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180 lines
6.3 KiB
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======================
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LLVM 3.9 Release Notes
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======================
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.. contents::
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:local:
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.. warning::
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These are in-progress notes for the upcoming LLVM 3.9 release. You may
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prefer the `LLVM 3.8 Release Notes <http://llvm.org/releases/3.8.0/docs
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/ReleaseNotes.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 3.9. 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 <http://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 <http://llvm.org/>`_. If you
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have questions or comments, the `LLVM Developer's Mailing List
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<http://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 Subversion 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 <http://llvm.org/releases/>`_.
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Non-comprehensive list of changes in this release
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=================================================
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* The LLVMContext gains a new runtime check (see
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LLVMContext::discardValueNames()) that can be set to discard Value names
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(other than GlobalValue). This is intended to be used in release builds by
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clients that are interested in saving CPU/memory as much as possible.
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* There is no longer a "global context" available in LLVM, except for the C API.
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* .. note about autoconf build having been removed.
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* .. note about C API functions LLVMParseBitcode,
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LLVMParseBitcodeInContext, LLVMGetBitcodeModuleInContext and
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LLVMGetBitcodeModule having been removed. LLVMGetTargetMachineData has been
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removed (use LLVMGetDataLayout instead).
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* The C API function LLVMLinkModules has been removed.
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* The C API function LLVMAddTargetData has been removed.
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* The C API function LLVMGetDataLayout is deprecated
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in favor of LLVMGetDataLayoutStr.
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* The C API enum LLVMAttribute is deprecated in favor of
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LLVMGetAttributeKindForName.
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* ``TargetFrameLowering::eliminateCallFramePseudoInstr`` now returns an
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iterator to the next instruction instead of ``void``. Targets that previously
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did ``MBB.erase(I); return;`` now probably want ``return MBB.erase(I);``.
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* ``SelectionDAGISel::Select`` now returns ``void``. Out of tree targets will
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need to be updated to replace the argument node and remove any dead nodes in
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cases where they currently return an ``SDNode *`` from this interface.
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* Introduction of ThinLTO: [FIXME: needs to be documented more extensively in
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/docs/ ; ping Mehdi/Teresa before the release if not done]
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* Raised the minimum required CMake version to 3.4.3.
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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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* ... next change ...
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.. NOTE
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If you would like to document a larger change, then you can add a
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subsection about it right here. You can copy the following boilerplate
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and un-indent it (the indentation causes it to be inside this comment).
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Special New Feature
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-------------------
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Makes programs 10x faster by doing Special New Thing.
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Changes to the LLVM IR
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----------------------
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* New intrinsics ``llvm.masked.load``, ``llvm.masked.store``,
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``llvm.masked.gather`` and ``llvm.masked.scatter`` were introduced to the
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LLVM IR to allow selective memory access for vector data types.
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Changes to LLVM's IPO model
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---------------------------
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LLVM no longer does inter-procedural analysis and optimization (except
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inlining) on functions with comdat linkage. Doing IPO over such
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functions is unsound because the implementation the linker chooses at
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link-time may be differently optimized than the one what was visible
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during optimization, and may have arbitrarily different observable
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behavior. See `PR26774 <http://llvm.org/PR26774>`_ for more details.
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Changes to the ARM Backend
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--------------------------
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During this release ...
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Changes to the MIPS Target
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--------------------------
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During this release ...
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Changes to the PowerPC Target
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-----------------------------
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Moved some optimizations from O3 to O2 (D18562)
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* Enable sibling call optimization on ppc64 ELFv1/ELFv2 abi
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Changes to the X86 Target
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-------------------------
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* LLVM now supports the Intel CPU codenamed Skylake Server with AVX-512
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extensions using ``-march=skylake-avx512``. The switch enables the
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ISA extensions AVX-512{F, CD, VL, BW, DQ}.
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* LLVM now supports the Intel CPU codenamed Knights Landing with AVX-512
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extensions using ``-march=knl``. The switch enables the ISA extensions
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AVX-512{F, CD, ER, PF}.
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Changes to the AMDGPU Target
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-----------------------------
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* Mesa 11.0.x is no longer supported
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Changes to the OCaml bindings
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-----------------------------
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During this release ...
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Support for attribute 'notail' has been added
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---------------------------------------------
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This marker prevents optimization passes from adding 'tail' or
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'musttail' markers to a call. It is used to prevent tail call
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optimization from being performed on the call.
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External Open Source Projects Using LLVM 3.9
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============================================
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An exciting aspect of LLVM is that it is used as an enabling technology for
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a lot of other language and tools projects. This section lists some of the
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projects that have already been updated to work with LLVM 3.9.
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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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<http://llvm.org/>`_, in particular in the `documentation
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<http://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 Subversion 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 <http://llvm.org/docs/#maillist>`_.
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