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======================
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LLVM 3.5 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 3.5 release. You may
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prefer the `LLVM 3.4 Release Notes <http://llvm.org/releases/3.4/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 3.5. 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.cs.uiuc.edu/mailman/listinfo/llvmdev>`_ 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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* All backends have been changed to use the MC asm printer and support for the
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non MC one has been removed.
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* Clang can now successfully self-host itself on Linux/Sparc64 and on
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FreeBSD/Sparc64.
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* LLVM now assumes the assembler supports ``.loc`` for generating debug line
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numbers. The old support for printing the debug line info directly was only
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used by ``llc`` and has been removed.
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* All inline assembly is parsed by the integrated assembler when it is enabled.
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Previously this was only the case for object-file output. It is now the case
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for assembly output as well. The integrated assembler can be disabled with
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the ``-no-integrated-as`` option,
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* llvm-ar now handles IR files like regular object files. In particular, a
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regular symbol table is created for symbols defined in IR files, including
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those in file scope inline assembly.
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* LLVM now always uses cfi directives for producing most stack
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unwinding information.
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* The prefix for loop vectorizer hint metadata has been changed from
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``llvm.vectorizer`` to ``llvm.loop.vectorize``.
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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 ARM Backend
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--------------------------
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Since release 3.3, a lot of new features have been included in the ARM
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back-end but weren't production ready (ie. well tested) on release 3.4.
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Just after the 3.4 release, we started heavily testing two major parts
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of the back-end: the integrated assembler (IAS) and the ARM exception
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handling (EHABI), and now they are enabled by default on LLVM/Clang.
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The IAS received a lot of GNU extensions and directives, as well as some
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specific pre-UAL instructions. Not all remaining directives will be
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implemented, as we made judgement calls on the need versus the complexity,
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and have chosen simplicity and future compatibility where hard decisions
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had to be made. The major difference is, as stated above, the IAS validates
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all inline ASM, not just for object emission, and that cause trouble with
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some uses of inline ASM as pre-processor magic.
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So, while the IAS is good enough to compile large projects (including most
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of the Linux kernel), there are a few things that we can't (and probably
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won't) do. For those cases, please use ``-fno-integrated-as`` in Clang.
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Exception handling is another big change. After extensive testing and
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changes to cooperate with Dwarf unwinding, EHABI is enabled by default.
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The options ``-arm-enable-ehabi`` and ``-arm-enable-ehabi-descriptors``,
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which were used to enable EHABI in the previous releases, are removed now.
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This means all ARM code will emit EH unwind tables, or CFI unwinding (for
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debug/profiling), or both. To avoid run-time inconsistencies, C code will
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also emit EH tables (in case they interoperate with C++ code), as is the
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case for other architectures (ex. x86_64).
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External Open Source Projects Using LLVM 3.5
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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 3.5.
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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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