LLVM 14 Release Notes

Introduction

This document contains the release notes for the LLVM Compiler Infrastructure, release 14. 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

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Changes to the LLVM IR

  • Using the legacy pass manager for the optimization pipeline is deprecated and will be removed after LLVM 14. In the meantime, only minimal effort will be made to maintain the legacy pass manager for the optimization pipeline.

  • Max allowed integer type was reduced from 2^24-1 bits to 2^23 bits.

  • Max allowed alignment was increased from 2^29 to 2^32.

Changes to building LLVM

  • Building LLVM with Visual Studio now requires version 2019 or later.

Changes to TableGen

Changes to the AArch64 Backend

  • Added support for the Armv9-A, Armv9.1-A and Armv9.2-A architectures.

  • The compiler now recognises the “tune-cpu” function attribute to support the use of the -mtune frontend flag. This allows certain scheduling features and optimisations to be enabled independently of the architecture. If the “tune-cpu” attribute is absent it tunes according to the “target-cpu”.

  • Fixed relocations against temporary symbols (e.g. in jump tables and constant pools) in large COFF object files.

Changes to the ARM Backend

  • Added support for the Armv9-A, Armv9.1-A and Armv9.2-A architectures.

  • Added support for the Armv8.1-M PACBTI-M extension.

  • Changed the assembly comment string for MSVC targets to @ (consistent with the MinGW and ELF targets), freeing up ; to be used as statement separator.

Changes to the MIPS Target

During this release …

Changes to the Hexagon Target

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Changes to the PowerPC Target

During this release …

Changes to the X86 Target

During this release …

  • Support for AVX512-FP16 instructions has been added.

  • Removed incomplete support for Intel MPX. (D111517)

Changes to the AMDGPU Target

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Changes to the AVR Target

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Changes to the WebAssembly Target

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Changes to the Windows Target

  • Changed how the .pdata sections refer to the code they’re describing, to avoid conflicting unwind info if weak symbols are overridden.

  • Fixed code generation for calling support routines for converting 128 bit integers from/to floats on x86_64.

  • The preferred path separator form (backslashes or forward slashes) can be configured in Windows builds of LLVM now, with the LLVM_WINDOWS_PREFER_FORWARD_SLASH CMake option. This defaults to true in MinGW builds of LLVM.

  • Set proper COFF symbol types for function aliases (e.g. for Itanium C++ constructors), making sure that GNU ld exports all of them correctly as functions, not data, when linking a DLL.

  • Handling of temporary files on more uncommon file systems (network mounts, ramdisks) on Windows is fixed now (which previously either errored out or left stray files behind).

Changes to the OCaml bindings

Changes to the C API

  • LLVMSetInstDebugLocation has been deprecated in favor of the more general LLVMAddMetadataToInst.

  • Fixed building LLVM-C.dll for i386 targets with MSVC, which had been broken since the LLVM 8.0.0 release.

Changes to the Go bindings

Changes to the FastISel infrastructure

  • …

Changes to the DAG infrastructure

Changes to the Debug Info

During this release …

Changes to the LLVM tools

  • llvm-cov: -name-allowlist is now accepted in addition to -name-whitelist. -name-whitelist is marked as deprecated and to be removed in future releases.

  • llvm-ar now supports --thin for creating a thin archive. The modifier T has a different meaning in some ar implementations. (D116979)

  • llvm-ar now supports reading big archives for XCOFF. (D111889)

  • llvm-nm now demangles Rust symbols. (D111937)

  • llvm-objcopy’s ELF port now avoids reordering section headers to preserve st_shndx fields of dynamic symbols. (D107653)

  • llvm-objcopy now supports --update-section for ELF and Mach-O. (D112116) (D117281)

  • llvm-objcopy now supports --subsystem for PE/COFF. (D116556)

  • llvm-objcopy now supports mips64le relocations for ELF. (D115635)

  • llvm-objcopy --rename-section now renames relocation sections together with their targets. (D110352)

  • llvm-objdump --symbolize-operands now supports PowerPC. (D114492)

  • llvm-objdump -p now dumps PE header. (D113356)

  • llvm-objdump -R now supports ELF position-dependent executables. (D110595)

  • llvm-objdump -T now prints symbol versions. (D108097)

  • llvm-readobj: Improved printing of symbols in Windows unwind data.

  • llvm-readobj now supports --elf-output-style=JSON for JSON output and --pretty-print for pretty printing of this output. (D114225)

  • llvm-readobj now supports several dump styles (--needed-libs, --relocs, --syms) for XCOFF.

  • llvm-symbolizer now supports –debuginfod <https://llvm.org/docs/CommandGuide/llvm-symbolizer.html>. (D113717)

Changes to LLDB

  • A change in Clang’s type printing has changed the way LLDB names array types (from int [N] to int[N]) - LLDB pretty printer type name matching code may need to be updated to handle this.

  • The following commands now ignore non-address bits (e.g. AArch64 pointer signatures) in address arguments. In addition, non-address bits will not be shown in the output of the commands.

    • memory find

    • memory read

    • memory region (see below)

    • memory tag read

    • memory tag write

  • The memory region command and GetMemoryRegionInfo API method now ignore non-address bits in the address parameter. This also means that on systems with non-address bits the last (usually unmapped) memory region will not extend to 0xF…F. Instead it will end at the end of the mappable range that the virtual address size allows.

  • The memory read command has a new option --show-tags. Use this option to show memory tags beside the contents of tagged memory ranges.

  • Fixed continuing from breakpoints and singlestepping on Windows on ARM/ARM64.

  • LLDB has been included in Windows on ARM64 binary release with Python support disabled.

Changes to Sanitizers

Changes to BOLT

  • BOLT project is added to the LLVM monorepo. BOLT is a post-link optimizer developed to speed up large applications. Build and usage instructions are given in README.

External Open Source Projects Using LLVM 14

  • 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.