| ======================== |
| LLVM 7.0.0 Release Notes |
| ======================== |
| |
| .. contents:: |
| :local: |
| |
| .. warning:: |
| These are in-progress notes for the upcoming LLVM 7 release. |
| Release notes for previous releases can be found on |
| `the Download Page <http://releases.llvm.org/download.html>`_. |
| |
| |
| Introduction |
| ============ |
| |
| This document contains the release notes for the LLVM Compiler Infrastructure, |
| release 7.0.0. Here we describe the status of LLVM, including major improvements |
| from the previous release, improvements in various subprojects of LLVM, and |
| some of the current users of the code. All LLVM releases may be downloaded |
| from the `LLVM releases web site <http://llvm.org/releases/>`_. |
| |
| For more information about LLVM, including information about the latest |
| release, please check out the `main LLVM web site <http://llvm.org/>`_. If you |
| have questions or comments, the `LLVM Developer's Mailing List |
| <http://lists.llvm.org/mailman/listinfo/llvm-dev>`_ is a good place to send |
| them. |
| |
| Note that if you are reading this file from a Subversion checkout or the main |
| LLVM web page, this document applies to the *next* release, not the current |
| one. To see the release notes for a specific release, please see the `releases |
| page <http://llvm.org/releases/>`_. |
| |
| Non-comprehensive list of changes in this release |
| ================================================= |
| .. NOTE |
| For small 1-3 sentence descriptions, just add an entry at the end of |
| this list. If your description won't fit comfortably in one bullet |
| point (e.g. maybe you would like to give an example of the |
| functionality, or simply have a lot to talk about), see the `NOTE` below |
| for adding a new subsection. |
| |
| * Libraries have been renamed from 7.0 to 7. This change also impacts |
| downstream libraries like lldb. |
| |
| * The LoopInstSimplify pass (-loop-instsimplify) has been removed. |
| |
| * Symbols starting with ``?`` are no longer mangled by LLVM when using the |
| Windows ``x`` or ``w`` IR mangling schemes. |
| |
| * A new tool named :doc:`llvm-exegesis <CommandGuide/llvm-exegesis>` has been |
| added. :program:`llvm-exegesis` automatically measures instruction scheduling |
| properties (latency/uops) and provides a principled way to edit scheduling |
| models. |
| |
| * A new tool named :doc:`llvm-mca <CommandGuide/llvm-mca>` has been added. |
| :program:`llvm-mca` is a static performance analysis tool that uses |
| information available in LLVM to statically predict the performance of |
| machine code for a specific CPU. |
| |
| * The optimization flag to merge constants (-fmerge-all-constants) is no longer |
| applied by default. |
| |
| * Optimization of floating-point casts is improved. This may cause surprising |
| results for code that is relying on the undefined behavior of overflowing |
| casts. The optimization can be disabled by specifying a function attribute: |
| "strict-float-cast-overflow"="false". This attribute may be created by the |
| clang option :option:`-fno-strict-float-cast-overflow`. |
| Code sanitizers can be used to detect affected patterns. The option for |
| detecting this problem alone is "-fsanitize=float-cast-overflow": |
| |
| .. code-block:: c |
| |
| int main() { |
| float x = 4294967296.0f; |
| x = (float)((int)x); |
| printf("junk in the ftrunc: %f\n", x); |
| return 0; |
| } |
| |
| .. code-block:: bash |
| |
| clang -O1 ftrunc.c -fsanitize=float-cast-overflow ; ./a.out |
| ftrunc.c:5:15: runtime error: 4.29497e+09 is outside the range of representable values of type 'int' |
| junk in the ftrunc: 0.000000 |
| |
| * ``LLVM_ON_WIN32`` is no longer set by ``llvm/Config/config.h`` and |
| ``llvm/Config/llvm-config.h``. If you used this macro, use the compiler-set |
| ``_WIN32`` instead which is set exactly when ``LLVM_ON_WIN32`` used to be set. |
| |
| * The ``DEBUG`` macro has been renamed to ``LLVM_DEBUG``, the interface remains |
| the same. If you used this macro you need to migrate to the new one. |
| You should also clang-format your code to make it easier to integrate future |
| changes locally. This can be done with the following bash commands: |
| |
| .. code-block:: bash |
| |
| git grep -l 'DEBUG' | xargs perl -pi -e 's/\bDEBUG\s?\(/LLVM_DEBUG(/g' |
| git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM |
| |
| * Early support for UBsan, X-Ray instrumentation and libFuzzer (x86 and x86_64) for OpenBSD. Support for MSan |
| (x86_64), X-Ray instrumentation and libFuzzer (x86 and x86_64) for FreeBSD. |
| |
| * Note.. |
| |
| .. NOTE |
| If you would like to document a larger change, then you can add a |
| subsection about it right here. You can copy the following boilerplate |
| and un-indent it (the indentation causes it to be inside this comment). |
| |
| Special New Feature |
| ------------------- |
| |
| Makes programs 10x faster by doing Special New Thing. |
| |
| Changes to the LLVM IR |
| ---------------------- |
| |
| * The signatures for the builtins @llvm.memcpy, @llvm.memmove, and @llvm.memset |
| have changed. Alignment is no longer an argument, and are instead conveyed as |
| parameter attributes. |
| |
| * invariant.group.barrier has been renamed to launder.invariant.group. |
| |
| * invariant.group metadata can now refer only empty metadata nodes. |
| |
| Changes to the ARM Backend |
| -------------------------- |
| |
| During this release ... |
| |
| |
| Changes to the MIPS Target |
| -------------------------- |
| |
| During this release ... |
| |
| |
| Changes to the PowerPC Target |
| ----------------------------- |
| |
| During this release ... |
| |
| Changes to the X86 Target |
| ------------------------- |
| |
| During this release ... |
| |
| Changes to the AMDGPU Target |
| ----------------------------- |
| |
| During this release ... |
| |
| Changes to the AVR Target |
| ----------------------------- |
| |
| During this release ... |
| |
| Changes to the OCaml bindings |
| ----------------------------- |
| |
| * Remove ``add_bb_vectorize``. |
| |
| |
| Changes to the C API |
| -------------------- |
| |
| * Remove ``LLVMAddBBVectorizePass``. The implementation was removed and the C |
| interface was made a deprecated no-op in LLVM 5. Use |
| ``LLVMAddSLPVectorizePass`` instead to get the supported SLP vectorizer. |
| |
| Changes to the DAG infrastructure |
| --------------------------------- |
| * ADDC/ADDE/SUBC/SUBE are now deprecated and will default to expand. Backends |
| that wish to continue to use these opcodes should explicitely request so |
| using ``setOperationAction`` in their ``TargetLowering``. New backends |
| should use UADDO/ADDCARRY/USUBO/SUBCARRY instead of the deprecated opcodes. |
| |
| * The SETCCE opcode has now been removed in favor of SETCCCARRY. |
| |
| External Open Source Projects Using LLVM 7 |
| ========================================== |
| |
| * A project... |
| |
| |
| Additional Information |
| ====================== |
| |
| A wide variety of additional information is available on the `LLVM web page |
| <http://llvm.org/>`_, in particular in the `documentation |
| <http://llvm.org/docs/>`_ section. The web page also contains versions of the |
| API documentation which is up-to-date with the Subversion version of the source |
| code. You can access versions of these documents specific to this release by |
| going into the ``llvm/docs/`` directory in the LLVM tree. |
| |
| If you have any questions or comments about LLVM, please feel free to contact |
| us via the `mailing lists <http://llvm.org/docs/#maillist>`_. |