172 lines
7.4 KiB
ReStructuredText
172 lines
7.4 KiB
ReStructuredText
===========================
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lld |release| Release Notes
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===========================
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.. contents::
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:local:
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.. only:: PreRelease
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.. warning::
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These are in-progress notes for the upcoming LLVM |release| release.
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Release notes for previous releases can be found on
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`the Download Page <https://releases.llvm.org/download.html>`_.
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Introduction
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============
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This document contains the release notes for the lld linker, release |release|.
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Here we describe the status of lld, including major improvements
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from the previous release. All lld releases may be downloaded
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from the `LLVM releases web site <https://llvm.org/releases/>`_.
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Non-comprehensive list of changes in this release
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=================================================
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ELF Improvements
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----------------
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* ``--fat-lto-objects`` option is added to support LLVM FatLTO.
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Without ``--fat-lto-objects``, LLD will link LLVM FatLTO objects using the
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relocatable object file. (`D146778 <https://reviews.llvm.org/D146778>`_)
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* ``-Bsymbolic-non-weak`` is added to directly bind non-weak definitions.
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(`D158322 <https://reviews.llvm.org/D158322>`_)
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* ``--lto-validate-all-vtables-have-type-infos``, which complements
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``--lto-whole-program-visibility``, is added to disable unsafe whole-program
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devirtualization. ``--lto-known-safe-vtables=<glob>`` can be used
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to mark known-safe vtable symbols.
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(`D155659 <https://reviews.llvm.org/D155659>`_)
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* ``--save-temps --lto-emit-asm`` now derives ELF/asm file names from bitcode file names.
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``ld.lld --save-temps a.o d/b.o -o out`` will create ELF relocatable files
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``out.lto.a.o``/``d/out.lto.b.o`` instead of ``out1.lto.o``/``out2.lto.o``.
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(`#78835 <https://github.com/llvm/llvm-project/pull/78835>`_)
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* ``--no-allow-shlib-undefined`` now reports errors for DSO referencing
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non-exported definitions.
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(`#70769 <https://github.com/llvm/llvm-project/pull/70769>`_)
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* common-page-size can now be larger than the system page-size.
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(`#57618 <https://github.com/llvm/llvm-project/issues/57618>`_)
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* When call graph profile information is available due to instrumentation or
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sample PGO, input sections are now sorted using the new ``cdsort`` algorithm,
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better than the previous ``hfsort`` algorithm.
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(`D152840 <https://reviews.llvm.org/D152840>`_)
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* Symbol assignments like ``a = DEFINED(a) ? a : 0;`` are now handled.
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(`#65866 <https://github.com/llvm/llvm-project/pull/65866>`_)
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* ``OVERLAY`` now supports optional start address and LMA
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(`#77272 <https://github.com/llvm/llvm-project/pull/77272>`_)
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* Relocations referencing a symbol defined in ``/DISCARD/`` section now lead to
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an error.
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(`#69295 <https://github.com/llvm/llvm-project/pull/69295>`_)
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* For AArch64 MTE, global variable descriptors have been implemented.
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(`D152921 <https://reviews.llvm.org/D152921>`_)
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* ``R_AARCH64_GOTPCREL32`` is now supported.
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(`#72584 <https://github.com/llvm/llvm-project/pull/72584>`_)
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* ``R_LARCH_PCREL20_S2``/``R_LARCH_ADD6``/``R_LARCH_CALL36`` and extreme code
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model relocations are now supported.
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* ``--emit-relocs`` is now supported for RISC-V linker relaxation.
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(`D159082 <https://reviews.llvm.org/D159082>`_)
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* Call relaxation respects RVC when mixing +c and -c relocatable files.
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(`#73977 <https://github.com/llvm/llvm-project/pull/73977>`_)
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* ``R_RISCV_GOT32_PCREL`` is now supported.
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(`#72587 <https://github.com/llvm/llvm-project/pull/72587>`_)
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* ``R_RISCV_SET_ULEB128``/``R_RISCV_SUB_ULEB128`` relocations are now supported.
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(`#72610 <https://github.com/llvm/llvm-project/pull/72610>`_)
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(`#77261 <https://github.com/llvm/llvm-project/pull/77261>`_)
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* RISC-V TLSDESC is now supported.
