c5b3de6745
This works with the automatic export of all symbols; in MinGW mode, when a DLL has no explicit dllexports, it exports all symbols (except for some that are hardcoded to be excluded, including some toolchain libraries). By hooking up the hidden visibility to the -exclude-symbols: directive, the automatic export of all symbols can be controlled in an easier way (with a mechanism that doesn't require strict annotation of every single symbol, but which allows gradually marking more unnecessary symbols as hidden). The primary use case is dylib builds of LLVM/Clang. These can be done in MinGW mode but not in MSVC mode, as MinGW builds can export all symbols (and the calling code can use APIs without corresponding dllimport directives). However, as all symbols are exported, it can easily overflow the max number of exported symbols in a DLL (65536). In the llvm-mingw distribution, only the X86, ARM and AArch64 backends are enabled; for the LLVM 13.0.0 release, libLLVM-13.dll ended up with 58112 exported symbols. For LLVM 14.0.0, it was 62015 symbols. Current builds of the 15.x branch end up at around 64650 symbols - i.e. extremely close to the limit. The msys2 packages of LLVM have had to progressively disable more of their backends in their builds, to be able to keep building with a dylib. This allows improving the current mingw dylib situation significantly, by using the same hidden visibility options and attributes as on Unix. With those in place, a current build of LLVM git main ends up at 35142 symbols instead of 64650. For code using hidden visibility, this now requires linking with either a current git lld or ld.bfd. (Older lld error out on the unknown directives, older ld.bfd will successfully link, but will print huge amounts of warnings.) Differential Revision: https://reviews.llvm.org/D130121
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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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* ...
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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 >= 9.3
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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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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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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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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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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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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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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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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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