shylie/llvm-project
1
0
Fork 0
Code Issues Pull Requests Actions 6 Packages Projects Releases Wiki Activity
llvm-project/llvm/docs/ReleaseNotes.rst
Nikita Popov 304f1d59ca [IR] Switch everything to use memory attribute 
This switches everything to use the memory attribute proposed in
https://discourse.llvm.org/t/rfc-unify-memory-effect-attributes/65579.
The old argmemonly, inaccessiblememonly and inaccessiblemem_or_argmemonly
attributes are dropped. The readnone, readonly and writeonly attributes
are restricted to parameters only.

The old attributes are auto-upgraded both in bitcode and IR.
The bitcode upgrade is a policy requirement that has to be retained
indefinitely. The IR upgrade is mainly there so it's not necessary
to update all tests using memory attributes in this patch, which
is already large enough. We could drop that part after migrating
tests, or retain it longer term, to make it easier to import IR
from older LLVM versions.

High-level Function/CallBase APIs like doesNotAccessMemory() or
setDoesNotAccessMemory() are mapped transparently to the memory
attribute. Code that directly manipulates attributes (e.g. via
AttributeList) on the other hand needs to switch to working with
the memory attribute instead.

Differential Revision: https://reviews.llvm.org/D135780
2022-11-04 10:21:38 +01:00

