[llvm-branch-commits] [lld] 2c6a593 - ReleaseNotes: add lld/ELF notes

Sat Aug 29 08:51:45 PDT 2020

Author: Fangrui Song
Date: 2020-08-29T08:51:20-07:00
New Revision: 2c6a593b5e186a686fdaf6b6082b0dbcae29c265

URL: https://github.com/llvm/llvm-project/commit/2c6a593b5e186a686fdaf6b6082b0dbcae29c265
DIFF: https://github.com/llvm/llvm-project/commit/2c6a593b5e186a686fdaf6b6082b0dbcae29c265.diff

LOG: ReleaseNotes: add lld/ELF notes

Differential Revision: https://reviews.llvm.org/D86579

Added: 
    

Modified: 
    lld/docs/ReleaseNotes.rst

Removed: 
    


################################################################################
diff  --git a/lld/docs/ReleaseNotes.rst b/lld/docs/ReleaseNotes.rst
index 513ad37e278e..466a7f707354 100644

--- a/lld/docs/ReleaseNotes.rst
+++ b/lld/docs/ReleaseNotes.rst
@@ -24,22 +24,143 @@ Non-comprehensive list of changes in this release
 ELF Improvements
 ----------------
 
-* New ``--time-trace`` option records a time trace file that can be viewed in
+* ``--lto-emit-asm`` is added to emit assembly output for debugging purposes.
+  (`D77231 <https://reviews.llvm.org/D77231>`_)
+* ``--lto-whole-program-visibility`` is added to support LTO whole-program devirtualization.
+  (`D71913 <https://reviews.llvm.org/D71913>`_)
+* ``--print-archive-stats=`` is added to print the number of members and the number of fetched members for each archive.
+  The feature is similar to GNU gold's ``--print-symbol-counts=``.
+  (`D78983 <https://reviews.llvm.org/D78983>`_)
+* ``--shuffle-sections=`` is added to introduce randomization in the output to help reduce measurement bias and detect static initialization order fiasco.
+  (`D74791 <https://reviews.llvm.org/D74791>`_)
+  (`D74887 <https://reviews.llvm.org/D74887>`_)
+* ``--time-trace`` is added. It records a time trace file that can be viewed in
   chrome://tracing. The file can be specified with ``--time-trace-file``.
   Trace granularity can be specified with ``--time-trace-granularity``.
   (`D71060 <https://reviews.llvm.org/D71060>`_)
-* For ARM architectures the default max page size was increased to 64k.
-  This increases compatibility with systems where a non standard page
-  size was configured. This also is inline with GNU ld defaults.
-  (`D77330 <https://reviews.llvm.org/D77330>`_)
-* ...
+* ``--thinlto-single-module`` is added to compile a subset of modules in ThinLTO for debugging purposes.
+  (`D80406 <https://reviews.llvm.org/D80406>`_)
+* ``--unique`` is added to create separate output sections for orphan sections.
+  (`D75536 <https://reviews.llvm.org/D75536>`_)
+* ``--warn-backrefs`` has been improved to emulate GNU ld's archive semantics.
+  If a link passes with warnings from ``--warn-backrefs``, it almost assuredly
+  means that the link will fail with GNU ld, or the symbol will get 
diff erent
+  resolutions in GNU ld and LLD. ``--warn-backrefs-exclude=`` is added to
+  exclude known issues.
+  (`D77522 <https://reviews.llvm.org/D77522>`_)
+  (`D77630 <https://reviews.llvm.org/D77630>`_)
+  (`D77512 <https://reviews.llvm.org/D77512>`_)
+* ``--no-relax`` is accepted but ignored. The Linux kernel's RISC-V port uses this option.
+  (`D81359 <https://reviews.llvm.org/D81359>`_)
+* ``--rosegment`` (default) is added to complement ``--no-rosegment``.
+  GNU gold from 2.35 onwards support both options.
+* ``--threads=N`` is added. The default uses all threads.
+  (`D76885 <https://reviews.llvm.org/D76885>`_)
+* ``--wrap`` has better compatibility with GNU ld.
+* ``-z dead-reloc-in-nonalloc=<section_glob>=<value>`` is added to resolve an absolute relocation
+  referencing a discarded symbol.
+  (`D83264 <https://reviews.llvm.org/D83264>`_)
+* Changed tombstone values to (``.debug_ranges``/``.debug_loc``) 1 and (other ``.debug_*``) 0.
+  A tombstone value is the computed value of a relocation referencing a discarded symbol (``--gc-sections``, ICF or ``/DISCARD/``).
+  (`D84825 <https://reviews.llvm.org/D84825>`_)
+  In the future many .debug_* may switch to 0xffffffff/0xffffffffffffffff as the tombstone value.
+* ``-z keep-text-section-prefix`` moves ``.text.unknown.*`` input sections to ``.text.unknown``.
+* ``-z rel`` and ``-z rela`` are added to select the REL/RELA format for dynamic relocations.
