GH-132554: "Virtual" iterators (GH-132555)

* FOR_ITER now pushes either the iterator and NULL or leaves the iterable and pushes tagged zero

* NEXT_ITER uses the tagged int as the index into the sequence or, if TOS is NULL, iterates as before.

Tools/cases_generator/analyzer.py

@@ -679,8 +679,11 @@ NON_ESCAPING_FUNCTIONS = (
     "PyStackRef_IsTaggedInt",
     "PyStackRef_TagInt",
     "PyStackRef_UntagInt",
+    "PyStackRef_IncrementTaggedIntNoOverflow",
+    "PyStackRef_IsNullOrInt",
 )
 
+
 def check_escaping_calls(instr: parser.CodeDef, escapes: dict[SimpleStmt, EscapingCall]) -> None:
     error: lexer.Token | None = None
     calls = {e.call for e in escapes.values()}

Tools/cases_generator/generators_common.py

@@ -140,6 +140,7 @@ class Emitter:
     ) -> bool:
         if storage.spilled:
             raise analysis_error("stack_pointer needs reloading before dispatch", tkn)
+        storage.stack.flush(self.out)
         self.emit(tkn)
         return False