Handle PUSH_EXC_INFO correctly

It leaves the TOS in place.

Author: mpage

Lib/test/test_peepholer.py

@@ -2681,6 +2681,13 @@ def test_get_yield_from_iter(self):
         ]
         self.cfg_optimization_test(insts, insts, consts=[None])
 
+    def test_push_exc_info(self):
+        insts = [
+            ("LOAD_FAST", 0, 1),
+            ("PUSH_EXC_INFO", None, 2),
+        ]
+        self.check(insts, insts)
+
     def test_del_in_finally(self):
         # This loads `obj` onto the stack, executes `del obj`, then returns the
         # `obj` from the stack. See gh-133371 for more details.

Python/flowgraph.c

@@ -2948,6 +2948,13 @@ optimize_load_fast(cfg_builder *g)
                     break;
                 }
 
+                case PUSH_EXC_INFO: {
+                    ref tos = ref_stack_pop(&refs);
+                    PUSH_REF(i, NOT_LOCAL);
+                    PUSH_REF(tos.instr, tos.local);
+                    break;
+                }
+
                 case SEND: {
                     load_fast_push_block(&sp, instr->i_target, refs.size);
                     ref_stack_pop(&refs);