Re: [Patch][aarch64] Use IFUNCs to enable LSE instructions in libatomic on aarch64

[Steve Ellcey <sellcey@cavium.com>]

On Tue, 2017-08-29 at 12:25 +0100, Szabolcs Nagy wrote:
> 
> it's a general bug that most ifunc users (e.g. in binutils
> tests) declare the ifunc resolvers incorrectly, the correct
> prototype is the way the dynamic linker invokes the resolver
> in sysdeps/aarch64/dl-irel.h:
> 
> static inline ElfW(Addr)
> __attribute ((always_inline))
> elf_ifunc_invoke (ElfW(Addr) addr)
> {
>   return ((ElfW(Addr) (*) (unsigned long int)) (addr))
> (GLRO(dl_hwcap));
> }
> 
> (that argument should be uint64_t for ilp32, but that's a
> separate issue)
> 
> in glibc the hwcap is not used, because it has accesses to
> cached dispatch info, but in libatomic using the hwcap
> argument is the right way.

OK, I changed my patch to use the argument and it did work but
since the type of the argument should be uint64_t instead of 'unsigned
long int' for aarch64 I think I will send a patch to libc-alpha
first to fix this before sending an updated libatomic patch.  That way
I won't have to update GCC when glibc changes the type.  I see that
different platforms use different types for the resolver argument so I
think I will have to update the libatomic configure.tgt script as well
to set the resolver arg type when I resbumit the gcc libatomic patch so
that we can have the correct prototype in libatomic_i.h.

Steve Ellcey
sellcey@cavium.com