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============================
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LLVM |release| Release Notes
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============================
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.. contents::
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:local:
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.. only:: PreRelease
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.. warning::
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These are in-progress notes for the upcoming LLVM |version| release.
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Release notes for previous releases can be found on
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`the Download Page <https://releases.llvm.org/download.html>`_.
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Introduction
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============
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This document contains the release notes for the LLVM Compiler Infrastructure,
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release |release|. Here we describe the status of LLVM, including major improvements
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from the previous release, improvements in various subprojects of LLVM, and
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some of the current users of the code. All LLVM releases may be downloaded
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from the `LLVM releases web site <https://llvm.org/releases/>`_.
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For more information about LLVM, including information about the latest
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release, please check out the `main LLVM web site <https://llvm.org/>`_. If you
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have questions or comments, the `Discourse forums
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<https://discourse.llvm.org>`_ is a good place to ask
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them.
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Note that if you are reading this file from a Git checkout or the main
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LLVM web page, this document applies to the *next* release, not the current
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one. To see the release notes for a specific release, please see the `releases
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page <https://llvm.org/releases/>`_.
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Non-comprehensive list of changes in this release
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=================================================
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.. NOTE
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For small 1-3 sentence descriptions, just add an entry at the end of
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this list. If your description won't fit comfortably in one bullet
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point (e.g. maybe you would like to give an example of the
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functionality, or simply have a lot to talk about), see the `NOTE` below
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for adding a new subsection.
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* The ``readnone`` calls which are crossing suspend points in coroutines will
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not be merged. Since ``readnone`` calls may access thread id and thread id
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is not a constant in coroutines. This decision may cause unnecessary
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performance regressions and we plan to fix it in later versions.
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* The LoopFlatten pass is now enabled by default.
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* ...
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Update on required toolchains to build LLVM
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-------------------------------------------
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LLVM is now built with C++17 by default. This means C++17 can be used in
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the code base.
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The previous "soft" toolchain requirements have now been changed to "hard".
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This means that the the following versions are now required to build LLVM
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and there is no way to suppress this error.
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* GCC >= 7.1
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* Clang >= 5.0
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* Apple Clang >= 10.0
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* Visual Studio 2019 >= 16.7
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Changes to the LLVM IR
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----------------------
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* The ``readnone``, ``readonly``, ``writeonly``, ``argmemonly``,
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``inaccessiblememonly`` and ``inaccessiblemem_or_argmemonly`` function
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attributes have been replaced by a single ``memory(...)`` attribute. The
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old attributes may be mapped to the new one as follows:
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* ``readnone`` -> ``memory(none)``
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* ``readonly`` -> ``memory(read)``
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* ``writeonly`` -> ``memory(write)``
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* ``argmemonly`` -> ``memory(argmem: readwrite)``
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* ``argmemonly readonly`` -> ``memory(argmem: read)``
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* ``argmemonly writeonly`` -> ``memory(argmem: write)``
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* ``inaccessiblememonly`` -> ``memory(inaccessiblemem: readwrite)``
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* ``inaccessiblememonly readonly`` -> ``memory(inaccessiblemem: read)``
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* ``inaccessiblememonly writeonly`` -> ``memory(inaccessiblemem: write)``
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* ``inaccessiblemem_or_argmemonly`` ->
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``memory(argmem: readwrite, inaccessiblemem: readwrite)``
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* ``inaccessiblemem_or_argmemonly readonly`` ->
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``memory(argmem: read, inaccessiblemem: read)``
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* ``inaccessiblemem_or_argmemonly writeonly`` ->
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``memory(argmem: write, inaccessiblemem: write)``
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* The constant expression variants of the following instructions has been
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removed:
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* ``fneg``
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Changes to building LLVM
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------------------------
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Changes to TableGen
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-------------------
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Changes to the AArch64 Backend
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------------------------------
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* Added support for the Cortex-A715 CPU.
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* Added support for the Cortex-X3 CPU.
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* Added support for assembly for RME MEC (Memory Encryption Contexts).
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Changes to the AMDGPU Backend
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-----------------------------
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Changes to the ARM Backend
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--------------------------
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* Support for targeting armv2, armv2A, armv3 and armv3M has been removed.
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LLVM did not, and was not ever likely to generate correct code for those
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architecture versions so their presence was misleading.
