gh-91276: Make JUMP_IF_TRUE_OR_POP/JUMP_IF_FALSE_OR_POP relative (GH-32215)

iritkatriel · web-flow · commit ea2ae026078b · 2022-04-15T20:19:24.000+01:00
diff --git a/Doc/library/dis.rst b/Doc/library/dis.rst
@@ -993,21 +993,26 @@ iterations of the loop.
    .. versionadded:: 3.11
 
 
-.. opcode:: JUMP_IF_TRUE_OR_POP (target)
+.. opcode:: JUMP_IF_TRUE_OR_POP (delta)
 
-   If TOS is true, sets the bytecode counter to *target* and leaves TOS on the
+   If TOS is true, increments the bytecode counter by *delta* and leaves TOS on the
    stack.  Otherwise (TOS is false), TOS is popped.
 
    .. versionadded:: 3.1
 
+   .. versionchanged:: 3.11
+      The oparg is now a relative delta rather than an absolute target.
 
-.. opcode:: JUMP_IF_FALSE_OR_POP (target)
+.. opcode:: JUMP_IF_FALSE_OR_POP (delta)
 
-   If TOS is false, sets the bytecode counter to *target* and leaves TOS on the
+   If TOS is false, increments the bytecode counter by *delta* and leaves TOS on the
    stack.  Otherwise (TOS is true), TOS is popped.
 
    .. versionadded:: 3.1
 
+   .. versionchanged:: 3.11
+      The oparg is now a relative delta rather than an absolute target.
+
 
 .. opcode:: FOR_ITER (delta)
 
diff --git a/Doc/whatsnew/3.11.rst b/Doc/whatsnew/3.11.rst
@@ -787,6 +787,9 @@ CPython bytecode changes
   :opcode:`POP_JUMP_FORWARD_IF_NONE` and :opcode:`POP_JUMP_BACKWARD_IF_NONE`
   opcodes to speed up conditional jumps.
 
+* :opcode:`JUMP_IF_TRUE_OR_POP` and :opcode:`JUMP_IF_FALSE_OR_POP` are now
+  relative rather than absolute.
+
 
 Deprecated
 ==========
diff --git a/Include/opcode.h b/Include/opcode.h
diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
@@ -401,6 +401,7 @@ def _write_atomic(path, data, mode=0o666):
 #     Python 3.11a6 3491 (remove JUMP_IF_NOT_EG_MATCH, add CHECK_EG_MATCH,
 #                         add JUMP_BACKWARD_NO_INTERRUPT, make JUMP_NO_INTERRUPT virtual)
 #     Python 3.11a7 3492 (make POP_JUMP_IF_NONE/NOT_NONE/TRUE/FALSE relative)
+#     Python 3.11a7 3493 (Make JUMP_IF_TRUE_OR_POP/JUMP_IF_FALSE_OR_POP relative)
 
 #     Python 3.12 will start with magic number 3500
 
@@ -415,7 +416,8 @@ 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 = (3492).to_bytes(2, 'little') + b'\r\n'
+MAGIC_NUMBER = (3493).to_bytes(2, 'little') + b'\r\n'
+
 _RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little')  # For import.c
 
