pythongh-138679: Opcodes which consume no inputs should indicate they produced the val… (python#138678)

Opcodes which consume no inputs should indicate they produced the value, not an arbitrary local

Author: DinoV

Lib/test/test_peepholer.py

@@ -1116,6 +1116,13 @@ def trace(frame, event, arg):
         self.assertInBytecode(f, "LOAD_FAST_BORROW")
         self.assertNotInBytecode(f, "LOAD_FAST_CHECK")
 
+    def test_import_from_doesnt_clobber_load_fast_borrow(self):
+        def f(self):
+            if x: pass
+            self.x
+            from shutil import ExecError
+            print(ExecError)
+        self.assertInBytecode(f, "LOAD_FAST_BORROW", "self")
 
 class DirectCfgOptimizerTests(CfgOptimizationTestCase):
 

Python/flowgraph.c

@@ -2891,7 +2891,7 @@ optimize_load_fast(cfg_builder *g)
                     int num_pushed = _PyOpcode_num_pushed(opcode, oparg);
                     int net_pushed = num_pushed - num_popped;
                     assert(net_pushed >= 0);
-                    for (int i = 0; i < net_pushed; i++) {
+                    for (int j = 0; j < net_pushed; j++) {
                         PUSH_REF(i, NOT_LOCAL);
                     }
                     break;