[all-commits] [llvm/llvm-project] 82a364: [LLD][COFF] Add support for ARM64EC auxiliary IAT ...

[Jacek Caban via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 82a36468c74a29b6154639d659550c62457e655b
      https://github.com/llvm/llvm-project/commit/82a36468c74a29b6154639d659550c62457e655b
  Author: Jacek Caban <jacek at codeweavers.com>
  Date:   2024-09-12 (Thu, 12 Sep 2024)

  Changed paths:
    M lld/COFF/DLL.cpp
    M lld/COFF/DLL.h
    M lld/COFF/Driver.cpp
    M lld/COFF/InputFiles.cpp
    M lld/COFF/InputFiles.h
    M lld/COFF/SymbolTable.cpp
    M lld/COFF/SymbolTable.h
    M lld/COFF/Symbols.h
    M lld/COFF/Writer.cpp
    M lld/test/COFF/Inputs/loadconfig-arm64ec.s
    M lld/test/COFF/arm64ec-import.test

  Log Message:
  -----------
  [LLD][COFF] Add support for ARM64EC auxiliary IAT (#108304)

In addition to the regular IAT, ARM64EC also includes an auxiliary IAT.
At runtime, the regular IAT is populated with the addresses of imported
functions, which may be x86_64 functions or the export thunks of ARM64EC
functions. The auxiliary IAT contains versions of functions that are
guaranteed to be directly callable by ARM64 code.

The linker fills the auxiliary IAT with the addresses of `__impchk_`
thunks. These thunks perform a call on the IAT address using
`__icall_helper_arm64ec` with the target address from the IAT. If the
imported function is an ARM64EC function, the OS may replace the address
in the auxiliary IAT with the address of the ARM64EC version of the
function (not its export thunk), avoiding the runtime call checker for
better performance.



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