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  * ``fadd``
80  * ``fsub``
81  * ``fmul``
82  * ``fdiv``
83  * ``frem``
84* Added the support for ``fmax`` and ``fmin`` in ``atomicrmw`` instruction. The
85  comparison is expected to match the behavior of ``llvm.maxnum.*`` and
86  ``llvm.minnum.*`` respectively.
87
88Changes to building LLVM
89------------------------
90
91* Omitting ``CMAKE_BUILD_TYPE`` when using a single configuration generator is now
92  an error. You now have to pass ``-DCMAKE_BUILD_TYPE=<type>`` in order to configure
93  LLVM. This is done to help new users of LLVM select the correct type: since building
94  LLVM in Debug mode is very resource intensive, we want to make sure that new users
95  make the choice that lines up with their usage. We have also improved documentation
96  around this setting that should help new users. You can find this documentation
97  `here <https://llvm.org/docs/CMake.html#cmake-build-type>`_.
98
99Changes to TableGen
100-------------------
101
102Changes to the AArch64 Backend
103------------------------------
104
105Changes to the AMDGPU Backend
106-----------------------------
107
108* 8 and 16-bit atomic loads and stores are now supported
109
110
111Changes to the ARM Backend
112--------------------------
113
114* Added support for the Armv9-A, Armv9.1-A and Armv9.2-A architectures.
115* Added support for the Armv8.1-M PACBTI-M extension.
116* Added support for the Armv9-A, Armv9.1-A and Armv9.2-A architectures.
117* Added support for the Armv8.1-M PACBTI-M extension.
118* Removed the deprecation of ARMv8-A T32 Complex IT blocks. No deprecation
119  warnings will be generated and -mrestrict-it is now always off by default.
120  Previously it was on by default for Armv8 and off for all other architecture
121  versions.
122* Added a pass to workaround Cortex-A57 Erratum 1742098 and Cortex-A72
123  Erratum 1655431. This is enabled by default when targeting either CPU.
124* Implemented generation of Windows SEH unwind information.
125* Switched the MinGW target to use SEH instead of DWARF for unwind information.
126* Added support for the Cortex-M85 CPU.
127* Added support for a new -mframe-chain=(none|aapcs|aapcs+leaf) command-line
128  option, which controls the generation of AAPCS-compliant Frame Records.
129
130Changes to the AVR Backend
131--------------------------
132
133* ...
134
135Changes to the DirectX Backend
136------------------------------
137
138* DirectX has been added as an experimental target. Specify
139  ``-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=DirectX`` in your CMake configuration
140  to enable it. The target is not packaged in pre-built binaries.
141* The DirectX backend supports the ``dxil`` architecture which is based on LLVM
142  3.6 IR encoded as bitcode and is the format used for DirectX GPU Shader
143  programs.
144
145Changes to the Hexagon Backend
146------------------------------
147
148* ...
149
150Changes to the MIPS Backend
151---------------------------
152
153* ...
154
155Changes to the PowerPC Backend
156------------------------------
157
158* ...
159
160Changes to the RISC-V Backend
161-----------------------------
162
163* The Zvfh extension was added.
164
165Changes to the WebAssembly Backend
166----------------------------------
167
168* ...
169
170Changes to the X86 Backend
171--------------------------
172
173* Support ``half`` type on SSE2 and above targets.
174* Support ``rdpru`` instruction on Zen2 and above targets.
175
176Changes to the OCaml bindings
177-----------------------------
178
179
180Changes to the C API
181--------------------
182
183* Add ``LLVMGetCastOpcode`` function to aid users of ``LLVMBuildCast`` in
184  resolving the best cast operation given a source value and destination type.
185  This function is a direct wrapper of ``CastInst::getCastOpcode``.
186
187* Add ``LLVMGetAggregateElement`` function as a wrapper for
188  ``Constant::getAggregateElement``, which can be used to fetch an element of a
189  constant struct, array or vector, independently of the underlying
190  representation. The ``LLVMGetElementAsConstant`` function is deprecated in
191  favor of the new function, which works on all constant aggregates, rather than
192  only instances of ``ConstantDataSequential``.