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(`#79239 <https://github.com/llvm/llvm-project/pull/79239>`_)
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Breaking changes
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----------------
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COFF Improvements
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-----------------
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* Added support for ``--time-trace`` and associated ``--time-trace-granularity``.
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This generates a .json profile trace of the linker execution.
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(`#68236 <https://github.com/llvm/llvm-project/pull/68236>`_)
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* The ``-dependentloadflag`` option was implemented.
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(`#71537 <https://github.com/llvm/llvm-project/pull/71537>`_)
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* LLD now prefers library paths specified with ``-libpath:`` over the implicitly
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detected toolchain paths.
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(`#78039 <https://github.com/llvm/llvm-project/pull/78039>`_)
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* Added new options ``-lldemit:llvm`` and ``-lldemit:asm`` for getting
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the output of LTO compilation as LLVM bitcode or assembly.
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(`#66964 <https://github.com/llvm/llvm-project/pull/66964>`_)
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(`#67079 <https://github.com/llvm/llvm-project/pull/67079>`_)
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* Added a new option ``-build-id`` for generating a ``.buildid`` section
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when not generating a PDB. A new symbol ``__buildid`` is generated by
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the linker, allowing code to reference the build ID of the binary.
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(`#71433 <https://github.com/llvm/llvm-project/pull/71433>`_)
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(`#74652 <https://github.com/llvm/llvm-project/pull/74652>`_)
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* A new, LLD specific option, ``-lld-allow-duplicate-weak``, was added
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for allowing duplicate weak symbols.
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(`#68077 <https://github.com/llvm/llvm-project/pull/68077>`_)
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* More correctly handle LTO of files that define ``__imp_`` prefixed dllimport
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redirections.
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(`#70777 <https://github.com/llvm/llvm-project/pull/70777>`_)
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(`#71376 <https://github.com/llvm/llvm-project/pull/71376>`_)
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(`#72989 <https://github.com/llvm/llvm-project/pull/72989>`_)
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* Linking undefined references to weak symbols with LTO now works.
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(`#70430 <https://github.com/llvm/llvm-project/pull/70430>`_)
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* Use the ``SOURCE_DATE_EPOCH`` environment variable for the PE header and
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debug directory timestamps, if neither the ``/Brepro`` nor ``/timestamp:``
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options have been specified. This makes the linker output reproducible by
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setting this environment variable.
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(`#81326 <https://github.com/llvm/llvm-project/pull/81326>`_)
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* Lots of incremental work towards supporting linking ARM64EC binaries.
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MinGW Improvements
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------------------
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* Added support for many LTO and ThinLTO options (most LTO options supported
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by the ELF driver, that are implemented by the COFF backend as well,
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should be supported now).
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(`D158412 <https://reviews.llvm.org/D158412>`_)
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(`D158887 <https://reviews.llvm.org/D158887>`_)
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(`#77387 <https://github.com/llvm/llvm-project/pull/77387>`_)
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(`#81475 <https://github.com/llvm/llvm-project/pull/81475>`_)
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* LLD no longer tries to autodetect and use library paths from MSVC/WinSDK
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installations when run in MinGW mode; that mode of operation shouldn't
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ever be needed in MinGW mode, and could be a source of unexpected
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behaviours.
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(`D144084 <https://reviews.llvm.org/D144084>`_)
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* The ``--icf=safe`` option now works as expected; it was previously a no-op.
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(`#70037 <https://github.com/llvm/llvm-project/pull/70037>`_)
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* The strip flags ``-S`` and ``-s`` now can be used to strip out DWARF debug
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info and symbol tables while emitting a PDB debug info file.
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(`#75181 <https://github.com/llvm/llvm-project/pull/75181>`_)
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* The option ``--dll`` is handled as an alias for the ``--shared`` option.
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(`#68575 <https://github.com/llvm/llvm-project/pull/68575>`_)
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* The option ``--sort-common`` is ignored now.
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(`#66336 <https://github.com/llvm/llvm-project/pull/66336>`_)
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MachO Improvements
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------------------
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WebAssembly Improvements
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------------------------
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* Indexes are no longer required on archive files. Instead symbol information
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is read from object files within the archive. This matches the behaviour of
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the ELF linker.
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SystemZ
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-------
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* Add target support for SystemZ (s390x).
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Fixes
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#####
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