docs/ReleaseNotes.rst - llvm - Git at Google

 ========================
 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>`_.
	========================
	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>`_.