llvm-project

82a36468 - [LLD][COFF] Add support for ARM64EC auxiliary IAT (#108304)

[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.