+  The default is target specific and typically matches the form used in relocatable objects.
+* ``-z start-stop-visibility={default,protected,internal,hidden}`` is added.
+  GNU ld/gold from 2.35 onwards support this option.
+  (`D55682 <https://reviews.llvm.org/D55682>`_)
+* When ``-r`` or ``--emit-relocs`` is specified, the GNU ld compatible
+  ``--discard-all`` and ``--discard-locals`` semantics are implemented.
+  (`D77807 <https://reviews.llvm.org/D77807>`_)
+* ``--emit-relocs --strip-debug`` can now be used together.
+  (`D74375 <https://reviews.llvm.org/D74375>`_)
+* ``--gdb-index`` supports DWARF v5.
+  (`D79061 <https://reviews.llvm.org/D79061>`_)
+  (`D85579 <https://reviews.llvm.org/D85579>`_)
+* ``-r`` allows SHT_X86_64_UNWIND to be merged into SHT_PROGBITS.
+  This allows clang/GCC produced object files to be mixed together.
+  (`D85785 <https://reviews.llvm.org/D85785>`_)
+* Better linker script support related to output section alignments and LMA regions.
+  (`D74286 <https://reviews.llvm.org/D75724>`_)
+  (`D74297 <https://reviews.llvm.org/D75724>`_)
+  (`D75724 <https://reviews.llvm.org/D75724>`_)
+  (`D81986 <https://reviews.llvm.org/D81986>`_)
+* In a input section description, the filename can be specified in double quotes.
+  ``archive:file`` syntax is added.
+  (`D72517 <https://reviews.llvm.org/D72517>`_)
+  (`D75100 <https://reviews.llvm.org/D75100>`_)
+* Linker script specified empty ``(.init|.preinit|.fini)_array`` are allowed with RELRO.
+  (`D76915 <https://reviews.llvm.org/D76915>`_)
+* ``INSERT AFTER`` and ``INSERT BEFORE`` work for orphan sections now.
+  (`D74375 <https://reviews.llvm.org/D74375>`_)
+* ``INPUT_SECTION_FLAGS`` is supported in linker scripts.
+  (`D72745 <https://reviews.llvm.org/D72745>`_)
+* ``DF_1_PIE`` is set for position-independent executables.
+  (`D80872 <https://reviews.llvm.org/D80872>`_)
+* For a symbol assignment ``alias = aliasee;``, ``alias`` inherits the ``aliasee``'s symbol type.
+  (`D86263 <https://reviews.llvm.org/D86263>`_)
+* ``SHT_GNU_verneed`` in shared objects are parsed, and versioned undefined symbols in shared objects are respected.
+  (`D80059 <https://reviews.llvm.org/D80059>`_)
+* SHF_LINK_ORDER and non-SHF_LINK_ORDER sections can be mixed along as the SHF_LINK_ORDER components are contiguous.
+  (`D77007 <https://reviews.llvm.org/D77007>`_)
+* An out-of-range relocation diagnostic mentions the referenced symbol now.
+  (`D73518 <https://reviews.llvm.org/D73518>`_)
+* AArch64: ``R_AARCH64_PLT32`` is supported.
+  (`D81184 <https://reviews.llvm.org/D81184>`_)
+* ARM: SBREL type relocations are supported.
+  (`D74375 <https://reviews.llvm.org/D74375>`_)
+* ARM: ``R_ARM_ALU_PC_G0``, ``R_ARM_LDR_PC_G0``, ``R_ARM_THUMB_PC8`` and ``R_ARM_THUMB__PC12`` are supported.
+  (`D75349 <https://reviews.llvm.org/D75349>`_)
+  (`D77200 <https://reviews.llvm.org/D77200>`_)
+* ARM: various improvements to .ARM.exidx: ``/DISCARD/`` support for a subset, out-of-range handling, support for non monotonic section order.
+  (`PR44824 <https://llvm.org/PR44824>`_)
+* AVR: many relocation types are supported.
+  (`D78741 <https://reviews.llvm.org/D78741>`_)
+* Hexagon: General Dynamic and some other relocation types are supported.
+* PPC: Canonical PLT and range extension thunks with addends are supported.
+  (`D73399 <https://reviews.llvm.org/D73399>`_)
+  (`D73424 <https://reviews.llvm.org/D73424>`_)
+  (`D75394 <https://reviews.llvm.org/D75394>`_)
+* PPC and PPC64: copy relocations.
+  (`D73255 <https://reviews.llvm.org/D73255>`_)
+* PPC64: ``_savegpr[01]_{14..31}`` and ``_restgpr[01]_{14..31}`` can be synthesized.
+  (`D79977 <https://reviews.llvm.org/D79977>`_)
+* PPC64: ``R_PPC64_GOT_PCREL34`` and ``R_PPC64_REL24_NOTOC`` are supported. r2 save stub is supported.
+  (`D81948 <https://reviews.llvm.org/D81948>`_)
+  (`D82950 <https://reviews.llvm.org/D82950>`_)
+  (`D82816 <https://reviews.llvm.org/D82816>`_)
+* RISC-V: ``R_RISCV_IRELATIVE`` is supported.
+  (`D74022 <https://reviews.llvm.org/D74022>`_)
+* RISC-V: ``R_RISCV_ALIGN`` is errored because GNU ld style linker relaxation is not supported.
+  (`D71820 <https://reviews.llvm.org/D71820>`_)
+* SPARCv9: more relocation types are supported.
+  (`D77672 <https://reviews.llvm.org/D77672>`_)
 