258 lines
8.3 KiB
ReStructuredText
Raw Blame History

============================
LLVM |release| Release Notes
============================
.. contents::
:local:
.. only:: PreRelease
.. warning::
These are in-progress notes for the upcoming LLVM |version| 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 |release|. 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 `Discourse forums
<https://discourse.llvm.org>`_ is a good place to ask
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.
* The ``readnone`` calls which are crossing suspend points in coroutines will
not be merged. Since ``readnone`` calls may access thread id and thread id
is not a constant in coroutines. This decision may cause unnecessary
performance regressions and we plan to fix it in later versions.
* ...
Update on required toolchains to build LLVM
-------------------------------------------
LLVM is now built with C++17 by default. This means C++17 can be used in
the code base.
The previous "soft" toolchain requirements have now been changed to "hard".
This means that the the following versions are now required to build LLVM
and there is no way to suppress this error.
* GCC >= 7.1
* Clang >= 5.0
* Apple Clang >= 10.0
* Visual Studio 2019 >= 16.7
Changes to the LLVM IR
----------------------
* The ``readnone``, ``readonly``, ``writeonly``, ``argmemonly``,
``inaccessiblememonly`` and ``inaccessiblemem_or_argmemonly`` function
attributes have been replaced by a single ``memory(...)`` attribute. The
old attributes may be mapped to the new one as follows:
* ``readnone`` -> ``memory(none)``
* ``readonly`` -> ``memory(read)``
* ``writeonly`` -> ``memory(write)``
* ``argmemonly`` -> ``memory(argmem: readwrite)``
* ``argmemonly readonly`` -> ``memory(argmem: read)``
* ``argmemonly writeonly`` -> ``memory(argmem: write)``
* ``inaccessiblememonly`` -> ``memory(inaccessiblemem: readwrite)``
* ``inaccessiblememonly readonly`` -> ``memory(inaccessiblemem: read)``
* ``inaccessiblememonly writeonly`` -> ``memory(inaccessiblemem: write)``
* ``inaccessiblemem_or_argmemonly`` ->
``memory(argmem: readwrite, inaccessiblemem: readwrite)``
* ``inaccessiblemem_or_argmemonly readonly`` ->
``memory(argmem: read, inaccessiblemem: read)``
* ``inaccessiblemem_or_argmemonly writeonly`` ->
``memory(argmem: write, inaccessiblemem: write)``
* The constant expression variants of the following instructions has been
removed:
* ``fneg``
Changes to building LLVM
------------------------
Changes to TableGen
-------------------
Changes to the AArch64 Backend
------------------------------
* Added support for the Cortex-A715 CPU.
Changes to the AMDGPU Backend
-----------------------------
Changes to the ARM Backend
--------------------------
* Support for targeting armv2, armv2A, armv3 and armv3M has been removed.
LLVM did not, and was not ever likely to generate correct code for those
architecture versions so their presence was misleading.
Changes to the AVR Backend
--------------------------
* ...
Changes to the DirectX Backend
------------------------------
Changes to the Hexagon Backend
------------------------------
* ...
Changes to the MIPS Backend
---------------------------
* ...
Changes to the PowerPC Backend
------------------------------
* ...
Changes to the RISC-V Backend
-----------------------------
* Support for the unratified Zbe, Zbf, Zbm, Zbp, Zbr, and Zbt extensions have
been removed.
* i32 is now a native type in the datalayout string. This enables
LoopStrengthReduce for loops with i32 induction variables, among other
optimizations.
Changes to the WebAssembly Backend
----------------------------------
* ...
Changes to the Windows Target
-----------------------------
* For MinGW, generate embedded ``-exclude-symbols:`` directives for symbols
with hidden visibility, omitting them from automatic export of all symbols.
This roughly makes hidden visibility work like it does for other object
file formats.
Changes to the X86 Backend
--------------------------
* Add support for the ``RDMSRLIST and WRMSRLIST`` instructions.
* Add support for the ``WRMSRNS`` instruction.
* Support ISA of ``AMX-FP16`` which contains ``tdpfp16ps`` instruction.
* Support ISA of ``CMPCCXADD``.
* Support ISA of ``AVX-IFMA``.
* Support ISA of ``AVX-VNNI-INT8``.
* Support ISA of ``AVX-NE-CONVERT``.
* ``-mcpu=raptorlake`` and ``-mcpu=meteorlake`` are now supported.
Changes to the OCaml bindings
-----------------------------
Changes to the C API
--------------------
* The following functions for creating constant expressions have been removed,
because the underlying constant expressions are no longer supported. Instead,
an instruction should be created using the ``LLVMBuildXYZ`` APIs, which will
constant fold the operands if possible and create an instruction otherwise:
* ``LLVMConstFNeg``
Changes to the Go bindings
--------------------------
Changes to the FastISel infrastructure
--------------------------------------
* ...
Changes to the DAG infrastructure
---------------------------------
Changes to the Metadata Info
---------------------------------
* Add Module Flags Metadata ``stack-protector-guard-symbol`` which specify a
symbol for addressing the stack-protector guard.
Changes to the Debug Info
---------------------------------
Previously when emitting DWARF v4 and tuning for GDB, llc would use DWARF v2's
``DW_AT_bit_offset`` and ``DW_AT_data_member_location``. llc now uses DWARF v4's
``DW_AT_data_bit_offset`` regardless of tuning.
Support for ``DW_AT_data_bit_offset`` was added in GDB 8.0. For earlier versions,
you can use llc's ``-dwarf-version=3`` option to emit compatible DWARF.
Changes to the LLVM tools
---------------------------------
* ``llvm-readobj --elf-output-style=JSON`` no longer prefixes each JSON object
with the file name. Previously, each object file's output looked like
``"main.o":{"FileSummary":{"File":"main.o"},...}`` but is now
``{"FileSummary":{"File":"main.o"},...}``. This allows each JSON object to be
parsed in the same way, since each object no longer has a unique key. Tools
that consume ``llvm-readobj``'s JSON output should update their parsers
accordingly.
* ``llvm-objdump`` now uses ``--print-imm-hex`` by default, which brings its
default behavior closer in line with ``objdump``.
Changes to LLDB
---------------------------------
Changes to Sanitizers
---------------------
Other Changes
-------------
External Open Source Projects Using LLVM 15
===========================================
* 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 `Discourse forums <https://discourse.llvm.org>`_.
Reference in New Issue View Git Blame Copy Permalink