LLVM 6.0.0 Release Notes


These are in-progress notes for the upcoming LLVM 6 release. Release notes for previous releases can be found on the Download Page.


This document contains the release notes for the LLVM Compiler Infrastructure, release 6.0.0. 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 Subversion 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

  • The Redirects argument of llvm::sys::ExecuteAndWait and llvm::sys::ExecuteNoWait was changed to an ArrayRef of optional StringRef‘s to make it safer and more convenient to use.
  • The backend name was added to the Target Registry to allow run-time information to be fed back into TableGen. Out-of-tree targets will need to add the name used in the def X : Target definition to the call to RegisterTarget.
  • The Debugify pass was added to opt to facilitate testing of debug info preservation. This pass attaches synthetic DILocations and DIVariables to the instructions in a Module. The CheckDebugify pass determines how much of the metadata is lost.
  • Significantly improved quality of CodeView debug info for Windows.
  • Note..

Changes to the AArch64 Target

During this release:

  • Enabled the new GlobalISel instruction selection framework by default at -O0.

Changes to the ARM Target

During this release the ARM target has:

  • Got support for enabling SjLj exception handling on platforms where it isn’t the default.

Changes to the Hexagon Target

  • The Hexagon backend now supports V65 ISA.
  • The -mhvx option now takes an optional value that specified the ISA version of the HVX coprocessor. The available values are v60, v62 and v65. By default, the value is set to be the same as the CPU version.
  • The compiler option -mhvx-double is deprecated and will be removed in the next release of the compiler. Programmers should use -mhvx-length option to specify the desired vector length: -mhvx-length=64b for 64-byte vectors and -mhvx-length=128b for 128-byte vectors. While the current default vector length is 64 bytes, users should always specify the length explicitly, since the default value may change in the future.
  • The target feature hvx-double is deprecated and will be removed in the next release. LLVM IR generators should use target features hvx-length64b and hvx-length128b to indicate the vector length. The length should always be specified when HVX code generation is enabled.

Changes to the MIPS Target

During this release ...

Changes to the PowerPC Target

During this release ...

Changes to the X86 Target

During this release ...

  • Got support for enabling SjLj exception handling on platforms where it isn’t the default.

Changes to the AMDGPU Target

During this release ...

Changes to the AVR Target

During this release ...

Changes to the OCaml bindings

During this release ...

Changes to the C API

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External Open Source Projects Using LLVM 6

JFS - JIT Fuzzing Solver

JFS is an experimental constraint solver designed to investigate using coverage guided fuzzing as an incomplete strategy for solving boolean, BitVector, and floating-point constraints. It is built on top of LLVM, Clang, LibFuzzer, and Z3.

The solver works by generating a C++ program where the reachability of an abort() statement is equivalent to finding a satisfying assignment to the constraints. This program is then compiled by Clang with SanitizerCoverage instrumentation and then fuzzed using LibFuzzer.

Zig Programming Language

Zig is an open-source programming language designed for robustness, optimality, and clarity. It is intended to replace C. It provides high level features such as Generics, Compile Time Function Execution, and Partial Evaluation, yet exposes low level LLVM IR features such as Aliases. Zig uses Clang to provide automatic import of .h symbols - even inline functions and macros. Zig uses LLD combined with lazily building compiler-rt to provide out-of-the-box cross-compiling for all supported targets.

LDC - the LLVM-based D compiler

D is a language with C-like syntax and static typing. It pragmatically combines efficiency, control, and modeling power, with safety and programmer productivity. D supports powerful concepts like Compile-Time Function Execution (CTFE) and Template Meta-Programming, provides an innovative approach to concurrency and offers many classical paradigms.

LDC uses the frontend from the reference compiler combined with LLVM as backend to produce efficient native code. LDC targets x86/x86_64 systems like Linux, OS X, FreeBSD and Windows and also Linux on ARM and PowerPC (32/64 bit). Ports to other architectures like AArch64 and MIPS64 are underway.

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 Subversion 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.