llvm/docs/ReleaseNotes.rst - third_party/llvm-project - Git at Google

 =========================
 LLVM 11.0.0 Release Notes
 =========================

 .. contents::
     :local:

 .. warning::
    These are in-progress notes for the upcoming LLVM 11 release.
    Release notes for previous releases can be found on
    `the Download Page <https://releases.llvm.org/download.html>`_.


 Introduction
 ============

 This document contains the release notes for the LLVM Compiler Infrastructure,
 release 11.0.0.  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 <https://llvm.org/releases/>`_.

 For more information about LLVM, including information about the latest
 release, please check out the `main LLVM web site <https://llvm.org/>`_.  If you
 have questions or comments, the `LLVM Developer's Mailing List
 <https://lists.llvm.org/mailman/listinfo/llvm-dev>`_ is a good place to send
 them.

 Note that if you are reading this file from a Git 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 <https://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.

 * ...


 .. 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 callsite attribute `vector-function-abi-variant
   <https://llvm.org/docs/LangRef.html#call-site-attributes>`_ has been
   added to describe the mapping between scalar functions and vector
   functions, to enable vectorization of call sites. The information
   provided by the attribute is interfaced via the API provided by the
   ``VFDatabase`` class.

 * `dereferenceable` attributes and metadata on pointers no longer imply
   anything about the alignment of the pointer in question. Previously, some
   optimizations would make assumptions based on the type of the pointer. This
   behavior was undocumented. To preserve optimizations, frontends may need to
   be updated to generate appropriate `align` attributes and metadata.

 * The DIModule metadata is extended to contain file and line number
   information. This information is used to represent Fortran modules debug
   info at IR level.

 Changes to building LLVM
 ------------------------

 Changes to the ARM Backend
 --------------------------

 During this release ...

 * Implemented C-language intrinsics for the full Arm v8.1-M MVE instruction
   set. ``<arm_mve.h>`` now supports the complete API defined in the Arm C
   Language Extensions.

 * Added support for assembly for the optional Custom Datapath Extension (CDE)
   for Arm M-profile targets.

 * Implemented C-language intrinsics ``<arm_cde.h>`` for the CDE instruction set.

 * Clang now defaults to ``-fomit-frame-pointer`` when targeting non-Android
   Linux for arm and thumb when optimizations are enabled. Users that were
   previously not specifying a value and relying on the implicit compiler
   default may wish to specify ``-fno-omit-frame-pointer`` to get the old
   behavior. This improves compatibility with GCC.

 Changes to the MIPS Target
 --------------------------

 During this release ...


 Changes to the PowerPC Target
 -----------------------------

 During this release ...

 Changes to the X86 Target
 -------------------------

 During this release ...


 * Functions with the probe-stack attribute set to "inline-asm" are now protected
   against stack clash without the need of a third-party probing function and
   with limited impact on performance.
 * -x86-enable-old-knl-abi command line switch has been removed. v32i16/v64i8
   vectors are always passed in ZMM register when avx512f is enabled and avx512bw
   is disabled.
 * Vectors larger than 512 bits with i16 or i8 elements will be passed in
   multiple ZMM registers when avx512f is enabled. Previously this required
   avx512bw otherwise they would split into multiple YMM registers. This means
   vXi16/vXi8 vectors are consistently treated the same as
   vXi32/vXi64/vXf64/vXf32 vectors of the same total width.

 Changes to the AMDGPU Target
 -----------------------------

 * The backend default denormal handling mode has been switched to on
   for all targets for all compute function types. Frontends wishing to
   retain the old behavior should explicitly request f32 denormal
   flushing.

 Changes to the AVR Target
 -----------------------------

 * Moved from an experimental backend to an official backend. AVR support is now
   included by default in all LLVM builds and releases and is available under
   the "avr-unknown-unknown" target triple.

 Changes to the WebAssembly Target
 ---------------------------------

 * Programs which don't have a "main" function, called "reactors" are now
   properly supported, with a new `-mexec-model=reactor` flag. Programs which
   previously used `-Wl,--no-entry` to avoid having a main function should
   switch to this new flag, so that static initialization is properly
   performed.

 * `__attribute__((visibility("protected")))` now evokes a warning, as
   WebAssembly does not support "protected" visibility.

 Changes to the OCaml bindings
 -----------------------------


 Changes to the C API
 --------------------


 Changes to the Go bindings
 --------------------------


 Changes to the DAG infrastructure
 ---------------------------------


 Changes to the Debug Info
 ---------------------------------

 * LLVM now supports the debug entry values (DW_OP_entry_value) production for
   the x86, ARM, and AArch64 targets by default. Other targets can use
   the utility by using the experimental option ("-debug-entry-values").
   This is a debug info feature that allows debuggers to recover the value of
   optimized-out parameters by going up a stack frame and interpreting the values
   passed to the callee. The feature improves the debugging user experience when
   debugging optimized code.

 Changes to the LLVM tools
 ---------------------------------

 * Added an option (--show-section-sizes) to llvm-dwarfdump to show the sizes
   of all debug sections within a file.

 * llvm-nm now implements the flag ``--special-syms`` and will filter out special
   symbols, i.e. mapping symbols on ARM and AArch64, by default. This matches
   the GNU nm behavior.

 Changes to LLDB
 ===============

 External Open Source Projects Using LLVM 11
 ===========================================

 * A project...


