LLVM 24.0.0git Release Notes#

Warning

These are in-progress notes for the upcoming LLVM 24.0.0git 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 24.0.0git. 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#

  • Added llvm.vector.reduce.fmaximumnum and llvm.vector.reduce.fminimumnum intrinsics, the reduction variants of llvm.maximumnum and llvm.minimumnum.

  • Added nofreeobj attribute for attributes and returns, which forbids freeing the underlying object (as opposed to only frees through that specific pointer). Renamed !nofree metadata to !nofreeobj, as it has the same semantics.

  • The following VP intrinsics have been removed:

    • llvm.vp.select.*

    • llvm.vp.add.*

    • llvm.vp.sub.*

    • llvm.vp.mul.*

    • llvm.vp.ashr.*

    • llvm.vp.lshr.*

    • llvm.vp.shl.*

    • llvm.vp.or.*

    • llvm.vp.and.*

    • llvm.vp.xor.*

    • llvm.vp.abs.*

    • llvm.vp.smax.*

    • llvm.vp.smin.*

    • llvm.vp.umax.*

    • llvm.vp.umin.*

    • llvm.vp.copysign.*

    • llvm.vp.minnum.*

    • llvm.vp.maxnum.*

    • llvm.vp.minimum.*

    • llvm.vp.maximum.*

    • llvm.vp.fadd.*

    • llvm.vp.fsub.*

    • llvm.vp.fmul.*

    • llvm.vp.fdiv.*

    • llvm.vp.frem.*

    • llvm.vp.fneg.*

    • llvm.vp.fabs.*

    • llvm.vp.sqrt.*

    • llvm.vp.fma.*

    • llvm.vp.fmuladd.*

    • llvm.vp.trunc.*

    • llvm.vp.zext.*

    • llvm.vp.sext.*

    • llvm.vp.fptrunc.*

    • llvm.vp.fpext.*

    • llvm.vp.fptoui.*

    • llvm.vp.fptosi.*

    • llvm.vp.uitofp.*

    • llvm.vp.sitofp.*

    • llvm.vp.ptrtoint.*

    • llvm.vp.inttoptr.*

    • llvm.vp.fcmp.*

    • llvm.vp.icmp.*

    • llvm.vp.ceil.*

    • llvm.vp.floor.*

    • llvm.vp.rint.*

    • llvm.vp.nearbyint.*

    • llvm.vp.round.*

    • llvm.vp.roundeven.*

    • llvm.vp.roundtozero.*

    • llvm.vp.lrint.*

    • llvm.vp.llrint.*

    • llvm.vp.bitreverse.*

    • llvm.vp.bswap.*

    • llvm.vp.ctpop.*

    • llvm.vp.ctlz.*

    • llvm.vp.cttz.*

    • llvm.vp.sadd.sat.*

    • llvm.vp.uadd.sat.*

    • llvm.vp.ssub.sat.*

    • llvm.vp.usub.sat.*

    • llvm.vp.fshl.*

    • llvm.vp.fshr.*

    • llvm.vp.is.fpclass.*

    These intrinsics previously only set masked-off lanes to poison, and will be automatically upgraded to their non-VP equivalent. On RISC-V the VL optimizer should automatically infer vl in most cases from a store or reduction instruction, so passing around an explicit EVL operand shouldn’t be required. If needed a “root” EVL can be synthesized with llvm.vp.merge, e.g:

    %x = add <vscale x 2 x i32> %y, %z
%res = call <vscale x 2 x i32> @llvm.vp.merge(<vscale x 2 x i32> %x, <vscale x 2 x i32> poison, <vscale x 2 x i1> splat (i1 true), i32 %evl)

    The llvm.vp.merge will be folded away but the %evl will be propagated to the add instruction.

Changes to LLVM infrastructure#

  • Removed TargetOptions::FloatABIType. The soft float ABI should be controlled by setting the "float-abi" module flag.

Changes to building LLVM#

  • The DirectX backend is now an official target and has moved from LLVM_ALL_EXPERIMENTAL_TARGETS to LLVM_ALL_TARGETS. It is now built by default and no longer requires LLVM_EXPERIMENTAL_TARGETS_TO_BUILD.

Changes to TableGen#

  • !cond operator short-circuits at the first true condition. Subsequent condition : value pairs, along with their corresponding side effects, are left unresolved.

