gh-101632: Add the new RETURN_CONST opcode (#101633)

Author: penguin-wwy

Doc/library/dis.rst

@@ -694,6 +694,13 @@ iterations of the loop.
    Returns with ``STACK[-1]`` to the caller of the function.
 
 
+.. opcode:: RETURN_CONST (consti)
+
+   Returns with ``co_consts[consti]`` to the caller of the function.
+
+   .. versionadded:: 3.12
+
+
 .. opcode:: YIELD_VALUE
 
    Yields ``STACK.pop()`` from a :term:`generator`.

Include/internal/pycore_opcode.h

@@ -34,6 +34,7 @@
 MAKE_FUNCTION_FLAGS = ('defaults', 'kwdefaults', 'annotations', 'closure')
 
 LOAD_CONST = opmap['LOAD_CONST']
+RETURN_CONST = opmap['RETURN_CONST']
 LOAD_GLOBAL = opmap['LOAD_GLOBAL']
 BINARY_OP = opmap['BINARY_OP']
 JUMP_BACKWARD = opmap['JUMP_BACKWARD']
@@ -363,7 +364,7 @@ def _get_const_value(op, arg, co_consts):
     assert op in hasconst
 
     argval = UNKNOWN
-    if op == LOAD_CONST:
+    if op == LOAD_CONST or op == RETURN_CONST:
         if co_consts is not None:
             argval = co_consts[arg]
     return argval

Include/opcode.h

@@ -431,6 +431,7 @@ def _write_atomic(path, data, mode=0o666):
 #     Python 3.12a5 3515 (Embed jump mask in COMPARE_OP oparg)
 #     Python 3.12a5 3516 (Add COMPARE_AND_BRANCH instruction)
 #     Python 3.12a5 3517 (Change YIELD_VALUE oparg to exception block depth)
+#     Python 3.12a5 3518 (Add RETURN_CONST instruction)
 
 #     Python 3.13 will start with 3550
 
@@ -443,7 +444,7 @@ 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 = (3517).to_bytes(2, 'little') + b'\r\n'
+MAGIC_NUMBER = (3518).to_bytes(2, 'little') + b'\r\n'
 
 _RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little')  # For import.c
 

Lib/dis.py

@@ -164,6 +164,8 @@ def pseudo_op(name, op, real_ops):
 def_op('CONTAINS_OP', 118)
 def_op('RERAISE', 119)
 def_op('COPY', 120)
+def_op('RETURN_CONST', 121)
+hasconst.append(121)
 def_op('BINARY_OP', 122)
 jrel_op('SEND', 123) # Number of bytes to skip
 def_op('LOAD_FAST', 124)        # Local variable number, no null check

Lib/importlib/_bootstrap_external.py

@@ -1900,7 +1900,7 @@ def get_load_const(self, tree):
         co = compile(tree, '<string>', 'exec')
         consts = []
         for instr in dis.get_instructions(co):
-            if instr.opname == 'LOAD_CONST':
+            if instr.opname == 'LOAD_CONST' or instr.opname == 'RETURN_CONST':
                 consts.append(instr.argval)
         return consts
 

Lib/opcode.py

@@ -723,6 +723,7 @@ def f():
             pass
         PY_CODE_LOCATION_INFO_NO_COLUMNS = 13
         f.__code__ = f.__code__.replace(
+            co_stacksize=1,
             co_firstlineno=42,
             co_code=bytes(
                 [

Lib/test/test_ast.py

@@ -741,7 +741,7 @@ def unused_code_at_end():
         # RETURN_VALUE opcode.  This does not always crash an interpreter.
         # When you build with the clang memory sanitizer it reliably aborts.
         self.assertEqual(
-            'RETURN_VALUE',
+            'RETURN_CONST',
             list(dis.get_instructions(unused_code_at_end))[-1].opname)
 
     def test_dont_merge_constants(self):
@@ -822,10 +822,9 @@ def unused_block_while_else():
 
         for func in funcs:
             opcodes = list(dis.get_instructions(func))
-            self.assertLessEqual(len(opcodes), 4)
-            self.assertEqual('LOAD_CONST', opcodes[-2].opname)
-            self.assertEqual(None, opcodes[-2].argval)
-            self.assertEqual('RETURN_VALUE', opcodes[-1].opname)
+            self.assertLessEqual(len(opcodes), 3)
+            self.assertEqual('RETURN_CONST', opcodes[-1].opname)
+            self.assertEqual(None, opcodes[-1].argval)
 
     def test_false_while_loop(self):
         def break_in_while():
@@ -841,10 +840,9 @@ def continue_in_while():
         # Check that we did not raise but we also don't generate bytecode
         for func in funcs:
             opcodes = list(dis.get_instructions(func))
-            self.assertEqual(3, len(opcodes))
-            self.assertEqual('LOAD_CONST', opcodes[1].opname)
+            self.assertEqual(2, len(opcodes))
+            self.assertEqual('RETURN_CONST', opcodes[1].opname)
             self.assertEqual(None, opcodes[1].argval)
-            self.assertEqual('RETURN_VALUE', opcodes[2].opname)
 
     def test_consts_in_conditionals(self):
         def and_true(x):
@@ -1311,7 +1309,7 @@ def test_multiline_generator_expression(self):
             line=1, end_line=2, column=1, end_column=8, occurrence=1)
         self.assertOpcodeSourcePositionIs(compiled_code, 'JUMP_BACKWARD',
             line=1, end_line=2, column=1, end_column=8, occurrence=1)
-        self.assertOpcodeSourcePositionIs(compiled_code, 'RETURN_VALUE',
+        self.assertOpcodeSourcePositionIs(compiled_code, 'RETURN_CONST',
             line=1, end_line=6, column=0, end_column=32, occurrence=1)
 
     def test_multiline_async_generator_expression(self):
@@ -1328,7 +1326,7 @@ def test_multiline_async_generator_expression(self):
         self.assertIsInstance(compiled_code, types.CodeType)
         self.assertOpcodeSourcePositionIs(compiled_code, 'YIELD_VALUE',
             line=1, end_line=2, column=1, end_column=8, occurrence=2)
-        self.assertOpcodeSourcePositionIs(compiled_code, 'RETURN_VALUE',
+        self.assertOpcodeSourcePositionIs(compiled_code, 'RETURN_CONST',
             line=1, end_line=6, column=0, end_column=32, occurrence=1)
 
     def test_multiline_list_comprehension(self):