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======================
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LLVM 3.6 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 3.6 release. You may
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prefer the `LLVM 3.5 Release Notes <http://llvm.org/releases/3.5.0/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 3.6. 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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.. 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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* Support for AuroraUX has been removed.
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* Added support for a `native object file-based bitcode wrapper format
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<BitCodeFormat.html#native-object-file>`_.
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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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Prefix data rework
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------------------
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The semantics of the ``prefix`` attribute have been changed. Users
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that want the previous ``prefix`` semantics should instead use
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``prologue``. To motivate this change, let's examine the primary
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usecases that these attributes aim to serve,
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1. Code sanitization metadata (e.g. Clang's undefined behavior
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sanitizer)
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2. Function hot-patching: Enable the user to insert ``nop`` operations
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at the beginning of the function which can later be safely replaced
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with a call to some instrumentation facility.
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3. Language runtime metadata: Allow a compiler to insert data for
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use by the runtime during execution. GHC is one example of a
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compiler that needs this functionality for its
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tables-next-to-code functionality.
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Previously ``prefix`` served cases (1) and (2) quite well by allowing the user
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to introduce arbitrary data at the entrypoint but before the function
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body. Case (3), however, was poorly handled by this approach as it
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required that prefix data was valid executable code.
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In this release the concept of prefix data has been redefined to be
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data which occurs immediately before the function entrypoint (i.e. the
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symbol address). Since prefix data now occurs before the function
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entrypoint, there is no need for the data to be valid code.
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The previous notion of prefix data now goes under the name "prologue
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data" to emphasize its duality with the function epilogue.
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The intention here is to handle cases (1) and (2) with prologue data and
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case (3) with prefix data. See the language reference for further details
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on the semantics of these attributes.
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This refactoring arose out of discussions_ with Reid Kleckner in
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response to a proposal to introduce the notion of symbol offsets to
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enable handling of case (3).
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.. _discussions: http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-May/073235.html
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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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During this release ...
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External Open Source Projects Using LLVM 3.6
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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 3.6.
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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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