python
diff --git a/Doc/c-api/init_config.rst b/Doc/c-api/init_config.rst
@@ -553,6 +553,14 @@ PyConfig
       by the function computing the :ref:`Path Configuration
       <init-path-config>`.
 
+   .. c:member:: int optimize
+
+      Should the compiler optimize bytecode? If equal to 0, disable the
+      compiler optimizations and set :c:member:`~PyConfig.optimization_level`
+      to 0. Set to 0 by :option:`-X noopt <-X>` command line option.
+
+      .. versionadded:: 3.9
+
    .. c:member:: int optimization_level
 
       Compilation optimization level:

diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
@@ -227,7 +227,7 @@ are always available.  They are listed here in alphabetical order.
    For more information on class methods, see :ref:`types`.
 
 
-.. function:: compile(source, filename, mode, flags=0, dont_inherit=False, optimize=-1)
+.. function:: compile(source, filename, mode, flags=0, dont_inherit=False, optimize=-1, noopt=None)
 
    Compile the *source* into a code or AST object.  Code objects can be executed
    by :func:`exec` or :func:`eval`.  *source* can either be a normal string, a
@@ -271,6 +271,9 @@ are always available.  They are listed here in alphabetical order.
    ``__debug__`` is true), ``1`` (asserts are removed, ``__debug__`` is false)
    or ``2`` (docstrings are removed too).
 
+   If *noopt* is false, disable compiler optimizations and ignore *optimize*
+   argument. If it is ``None``, use ``sys.flags.noopt`` value.
+
    This function raises :exc:`SyntaxError` if the compiled source is invalid,
    and :exc:`ValueError` if the source contains null bytes.
 
@@ -304,10 +307,13 @@ are always available.  They are listed here in alphabetical order.
       Previously, :exc:`TypeError` was raised when null bytes were encountered
       in *source*.
 
-   .. versionadded:: 3.8
+   .. versionchanged:: 3.8
       ``ast.PyCF_ALLOW_TOP_LEVEL_AWAIT`` can now be passed in flags to enable
       support for top-level ``await``, ``async for``, and ``async with``.
 
+   .. versionachanged:: 3.9
+      New *noopt* optional keyword-only parameter.
+
 
 .. class:: complex([real[, imag]])
 

diff --git a/Doc/library/importlib.rst b/Doc/library/importlib.rst
@@ -1366,7 +1366,7 @@ an :term:`importer`.
 
    .. versionadded:: 3.4
 
-.. function:: cache_from_source(path, debug_override=None, *, optimization=None)
+.. function:: cache_from_source(path, debug_override=None, *, optimization=None, noopt=None)
 
    Return the :pep:`3147`/:pep:`488` path to the byte-compiled file associated
    with the source *path*.  For example, if *path* is ``/foo/bar/baz.py`` the return
@@ -1385,6 +1385,11 @@ an :term:`importer`.
    ``/foo/bar/__pycache__/baz.cpython-32.opt-2.pyc``. The string representation
    of *optimization* can only be alphanumeric, else :exc:`ValueError` is raised.
 
+   The *noopt* parameter is used to specify if compiler optimization are
+   disabled. If it is true, *optimization* is ignored and ``.noopt`` suffix is
+   used (ex: ``baz.cpython-32.noopt.pyc``). If it is ``None``, use
+   ``sys.flags.noopt`` value.
+
    The *debug_override* parameter is deprecated and can be used to override
    the system's value for ``__debug__``. A ``True`` value is the equivalent of
    setting *optimization* to the empty string. A ``False`` value is the same as
@@ -1400,6 +1405,9 @@ an :term:`importer`.
    .. versionchanged:: 3.6
       Accepts a :term:`path-like object`.
 
+   .. versionchanged:: 3.9
+      Added *noopt* parameter.
+
 
 .. function:: source_from_cache(path)
 

diff --git a/Doc/library/py_compile.rst b/Doc/library/py_compile.rst
@@ -27,7 +27,7 @@ byte-code cache files in the directory containing the source code.
    Exception raised when an error occurs while attempting to compile the file.
 
 
-.. function:: compile(file, cfile=None, dfile=None, doraise=False, optimize=-1, invalidation_mode=PycInvalidationMode.TIMESTAMP)
+.. function:: compile(file, cfile=None, dfile=None, doraise=False, optimize=-1, invalidation_mode=PycInvalidationMode.TIMESTAMP, *, noopt=False)
 
    Compile a source file to byte-code and write out the byte-code cache file.
    The source code is loaded from the file named *file*.  The byte-code is
@@ -60,6 +60,9 @@ byte-code cache files in the directory containing the source code.
    :func:`compile` function.  The default of ``-1`` selects the optimization
    level of the current interpreter.
 
