[all-commits] [llvm/llvm-project] 4f0325: [ORC] Enable JIT support for the compact-unwind fr...

[Lang Hames via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4f0325873faccfbe171bae4babceb65975ca892e
      https://github.com/llvm/llvm-project/commit/4f0325873faccfbe171bae4babceb65975ca892e
  Author: Lang Hames <lhames at gmail.com>
  Date:   2025-01-23 (Thu, 23 Jan 2025)

  Changed paths:
    M compiler-rt/lib/orc/macho_platform.cpp
    A compiler-rt/test/orc/TestCases/Darwin/Generic/exceptions.cpp
    M llvm/include/llvm/ExecutionEngine/Orc/ExecutorProcessControl.h
    M llvm/include/llvm/ExecutionEngine/Orc/Shared/OrcRTBridge.h
    A llvm/include/llvm/ExecutionEngine/Orc/TargetProcess/UnwindInfoManager.h
    A llvm/include/llvm/ExecutionEngine/Orc/UnwindInfoRegistrationPlugin.h
    M llvm/lib/ExecutionEngine/JITLink/CMakeLists.txt
    A llvm/lib/ExecutionEngine/JITLink/CompactUnwindSupport.cpp
    A llvm/lib/ExecutionEngine/JITLink/CompactUnwindSupport.h
    M llvm/lib/ExecutionEngine/JITLink/MachOLinkGraphBuilder.cpp
    M llvm/lib/ExecutionEngine/JITLink/MachOLinkGraphBuilder.h
    M llvm/lib/ExecutionEngine/JITLink/MachO_arm64.cpp
    M llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp
    M llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
    M llvm/lib/ExecutionEngine/Orc/CompileUtils.cpp
    M llvm/lib/ExecutionEngine/Orc/ExecutorProcessControl.cpp
    M llvm/lib/ExecutionEngine/Orc/LLJIT.cpp
    M llvm/lib/ExecutionEngine/Orc/Shared/OrcRTBridge.cpp
    M llvm/lib/ExecutionEngine/Orc/TargetProcess/CMakeLists.txt
    A llvm/lib/ExecutionEngine/Orc/TargetProcess/UnwindInfoManager.cpp
    A llvm/lib/ExecutionEngine/Orc/UnwindInfoRegistrationPlugin.cpp

  Log Message:
  -----------
  [ORC] Enable JIT support for the compact-unwind frame info format on Darwin.

For Darwin/arm64 (including Apple Silicon Macs) this will enable exception
handling and stack unwinding in JIT'd code.

Darwin supports two unwind-info formats: DWARF eh-frames and compact-unwind. On
Darwin/x86-64 compilers usually produce both by default, and ORC supported
exceptions and unwinding via eh-frames (same as on Linux), discarding the
redundant compact-unwind info. On Darwin/arm64 compilers typically default to
producing compact-unwind only, with DWARF eh-frames as a fallback for functions
that can't be described in compact-unwind. Since ORC did not previously support
the compact-unwind format and eh-frames were not present ORC was unable to
handle exceptions or unwinding by default in Darwin/arm64 JIT'd code.

This patch enables support for the compact-unwind-info format, and contains
three major moving parts:

(1) The JITLink CompactUnwindManager class is responsible for transforming the
    __compact_unwind records produced by the linker into the __unwind_info
    tables that libunwind parses during unwinding. To enable this the
    CompactUnwindManager class provides three JITLink passes: The
    prepareForPrune pass that splits the __compact_unwind section into
    single-record blocks, allowing unused records to be dead-stripped; the
    processAndReserveUnwindInfo pass that reserves space for the final
    __unwind_info section, and the writeUnwindInfo pass that writes the
    __unwind_info section.

(2) The OrcTargetProcess UnwindInfoManager class maintains a table of
    registered JIT'd __unwind_info and __eh_frame sections, and handles
    requests from libunwind for unwind info sections (by registering a callback
    with libunwind's __unw_add_find_dynamic_unwind_sections function).

(3) The Orc UnwindInfoRegistrationPlugin, which scans LinkGraphs for
    __unwind_info and __eh_frame sections to register with the
    UnwindInfoManager.

This commit adds the CompactUnwindManager passes to the default JITLink
pipelines for Darwin/arm64 and Darwin/x86-64, and UnwindInfoManager intances to
the SelfExecutorProcessControl class (when built for apple platforms) and the
llvm-jitlink-executor tool.

The LLJIT class will now create an UnwindInfoRegistrationPlugin when targeting
a process running on Darwin if it detects that an UnwindInfoManager is
available to handle the registrations.

The ORC runtime macho_platform class already supported libunwind callbacks, so
out-of-process execution and unwinding support will work when loading the ORC
runtime.

The llvm-jitlink tool will only support compact-unwind when the orc-runtime is
loaded, as the UnwindInfoRegistrationPlugin requires access to an IR compiler
to load a helper module and llvm-jitlink does not provide an IR compiler.



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