Re: RISC-V support

[Kurt Roeckx <kurt@roeckx.be>]

On Tue, Jan 08, 2019 at 02:52:33PM +0100, Mark Wielaard wrote:
> > There is a problem here though.  The riscv support was written to try
> > to handle both 32-bit and 64-bit targets with a single elfutils
> > backend.  But I have 6 ABIs I need to (theoretically) handle in
> > riscv_retval.c.  The return_value_location function doesn't take any
> > ebl or elf pointer, so I can't handle it there.  I can handle it in
> > riscv_init.c by checking ebl and elf pointers there, and calling an
> > appropriate function, but I'm not sure if that is OK.  Currently,
> > none
> > of the *_init.c files are using the elf pointer argument.
> 
> The ppc64 init does (to lookup the odp table which is necessary for
> ppc64[be], but not ppc64le). It is allowed. And the backends/ebl
> interface is completely internal, so feel free to suggest changes if
> they make sense for riscv. If it is necessary we'll just update the
> other backends.

I've been looking at mips, and it seems to have many different
ABIs too. A patch I've received does this:
int
mips_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
{
  /* First find the ABI used by the elf object */
  enum mips_abi abi = find_mips_abi(functypedie->cu->dbg->elf);

The patch only supports 6 ABIs, but I think there are really over
10 ABIs.

Maybe it would be good that we only need to determine the ABI
once, instead of each time the function is called.


Kurt