 Additional Information
 ======================

 A wide variety of additional information is available on the `LLVM web page
 <https://llvm.org/>`_, in particular in the `documentation
 <https://llvm.org/docs/>`_ section.  The web page also contains versions of the
 API documentation which is up-to-date with the Git 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 <https://llvm.org/docs/#mailing-lists>`_.
	=========================
	LLVM 11.0.0 Release Notes
	=========================

	.. contents::
	:local:

	.. warning::
	These are in-progress notes for the upcoming LLVM 11 release.
	Release notes for previous releases can be found on
	`the Download Page <https://releases.llvm.org/download.html>`_.


	Introduction
	============

	This document contains the release notes for the LLVM Compiler Infrastructure,
	release 11.0.0. 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 <https://llvm.org/releases/>`_.

	For more information about LLVM, including information about the latest
	release, please check out the `main LLVM web site <https://llvm.org/>`_. If you
	have questions or comments, the `LLVM Developer's Mailing List
	<https://lists.llvm.org/mailman/listinfo/llvm-dev>`_ is a good place to send
	them.

	Note that if you are reading this file from a Git 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 <https://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.

	* ...


	.. 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 callsite attribute `vector-function-abi-variant
	<https://llvm.org/docs/LangRef.html#call-site-attributes>`_ has been
	added to describe the mapping between scalar functions and vector
	functions, to enable vectorization of call sites. The information
	provided by the attribute is interfaced via the API provided by the
	``VFDatabase`` class.

	* `dereferenceable` attributes and metadata on pointers no longer imply
	anything about the alignment of the pointer in question. Previously, some
	optimizations would make assumptions based on the type of the pointer. This
	behavior was undocumented. To preserve optimizations, frontends may need to
	be updated to generate appropriate `align` attributes and metadata.

	* The DIModule metadata is extended to contain file and line number
	information. This information is used to represent Fortran modules debug
	info at IR level.

	Changes to building LLVM
	------------------------

	Changes to the ARM Backend
	--------------------------

	During this release ...

	* Implemented C-language intrinsics for the full Arm v8.1-M MVE instruction
	set. ``<arm_mve.h>`` now supports the complete API defined in the Arm C
	Language Extensions.

	* Added support for assembly for the optional Custom Datapath Extension (CDE)
	for Arm M-profile targets.

	* Implemented C-language intrinsics ``<arm_cde.h>`` for the CDE instruction set.

	* Clang now defaults to ``-fomit-frame-pointer`` when targeting non-Android
	Linux for arm and thumb when optimizations are enabled. Users that were
	previously not specifying a value and relying on the implicit compiler
	default may wish to specify ``-fno-omit-frame-pointer`` to get the old
	behavior. This improves compatibility with GCC.

	Changes to the MIPS Target
	--------------------------

	During this release ...


	Changes to the PowerPC Target
	-----------------------------

	During this release ...

	Changes to the X86 Target
	-------------------------

	During this release ...


	* Functions with the probe-stack attribute set to "inline-asm" are now protected
	against stack clash without the need of a third-party probing function and
	with limited impact on performance.
	* -x86-enable-old-knl-abi command line switch has been removed. v32i16/v64i8
	vectors are always passed in ZMM register when avx512f is enabled and avx512bw
	is disabled.
	* Vectors larger than 512 bits with i16 or i8 elements will be passed in
	multiple ZMM registers when avx512f is enabled. Previously this required
	avx512bw otherwise they would split into multiple YMM registers. This means
	vXi16/vXi8 vectors are consistently treated the same as
	vXi32/vXi64/vXf64/vXf32 vectors of the same total width.

	Changes to the AMDGPU Target
	-----------------------------

	* The backend default denormal handling mode has been switched to on
	for all targets for all compute function types. Frontends wishing to
	retain the old behavior should explicitly request f32 denormal
	flushing.

	Changes to the AVR Target
	-----------------------------

	* Moved from an experimental backend to an official backend. AVR support is now
	included by default in all LLVM builds and releases and is available under
	the "avr-unknown-unknown" target triple.

	Changes to the WebAssembly Target
	---------------------------------

	* Programs which don't have a "main" function, called "reactors" are now
	properly supported, with a new `-mexec-model=reactor` flag. Programs which
	previously used `-Wl,--no-entry` to avoid having a main function should
	switch to this new flag, so that static initialization is properly
	performed.

	* `__attribute__((visibility("protected")))` now evokes a warning, as
	WebAssembly does not support "protected" visibility.

	Changes to the OCaml bindings
	-----------------------------



	Changes to the C API
	--------------------


	Changes to the Go bindings
	--------------------------


	Changes to the DAG infrastructure
	---------------------------------


	Changes to the Debug Info
	---------------------------------

	* LLVM now supports the debug entry values (DW_OP_entry_value) production for
	the x86, ARM, and AArch64 targets by default. Other targets can use
	the utility by using the experimental option ("-debug-entry-values").
	This is a debug info feature that allows debuggers to recover the value of
	optimized-out parameters by going up a stack frame and interpreting the values
	passed to the callee. The feature improves the debugging user experience when
	debugging optimized code.

	Changes to the LLVM tools
	---------------------------------

	* Added an option (--show-section-sizes) to llvm-dwarfdump to show the sizes
	of all debug sections within a file.

	* llvm-nm now implements the flag ``--special-syms`` and will filter out special
	symbols, i.e. mapping symbols on ARM and AArch64, by default. This matches
	the GNU nm behavior.

	Changes to LLDB
	===============

	External Open Source Projects Using LLVM 11
	===========================================

	* A project...


	Additional Information
	======================

	A wide variety of additional information is available on the `LLVM web page
	<https://llvm.org/>`_, in particular in the `documentation
	<https://llvm.org/docs/>`_ section. The web page also contains versions of the
	API documentation which is up-to-date with the Git 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 <https://llvm.org/docs/#mailing-lists>`_.