 _PYCACHE = '__pycache__'
diff --git a/Lib/opcode.py b/Lib/opcode.py
@@ -131,8 +131,8 @@ def jabs_op(name, op, entries=0):
 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 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)  # ""
+jrel_op('JUMP_IF_FALSE_OR_POP', 111) # Number of words to skip
+jrel_op('JUMP_IF_TRUE_OR_POP', 112)  # ""
 jrel_op('POP_JUMP_FORWARD_IF_FALSE', 114)
 jrel_op('POP_JUMP_FORWARD_IF_TRUE', 115)
 name_op('LOAD_GLOBAL', 116, 5)     # Index in name list
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-03-31-14-33-48.bpo-47120.6S_uoU.rst b/Misc/NEWS.d/next/Core and Builtins/2022-03-31-14-33-48.bpo-47120.6S_uoU.rst
@@ -0,0 +1 @@
+Make opcodes :opcode:`JUMP_IF_TRUE_OR_POP` and :opcode:`JUMP_IF_FALSE_OR_POP` relative rather than absolute.
diff --git a/Python/ceval.c b/Python/ceval.c
@@ -4081,7 +4081,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
                 DISPATCH();
             }
             if (Py_IsFalse(cond)) {
-                JUMPTO(oparg);
+                JUMPBY(oparg);
                 DISPATCH();
             }
             err = PyObject_IsTrue(cond);
@@ -4090,7 +4090,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
                 Py_DECREF(cond);
             }
             else if (err == 0)
-                JUMPTO(oparg);
+                JUMPBY(oparg);
             else
                 goto error;
             DISPATCH();
@@ -4105,12 +4105,12 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
                 DISPATCH();
             }
             if (Py_IsTrue(cond)) {
-                JUMPTO(oparg);
+                JUMPBY(oparg);
                 DISPATCH();
             }
             err = PyObject_IsTrue(cond);
             if (err > 0) {
-                JUMPTO(oparg);
+                JUMPBY(oparg);
             }
             else if (err == 0) {
                 STACK_SHRINK(1);
diff --git a/Python/compile.c b/Python/compile.c
@@ -7672,6 +7672,21 @@ normalize_jumps(struct assembler *a)
                     last->i_opcode = is_forward ?
                         POP_JUMP_FORWARD_IF_TRUE : POP_JUMP_BACKWARD_IF_TRUE;
                     break;
+                case JUMP_IF_TRUE_OR_POP:
+                case JUMP_IF_FALSE_OR_POP:
+                    if (!is_forward) {
+                        /* As far as we can tell, the compiler never emits
+                         * these jumps with a backwards target. If/when this
+                         * exception is raised, we have found a use case for
+                         * a backwards version of this jump (or to replace
+                         * it with the sequence (COPY 1, POP_JUMP_IF_T/F, POP)
+                         */
+                        PyErr_Format(PyExc_SystemError,
+                            "unexpected %s jumping backwards",
+                            last->i_opcode == JUMP_IF_TRUE_OR_POP ?
+                                "JUMP_IF_TRUE_OR_POP" : "JUMP_IF_FALSE_OR_POP");
+                    }
+                    break;
             }
         }
     }

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	+Make opcodes :opcode:`JUMP_IF_TRUE_OR_POP` and :opcode:`JUMP_IF_FALSE_OR_POP` relative rather than absolute.
Original file line number	Diff line number	Diff line change
`@@ -4081,7 +4081,7 @@ _PyEval_EvalFrameDefault(PyThreadState tstate, _PyInterpreterFrame frame, int`
`4081`	`4081`	`DISPATCH();`
`4082`	`4082`	`}`
`4083`	`4083`	`if (Py_IsFalse(cond)) {`
`4084`		`- JUMPTO(oparg);`
	`4084`	`+ JUMPBY(oparg);`
`4085`	`4085`	`DISPATCH();`
`4086`	`4086`	`}`
`4087`	`4087`	`err = PyObject_IsTrue(cond);`
`@@ -4090,7 +4090,7 @@ _PyEval_EvalFrameDefault(PyThreadState tstate, _PyInterpreterFrame frame, int`
`4090`	`4090`	`Py_DECREF(cond);`
`4091`	`4091`	`}`
`4092`	`4092`	`else if (err == 0)`
`4093`		`- JUMPTO(oparg);`
	`4093`	`+ JUMPBY(oparg);`
`4094`	`4094`	`else`
`4095`	`4095`	`goto error;`
`4096`	`4096`	`DISPATCH();`
`@@ -4105,12 +4105,12 @@ _PyEval_EvalFrameDefault(PyThreadState tstate, _PyInterpreterFrame frame, int`
`4105`	`4105`	`DISPATCH();`
`4106`	`4106`	`}`
`4107`	`4107`	`if (Py_IsTrue(cond)) {`
`4108`		`- JUMPTO(oparg);`
	`4108`	`+ JUMPBY(oparg);`
`4109`	`4109`	`DISPATCH();`
`4110`	`4110`	`}`
`4111`	`4111`	`err = PyObject_IsTrue(cond);`
`4112`	`4112`	`if (err > 0) {`
`4113`		`- JUMPTO(oparg);`
	`4113`	`+ JUMPBY(oparg);`
`4114`	`4114`	`}`
`4115`	`4115`	`else if (err == 0) {`
`4116`	`4116`	`STACK_SHRINK(1);`