193
194* The following functions for creating constant expressions have been removed,
195  because the underlying constant expressions are no longer supported. Instead,
196  an instruction should be created using the ``LLVMBuildXYZ`` APIs, which will
197  constant fold the operands if possible and create an instruction otherwise:
198  * ``LLVMConstExtractValue``
199  * ``LLVMConstInsertValue``
200  * ``LLVMConstUDiv``
201  * ``LLVMConstExactUDiv``
202  * ``LLVMConstSDiv``
203  * ``LLVMConstExactSDiv``
204  * ``LLVMConstURem``
205  * ``LLVMConstSRem``
206  * ``LLVMConstFAdd``
207  * ``LLVMConstFSub``
208  * ``LLVMConstFMul``
209  * ``LLVMConstFDiv``
210  * ``LLVMConstFRem``
211
212* Add ``LLVMDeleteInstruction`` function which allows deleting instructions that
213  are not inserted into a basic block.
214
215* Refactor compression namespaces across the project, making way for a possible
216  introduction of alternatives to zlib compression in the llvm toolchain.
217  Changes are as follows:
218  * Relocate the ``llvm::zlib`` namespace to ``llvm::compression::zlib``.
219  * Remove crc32 from zlib compression namespace, people should use the ``llvm::crc32`` instead.
220
221Changes to the Go bindings
222--------------------------
223
224
225Changes to the FastISel infrastructure
226--------------------------------------
227
228* ...
229
230Changes to the DAG infrastructure
231---------------------------------
232
233
234Changes to the Metadata Info
235---------------------------------
236
237* Add Module Flags Metadata ``stack-protector-guard-symbol`` which specify a
238  symbol for addressing the stack-protector guard.
239
240Changes to the Debug Info
241---------------------------------
242
243During this release ...
244
245Changes to the LLVM tools
246---------------------------------
247
248* (Experimental) :manpage:`llvm-symbolizer(1)` now has ``--filter-markup`` to
249  filter :doc:`Symbolizer Markup </SymbolizerMarkupFormat>` into human-readable
250  form.
251* :doc:`llvm-objcopy <CommandGuide/llvm-objcopy>` has removed support for the legacy ``zlib-gnu`` format.
252* :doc:`llvm-objcopy <CommandGuide/llvm-objcopy>` now allows ``--set-section-flags src=... --rename-section src=tst``.
253  ``--add-section=.foo1=... --rename-section=.foo1=.foo2`` now adds ``.foo1`` instead of ``.foo2``.
254
255Changes to LLDB
256---------------------------------
257
258* The "memory region" command now has a "--all" option to list all
259  memory regions (including unmapped ranges). This is the equivalent
260  of using address 0 then repeating the command until all regions
261  have been listed.
262* Added "--show-tags" option to the "memory find" command. This is off by default.
263  When enabled, if the target value is found in tagged memory, the tags for that
264  memory will be shown inline with the memory contents.
265* Various memory related parts of LLDB have been updated to handle
266  non-address bits (such as AArch64 pointer signatures):
267
268  * "memory read", "memory write" and "memory find" can now be used with
269    addresses with non-address bits.
270  * All the read and write memory methods on SBProccess and SBTarget can
271    be used with addreses with non-address bits.
272  * When printing a pointer expression, LLDB can now dereference the result
273    even if it has non-address bits.
274  * The memory cache now ignores non-address bits when looking up memory
275    locations. This prevents us reading locations multiple times, or not
276    writing out new values if the addresses have different non-address bits.
277
278Changes to Sanitizers
279---------------------
280
281
282Other Changes
283-------------
284* The code for the `LLVM Visual Studio integration
285  <https://marketplace.visualstudio.com/items?itemName=LLVMExtensions.llvm-toolchain>`_
286  has been removed. This had been obsolete and abandoned since Visual Studio
287  started including an integration by default in 2019.
288
289External Open Source Projects Using LLVM 15
290===========================================
291
292* A project...
293
294Additional Information
295======================
296
297A wide variety of additional information is available on the `LLVM web page
298<https://llvm.org/>`_, in particular in the `documentation
299<https://llvm.org/docs/>`_ section.  The web page also contains versions of the
300API documentation which is up-to-date with the Git version of the source
301code.  You can access versions of these documents specific to this release by
302going into the ``llvm/docs/`` directory in the LLVM tree.
303
304If you have any questions or comments about LLVM, please feel free to contact
305us via the `mailing lists <https://llvm.org/docs/#mailing-lists>`_.
306