LLVM 17.0.0git Release Notes

Warning

These are in-progress notes for the upcoming LLVM 17 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 17.0.0git. 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 Discourse forums is a good place to ask 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

  • Typed pointers are no longer supported. See the opaque pointers documentation for migration instructions.
  • The nofpclass attribute was introduced. This allows more optimizations around special floating point value comparisons.
  • The constant expression variants of the following instructions have been removed:
    • select

Changes to LLVM infrastructure

  • The legacy optimization pipeline has been removed.
  • Alloca merging in the inliner has been removed, since it only worked with the legacy inliner pass. Backend stack coloring should handle cases alloca merging initially set out to handle.

Changes to the AMDGPU Backend

  • More fine-grained synchronization around barriers for newer architectures (gfx90a+, gfx10+). The AMDGPU backend now omits previously automatically generated waitcnt instructions before barriers, allowing for more precise control. Users must now use memory fences to implement fine-grained synchronization strategies around barriers. Refer to AMDGPU memory model.

Changes to the ARM Backend

  • The hard-float ABI is now available in Armv8.1-M configurations that have integer MVE instructions (and therefore have FP registers) but no scalar or vector floating point computation.

Changes to the RISC-V Backend

  • Assembler support for version 1.0.1 of the Zcb extension was added.
  • Zca, Zcf, and Zcd extensions were upgraded to version 1.0.1.
  • vsetvli intrinsics no longer have side effects. They may now be combined, moved, deleted, etc. by optimizations.
  • Adds support for the vendor-defined XTHeadBa (address-generation) extension.
  • Adds support for the vendor-defined XTHeadBb (basic bit-manipulation) extension.
  • Adds support for the vendor-defined XTHeadBs (single-bit) extension.
  • Adds support for the vendor-defined XTHeadCondMov (conditional move) extension.
  • Adds support for the vendor-defined XTHeadMac (multiply-accumulate instructions) extension.
  • Added support for the vendor-defined XTHeadMemPair (two-GPR memory operations) extension disassembler/assembler.
  • Added support for the vendor-defined XTHeadMemIdx (indexed memory operations) extension disassembler/assembler.
  • Support for the now-ratified Zawrs extension is no longer experimental.
  • Adds support for the vendor-defined XTHeadCmo (cache management operations) extension.
  • Adds support for the vendor-defined XTHeadSync (multi-core synchronization instructions) extension.
  • Added support for the vendor-defined XTHeadFMemIdx (indexed memory operations for floating point) extension.

Changes to the C API

  • LLVMContextSetOpaquePointers, a temporary API to pin to legacy typed pointer, has been removed.
  • Functions for adding legacy passes like LLVMAddInstructionCombiningPass have been removed.
  • Removed LLVMPassManagerBuilderRef and functions interacting with it. These belonged to the no longer supported legacy pass manager.
  • As part of the opaque pointer transition, LLVMGetElementType no longer gives the pointee type of a pointer type.
  • The following functions for creating constant expressions have been removed, because the underlying constant expressions are no longer supported. Instead, an instruction should be created using the LLVMBuildXYZ APIs, which will constant fold the operands if possible and create an instruction otherwise:
    • LLVMConstSelect

Changes to the Debug Info

  • The DWARFv5 feature of attaching DW_AT_default_value to defaulted template parameters will now be available in any non-strict DWARF mode and in a wider range of cases than previously. (D139953, D139988)
  • The DW_AT_name on DW_AT_typedefs for alias templates will now omit defaulted template parameters. (D142268)
  • The experimental @llvm.dbg.addr intrinsic has been removed (D144801). IR inputs with this intrinsic are auto-upgraded to @llvm.dbg.value with DW_OP_deref appended to the DIExpression (D144793).

Changes to the LLVM tools

  • llvm-lib now supports the /def option for generating a Windows import library from a definition file.
  • Made significant changes to JSON output format of llvm-readobj/llvm-readelf to improve correctness and clarity.

Changes to LLDB

  • In the results of commands such as expr and frame var, type summaries will now omit defaulted template parameters. The full template parameter list can still be viewed with expr --raw-output/frame var --raw-output. (D141828)
  • LLDB is now able to show the subtype of signals found in a core file. For example memory tagging specific segfaults such as SIGSEGV: sync tag check fault.

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.

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