+   If *noopt* is true, disable compiler optimizations and ignore *optimize*
+   argument. If it is ``None``, use ``sys.flags.noopt`` value.
+
    *invalidation_mode* should be a member of the :class:`PycInvalidationMode`
    enum and controls how the generated bytecode cache is invalidated at
    runtime.  The default is :attr:`PycInvalidationMode.CHECKED_HASH` if
@@ -92,6 +95,9 @@ byte-code cache files in the directory containing the source code.
    .. versionchanged:: 3.8
       The *quiet* parameter was added.
 
+   .. versionchanged:: 3.9
+      The *noopt* parameter was added.
+
 
 .. class:: PycInvalidationMode
 

diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
@@ -418,6 +418,7 @@ always available.
    :const:`inspect`              :option:`-i`
    :const:`interactive`          :option:`-i`
    :const:`isolated`             :option:`-I`
+   :const:`noopt`                :option:`-X noopt <-X>`
    :const:`optimize`             :option:`-O` or :option:`-OO`
    :const:`dont_write_bytecode`  :option:`-B`
    :const:`no_user_site`         :option:`-s`
@@ -447,6 +448,9 @@ always available.
       Added ``dev_mode`` attribute for the new :option:`-X` ``dev`` flag
       and ``utf8_mode`` attribute for the new  :option:`-X` ``utf8`` flag.
 
+   .. versionchanged:: 3.9
+      Added ``noopt`` attribute for the new :option:`-X noopt <-X>` option.
+
 
 .. data:: float_info
 

diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
@@ -454,6 +454,7 @@ Miscellaneous options
    * ``-X pycache_prefix=PATH`` enables writing ``.pyc`` files to a parallel
      tree rooted at the given directory instead of to the code tree. See also
      :envvar:`PYTHONPYCACHEPREFIX`.
+   * ``-X noopt`` disables the compiler optimizations.
 
    It also allows passing arbitrary values and retrieving them through the
    :data:`sys._xoptions` dictionary.
@@ -477,9 +478,9 @@ Miscellaneous options
       The ``-X pycache_prefix`` option. The ``-X dev`` option now logs
       ``close()`` exceptions in :class:`io.IOBase` destructor.
 
-   .. versionchanged:: 3.9
-      Using ``-X dev`` option, check *encoding* and *errors* arguments on
-      string encoding and decoding operations.
+   .. versionadded:: 3.9
+      The ``-X noopt`` option. Using ``-X dev`` option, check *encoding* and
+      *errors* arguments on string encoding and decoding operations.
 
 
 Options you shouldn't use

diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst
@@ -99,6 +99,10 @@ Other Language Changes
   ignored for empty strings.
   (Contributed by Victor Stinner in :issue:`37388`.)
 
+* Added :option:`-X noopt <-X>` command line to disable compiler optimizations.
+  :mod:`importlib` uses ``.noopt.pyc`` suffix for ``.pyc`` filenames if
+  :data:`sys.flags.noopt` is true.
+  (Contributed by Yury Selivanov and Victor Stinner in :issue:`2506`)
 
 New Modules
 ===========
@@ -109,6 +113,12 @@ New Modules
 Improved Modules
 ================
 
+builtins
+--------
+
+The :func:`compile` function gets a new optional keyword-only *noopt* parameter
+to disable compiler optimizations.
+
 threading
 ---------
 
@@ -132,6 +142,22 @@ now raises :exc:`ImportError` instead of :exc:`ValueError` for invalid relative
 import attempts.
 (Contributed by Ngalim Siregar in :issue:`37444`.)
 
+Add a new *noopt* optional keyword-only parameter to
+:func:`importlib.util.cache_from_source` to disable compiler optimizations.
+
+py_compile
+----------
+
+Add a new *noopt* optional keyword-only parameter to :func:`py_compile.compile`
+to disable compiler optimizations.
+
+sys
+---
+
+Add new :data:`sys.flags.noopt` flag for the new :option:`-X noopt <-X>` option
+(disable compiler optimizations).
+(Contributed by Yury Selivanov and Victor Stinner in :issue:`2506`)
+
 Optimizations
 =============
 

diff --git a/Include/compile.h b/Include/compile.h
@@ -67,6 +67,14 @@ PyAPI_FUNC(PyCodeObject *) PyAST_CompileObject(
     PyCompilerFlags *flags,
     int optimize,
     PyArena *arena);
+PyAPI_FUNC(PyCodeObject *) _PyAST_Compile(
+    struct _mod *mod,
+    PyObject *filename,
+    PyCompilerFlags *flags,
+    int optimization_level,
+    PyArena *arena,
+    int noopt);
+
 PyAPI_FUNC(PyFutureFeatures *) PyFuture_FromAST(
     struct _mod * mod,
     const char *filename        /* decoded from the filesystem encoding */

diff --git a/Include/cpython/initconfig.h b/Include/cpython/initconfig.h
@@ -401,6 +401,18 @@ typedef struct {
     /* If equal to 0, stop Python initialization before the "main" phase */
     int _init_main;
 
