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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 `LLVM Developer's Mailing List
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<https://lists.llvm.org/mailman/listinfo/llvm-dev>`_ is a good place to send
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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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* ...
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Update on required toolchains to build LLVM
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-------------------------------------------
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With LLVM 15.x we will raise the version requirements of the toolchain used
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to build LLVM. The new requirements are as follows:
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* GCC >= 7.1
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* Clang >= 5.0
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* Apple Clang >= 9.3
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* Visual Studio 2019 >= 16.7
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In LLVM 15.x these requirements will be "soft" requirements and the version
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check can be skipped by passing -DLLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN=ON
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to CMake.
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With the release of LLVM 16.x these requirements will be hard and LLVM developers
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can start using C++17 features, making it impossible to build with older
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versions of these toolchains.
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Changes to the LLVM IR
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----------------------
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* Renamed ``llvm.experimental.vector.extract`` intrinsic to ``llvm.vector.extract``.
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* Renamed ``llvm.experimental.vector.insert`` intrinsic to ``llvm.vector.insert``.
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* The constant expression variants of the following instructions have been
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removed:
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* ``extractvalue``
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* ``insertvalue``
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* ``udiv``
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* ``sdiv``
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* ``urem``
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* ``srem``
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* ``fadd``
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* ``fsub``
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* ``fmul``
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* ``fdiv``
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* ``frem``
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* Added the support for ``fmax`` and ``fmin`` in ``atomicrmw`` instruction. The
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comparison is expected to match the behavior of ``llvm.maxnum.*`` and
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``llvm.minnum.*`` respectively.
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* ``callbr`` instructions no longer use ``blockaddress`` arguments for labels.
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Instead, label constraints starting with ``!`` refer directly to entries in
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the ``callbr`` indirect destination list.
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.. code-block:: llvm
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; Old representation
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%res = callbr i32 asm "", "=r,r,i"(i32 %x, i8 *blockaddress(@foo, %indirect))
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to label %fallthrough [label %indirect]
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; New representation
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%res = callbr i32 asm "", "=r,r,!i"(i32 %x)
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to label %fallthrough [label %indirect]
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Changes to building LLVM
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------------------------
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* Omitting ``CMAKE_BUILD_TYPE`` when using a single configuration generator is now
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an error. You now have to pass ``-DCMAKE_BUILD_TYPE=<type>`` in order to configure
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LLVM. This is done to help new users of LLVM select the correct type: since building
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LLVM in Debug mode is very resource intensive, we want to make sure that new users
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make the choice that lines up with their usage. We have also improved documentation
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around this setting that should help new users. You can find this documentation
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`here <https://llvm.org/docs/CMake.html#cmake-build-type>`_.
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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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Changes to the AMDGPU Backend
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-----------------------------
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* 8 and 16-bit atomic loads and stores are now supported
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Changes to the ARM Backend
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--------------------------
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* Added support for the Armv9-A, Armv9.1-A and Armv9.2-A architectures.
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* Added support for the Armv8.1-M PACBTI-M extension.
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* Added support for the Armv9-A, Armv9.1-A and Armv9.2-A architectures.
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* Added support for the Armv8.1-M PACBTI-M extension.
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* Removed the deprecation of ARMv8-A T32 Complex IT blocks. No deprecation
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warnings will be generated and -mrestrict-it is now always off by default.
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Previously it was on by default for Armv8 and off for all other architecture
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versions.
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* Added a pass to workaround Cortex-A57 Erratum 1742098 and Cortex-A72
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Erratum 1655431. This is enabled by default when targeting either CPU.
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* Implemented generation of Windows SEH unwind information.
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* Switched the MinGW target to use SEH instead of DWARF for unwind information.
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* Added support for the Cortex-M85 CPU.
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* Added support for a new -mframe-chain=(none|aapcs|aapcs+leaf) command-line
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option, which controls the generation of AAPCS-compliant Frame Records.
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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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* DirectX has been added as an experimental target. Specify
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``-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=DirectX`` in your CMake configuration
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to enable it. The target is not packaged in pre-built binaries.
