create yield labels purely during code generation instead of counting them upfront

Cython/Compiler/Code.py

@@ -505,6 +505,7 @@ class FunctionState(object):
         self.new_error_label()
         self.continue_label = None
         self.break_label = None
+        self.yield_labels = []
 
         self.in_try_finally = 0
         self.exc_vars = None
@@ -537,6 +538,12 @@ class FunctionState(object):
             label += '_' + name
         return label
 
+    def new_yield_label(self):
+        label = self.new_label('resume_from_yield')
+        num_and_label = (len(self.yield_labels) + 1, label)
+        self.yield_labels.append(num_and_label)
+        return num_and_label
+
     def new_error_label(self):
         old_err_lbl = self.error_label
         self.error_label = self.new_label('error')
@@ -1474,10 +1481,12 @@ class CCodeWriter(object):
     continue_label = funccontext_property("continue_label")
     break_label = funccontext_property("break_label")
     return_from_error_cleanup_label = funccontext_property("return_from_error_cleanup_label")
+    yield_labels = funccontext_property("yield_labels")
 
     # Functions delegated to function scope
     def new_label(self, name=None):    return self.funcstate.new_label(name)
     def new_error_label(self):         return self.funcstate.new_error_label()
+    def new_yield_label(self):         return self.funcstate.new_yield_label()
     def get_loop_labels(self):         return self.funcstate.get_loop_labels()
     def set_loop_labels(self, labels): return self.funcstate.set_loop_labels(labels)
     def new_loop_labels(self):         return self.funcstate.new_loop_labels()

Cython/Compiler/ExprNodes.py

@@ -7750,7 +7750,6 @@ class YieldExprNode(ExprNode):
     # Yield expression node
     #
     # arg         ExprNode   the value to return from the generator
-    # label_name  string     name of the C label used for this yield
     # label_num   integer    yield label number
     # is_yield_from  boolean is a YieldFromExprNode to delegate to another generator
 
@@ -7791,8 +7790,8 @@ class YieldExprNode(ExprNode):
         Generate the code to return the argument in 'Naming.retval_cname'
         and to continue at the yield label.
         """
-        self.label_name = code.new_label('resume_from_yield')
-        code.use_label(self.label_name)
+        label_num, label_name = code.new_yield_label()
+        code.use_label(label_name)
 
         saved = []
         code.funcstate.closure_temps.reset()
@@ -7807,10 +7806,10 @@ class YieldExprNode(ExprNode):
         code.put_finish_refcount_context()
         code.putln("/* return from generator, yielding value */")
         code.putln("%s->resume_label = %d;" % (
-            Naming.generator_cname, self.label_num))
+            Naming.generator_cname, label_num))
         code.putln("return %s;" % Naming.retval_cname)
 
-        code.put_label(self.label_name)
+        code.put_label(label_name)
         for cname, save_cname, type in saved:
             code.putln('%s = %s->%s;' % (cname, Naming.cur_scope_cname, save_cname))
             if type.is_pyobject:

Cython/Compiler/Nodes.py

@@ -3828,12 +3828,8 @@ class GeneratorBodyDefNode(DefNode):
                        Naming.generator_cname))
         resume_code.putln("case 0: goto %s;" % first_run_label)
 
-        from ParseTreeTransforms import YieldNodeCollector
-        collector = YieldNodeCollector()
-        collector.visitchildren(self)
-        for yield_expr in collector.yields:
-            resume_code.putln("case %d: goto %s;" % (
-                yield_expr.label_num, yield_expr.label_name))
+        for i, label in code.yield_labels:
+            resume_code.putln("case %d: goto %s;" % (i, label))
         resume_code.putln("default: /* CPython raises the right error here */")
         resume_code.put_finish_refcount_context()
         resume_code.putln("return NULL;")