+    /* --- Configuration version 2 (new fields) ------ */
+
+    /* Should the compiler optimize bytecode?
+
+       If equal to 0, disable compiler optimizations and set optimization_level
+       to 0.
+
+       If equal to 1, enable compiler optimizations.
+
+       Set to 0 by -X noopt. */
+    int optimize;
+
 } PyConfig;
 
 PyAPI_FUNC(PyStatus) PyConfig_InitPythonConfig(PyConfig *config);

diff --git a/Include/internal/pycore_initconfig.h b/Include/internal/pycore_initconfig.h
@@ -135,7 +135,9 @@ extern PyStatus _PyPreConfig_Write(const PyPreConfig *preconfig);
 
 /* --- PyConfig ---------------------------------------------- */
 
-#define _Py_CONFIG_VERSION 1
+/* Version 2: Add optimize field.
+   Version 1: Initial version (Python 3.8.0) */
+#define _Py_CONFIG_VERSION 2
 
 typedef enum {
     /* Py_Initialize() API: backward compatibility with Python 3.6 and 3.7 */

diff --git a/Include/pythonrun.h b/Include/pythonrun.h
@@ -112,6 +112,12 @@ PyAPI_FUNC(PyObject *) Py_CompileStringObject(
     PyObject *filename, int start,
     PyCompilerFlags *flags,
     int optimize);
+PyAPI_FUNC(PyObject *) _Py_CompileString(
+    const char *str,
+    PyObject *filename, int start,
+    PyCompilerFlags *flags,
+    int optimize,
+    int noopt);
 #endif
 PyAPI_FUNC(struct symtable *) Py_SymtableString(
     const char *str,

diff --git a/Lib/distutils/command/build_py.py b/Lib/distutils/command/build_py.py
@@ -314,10 +314,10 @@ def get_outputs(self, include_bytecode=1):
             if include_bytecode:
                 if self.compile:
                     outputs.append(importlib.util.cache_from_source(
-                        filename, optimization=''))
+                        filename, optimization='', noopt=False))
                 if self.optimize > 0:
                     outputs.append(importlib.util.cache_from_source(
-                        filename, optimization=self.optimize))
+                        filename, optimization=self.optimize, noopt=False))
 
         outputs += [
             os.path.join(build_dir, filename)

diff --git a/Lib/distutils/command/install_lib.py b/Lib/distutils/command/install_lib.py
@@ -166,10 +166,10 @@ def _bytecode_filenames(self, py_filenames):
                 continue
             if self.compile:
                 bytecode_files.append(importlib.util.cache_from_source(
-                    py_file, optimization=''))
+                    py_file, optimization='', noopt=False))
             if self.optimize > 0:
                 bytecode_files.append(importlib.util.cache_from_source(
-                    py_file, optimization=self.optimize))
+                    py_file, optimization=self.optimize, noopt=False))
 
         return bytecode_files
 

diff --git a/Lib/distutils/tests/test_install_lib.py b/Lib/distutils/tests/test_install_lib.py
@@ -44,9 +44,11 @@ def test_byte_compile(self):
         f = os.path.join(project_dir, 'foo.py')
         self.write_file(f, '# python file')
         cmd.byte_compile([f])
-        pyc_file = importlib.util.cache_from_source('foo.py', optimization='')
+        pyc_file = importlib.util.cache_from_source('foo.py', optimization='',
+                                                    noopt=False)
         pyc_opt_file = importlib.util.cache_from_source('foo.py',
-                                                    optimization=cmd.optimize)
+                                                    optimization=cmd.optimize,
+                                                    noopt=False)
         self.assertTrue(os.path.exists(pyc_file))
         self.assertTrue(os.path.exists(pyc_opt_file))
 

diff --git a/Lib/distutils/util.py b/Lib/distutils/util.py
@@ -443,10 +443,11 @@ def byte_compile (py_files,
             #   dfile - purported source filename (same as 'file' by default)
             if optimize >= 0:
                 opt = '' if optimize == 0 else optimize
-                cfile = importlib.util.cache_from_source(
-                    file, optimization=opt)
+                cfile = importlib.util.cache_from_source(file,
+                                                         optimization=opt,
+                                                         noopt=False)
             else:
-                cfile = importlib.util.cache_from_source(file)
+                cfile = importlib.util.cache_from_source(file, noopt=False)
             dfile = file
             if prefix:
                 if file[:len(prefix)] != prefix:
@@ -461,7 +462,7 @@ def byte_compile (py_files,
                 if force or newer(file, cfile):
                     log.info("byte-compiling %s to %s", file, cfile_base)
                     if not dry_run:
-                        compile(file, cfile, dfile)
+                        compile(file, cfile, dfile, noopt=False)
                 else:
                     log.debug("skipping byte-compilation of %s to %s",
                               file, cfile_base)