On Fri, Jan 26, 2024 at 12:04 AM Tobias Burnus <tbur...@baylibre.com> wrote:
>
> When targeting AMD GPUs, the LLVM assembler (and linker) are used.
>
> Two days ago LLVM changed the default for the AMDHSA code object
> version (COV) from 4 to 5.
>
> In principle, we do not care which COV is used as long as it works;
> unfortunately, "mkoffload.cc" also generates an object file directly,
> bypassing the AMD GPU compiler as it copies debugging data to that
> file. That object file must have the same COV version (ELF ABI version)
> as compiler + llvm-mc assembler generated files.
>
> In order to ensure those are the same, this patch forces the use of
> COV 4 instead of using the default. Once GCC requires LLVM >= 14
> instead of LLVM >= 13.0.1 we could change it. (Assuming that COV 5
> is sufficiently stable in LLVM 14.) - But for now COV 4 will do.
>
> If you wonder how this LLVM issue shows up, simply compile any OpenMP
> or OpenACC program with AMD GPU offloading and enable debugging ("-g"),
> e.g.
> gcc -fopenmp -g test.f90 -foffload=amdgcn-amdhsa
> -foffload-options=-march=gfx908
>
> With LLVM main (to become LLVM 18), you will then get the error:
>
> ld: error: incompatible ABI version: /tmp/ccAKx5cz.mkoffload.dbg.o
>
> OK for mainline?
If you link against prebuilt objects with COV 5 it seems there's no way to
override the COV version GCC uses? That is, do we want to add
a -mcode-object-version=... option to allow the user to override this
(and ABI_VERSION_SPEC honoring that, if specified and of course
mkoffload following suit)?
Otherwise looks OK in the meantime.
Richard.
> Tobias
