On 01/20/2011 01:26 PM, Sergei Trofimovich wrote:
> So I would like to have "large data segment" feature!
> Can you elaborate what exactly needs to be implemented?
>
> From what I see:
> 0. We need additional flag for gcc: let's call it -mhuge-pic
>
> 1. We need to force GCC to generate any GP (r1) offsets.
> Seems, we need to emit some kind of LX instruction to
> compute absolute data offset in a separate register.
> What kind of relocation should be that to have ability
> to mix them with stock ones?
>
> 2. We need to fix binutils to be able to relax sections with
> usual and "huge" types of access to GP.
Depending on how Haskell programs are built, it may be better
to avoid the GOT entirely. E.g.
-mcmodel=large
a-la the x86_64 port. This generates full 64-bit absolute
relocations. For ia64 code this would look like
movl r32 = foo#
Offset Info Type Sym. Value Sym. Name + Addend
000000000002 000400000023 R_IA64_IMM64 0000000000000000 foo + 0
Of course, you wouldn't put this code into a shared library.
For that you really would want a 64-bit GPREL offset. E.g.
movl r32 = @gprel(foo)
add r32 = r32, r1
Offset Info Type Sym. Value Sym. Name + Addend
000000000002 00040000002b R_IA64_GPREL64I 0000000000000000 foo + 0
Since both of these assemble now, really doubt there's any
binutils work that needs to be done.
What you'd have to do is add some command-line switches (and perhaps
clean up the ones that are there wrt code models), and adjust the
code in ia64_expand_load_address to handle your new options. It really
shouldn't be very difficult.
r~
