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llvm-project/llvm/docs/ReleaseNotes.rst
Shaw Young 49fdbbcfed
[BOLT] Match functions with exact hash (#96572) 
Added flag '--match-profile-with-function-hash' to match functions 
based on exact hash. After identical and LTO name matching, more 
functions can be recovered for inference with exact hash, in the case
of function renaming with no functional changes. Collisions are 
possible in the unlikely case where multiple functions share the same
exact hash. The flag is off by default as it requires the processing of 
all binary functions and subsequently is expensive.

Test Plan: added hashing-based-function-matching.test.
2024-06-29 21:19:00 -07:00

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============================
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.
* ...
Update on required toolchains to build LLVM
-------------------------------------------
* The minimum Python version has been raised from 3.6 to 3.8 across all of LLVM.
This enables the use of many new Python features, aligning more closely with
modern Python best practices, and improves CI maintainability
See `#78828 <https://github.com/llvm/llvm-project/pull/78828>`_ for more info.
Changes to the LLVM IR
----------------------
* Added Memory Model Relaxation Annotations (MMRAs).
* Added ``nusw`` and ``nuw`` flags to ``getelementptr`` instruction.
* Renamed ``llvm.experimental.vector.reverse`` intrinsic to ``llvm.vector.reverse``.
* Renamed ``llvm.experimental.vector.splice`` intrinsic to ``llvm.vector.splice``.
* Renamed ``llvm.experimental.vector.interleave2`` intrinsic to ``llvm.vector.interleave2``.
* Renamed ``llvm.experimental.vector.deinterleave2`` intrinsic to ``llvm.vector.deinterleave2``.
* The constant expression variants of the following instructions have been
removed:
* ``icmp``
* ``fcmp``
* ``shl``
* LLVM has switched from using debug intrinsics in textual IR to using debug
records by default. Details of the change and instructions on how to update
any downstream tools and tests can be found in the `migration docs
<https://llvm.org/docs/RemoveDIsDebugInfo.html>`_.
* Semantics of MC/DC intrinsics have been changed.
* ``llvm.instprof.mcdc.parameters``: 3rd argument has been changed
from bytes to bits.
* ``llvm.instprof.mcdc.condbitmap.update``: Removed.
* ``llvm.instprof.mcdc.tvbitmap.update``: 3rd argument has been
removed. The next argument has been changed from byte index to bit
index.
Changes to LLVM infrastructure
------------------------------
Changes to building LLVM
------------------------
* LLVM now has rpmalloc version 1.4.5 in-tree, as a replacement C allocator for
hosted toolchains. This supports several host platforms such as Mac or Unix,
however currently only the Windows 64-bit LLVM release uses it.
This has a great benefit in terms of build times on Windows when using ThinLTO
linking, especially on machines with lots of cores, to an order of magnitude
or more. Clang compilation is also improved. Please see some build timings in
(`#91862 <https://github.com/llvm/llvm-project/pull/91862#issue-2291033962>`_)
For more information, refer to the **LLVM_ENABLE_RPMALLOC** option in `CMake variables <https://llvm.org/docs/CMake.html#llvm-related-variables>`_.
* The ``LLVM_ENABLE_TERMINFO`` flag has been removed. LLVM no longer depends on
terminfo and now always uses the ``TERM`` environment variable for color
support autodetection.
Changes to TableGen
-------------------
- We can define type aliases via new keyword ``deftype``.
Changes to Interprocedural Optimizations
----------------------------------------
Changes to the AArch64 Backend
------------------------------
* Added support for Cortex-R82AE, Cortex-A78AE, Cortex-A520AE, Cortex-A720AE,
Cortex-A725, Cortex-X925, Neoverse-N3, Neoverse-V3 and Neoverse-V3AE CPUs.
* ``-mbranch-protection=standard`` now enables FEAT_PAuth_LR by
default when the feature is enabled. The new behaviour results
in ``standard`` being equal to ``bti+pac-ret+pc`` when ``+pauth-lr``
is passed as part of ``-mcpu=`` options.
* SVE and SVE2 have been moved to the default extensions list for ARMv9.0,
making them optional per the Arm ARM. Existing v9.0+ CPUs in the backend that
support these extensions continue to have these features enabled by default
when specified via ``-march=`` or an ``-mcpu=`` that supports them. The
attribute ``"target-features"="+v9a"`` no longer implies ``"+sve"`` and
``"+sve2"`` respectively.
Changes to the AMDGPU Backend
-----------------------------
* Implemented the ``llvm.get.fpenv`` and ``llvm.set.fpenv`` intrinsics.
* Implemented :ref:`llvm.get.rounding <int_get_rounding>` and :ref:`llvm.set.rounding <int_set_rounding>`
* Removed ``llvm.amdgcn.ds.fadd``, ``llvm.amdgcn.ds.fmin`` and
``llvm.amdgcn.ds.fmax`` intrinsics. Users should use the
:ref:`atomicrmw <i_atomicrmw>` instruction with `fadd`, `fmin` and
`fmax` with addrspace(3) instead.
