1============================
2LLVM |release| Release Notes
3============================
4
5.. contents::
6    :local:
7
8.. only:: PreRelease
9
10  .. warning::
11     These are in-progress notes for the upcoming LLVM |version| release.
12     Release notes for previous releases can be found on
13     `the Download Page <https://releases.llvm.org/download.html>`_.
14
15
16Introduction
17============
18
19This document contains the release notes for the LLVM Compiler Infrastructure,
20release |release|.  Here we describe the status of LLVM, including major improvements
21from the previous release, improvements in various subprojects of LLVM, and
22some of the current users of the code.  All LLVM releases may be downloaded
23from the `LLVM releases web site <https://llvm.org/releases/>`_.
24
25For more information about LLVM, including information about the latest
26release, please check out the `main LLVM web site <https://llvm.org/>`_.  If you
27have questions or comments, the `LLVM Developer's Mailing List
28<https://lists.llvm.org/mailman/listinfo/llvm-dev>`_ is a good place to send
29them.
30
31Note that if you are reading this file from a Git checkout or the main
32LLVM web page, this document applies to the *next* release, not the current
33one.  To see the release notes for a specific release, please see the `releases
34page <https://llvm.org/releases/>`_.
35
36Non-comprehensive list of changes in this release
37=================================================
38.. NOTE
39   For small 1-3 sentence descriptions, just add an entry at the end of
40   this list. If your description won't fit comfortably in one bullet
41   point (e.g. maybe you would like to give an example of the
42   functionality, or simply have a lot to talk about), see the `NOTE` below
43   for adding a new subsection.
44
45* ...
46
47Update on required toolchains to build LLVM
48-------------------------------------------
49
50With LLVM 15.x we will raise the version requirements of the toolchain used
51to build LLVM. The new requirements are as follows:
52
53* GCC >= 7.1
54* Clang >= 5.0
55* Apple Clang >= 9.3
56* Visual Studio 2019 >= 16.7
57
58In LLVM 15.x these requirements will be "soft" requirements and the version
59check can be skipped by passing -DLLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN=ON
60to CMake.
61
62With the release of LLVM 16.x these requirements will be hard and LLVM developers
63can start using C++17 features, making it impossible to build with older
64versions of these toolchains.
65
66Changes to the LLVM IR
67----------------------
68
69* Renamed ``llvm.experimental.vector.extract`` intrinsic to ``llvm.vector.extract``.
70* Renamed ``llvm.experimental.vector.insert`` intrinsic to ``llvm.vector.insert``.
71* The constant expression variants of the following instructions have been
72  removed:
73  * ``extractvalue``
74  * ``insertvalue``
75  * ``udiv``
76  * ``sdiv``
77  * ``urem``
78  * ``srem``
79* Added the support for ``fmax`` and ``fmin`` in ``atomicrmw`` instruction. The
80  comparison is expected to match the behavior of ``llvm.maxnum.*`` and
81  ``llvm.minnum.*`` respectively.
82
83Changes to building LLVM
84------------------------
85
86* Omitting ``CMAKE_BUILD_TYPE`` when using a single configuration generator is now
87  an error. You now have to pass ``-DCMAKE_BUILD_TYPE=<type>`` in order to configure
88  LLVM. This is done to help new users of LLVM select the correct type: since building
89  LLVM in Debug mode is very resource intensive, we want to make sure that new users
90  make the choice that lines up with their usage. We have also improved documentation
91  around this setting that should help new users. You can find this documentation
92  `here <https://llvm.org/docs/CMake.html#cmake-build-type>`_.
93
94Changes to TableGen
95-------------------
96
97Changes to the AArch64 Backend
98------------------------------
99
100Changes to the AMDGPU Backend
101-----------------------------
102
103* 8 and 16-bit atomic loads and stores are now supported
104
105
106Changes to the ARM Backend
107--------------------------
108
109* Added support for the Armv9-A, Armv9.1-A and Armv9.2-A architectures.
110* Added support for the Armv8.1-M PACBTI-M extension.
111* Added support for the Armv9-A, Armv9.1-A and Armv9.2-A architectures.
112* Added support for the Armv8.1-M PACBTI-M extension.
113* Removed the deprecation of ARMv8-A T32 Complex IT blocks. No deprecation
114  warnings will be generated and -mrestrict-it is now always off by default.
115  Previously it was on by default for Armv8 and off for all other architecture
116  versions.
117* Added a pass to workaround Cortex-A57 Erratum 1742098 and Cortex-A72
118  Erratum 1655431. This is enabled by default when targeting either CPU.
119* Implemented generation of Windows SEH unwind information.
120* Switched the MinGW target to use SEH instead of DWARF for unwind information.
121* Added support for the Cortex-M85 CPU.
122* Added support for a new -mframe-chain=(none|aapcs|aapcs+leaf) command-line
123  option, which controls the generation of AAPCS-compliant Frame Records.
124
125Changes to the AVR Backend
126--------------------------
127
128* ...
129
130Changes to the DirectX Backend
131------------------------------
132
133* DirectX has been added as an experimental target. Specify
134  ``-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=DirectX`` in your CMake configuration
135  to enable it. The target is not packaged in pre-built binaries.
