LLVM 5.0.0 Release Notes

Warning

These are in-progress notes for the upcoming LLVM 5 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 5.0.0. 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

• LLVM’s WeakVH has been renamed to WeakTrackingVH and a new WeakVH has been introduced. The new WeakVH nulls itself out on deletion, but does not track values across RAUW.
• A new library named BinaryFormat has been created which holds a collection of code which previously lived in Support. This includes the file_magic structure and identify_magic functions, as well as all the structure and type definitions for DWARF, ELF, COFF, WASM, and MachO file formats.
• The tool llvm-pdbdump has been renamed llvm-pdbutil to better reflect its nature as a general purpose PDB manipulation / diagnostics tool that does more than just dumping contents.
• The BBVectorize pass has been removed. It was fully replaced and no longer used back in 2014 but we didn’t get around to removing it. Now it is gone. The SLP vectorizer is the suggested non-loop vectorization pass.

Changes to the LLVM IR

• The datalayout string may now indicate an address space to use for the pointer type of alloca rather than the default of 0.
• Added speculatable attribute indicating a function which does has no side-effects which could inhibit hoisting of calls.

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

• Added initial AMD Ryzen (znver1) scheduler support.
• Added support for Intel Goldmont CPUs.
• Add support for avx512vpopcntdq instructions.
• Added heuristics to convert CMOV into branches when it may be profitable.
• More aggressive inlining of memcmp calls.
• Improve vXi64 shuffles on 32-bit targets.
• Improved use of PMOVMSKB for any_of/all_of comparision reductions.
• Improved Silvermont, Sandybridge, and Jaguar (btver2) schedulers.
• Improved support for AVX512 vector rotations.
• Added support for AMD Lightweight Profiling (LWP) instructions.
• Avoid using slow LEA instructions.
• Use alternative sequences for multiply by constant.
• Improved lowering of strided shuffles.
• Improved the AVX512 cost model used by the vectorizer.
• Fix scalar code performance when AVX512 is enabled by making i1’s illegal.
• Fixed many inline assembly bugs.

Changes to the AMDGPU Target

• Initial gfx9 support

Changes to the AVR Target

This release consists mainly of bugfixes and implementations of features required for compiling basic Rust programs.

• Enable the branch relaxation pass so that we don’t crash on large stack load/stores
• Add support for lowering bit-rotations to the native ror and rol instructions
• Fix bug where function pointers were treated as pointers to RAM and not pointers to program memory
• Fix broken code generaton for shift-by-variable expressions
• Support zero-sized types in argument lists; this is impossible in C, but possible in Rust

Changes to the OCaml bindings

During this release ...

Changes to the C API

• Deprecated the LLVMAddBBVectorizePass interface since the BBVectorize pass has been removed. It is now a no-op and will be removed in the next release. Use LLVMAddSLPVectorizePass instead to get the supported SLP vectorizer.

External Open Source Projects Using LLVM 5

Zig Programming Language

Zig is an open-source programming language designed for robustness, optimality, and clarity. It integrates closely with C and is intended to eventually take the place of C. It uses LLVM to produce highly optimized native code and to cross-compile for any target out of the box. Zig is in alpha; with a beta release expected in September.

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.