bpo-47120: Replace the JUMP_ABSOLUTE opcode by the relative JUMP_BACKWARD

Doc/library/dis.rst

@@ -895,6 +895,13 @@ iterations of the loop.
    Increments bytecode counter by *delta*.
 
 
+.. opcode:: JUMP_BACKWARD (delta)
+
+   Decrements bytecode counter by *delta*.
+
+   .. versionadded:: 3.11
+
+
 .. opcode:: POP_JUMP_IF_TRUE (target)
 
    If TOS is true, sets the bytecode counter to *target*.  TOS is popped.
@@ -974,11 +981,6 @@ iterations of the loop.
    .. versionadded:: 3.1
 
 
-.. opcode:: JUMP_ABSOLUTE (target)
-
-   Set bytecode counter to *target*.
-
-
 .. opcode:: JUMP_NO_INTERRUPT (target)
 
    Set bytecode counter to *target*. Do not check for interrupts.

Doc/whatsnew/3.11.rst

@@ -509,6 +509,7 @@ CPython bytecode changes
 
 * :opcode:`JUMP_IF_NOT_EXC_MATCH` no longer pops the active exception.
 
+* Replaced :opcode:`JUMP_ABSOLUTE` by the relative :opcode:`JUMP_BACKWARD`.
 
 Deprecated
 ==========

Lib/dis.py

@@ -30,6 +30,7 @@
 LOAD_CONST = opmap['LOAD_CONST']
 LOAD_GLOBAL = opmap['LOAD_GLOBAL']
 BINARY_OP = opmap['BINARY_OP']
+JUMP_BACKWARD = opmap['JUMP_BACKWARD']
 
 CACHE = opmap["CACHE"]
 
@@ -441,7 +442,8 @@ def _get_instructions_bytes(code, varname_from_oparg=None,
                 argval = arg*2
                 argrepr = "to " + repr(argval)
             elif op in hasjrel:
-                argval = offset + 2 + arg*2
+                signed_arg = -arg if op == JUMP_BACKWARD else arg
+                argval = offset + 2 + signed_arg*2
                 argrepr = "to " + repr(argval)
             elif op in haslocal or op in hasfree:
                 argval, argrepr = _get_name_info(arg, varname_from_oparg)
@@ -566,6 +568,8 @@ def findlabels(code):
     for offset, op, arg in _unpack_opargs(code):
         if arg is not None:
             if op in hasjrel:
+                if op == JUMP_BACKWARD:
+                    arg = -arg
                 label = offset + 2 + arg*2
             elif op in hasjabs:
                 label = arg*2

Lib/importlib/_bootstrap_external.py

@@ -396,6 +396,7 @@ def _write_atomic(path, data, mode=0o666):
 #     Python 3.11a6 3486 (Use inline caching for PRECALL and CALL)
 #     Python 3.11a6 3487 (Remove the adaptive "oparg counter" mechanism)
 #     Python 3.11a6 3488 (LOAD_GLOBAL can push additional NULL)
+#     Python 3.11a6 3489 (Add JUMP_BACK)
 
 #     Python 3.12 will start with magic number 3500
 
@@ -410,7 +411,7 @@ def _write_atomic(path, data, mode=0o666):
 # Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
 # in PC/launcher.c must also be updated.
 
-MAGIC_NUMBER = (3488).to_bytes(2, 'little') + b'\r\n'
+MAGIC_NUMBER = (3489).to_bytes(2, 'little') + b'\r\n'
 _RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little')  # For import.c
 
 _PYCACHE = '__pycache__'

Lib/opcode.py

@@ -128,10 +128,9 @@ def jabs_op(name, op, entries=0):
 hascompare.append(107)
 name_op('IMPORT_NAME', 108)     # Index in name list
 name_op('IMPORT_FROM', 109)     # Index in name list
-jrel_op('JUMP_FORWARD', 110)    # Number of bytes to skip
+jrel_op('JUMP_FORWARD', 110)    # Number of words to skip
 jabs_op('JUMP_IF_FALSE_OR_POP', 111) # Target byte offset from beginning of code
 jabs_op('JUMP_IF_TRUE_OR_POP', 112)  # ""
-jabs_op('JUMP_ABSOLUTE', 113)        # ""
 jabs_op('POP_JUMP_IF_FALSE', 114)    # ""
 jabs_op('POP_JUMP_IF_TRUE', 115)     # ""
 name_op('LOAD_GLOBAL', 116, 5)     # Index in name list
@@ -166,6 +165,7 @@ def jabs_op(name, op, entries=0):
 hasfree.append(138)
 def_op('DELETE_DEREF', 139)
 hasfree.append(139)
+jrel_op('JUMP_BACKWARD', 140)    # Number of words to skip (backwards)
 
