========================= 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 `_. 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 `_. For more information about LLVM, including information about the latest release, please check out the `main LLVM web site `_. If you have questions or comments, the `LLVM Developer's Mailing List `_ 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 `_. 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 ... 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. 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. External Open Source Projects Using LLVM 12 =========================================== * A project... Additional Information ====================== A wide variety of additional information is available on the `LLVM web page `_, in particular in the `documentation `_ 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 `_.