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This is a step towards removing the rampant undefined behaviour in SelectionDAG, which is a part of llvm.org/PR26808. We rename SelectionDAGISel::Select to SelectImpl and update targets to match, and then change Select to return void and consolidate the sketchy behaviour we're trying to get away from there. Next, we'll update backends to implement `void Select(...)` instead of SelectImpl and eventually drop the base Select implementation. llvm-svn: 268693
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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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LLVMGetAttrKindID.
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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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.. 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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