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* The DirectX backend supports the ``dxil`` architecture which is based on LLVM
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3.6 IR encoded as bitcode and is the format used for DirectX GPU Shader
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programs.
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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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* The Zvfh extension was added.
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Changes to the WebAssembly Backend
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----------------------------------
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* ...
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Changes to the X86 Backend
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--------------------------
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* Support ``half`` type on SSE2 and above targets.
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* Support ``rdpru`` instruction on Zen2 and above targets.
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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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* Add ``LLVMGetCastOpcode`` function to aid users of ``LLVMBuildCast`` in
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resolving the best cast operation given a source value and destination type.
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This function is a direct wrapper of ``CastInst::getCastOpcode``.
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* Add ``LLVMGetAggregateElement`` function as a wrapper for
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``Constant::getAggregateElement``, which can be used to fetch an element of a
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constant struct, array or vector, independently of the underlying
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representation. The ``LLVMGetElementAsConstant`` function is deprecated in
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favor of the new function, which works on all constant aggregates, rather than
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only instances of ``ConstantDataSequential``.
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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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* ``LLVMConstExtractValue``
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* ``LLVMConstInsertValue``
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* ``LLVMConstUDiv``
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* ``LLVMConstExactUDiv``
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* ``LLVMConstSDiv``
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* ``LLVMConstExactSDiv``
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* ``LLVMConstURem``
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* ``LLVMConstSRem``
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* ``LLVMConstFAdd``
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* ``LLVMConstFSub``
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* ``LLVMConstFMul``
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* ``LLVMConstFDiv``
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* ``LLVMConstFRem``
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* Add ``LLVMDeleteInstruction`` function which allows deleting instructions that
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are not inserted into a basic block.
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* Refactor compression namespaces across the project, making way for a possible
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introduction of alternatives to zlib compression in the llvm toolchain.
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Changes are as follows:
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* Relocate the ``llvm::zlib`` namespace to ``llvm::compression::zlib``.
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* Remove crc32 from zlib compression namespace, people should use the ``llvm::crc32`` instead.
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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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During this release ...
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Changes to the LLVM tools
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---------------------------------
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* (Experimental) :manpage:`llvm-symbolizer(1)` now has ``--filter-markup`` to
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filter :doc:`Symbolizer Markup </SymbolizerMarkupFormat>` into human-readable
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form.
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* :doc:`llvm-objcopy <CommandGuide/llvm-objcopy>` has removed support for the legacy ``zlib-gnu`` format.
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* :doc:`llvm-objcopy <CommandGuide/llvm-objcopy>` now allows ``--set-section-flags src=... --rename-section src=tst``.
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``--add-section=.foo1=... --rename-section=.foo1=.foo2`` now adds ``.foo1`` instead of ``.foo2``.
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* The LLVM gold plugin now ignores bitcode from the ``.llvmbc`` section of ELF
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files when doing LTO. https://github.com/llvm/llvm-project/issues/47216
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Changes to LLDB
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---------------------------------
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* The "memory region" command now has a "--all" option to list all
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memory regions (including unmapped ranges). This is the equivalent
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of using address 0 then repeating the command until all regions
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have been listed.
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* Added "--show-tags" option to the "memory find" command. This is off by default.
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When enabled, if the target value is found in tagged memory, the tags for that
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memory will be shown inline with the memory contents.
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* Various memory related parts of LLDB have been updated to handle
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non-address bits (such as AArch64 pointer signatures):
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* "memory read", "memory write" and "memory find" can now be used with
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addresses with non-address bits.
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* All the read and write memory methods on SBProccess and SBTarget can
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be used with addreses with non-address bits.
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* When printing a pointer expression, LLDB can now dereference the result
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even if it has non-address bits.
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* The memory cache now ignores non-address bits when looking up memory
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locations. This prevents us reading locations multiple times, or not
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writing out new values if the addresses have different non-address bits.
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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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* The code for the `LLVM Visual Studio integration
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<https://marketplace.visualstudio.com/items?itemName=LLVMExtensions.llvm-toolchain>`_
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has been removed. This had been obsolete and abandoned since Visual Studio
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started including an integration by default in 2019.
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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 `mailing lists <https://llvm.org/docs/#mailing-lists>`_.
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