Changes to the ARM Backend
--------------------------
* Added support for Cortex-R52+ CPU.
* FEAT_F32MM is no longer activated by default when using `+sve` on v8.6-A or greater. The feature is still available and can be used by adding `+f32mm` to the command line options.
* armv8-r now implies only fp-armv8d16sp, rather than neon and full fp-armv8. These features are still included by default for cortex-r52. The default cpu for armv8-r is now "generic", for compatibility with variants that do not include neon, fp64, and d32.
Changes to the AVR Backend
--------------------------
Changes to the DirectX Backend
------------------------------
Changes to the Hexagon Backend
------------------------------
Changes to the LoongArch Backend
--------------------------------
* 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 MIPS Backend
---------------------------
Changes to the PowerPC Backend
------------------------------
Changes to the RISC-V Backend
-----------------------------
* Added full support for the experimental Zabha (Byte and
Halfword Atomic Memory Operations) extension.
* Added assembler/disassembler support for the experimenatl Zalasr
(Load-Acquire and Store-Release) extension.
* The names of the majority of the S-prefixed (supervisor-level) extension
names in the RISC-V profiles specification are now recognised.
* Codegen support was added for the Zimop (May-Be-Operations) extension.
* The experimental Ssnpm, Smnpm, Smmpm, Sspm, and Supm 1.0.0 Pointer Masking extensions are supported.
* The experimental Ssqosid extension is supported.
* Zacas is no longer experimental.
* Added the CSR names from the Resumable Non-Maskable Interrupts (Smrnmi) extension.
* llvm-objdump now prints disassembled opcode bytes in groups of 2 or 4 bytes to
match GNU objdump. The bytes within the groups are in big endian order.
* Added smstateen extension to -march. CSR names for smstateen were already supported.
* Zaamo and Zalrsc are no longer experimental.
* Processors that enable post reg-alloc scheduling (PostMachineScheduler) by default should use the `UsePostRAScheduler` subtarget feature. Setting `PostRAScheduler = 1` in the scheduler model will have no effect on the enabling of the PostMachineScheduler.
* Zabha is no longer experimental.
* B (the collection of the Zba, Zbb, Zbs extensions) is supported.
* Added smcdeleg, ssccfg, smcsrind, and sscsrind extensions to -march.
* ``-mcpu=syntacore-scr3-rv32`` and ``-mcpu=syntacore-scr3-rv64`` were added.
Changes to the WebAssembly Backend
----------------------------------
Changes to the Windows Target
-----------------------------
Changes to the X86 Backend
--------------------------
- Removed knl/knm specific ISA intrinsics: AVX512PF, AVX512ER, PREFETCHWT1,
while assembly encoding/decoding supports are kept.
Changes to the OCaml bindings
-----------------------------
Changes to the Python bindings
------------------------------
Changes to the C API
--------------------
* Added ``LLVMGetBlockAddressFunction`` and ``LLVMGetBlockAddressBasicBlock``
functions for accessing the values in a blockaddress constant.
* Added ``LLVMConstStringInContext2`` function, which better matches the C++
API by using ``size_t`` for string length. Deprecated ``LLVMConstStringInContext``.
* Added the following functions for accessing a function's prefix data:
* ``LLVMHasPrefixData``
* ``LLVMGetPrefixData``
* ``LLVMSetPrefixData``
* Added the following functions for accessing a function's prologue data:
* ``LLVMHasPrologueData``
* ``LLVMGetPrologueData``
* ``LLVMSetPrologueData``
* Deprecated ``LLVMConstNUWNeg`` and ``LLVMBuildNUWNeg``.
* Added ``LLVMAtomicRMWBinOpUIncWrap`` and ``LLVMAtomicRMWBinOpUDecWrap`` to
``LLVMAtomicRMWBinOp`` enum for AtomicRMW instructions.
* Added ``LLVMCreateConstantRangeAttribute`` function for creating ConstantRange Attributes.
* Added the following functions for creating and accessing data for CallBr instructions:
* ``LLVMBuildCallBr``
* ``LLVMGetCallBrDefaultDest``
* ``LLVMGetCallBrNumIndirectDests``
* ``LLVMGetCallBrIndirectDest``
* 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:
* ``LLVMConstICmp``
* ``LLVMConstFCmp``
* ``LLVMConstShl``
**Note:** The following changes are due to the removal of the debug info
intrinsics from LLVM and to the introduction of debug records into LLVM.
They are described in detail in the `debug info migration guide <https://llvm.org/docs/RemoveDIsDebugInfo.html>`_.
* Added the following functions to insert before the indicated instruction but
after any attached debug records.
* ``LLVMPositionBuilderBeforeDbgRecords``
* ``LLVMPositionBuilderBeforeInstrAndDbgRecords``
Same as ``LLVMPositionBuilder`` and ``LLVMPositionBuilderBefore`` except the
insertion position is set to before the debug records that precede the target
instruction. ``LLVMPositionBuilder`` and ``LLVMPositionBuilderBefore`` are
unchanged.