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Changes to the AVR Backend
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--------------------------
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* ...
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Changes to the DirectX Backend
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------------------------------
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Changes to the Hexagon Backend
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------------------------------
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* ...
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Changes to the MIPS Backend
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---------------------------
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* ...
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Changes to the PowerPC Backend
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------------------------------
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* ...
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Changes to the RISC-V Backend
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-----------------------------
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* Support for the unratified Zbe, Zbf, Zbm, Zbp, Zbr, and Zbt extensions have
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been removed.
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* i32 is now a native type in the datalayout string. This enables
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LoopStrengthReduce for loops with i32 induction variables, among other
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optimizations.
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Changes to the WebAssembly Backend
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----------------------------------
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* ...
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Changes to the Windows Target
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-----------------------------
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* For MinGW, generate embedded ``-exclude-symbols:`` directives for symbols
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with hidden visibility, omitting them from automatic export of all symbols.
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This roughly makes hidden visibility work like it does for other object
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file formats.
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Changes to the X86 Backend
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--------------------------
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* Add support for the ``RDMSRLIST and WRMSRLIST`` instructions.
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* Add support for the ``WRMSRNS`` instruction.
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* Support ISA of ``AMX-FP16`` which contains ``tdpfp16ps`` instruction.
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* Support ISA of ``CMPCCXADD``.
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* Support ISA of ``AVX-IFMA``.
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* Support ISA of ``AVX-VNNI-INT8``.
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* Support ISA of ``AVX-NE-CONVERT``.
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* ``-mcpu=raptorlake`` and ``-mcpu=meteorlake`` are now supported.
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* ``-mcpu=sierraforest``, ``-mcpu=graniterapids`` and ``-mcpu=grandridge`` are now supported.
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Changes to the OCaml bindings
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-----------------------------
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Changes to the C API
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--------------------
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* The following functions for creating constant expressions have been removed,
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because the underlying constant expressions are no longer supported. Instead,
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an instruction should be created using the ``LLVMBuildXYZ`` APIs, which will
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constant fold the operands if possible and create an instruction otherwise:
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* ``LLVMConstFNeg``
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Changes to the Go bindings
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--------------------------
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Changes to the FastISel infrastructure
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--------------------------------------
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* ...
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Changes to the DAG infrastructure
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---------------------------------
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Changes to the Metadata Info
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---------------------------------
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* Add Module Flags Metadata ``stack-protector-guard-symbol`` which specify a
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symbol for addressing the stack-protector guard.
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Changes to the Debug Info
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---------------------------------
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Previously when emitting DWARF v4 and tuning for GDB, llc would use DWARF v2's
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``DW_AT_bit_offset`` and ``DW_AT_data_member_location``. llc now uses DWARF v4's
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``DW_AT_data_bit_offset`` regardless of tuning.
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Support for ``DW_AT_data_bit_offset`` was added in GDB 8.0. For earlier versions,
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you can use llc's ``-dwarf-version=3`` option to emit compatible DWARF.
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Changes to the LLVM tools
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---------------------------------
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* ``llvm-readobj --elf-output-style=JSON`` no longer prefixes each JSON object
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with the file name. Previously, each object file's output looked like
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``"main.o":{"FileSummary":{"File":"main.o"},...}`` but is now
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``{"FileSummary":{"File":"main.o"},...}``. This allows each JSON object to be
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parsed in the same way, since each object no longer has a unique key. Tools
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that consume ``llvm-readobj``'s JSON output should update their parsers
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accordingly.
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* ``llvm-objdump`` now uses ``--print-imm-hex`` by default, which brings its
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default behavior closer in line with ``objdump``.
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Changes to LLDB
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---------------------------------
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Changes to Sanitizers
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---------------------
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Other Changes
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-------------
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External Open Source Projects Using LLVM 15
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===========================================
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* A project...
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Additional Information
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======================
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A wide variety of additional information is available on the `LLVM web page
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<https://llvm.org/>`_, in particular in the `documentation
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<https://llvm.org/docs/>`_ section. The web page also contains versions of the
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API documentation which is up-to-date with the Git version of the source
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code. You can access versions of these documents specific to this release by
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going into the ``llvm/docs/`` directory in the LLVM tree.
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If you have any questions or comments about LLVM, please feel free to contact
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us via the `Discourse forums <https://discourse.llvm.org>`_.
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