gh-145749: Optimize named exception blocks

Author: brijkapadia

Lib/test/test_dis.py

@@ -469,24 +469,22 @@ def foo(a: int, b: str) -> str:
 
 %4d            LOAD_GLOBAL              0 (Exception)
                 CHECK_EXC_MATCH
-                POP_JUMP_IF_FALSE       24 (to L9)
+                POP_JUMP_IF_FALSE       22 (to L9)
         L4:     NOT_TAKEN
         L5:     STORE_FAST               0 (e)
 
 %4d    L6:     LOAD_FAST                0 (e)
                 LOAD_ATTR                2 (__traceback__)
                 STORE_FAST               1 (tb)
         L7:     POP_EXCEPT
-                LOAD_CONST               1 (None)
+                PUSH_NULL
                 STORE_FAST               0 (e)
-                DELETE_FAST              0 (e)
 
 %4d            LOAD_FAST                1 (tb)
                 RETURN_VALUE
 
-  --    L8:     LOAD_CONST               1 (None)
+  --    L8:     PUSH_NULL
                 STORE_FAST               0 (e)
-                DELETE_FAST              0 (e)
                 RERAISE                  1
 
 %4d    L9:     RERAISE                  0

Python/codegen.c

@@ -2526,7 +2526,7 @@ codegen_try_except(compiler *c, stmt_ty s)
                   try:
                       # body
                   finally:
-                      name = None # in case body contains "del name"
+                      name = <NULL> # in case body contains "del name"
                       del name
             */
 
@@ -2541,26 +2541,22 @@ codegen_try_except(compiler *c, stmt_ty s)
             /* second # body */
             VISIT_SEQ(c, stmt, handler->v.ExceptHandler.body);
             _PyCompile_PopFBlock(c, COMPILE_FBLOCK_HANDLER_CLEANUP, cleanup_body);
-            /* name = None; del name; # Mark as artificial */
+            /* name = <NULL>; del name; # Mark as artificial */
             ADDOP(c, NO_LOCATION, POP_BLOCK);
             ADDOP(c, NO_LOCATION, POP_BLOCK);
             ADDOP(c, NO_LOCATION, POP_EXCEPT);
-            ADDOP_LOAD_CONST(c, NO_LOCATION, Py_None);
+            ADDOP(c, NO_LOCATION, PUSH_NULL);
             RETURN_IF_ERROR(
                 codegen_nameop(c, NO_LOCATION, handler->v.ExceptHandler.name, Store));
-            RETURN_IF_ERROR(
-                codegen_nameop(c, NO_LOCATION, handler->v.ExceptHandler.name, Del));
             ADDOP_JUMP(c, NO_LOCATION, JUMP_NO_INTERRUPT, end);
 
             /* except: */
             USE_LABEL(c, cleanup_end);
 
-            /* name = None; del name; # artificial */
-            ADDOP_LOAD_CONST(c, NO_LOCATION, Py_None);
+            /* name = <NULL>; del name; # artificial */
+            ADDOP(c, NO_LOCATION, PUSH_NULL);
             RETURN_IF_ERROR(
                 codegen_nameop(c, NO_LOCATION, handler->v.ExceptHandler.name, Store));
-            RETURN_IF_ERROR(
-                codegen_nameop(c, NO_LOCATION, handler->v.ExceptHandler.name, Del));
 
             ADDOP_I(c, NO_LOCATION, RERAISE, 1);
         }
@@ -2725,7 +2721,7 @@ codegen_try_star_except(compiler *c, stmt_ty s)
               try:
                   # body
               finally:
-                  name = None # in case body contains "del name"
+                  name = <NULL> # in case body contains "del name"
                   del name
         */
         /* second try: */
@@ -2739,27 +2735,23 @@ codegen_try_star_except(compiler *c, stmt_ty s)
         /* second # body */
         VISIT_SEQ(c, stmt, handler->v.ExceptHandler.body);
         _PyCompile_PopFBlock(c, COMPILE_FBLOCK_HANDLER_CLEANUP, cleanup_body);
-        /* name = None; del name; # artificial */
+        /* name = <NULL>; del name; # artificial */
         ADDOP(c, NO_LOCATION, POP_BLOCK);
         if (handler->v.ExceptHandler.name) {
-            ADDOP_LOAD_CONST(c, NO_LOCATION, Py_None);
+            ADDOP(c, NO_LOCATION, PUSH_NULL);
             RETURN_IF_ERROR(
                 codegen_nameop(c, NO_LOCATION, handler->v.ExceptHandler.name, Store));
-            RETURN_IF_ERROR(
-                codegen_nameop(c, NO_LOCATION, handler->v.ExceptHandler.name, Del));
         }
         ADDOP_JUMP(c, NO_LOCATION, JUMP_NO_INTERRUPT, except);
 
         /* except: */
         USE_LABEL(c, cleanup_end);
 
-        /* name = None; del name; # artificial */
+        /* name = <NULL>; del name; # artificial */
         if (handler->v.ExceptHandler.name) {
-            ADDOP_LOAD_CONST(c, NO_LOCATION, Py_None);
+            ADDOP(c, NO_LOCATION, PUSH_NULL);
             RETURN_IF_ERROR(
                 codegen_nameop(c, NO_LOCATION, handler->v.ExceptHandler.name, Store));
-            RETURN_IF_ERROR(
-                codegen_nameop(c, NO_LOCATION, handler->v.ExceptHandler.name, Del));
         }
 
         /* add exception raised to the res list */