LLVM 14.0.0 Release Notes

Introduction

This document contains the release notes for the LLVM Compiler Infrastructure, release 14.0.0. 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

  • …

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 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.

  • Auto-vectorization now targets SVE by default when available.

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 PowerPC Target

Linux improvements:

  • Provided a number of builtins for compatibility with the XL compiler.

  • Allow MMA builtin types in pre-P10 compilation units.

  • Add support for Return Oriented Programming (ROP) protection for 32 bit.

  • Refactored code to use more inclusive language.

  • Switched to LLD as the default linker for pre-built Linux binaries.

  • Enabled IEEE quad long double on Linux via PPC_LINUX_DEFAULT_IEEELONGDOUBLE in cmake config.

    • Added __ibm128 type to represent IBM double-double format, also available as __attribute__((mode(IF))).

    • -mfloat128 can now be used in Linux subtargets with VSX enabled.

  • Added quadword atomic load/store support in codegen; not enabled by default.

  • Codegen improvements for splat load, byval parameter, stack lowering, etc.

  • Implemented P10 instruction scheduling model.

  • Implemented P10 instruction fusion pairs.

  • Improved handling of #pragma clang loop unroll_and_jam.

  • Various bug fixes.

AIX Support/improvements:

  • Variadic (ellipsis) functions with C complex types are now supported.

  • Added toc-data support for AIX 64-bit.

  • Added toc-data support for read-only globals.

  • Updated default target on AIX from pwr4 to pwr7.

  • AIX 64-bit code generation now uses fast-isel for O0.

  • Added DWARF support for 32-bit XCOFF.

Changes to the RISC-V Target

  • Codegen improvements for RV64 around the selection of addw/subw/mulw/slliw instructions and removal of redundant sext.w instructions (using the new RISCVSExtWRemoval pass).

  • The various RISC-V vector extensions were updated to version 1.0 and are no longer experimental.

  • The Zba, Zbb, Zbc, and Zbs bit-manipulation extensions were updated to version 1.0 and are no longer experimental.

  • Added MC layer support for the ratified scalar cryptography extensions.

  • The Zfh and Zfhmin extensions for half-precision floating point were updated to version 1.0 and are no longer experimental.

  • Added support for the .insn directive.

  • Various improvements to immediate materialisation, including when bit-manipulation extensions are enabled. Additionally, the constant pool is now used for large integers.

  • Added support for constrained FP intrinsics for scalar types.

  • Added support for CSRs introduced in the Sscofpmf, Smstateen, and Sstc extensions.

  • The experimental ‘Zbproposedc’ extension was removed, as was the ‘B’ extension (including all bit-manipulation sub-extensions). Individual ‘Zb*’ extensions should be used instead.

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

During this release …

Changes to the AVR Target

During this release …

Changes to the WebAssembly Target

During this release …

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 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 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)

  • llvm-cov now accepts “allowlist” spelling for -name-allowlist.

  • llvm-nm now supports XCOFF object files.

  • Added --needed-libs, aux header, and symbols support in llvm-readobj.

  • Added --symbolize-operands support in llvm-objdump.

  • Tools that read archive files now support reading AIX big format archive files.

  • Added dump section support in obj2yaml.

  • Added yaml2obj support for 64-bit XCOFF.

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 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.

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.