136* The DirectX backend supports the ``dxil`` architecture which is based on LLVM
137  3.6 IR encoded as bitcode and is the format used for DirectX GPU Shader
138  programs.
139
140Changes to the Hexagon Backend
141------------------------------
142
143* ...
144
145Changes to the MIPS Backend
146---------------------------
147
148* ...
149
150Changes to the PowerPC Backend
151------------------------------
152
153* ...
154
155Changes to the RISC-V Backend
156-----------------------------
157
158* The Zvfh extension was added.
159
160Changes to the WebAssembly Backend
161----------------------------------
162
163* ...
164
165Changes to the X86 Backend
166--------------------------
167
168* Support ``half`` type on SSE2 and above targets.
169* Support ``rdpru`` instruction on Zen2 and above targets.
170
171Changes to the OCaml bindings
172-----------------------------
173
174
175Changes to the C API
176--------------------
177
178* Add ``LLVMGetCastOpcode`` function to aid users of ``LLVMBuildCast`` in
179  resolving the best cast operation given a source value and destination type.
180  This function is a direct wrapper of ``CastInst::getCastOpcode``.
181
182* Add ``LLVMGetAggregateElement`` function as a wrapper for
183  ``Constant::getAggregateElement``, which can be used to fetch an element of a
184  constant struct, array or vector, independently of the underlying
185  representation. The ``LLVMGetElementAsConstant`` function is deprecated in
186  favor of the new function, which works on all constant aggregates, rather than
187  only instances of ``ConstantDataSequential``.
188
189* The following functions for creating constant expressions have been removed,
190  because the underlying constant expressions are no longer supported. Instead,
191  an instruction should be created using the ``LLVMBuildXYZ`` APIs, which will
192  constant fold the operands if possible and create an instruction otherwise:
193  * ``LLVMConstExtractValue``
194  * ``LLVMConstInsertValue``
195  * ``LLVMConstUDiv``
196  * ``LLVMConstExactUDiv``
197  * ``LLVMConstSDiv``
198  * ``LLVMConstExactSDiv``
199  * ``LLVMConstURem``
200  * ``LLVMConstSRem``
201
202* Add ``LLVMDeleteInstruction`` function which allows deleting instructions that
203  are not inserted into a basic block.
204
205* Refactor compression namespaces across the project, making way for a possible
206  introduction of alternatives to zlib compression in the llvm toolchain.
207  Changes are as follows:
208  * Relocate the ``llvm::zlib`` namespace to ``llvm::compression::zlib``.
209  * Remove crc32 from zlib compression namespace, people should use the ``llvm::crc32`` instead.
210
211Changes to the Go bindings
212--------------------------
213
214
215Changes to the FastISel infrastructure
216--------------------------------------
217
218* ...
219
220Changes to the DAG infrastructure
221---------------------------------
222
223
224Changes to the Debug Info
225---------------------------------
226
227During this release ...
228
229Changes to the LLVM tools
230---------------------------------
231
232* (Experimental) :manpage:`llvm-symbolizer(1)` now has ``--filter-markup`` to
233  filter :doc:`Symbolizer Markup </SymbolizerMarkupFormat>` into human-readable
234  form.
235* :doc:`llvm-objcopy <CommandGuide/llvm-objcopy>` has removed support for the legacy ``zlib-gnu`` format.
236
237Changes to LLDB
238---------------------------------
239
240* The "memory region" command now has a "--all" option to list all
241  memory regions (including unmapped ranges). This is the equivalent
242  of using address 0 then repeating the command until all regions
243  have been listed.
244* Added "--show-tags" option to the "memory find" command. This is off by default.
245  When enabled, if the target value is found in tagged memory, the tags for that
246  memory will be shown inline with the memory contents.
247* Various memory related parts of LLDB have been updated to handle
248  non-address bits (such as AArch64 pointer signatures):
249
250  * "memory read", "memory write" and "memory find" can now be used with
251    addresses with non-address bits.
252  * All the read and write memory methods on SBProccess and SBTarget can
253    be used with addreses with non-address bits.
254  * When printing a pointer expression, LLDB can now dereference the result
255    even if it has non-address bits.
256  * The memory cache now ignores non-address bits when looking up memory
257    locations. This prevents us reading locations multiple times, or not
258    writing out new values if the addresses have different non-address bits.
259
260Changes to Sanitizers
261---------------------
262
263
264Other Changes
265-------------
266* The code for the `LLVM Visual Studio integration
267  <https://marketplace.visualstudio.com/items?itemName=LLVMExtensions.llvm-toolchain>`_
268  has been removed. This had been obsolete and abandoned since Visual Studio
269  started including an integration by default in 2019.
270
271External Open Source Projects Using LLVM 15
272===========================================
273
274* A project...
275
276Additional Information
277======================
278
279A wide variety of additional information is available on the `LLVM web page
280<https://llvm.org/>`_, in particular in the `documentation
281<https://llvm.org/docs/>`_ section.  The web page also contains versions of the
282API documentation which is up-to-date with the Git version of the source
283code.  You can access versions of these documents specific to this release by
284going into the ``llvm/docs/`` directory in the LLVM tree.
285
286If you have any questions or comments about LLVM, please feel free to contact
287us via the `mailing lists <https://llvm.org/docs/#mailing-lists>`_.
288