Bump version to 21.0.0git (#124870)

Also clear the release notes.

cmake/Modules/LLVMVersion.cmake

@@ -1,7 +1,7 @@
 # The LLVM Version number information
 
 if(NOT DEFINED LLVM_VERSION_MAJOR)
-  set(LLVM_VERSION_MAJOR 20)
+  set(LLVM_VERSION_MAJOR 21)
 endif()
 if(NOT DEFINED LLVM_VERSION_MINOR)
   set(LLVM_VERSION_MINOR 0)

libcxx/docs/ReleaseNotes.rst

@@ -1,9 +1,10 @@
-.. include:: ReleaseNotes/20.rst
+.. include:: ReleaseNotes/21.rst
 
 .. Make sure to reference the non-live release notes in a toctree to avoid Sphinx errors.
 .. toctree::
     :hidden:
 
+    ReleaseNotes/20
     ReleaseNotes/19
 
 .. The release notes are in versioned files, but we make sure to keep publishing

libcxx/docs/ReleaseNotes/21.rst

@@ -0,0 +1,71 @@
+===========================================
+Libc++ 21.0.0 (In-Progress) Release Notes
+===========================================
+
+.. contents::
+   :local:
+   :depth: 2
+
+Written by the `Libc++ Team <https://libcxx.llvm.org>`_
+
+.. warning::
+
+   These are in-progress notes for the upcoming libc++ 20.0.0 release.
+   Release notes for previous releases can be found on
+   `the Download Page <https://releases.llvm.org/download.html>`_.
+
+Introduction
+============
+
+This document contains the release notes for the libc++ C++ Standard Library,
+part of the LLVM Compiler Infrastructure, release 20.0.0. Here we describe the
+status of libc++ in some detail, including major improvements from the previous
+release and new feature work. For the general LLVM release notes, see `the LLVM
+documentation <https://llvm.org/docs/ReleaseNotes.html>`_. All LLVM releases may
+be downloaded from the `LLVM releases web site <https://llvm.org/releases/>`_.
+
+For more information about libc++, please see the `Libc++ Web Site
+<https://libcxx.llvm.org>`_ or the `LLVM Web Site <https://llvm.org>`_.
+
+Note that if you are reading this file from a Git checkout or the
+main Libc++ web page, this document applies to the *next* release, not
+the current one. To see the release notes for a specific release, please
+see the `releases page <https://llvm.org/releases/>`_.
+
+What's New in Libc++ 21.0.0?
+==============================
+
+Implemented Papers
+------------------
+
+- TODO
+
+
+Improvements and New Features
+-----------------------------
+
+- TODO
+
+
+Deprecations and Removals
+-------------------------
+
+Upcoming Deprecations and Removals
+----------------------------------
+
+LLVM 22
+~~~~~~~
+
+- TODO
+
+
+ABI Affecting Changes
+---------------------
+
+- TODO
+
+
+Build System Changes
+--------------------
+
+- TODO

libcxx/include/__config

@@ -28,7 +28,7 @@
 // _LIBCPP_VERSION represents the version of libc++, which matches the version of LLVM.
 // Given a LLVM release LLVM XX.YY.ZZ (e.g. LLVM 17.0.1 == 17.00.01), _LIBCPP_VERSION is
 // defined to XXYYZZ.
-#  define _LIBCPP_VERSION 200000
+#  define _LIBCPP_VERSION 210000
 
 #  define _LIBCPP_CONCAT_IMPL(_X, _Y) _X##_Y
 #  define _LIBCPP_CONCAT(_X, _Y) _LIBCPP_CONCAT_IMPL(_X, _Y)

lld/docs/ReleaseNotes.rst

@@ -26,73 +26,14 @@ Non-comprehensive list of changes in this release
 ELF Improvements
 ----------------
 
