| ========================= |
| LLVM 12.0.0 Release Notes |
| ========================= |
| |
| .. contents:: |
| :local: |
| |
| .. warning:: |
| These are in-progress notes for the upcoming LLVM 12 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 12.0.0. 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. |
| |
| * The ConstantPropagation pass was removed. Users should use the InstSimplify |
| pass instead. |
| |
| |
| .. 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 |
| ---------------------- |
| |
| * ... |
| |
| * Added the ``byref`` attribute to better represent argument passing |
| for the `amdgpu_kernel` calling convention. |
| |
| * Added type parameter to the ``sret`` attribute to continue work on |
| removing pointer element types. |
| |
| * The ``llvm.experimental.vector.reduce`` family of intrinsics have been renamed |
| to drop the "experimental" from the name, reflecting their now fully supported |
| status in the IR. |
| |
| |
| Changes to building LLVM |
| ------------------------ |
| |
| * The internal ``llvm-build`` Python script and the associated ``LLVMBuild.txt`` |
| files used to describe the LLVM component structure have been removed and |
| replaced by a pure ``CMake`` approach, where each component stores extra |
| properties in the created targets. These properties are processed once all |
| components are defined to resolve library dependencies and produce the header |
| expected by llvm-config. |
| |
| Changes to TableGen |
| ------------------- |
| |
| * The new "TableGen Programmer's Reference" replaces the "TableGen Language |
| Introduction" and "TableGen Language Reference" documents. |
| |
| * The syntax for specifying an integer range in a range list has changed. |
| The old syntax used a hyphen in the range (e.g., ``{0-9}``). The new syntax |
| uses the "`...`" range punctuation (e.g., ``{0...9}``). The hyphen syntax |
| is deprecated. |
| |
| 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 ... |
| |
| * The 'mpx' feature was removed from the backend. It had been removed from clang |
| frontend in 10.0. Mention of the 'mpx' feature in an IR file will print a |
| message to stderr, but IR should still compile. |
| * Support for ``-march=alderlake``, ``-march=sapphirerapids``, |
| ``-march=znver3`` and ``-march=x86-64-v[234]`` has been added. |
| * The assembler now has support for {disp32} and {disp8} pseudo prefixes for |
| controlling displacement size for memory operands and jump displacements. The |
| assembler also supports the .d32 and .d8 mnemonic suffixes to do the same. |
| * A new function attribute "tune-cpu" has been added to support -mtune like gcc. |
| This allows microarchitectural optimizations to be applied independent from |
| the "target-cpu" attribute or TargetMachine CPU which will be used to select |
| Instruction Set. If the attribute is not present, the tune CPU will follow |
| the target CPU. |
| * Support for ``HRESET`` instructions has been added. |
| * Support for ``UINTR`` instructions has been added. |
| * Support for ``AVXVNNI`` instructions has been added. |
| |
| Changes to the AMDGPU Target |
| ----------------------------- |
| |
| During this release ... |
| |
| * The new ``byref`` attribute is now the preferred method for |
| representing aggregate kernel arguments. |
| |
| Changes to the AVR Target |
| ----------------------------- |
| |
| During this release ... |
| |
| Changes to the WebAssembly Target |
| --------------------------------- |
| |
| During this release ... |
| |
| 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 |
| --------------------------------- |
| |
| During this release ... |
| |
| * The DIModule metadata is extended with a field to indicate if it is a |
| module declaration. This extension enables the emission of debug info |
| for a Fortran 'use <external module>' statement. For more information |
| on what the debug info entries should look like and how the debugger |
| can use them, please see test/DebugInfo/X86/dimodule-external-fortran.ll. |
| |
| Changes to the LLVM tools |
| --------------------------------- |
| |
| * llvm-readobj and llvm-readelf behavior has changed to report an error when |
| executed with no input files instead of reading an input from stdin. |
| Reading from stdin can still be achieved by specifying `-` as an input file. |
| |
| * llvm-mca supports serialization of the timeline and summary views. |
| The `--json` command line option prints a JSON representation of |
| these views to stdout. |
| |
| Changes to LLDB |
| --------------------------------- |
| |
| Changes to Sanitizers |
| --------------------- |
| |
| The integer sanitizer `-fsanitize=integer` now has a new sanitizer: |
| `-fsanitize=unsigned-shift-base`. It's not undefined behavior for an unsigned |
| left shift to overflow (i.e. to shift bits out), but it has been the source of |
| bugs and exploits in certain codebases in the past. |
| |
| Many Sanitizers (asan, cfi, lsan, msan, tsan, ubsan) have support for |
| musl-based Linux distributions. Some of them may be rudimentary. |
| |
| External Open Source Projects Using LLVM 12 |
| =========================================== |
| |
| * 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>`_. |
