Unused linker options when compiling for AMD GPUs

[AlexanderSinn]

Every time I compile HiPACE++ (using AMReX development) for MI250X, I get the following warning:

clang++: warning: argument unused during compilation: '-Xoffload-linker --whole-archive' [-Wunused-command-line-argument]

It also happens in the CI of hipace; however, seemingly not with amrex.
https://github.com/Hi-PACE/hipace/actions/runs/18302787740/job/52113807454#step:5:586
https://github.com/Hi-PACE/hipace/actions/runs/18302787740/workflow

I noticed that the two options are explicitly set by AMReX; however, I don't know for which HIP versions this is/was necessary or if the compiler or linker prints the warning.

amrex/Tools/CMake/AMReXParallelBackends.cmake

Lines 347 to 360 in 26054b2

	# ROCm 5.5: hipcc now relies on clang to offload code objects from (.a) archive files,
	# so we need to tell the offload-linker to include all code objects in archives.
	include(CheckLinkerFlag)
	check_linker_flag(
	CXX
	"SHELL:-Xoffload-linker --whole-archive"
	LINKER_HAS_WHOLE_ARCHIVE_OFFLOAD)
	if(LINKER_HAS_WHOLE_ARCHIVE_OFFLOAD)
	foreach(D IN LISTS AMReX_SPACEDIM)
	target_link_options(amrex_${D}d PUBLIC
	"$<$<LINK_LANGUAGE:HIP>:SHELL:-Xoffload-linker --whole-archive>"
	"$<$<LINK_LANGUAGE:CXX>:SHELL:-Xoffload-linker --whole-archive>")
	endforeach()
	endif()

[WeiqunZhang]

Also not with WarpX. The difference seems to be LINKER_HAS_WHOLE_ARCHIVE_OFFLOAD is set to true by check_linker_flag in the hipace++ CI, whereas it is false in amrex and warpx CIs.

[AlexanderSinn]

For me, the code compiles without the warning and works fine with the section removed. Should I make a PR to remove it?

[WeiqunZhang]

The problem is it was needed at one point, and it's not clear starting from which version of rocm we no longer needed it. Do you know why the cmake linker flag test does not work in hipace++?