-* ``-z nosectionheader`` has been implemented to omit the section header table.
-  The operation is similar to ``llvm-objcopy --strip-sections``.
-  (`#101286 <https://github.com/llvm/llvm-project/pull/101286>`_)
-* ``--randomize-section-padding=<seed>`` is introduced to insert random padding
-  between input sections and at the start of each segment. This can be used to
-  control measurement bias in A/B experiments.
-  (`#117653 <https://github.com/llvm/llvm-project/pull/117653>`_)
-* The reproduce tarball created with ``--reproduce=`` now excludes directories
-  specified in the ``--dependency-file`` argument (used by Ninja). This
-  resolves an error where non-existent directories could cause issues when
-  invoking ``ld.lld @response.txt``.
-* ``--symbol-ordering-file=`` and call graph profile can now be used together.
-* When ``--call-graph-ordering-file=`` is specified, ``.llvm.call-graph-profile``
-  sections in relocatable files are no longer used.
-* ``--lto-basic-block-sections=labels`` is deprecated in favor of
-  ``--lto-basic-block-address-map``.
-  (`#110697 <https://github.com/llvm/llvm-project/pull/110697>`_)
-* In non-relocatable links, a ``.note.GNU-stack`` section with the
-  ``SHF_EXECINSTR`` flag is now rejected unless ``-z execstack`` is specified.
-  (`#124068 <https://github.com/llvm/llvm-project/pull/124068>`_)
-* In relocatable links, the ``sh_entsize`` member of a ``SHF_MERGE`` section
-  with relocations is now respected in the output.
-* Quoted names can now be used in output section phdr, memory region names,
-  ``OVERLAY``, the LHS of ``--defsym``, and ``INSERT AFTER``.
-* Section ``CLASS`` linker script syntax binds input sections to named classes,
-  which are referenced later one or more times. This provides access to the
-  automatic spilling mechanism of `--enable-non-contiguous-regions` without
-  globally changing the semantics of section matching. It also independently
-  increases the expressive power of linker scripts.
-  (`#95323 <https://github.com/llvm/llvm-project/pull/95323>`_)
-* ``INCLUDE`` cycle detection has been fixed. A linker script can now be
-  included twice.
-* The ``archivename:`` syntax when matching input sections is now supported.
-  (`#119293 <https://github.com/llvm/llvm-project/pull/119293>`_)
-* To support Arm v6-M, short thunks using B.w are no longer generated.
-  (`#118111 <https://github.com/llvm/llvm-project/pull/118111>`_)
-* For AArch64, BTI-aware long branch thunks can now be created to a destination
-  function without a BTI instruction.
-  (`#108989 <https://github.com/llvm/llvm-project/pull/108989>`_)
-  (`#116402 <https://github.com/llvm/llvm-project/pull/116402>`_)
-* Relocations related to GOT and TLSDESC for the AArch64 Pointer Authentication ABI
-  are now supported.
-* Supported relocation types for x86-64 target:
-  * ``R_X86_64_CODE_4_GOTPCRELX`` (`#109783 <https://github.com/llvm/llvm-project/pull/109783>`_) (`#116737 <https://github.com/llvm/llvm-project/pull/116737>`_)
-  * ``R_X86_64_CODE_4_GOTTPOFF`` (`#116634 <https://github.com/llvm/llvm-project/pull/116634>`_)
-  * ``R_X86_64_CODE_4_GOTPC32_TLSDESC`` (`#116909 <https://github.com/llvm/llvm-project/pull/116909>`_)
-  * ``R_X86_64_CODE_6_GOTTPOFF``  (`#117675 <https://github.com/llvm/llvm-project/pull/117675>`_)
-* Supported relocation types for LoongArch target: ``R_LARCH_TLS_{LD,GD,DESC}_PCREL20_S2``.
-  (`#100105 <https://github.com/llvm/llvm-project/pull/100105>`_)
-
 Breaking changes
 ----------------
 
-* Removed support for the (deprecated) `R_RISCV_RVC_LUI` relocation. This
-  was a binutils-internal relocation used during relaxation, and was not
-  emitted by compilers/assemblers.
-
 COFF Improvements
 -----------------
-* ``/includeglob`` has been implemented to match the behavior of ``--undefined-glob`` available for ELF.
-* ``/lldsavetemps`` allows saving select intermediate LTO compilation results (e.g. resolution, preopt, promote, internalize, import, opt, precodegen, prelink, combinedindex).
-* ``/machine:arm64ec`` support completed, enabling the linking of ARM64EC images.
-* COFF weak anti-dependency alias symbols are now supported.
 
 MinGW Improvements
 ------------------
-* ``--undefined-glob`` is now supported by translating into the ``/includeglob`` flag.
 
 MachO Improvements
 ------------------