LLVM 20.0.0git Release Notes

Warning

These are in-progress notes for the upcoming LLVM 20 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 20.0.0git. 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

  • …

Update on required toolchains to build LLVM

Changes to the LLVM IR

  • The x86_mmx IR type has been removed. It will be translated to the standard vector type <1 x i64> in bitcode upgrade.

  • Renamed llvm.experimental.stepvector intrinsic to llvm.stepvector.

  • Added usub_cond and usub_sat operations to atomicrmw.

Changes to LLVM infrastructure

Changes to building LLVM

Changes to TableGen

Changes to Interprocedural Optimizations

Changes to the AArch64 Backend

  • .balign N, 0, .p2align N, 0, .align N, 0 in code sections will now fill the required alignment space with a sequence of 0x0 bytes (the requested fill value) rather than NOPs.

Changes to the AMDGPU Backend

  • Removed llvm.amdgcn.flat.atomic.fadd and llvm.amdgcn.global.atomic.fadd intrinsics. Users should use the atomicrmw instruction with fadd and addrspace(0) or addrspace(1) instead.

Changes to the ARM Backend

  • .balign N, 0, .p2align N, 0, .align N, 0 in code sections will now fill the required alignment space with a sequence of 0x0 bytes (the requested fill value) rather than NOPs.

Changes to the AVR Backend

Changes to the DirectX Backend

Changes to the Hexagon Backend

Changes to the LoongArch Backend

Changes to the MIPS Backend

Changes to the PowerPC Backend

Changes to the RISC-V Backend

  • .balign N, 0, .p2align N, 0, .align N, 0 in code sections will now fill the required alignment space with a sequence of 0x0 bytes (the requested fill value) rather than NOPs.

  • Added Syntacore SCR4 and SCR5 CPUs: -mcpu=syntacore-scr4/5-rv32/64

  • -mcpu=sifive-p470 was added.

  • Added Hazard3 CPU as taped out for RP2350: -mcpu=rp2350-hazard3 (32-bit only).

  • Fixed length vector support using RVV instructions now requires VLEN>=64. This means Zve32x and Zve32f will also require Zvl64b. The prior support was largely untested.

  • The Zvbc32e and Zvkgs extensions are now supported experimentally.

  • Added Smctr and Ssctr extensions.

  • -mcpu=syntacore-scr7 was added.

Changes to the WebAssembly Backend

Changes to the Windows Target

Changes to the X86 Backend

  • .balign N, 0x90, .p2align N, 0x90, and .align N, 0x90 in code sections now fill the required alignment space with repeating 0x90 bytes, rather than using optimised NOP filling. Optimised NOP filling fills the space with NOP instructions of various widths, not just those that use the 0x90 byte encoding. To use optimised NOP filling in a code section, leave off the “fillval” argument, i.e. .balign N, .p2align N or .align N respectively.

  • Due to the removal of the x86_mmx IR type, functions with x86_mmx arguments or return values will use a different, incompatible, calling convention ABI. Such functions are not generally seen in the wild (Clang never generates them!), so this is not expected to result in real-world compatibility problems.

  • Support ISA of AVX10.2-256 and AVX10.2-512.

Changes to the OCaml bindings

Changes to the Python bindings

Changes to the C API

  • The following symbols are deleted due to the removal of the x86_mmx IR type:

    • LLVMX86_MMXTypeKind

    • LLVMX86MMXTypeInContext

    • LLVMX86MMXType

  • The following functions are added to further support non-null-terminated strings:

  • LLVMGetNamedFunctionWithLength

  • LLVMGetNamedGlobalWithLength

  • The following functions are added to access the LLVMContextRef associated

    with LLVMValueRef and LLVMBuilderRef objects:

    • LLVMGetValueContext

    • LLVMGetBuilderContext

  • The new pass manager can now be invoked with a custom alias analysis pipeline, using the LLVMPassBuilderOptionsSetAAPipeline function.

  • It is now also possible to run the new pass manager on a single function, by calling LLVMRunPassesOnFunction instead of LLVMRunPasses.

  • Support for creating instructions with custom synchronization scopes has been added:

    • LLVMGetSyncScopeID to map a synchronization scope name to an ID.

    • LLVMBuildFenceSyncScope, LLVMBuildAtomicRMWSyncScope and LLVMBuildAtomicCmpXchgSyncScope versions of the existing builder functions with an additional synchronization scope ID parameter.

    • LLVMGetAtomicSyncScopeID and LLVMSetAtomicSyncScopeID to get and set the synchronization scope of any atomic instruction.

    • LLVMIsAtomic to check if an instruction is atomic, for use with the above functions. Because of backwards compatibility, LLVMIsAtomicSingleThread and LLVMSetAtomicSingleThread continue to work with any instruction type.

  • The LLVMSetPersonalityFn and LLVMSetInitializer APIs now support clearing the personality function and initializer respectively by passing a null pointer.

Changes to the CodeGen infrastructure

Changes to the Metadata Info

Changes to the Debug Info

Changes to the LLVM tools

Changes to LLDB

Changes to BOLT

Changes to Sanitizers

Other Changes

External Open Source Projects Using LLVM 19

  • 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.

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