """
     Represents zip(*iterables)