* Added the following functions to get/set the new non-instruction debug info format.
They will be deprecated in the future and they are just a transition aid.
* ``LLVMIsNewDbgInfoFormat``
* ``LLVMSetIsNewDbgInfoFormat``
* Added the following functions to insert a debug record (new debug info format).
* ``LLVMDIBuilderInsertDeclareRecordBefore``
* ``LLVMDIBuilderInsertDeclareRecordAtEnd``
* ``LLVMDIBuilderInsertDbgValueRecordBefore``
* ``LLVMDIBuilderInsertDbgValueRecordAtEnd``
* Deleted the following functions that inserted a debug intrinsic (old debug info format).
* ``LLVMDIBuilderInsertDeclareBefore``
* ``LLVMDIBuilderInsertDeclareAtEnd``
* ``LLVMDIBuilderInsertDbgValueBefore``
* ``LLVMDIBuilderInsertDbgValueAtEnd``
* Added the following functions for accessing a Target Extension Type's data:
* ``LLVMGetTargetExtTypeName``
* ``LLVMGetTargetExtTypeNumTypeParams``/``LLVMGetTargetExtTypeTypeParam``
* ``LLVMGetTargetExtTypeNumIntParams``/``LLVMGetTargetExtTypeIntParam``
Changes to the CodeGen infrastructure
-------------------------------------
Changes to the Metadata Info
---------------------------------
Changes to the Debug Info
---------------------------------
* LLVM has switched from using debug intrinsics internally to using debug
records by default. This should happen transparently when using the DIBuilder
to construct debug variable information, but will require changes for any code
that interacts with debug intrinsics directly. Debug intrinsics will only be
supported on a best-effort basis from here onwards; for more information, see
the `migration docs <https://llvm.org/docs/RemoveDIsDebugInfo.html>`_.
Changes to the LLVM tools
---------------------------------
* llvm-nm and llvm-objdump can now print symbol information from linked
WebAssembly binaries, using information from exports or the "name"
section for functions, globals and data segments. Symbol addresses and sizes
are printed as offsets in the file, allowing for binary size analysis. Wasm
files using reference types and GC are also supported (but also only for
functions, globals, and data, and only for listing symbols and names).
* llvm-ar now utilizes LLVM_DEFAULT_TARGET_TRIPLE to determine the archive format
if it's not specified with the ``--format`` argument and cannot be inferred from
input files.
* llvm-ar now allows specifying COFF archive format with ``--format`` argument
and uses it by default for COFF targets.
* llvm-ranlib now supports ``-V`` as an alias for ``--version``.
``-v`` (``--verbose`` in llvm-ar) has been removed.
(`#87661 <https://github.com/llvm/llvm-project/pull/87661>`_)
* llvm-objcopy now supports ``--set-symbol-visibility`` and
``--set-symbols-visibility`` options for ELF input to change the
visibility of symbols.
* llvm-objcopy now supports ``--skip-symbol`` and ``--skip-symbols`` options
for ELF input to skip the specified symbols when executing other options
that can change a symbol's name, binding or visibility.
* llvm-objcopy now supports ``--compress-sections`` to compress or decompress
arbitrary sections not within a segment.
(`#85036 <https://github.com/llvm/llvm-project/pull/85036>`_.)
* llvm-profgen now supports COFF+DWARF binaries. This enables Sample-based PGO
on Windows using Intel VTune's SEP. For details on usage, see the `end-user
documentation for SPGO
<https://clang.llvm.org/docs/UsersManual.html#using-sampling-profilers>`_.
* llvm-readelf's ``-r`` output for RELR has been improved.
(`#89162 <https://github.com/llvm/llvm-project/pull/89162>`_)
``--raw-relr`` has been removed.
* llvm-mca now aborts by default if it is given bad input where previously it
would continue. Additionally, it can now continue when it encounters
instructions which lack scheduling information. The behaviour can be
controlled by the newly introduced
`--skip-unsupported-instructions=<none|lack-sched|parse-failure|any>`, as
documented in `--help` output and the command guide. (`#90474
<https://github.com/llvm/llvm-project/pull/90474>`)
* llvm-readobj's LLVM output format for ELF core files has been changed.
Similarly, the JSON format has been fixed for this case. The NT_FILE note
now has a map for the mapped files. (`#92835
<https://github.com/llvm/llvm-project/pull/92835>`).
* llvm-cov now generates HTML report with JavaScript code to allow simple
jumping between uncovered parts (lines/regions/branches) of code
using buttons on top-right corner of the page or using keys (L/R/B or
jumping in reverse direction with shift+L/R/B). (`#95662
<https://github.com/llvm/llvm-project/pull/95662>`).
Changes to LLDB
---------------------------------
Changes to BOLT
---------------------------------
* Now supports ``--match-profile-with-function-hash`` to match profiled and
binary functions with exact hash, allowing for the matching of renamed but
identical functions.
Changes to Sanitizers
---------------------
Other Changes
-------------
External Open Source Projects Using LLVM 19
===========================================
* 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>`_.
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