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LLVM 7.0.0 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 7 release.
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Release notes for previous releases can be found on
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`the Download Page <http://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 7.0.0. 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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.. 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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* Libraries have been renamed from 7.0 to 7. This change also impacts
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downstream libraries like lldb.
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* The LoopInstSimplify pass (-loop-instsimplify) has been removed.
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* Symbols starting with ``?`` are no longer mangled by LLVM when using the
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Windows ``x`` or ``w`` IR mangling schemes.
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* A new tool named :doc:`llvm-exegesis <CommandGuide/llvm-exegesis>` has been
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added. :program:`llvm-exegesis` automatically measures instruction scheduling
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properties (latency/uops) and provides a principled way to edit scheduling
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models.
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* A new tool named :doc:`llvm-mca <CommandGuide/llvm-mca>` has been added.
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:program:`llvm-mca` is a static performance analysis tool that uses
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information available in LLVM to statically predict the performance of
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machine code for a specific CPU.
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* The optimization flag to merge constants (-fmerge-all-constants) is no longer
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applied by default.
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* Optimization of floating-point casts is improved. This may cause surprising
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results for code that is relying on the undefined behavior of overflowing
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casts. The optimization can be disabled by specifying a function attribute:
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"strict-float-cast-overflow"="false". This attribute may be created by the
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clang option :option:`-fno-strict-float-cast-overflow`.
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Code sanitizers can be used to detect affected patterns. The option for
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detecting this problem alone is "-fsanitize=float-cast-overflow":
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.. code-block:: c
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int main() {
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float x = 4294967296.0f;
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x = (float)((int)x);
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printf("junk in the ftrunc: %f\n", x);
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return 0;
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}
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.. code-block:: bash
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clang -O1 ftrunc.c -fsanitize=float-cast-overflow ; ./a.out
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ftrunc.c:5:15: runtime error: 4.29497e+09 is outside the range of representable values of type 'int'
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junk in the ftrunc: 0.000000
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* ``LLVM_ON_WIN32`` is no longer set by ``llvm/Config/config.h`` and
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``llvm/Config/llvm-config.h``. If you used this macro, use the compiler-set
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``_WIN32`` instead which is set exactly when ``LLVM_ON_WIN32`` used to be set.
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* The ``DEBUG`` macro has been renamed to ``LLVM_DEBUG``, the interface remains
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the same. If you used this macro you need to migrate to the new one.
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You should also clang-format your code to make it easier to integrate future
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changes locally. This can be done with the following bash commands:
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.. code-block:: bash
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git grep -l 'DEBUG' | xargs perl -pi -e 's/\bDEBUG\s?\(/LLVM_DEBUG(/g'
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git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
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* Early support for UBsan, X-Ray instrumentation and libFuzzer (x86 and x86_64) for OpenBSD. Support for MSan
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(x86_64), X-Ray instrumentation and libFuzzer (x86 and x86_64) for FreeBSD.
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* Note..
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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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* The signatures for the builtins @llvm.memcpy, @llvm.memmove, and @llvm.memset
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have changed. Alignment is no longer an argument, and are instead conveyed as
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parameter attributes.
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* invariant.group.barrier has been renamed to launder.invariant.group.
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* invariant.group metadata can now refer only empty metadata nodes.
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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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Changes to the X86 Target
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-------------------------
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During this release ...
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Changes to the AMDGPU Target
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-----------------------------
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During this release ...
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Changes to the AVR Target
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-----------------------------
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During this release ...
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Changes to the OCaml bindings
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-----------------------------
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* Remove ``add_bb_vectorize``.
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Changes to the C API
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--------------------
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* Remove ``LLVMAddBBVectorizePass``. The implementation was removed and the C
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interface was made a deprecated no-op in LLVM 5. Use
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``LLVMAddSLPVectorizePass`` instead to get the supported SLP vectorizer.
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Changes to the DAG infrastructure
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---------------------------------
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* ADDC/ADDE/SUBC/SUBE are now deprecated and will default to expand. Backends
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that wish to continue to use these opcodes should explicitely request so
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using ``setOperationAction`` in their ``TargetLowering``. New backends
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should use UADDO/ADDCARRY/USUBO/SUBCARRY instead of the deprecated opcodes.
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* The SETCCE opcode has now been removed in favor of SETCCCARRY.
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External Open Source Projects Using LLVM 7
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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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<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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