Changes to Interprocedural Optimizations#

  • Interprocedural passes no longer rewrite the signature of functions marked optnone, so their argument list, return type, and calling convention are preserved. Interprocedural analysis and transformation of such functions is otherwise unaffected.

  • The IR Outliner has been removed, due to lack of a maintainer and the presence of correctness issues.

Changes to Vectorizers#

Changes to the AArch64 Backend#

Changes to the AMDGPU Backend#

  • Replaced xnack and sramecc target features with amdgpu.xnack and amdgpu.sramecc module flags.

  • llvm.amdgcn.make.buffer.rsrc now accepts any integer width for its numRecords argument to account for targets that use 32-bit and 45-bit numRecords widths more accurately. If an integer of the incorrect width is used, it will be zero-extended or truncated as needed.

  • These intrinsics have been removed in favour of llvm.amdgcn.ballot:

    • llvm.amdgcn.icmp

    • llvm.amdgcn.fcmp

Changes to the ARM Backend#

  • Using the hard-float procedure call standard without floating-point registers is now an error. Previously this would fall back to the soft-float PCS while still emitting the hard-float ABI attribute tag.

Changes to the AVR Backend#

Changes to the DirectX Backend#

  • The DirectX backend has been promoted from experimental to an official, fully supported LLVM target.

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#

  • Added experimental MC support for the Smcsps and Sscsps conditional stack pointer swap extensions.

  • Adds experimental assembler/CodeGen support for the Zilx (Indexed Integer Load) extension.

  • Added experimental MC support for the Smijt and Ssijt interrupt jump table extensions and the Smehv and Ssehv synchronous exception hardware vectoring extensions.

  • Added experimental MC support for the Smip and Ssip interrupt handler push/pop extensions.

  • Bump Svukte extension to 1.0.

  • Remove experimental from Zicfiss.

  • Added support for Sspmp, Sspmpen and Smpmpdeleg extensions.

Changes to the WebAssembly Backend#

  • Added support for emitting common symbols (.comm) using the WASM_SYMBOL_BINDING_COMMON flag (see https://github.com/WebAssembly/tool-conventions/pull/267)

  • Added @llvm.wasm.memory.copy and @llvm.wasm.memory.fill intrinsics for the WebAssembly memory.copy and memory.fill instructions.

Changes to the Windows Target#

Changes to the X86 Backend#

Changes to the OCaml bindings#

Changes to the Python bindings#

Changes to the C API#

Changes to the CodeGen infrastructure#

  • Fixed a crash (#214750) when compiling a function containing a static alloca of (size_t)-1 bytes, whose size collided with the sentinel value MachineFrameInfo used to mark dead stack objects.

Changes to the Metadata Info#

Changes to the Debug Info#

Changes to the LLVM tools#

  • llvm-mca no longer defaults -mcpu to “native”

Changes to LLDB#

  • platform.plugin.wasm.runtime-args now precede the port argument on the Wasm runtime’s command line instead of following it. A runtime that dispatches on a leading subcommand can therefore name that subcommand through this setting, rather than needing a wrapper script.

SBAPI#

  • A bug involving SBValues representing a register set was fixed. The methods GetIndexOfChildWithName and GetChildMemberWithName were incorrectly looking up values in all register sets. This meant that GetIndexOfChildWithName could return an index greater than the size of the set, and that GetChildMemberWithName could return values that were actually in a different set. Both methods are now fixed so that they are limited to the registers within the register set. Scripts using these methods may have to be updated as a result.

Windows#

  • Python 3.11 or later is now required for building LLDB 24 on Windows.

  • For better performance, LLDB now turns off the Windows debug heap by default when debugging. If you need the debug heap enabled, set platform.plugin.windows.disable-debug-heap to false.

Changes to BOLT#

Changes to Sanitizers#

Other Changes#

  • cas::ObjectStore::getMemoryBuffer() was documented as returning a buffer whose lifetime is independent of the CAS, but the buffer it returns may alias storage the CAS owns and so cannot outlive it. The documentation now matches the behavior, and the new getStandaloneMemoryBuffer() provides a buffer that does stay valid after the ObjectStore is destroyed.

External Open Source Projects Using LLVM 24.0.0git#

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 Discourse forums.