 def_op('CALL_FUNCTION_EX', 142)  # Flags
 
@@ -259,9 +259,6 @@ def jabs_op(name, op, entries=0):
         "COMPARE_OP_INT_JUMP",
         "COMPARE_OP_STR_JUMP",
     ],
-    "JUMP_ABSOLUTE": [
-        "JUMP_ABSOLUTE_QUICK",
-    ],
     "LOAD_ATTR": [
         "LOAD_ATTR_ADAPTIVE",
         "LOAD_ATTR_INSTANCE_VALUE",

Lib/test/test_dis.py

@@ -149,7 +149,7 @@ def bug708901():
         >> FOR_ITER                 2 (to 40)
            STORE_FAST               0 (res)
 
-%3d        JUMP_ABSOLUTE           17 (to 34)
+%3d        JUMP_BACKWARD            3 (to 34)
 
 %3d     >> LOAD_CONST               0 (None)
            RETURN_VALUE
@@ -354,7 +354,7 @@ def bug42562():
            BINARY_OP               13 (+=)
            STORE_NAME               0 (x)
 
-  2        JUMP_ABSOLUTE            4 (to 8)
+  2        JUMP_BACKWARD            6 (to 8)
 """
 
 dis_traceback = """\
@@ -574,7 +574,7 @@ def foo(x):
            LOAD_FAST                1 (z)
            BINARY_OP                0 (+)
            LIST_APPEND              2
-           JUMP_ABSOLUTE            4 (to 8)
+           JUMP_BACKWARD            8 (to 8)
         >> RETURN_VALUE
 """ % (dis_nested_1,
        __file__,
@@ -1227,14 +1227,14 @@ def _prepare_test_cases():
   Instruction(opname='LOAD_CONST', opcode=100, arg=2, argval=4, argrepr='4', offset=68, starts_line=None, is_jump_target=False, positions=None),
   Instruction(opname='COMPARE_OP', opcode=107, arg=0, argval='<', argrepr='<', offset=70, starts_line=None, is_jump_target=False, positions=None),
   Instruction(opname='POP_JUMP_IF_FALSE', opcode=114, arg=40, argval=80, argrepr='to 80', offset=76, starts_line=None, is_jump_target=False, positions=None),
-  Instruction(opname='JUMP_ABSOLUTE', opcode=113, arg=16, argval=32, argrepr='to 32', offset=78, starts_line=6, is_jump_target=False, positions=None),
+  Instruction(opname='JUMP_BACKWARD', opcode=140, arg=24, argval=32, argrepr='to 32', offset=78, starts_line=6, is_jump_target=False, positions=None),
   Instruction(opname='LOAD_FAST', opcode=124, arg=0, argval='i', argrepr='i', offset=80, starts_line=7, is_jump_target=True, positions=None),
   Instruction(opname='LOAD_CONST', opcode=100, arg=3, argval=6, argrepr='6', offset=82, starts_line=None, is_jump_target=False, positions=None),
   Instruction(opname='COMPARE_OP', opcode=107, arg=4, argval='>', argrepr='>', offset=84, starts_line=None, is_jump_target=False, positions=None),
   Instruction(opname='POP_JUMP_IF_FALSE', opcode=114, arg=48, argval=96, argrepr='to 96', offset=90, starts_line=None, is_jump_target=False, positions=None),
   Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=92, starts_line=8, is_jump_target=False, positions=None),
   Instruction(opname='JUMP_FORWARD', opcode=110, arg=16, argval=128, argrepr='to 128', offset=94, starts_line=None, is_jump_target=False, positions=None),
-  Instruction(opname='JUMP_ABSOLUTE', opcode=113, arg=16, argval=32, argrepr='to 32', offset=96, starts_line=7, is_jump_target=True, positions=None),
+  Instruction(opname='JUMP_BACKWARD', opcode=140, arg=33, argval=32, argrepr='to 32', offset=96, starts_line=7, is_jump_target=True, positions=None),