 Breaking changes
 ----------------
 
 * One-dash form of some long option (``--thinlto-*``, ``--lto-*``, ``--shuffle-sections=``)
   are no longer supported.
+  (`D79371 <https://reviews.llvm.org/D79371>`_)
 * ``--export-dynamic-symbol`` no longer implies ``-u``.
+  The new behavior matches GNU ld from binutils 2.35 onwards.
+  (`D80487 <https://reviews.llvm.org/D80487>`_)
+* ARM: the default max page size was increased from 4096 to 65536.
+  This increases compatibility with systems where a non standard page
+  size was configured. This also is inline with GNU ld defaults.
+  (`D77330 <https://reviews.llvm.org/D77330>`_)
+* ARM: for non-STT_FUNC symbols, Thumb interworking thunks are not added and BL/BLX are not substituted.
+  (`D73474 <https://reviews.llvm.org/D73474>`_)
+  (`D73542 <https://reviews.llvm.org/D73542>`_)
+* AArch64: ``--force-bti`` is renamed to ``-z force-bti`. ``--pac-plt`` is renamed to ``-z pac-plt``.
+  This change is compatibile with GNU ld.
+* A readonly ``PT_LOAD`` is created in the presence of a ``SECTIONS`` command.
+  The new behavior is consistent with the longstanding behavior in the absence of a SECTIONS command.
+* Orphan section names like ``.rodata.foo`` and ``.text.foo`` are not grouped into ``.rodata`` and ``.text`` in the presence of a ``SECTIONS`` command.
+  The new behavior matches GNU ld.
+  (`D75225 <https://reviews.llvm.org/D75225>`_)
+* ``--no-threads`` is removed. Use ``--threads=1`` instead. ``--threads`` (no-op) is removed.
 
 COFF Improvements
 -----------------


        