   Instruction(opname='LOAD_GLOBAL', opcode=116, arg=3, argval='print', argrepr='NULL + print', offset=98, starts_line=10, is_jump_target=True, positions=None),
   Instruction(opname='LOAD_CONST', opcode=100, arg=4, argval='I can haz else clause?', argrepr="'I can haz else clause?'", offset=110, starts_line=None, is_jump_target=False, positions=None),
   Instruction(opname='PRECALL', opcode=166, arg=1, argval=1, argrepr='', offset=112, starts_line=None, is_jump_target=False, positions=None),
@@ -1255,7 +1255,7 @@ def _prepare_test_cases():
   Instruction(opname='LOAD_CONST', opcode=100, arg=3, argval=6, argrepr='6', offset=174, starts_line=None, is_jump_target=False, positions=None),
   Instruction(opname='COMPARE_OP', opcode=107, arg=4, argval='>', argrepr='>', offset=176, starts_line=None, is_jump_target=False, positions=None),
   Instruction(opname='POP_JUMP_IF_FALSE', opcode=114, arg=93, argval=186, argrepr='to 186', offset=182, starts_line=None, is_jump_target=False, positions=None),
-  Instruction(opname='JUMP_ABSOLUTE', opcode=113, arg=64, argval=128, argrepr='to 128', offset=184, starts_line=15, is_jump_target=False, positions=None),
+  Instruction(opname='JUMP_BACKWARD', opcode=140, arg=29, argval=128, argrepr='to 128', offset=184, starts_line=15, is_jump_target=False, positions=None),
   Instruction(opname='LOAD_FAST', opcode=124, arg=0, argval='i', argrepr='i', offset=186, starts_line=16, is_jump_target=True, positions=None),
   Instruction(opname='LOAD_CONST', opcode=100, arg=2, argval=4, argrepr='4', offset=188, starts_line=None, is_jump_target=False, positions=None),
   Instruction(opname='COMPARE_OP', opcode=107, arg=0, argval='<', argrepr='<', offset=190, starts_line=None, is_jump_target=False, positions=None),

Lib/test/test_peepholer.py

@@ -127,7 +127,7 @@ def f():
             return list
         for elem in ('LOAD_CONST', 'POP_JUMP_IF_FALSE'):
             self.assertNotInBytecode(f, elem)
-        for elem in ('JUMP_ABSOLUTE',):
+        for elem in ('JUMP_BACKWARD',):
             self.assertInBytecode(f, elem)
         self.check_lnotab(f)
 

Misc/NEWS.d/next/Core and Builtins/2022-03-25-21-51-10.bpo-47120.9YJ-Xw.rst

@@ -0,0 +1,2 @@
+Replaced :opcode:`JUMP_ABSOLUTE` by the relative jump :opcode:`JUMP_BACKWARD`.
+

Objects/frameobject.c

@@ -237,7 +237,6 @@ mark_stacks(PyCodeObject *code_obj, int len)
                     stacks[i+1] = next_stack;
                     break;
                 }
-                case JUMP_ABSOLUTE:
                 case JUMP_NO_INTERRUPT:
                     j = get_arg(code, i);
                     assert(j < len);
@@ -264,6 +263,12 @@ mark_stacks(PyCodeObject *code_obj, int len)
                     assert(stacks[j] == UNINITIALIZED || stacks[j] == next_stack);
                     stacks[j] = next_stack;
                     break;
+                case JUMP_BACKWARD:
+                    j = i + 1 - get_arg(code, i);
+                    assert(j >= 0);
+                    assert(stacks[j] == UNINITIALIZED || stacks[j] == next_stack);
+                    stacks[j] = next_stack;
+                    break;
                 case GET_ITER:
                 case GET_AITER:
                     next_stack = push_value(pop_value(next_stack), Iterator);