Miscompilation on arm64 with GCC LTO

Sam James sam at gentoo.org
Wed May 10 15:01:29 CEST 2023

Niels Möller <nisse at lysator.liu.se> writes:

> Sam James <sam at gentoo.org> writes:
>> Note that Jannik identified the bad commit [0] as 18082:c5d0fcb06969 [4].
> [...]
>> [0] https://gmplib.org/list-archives/gmp-bugs/2020-December/004981.html
>> [1] https://gmplib.org/list-archives/gmp-bugs/2023-January/005223.html
>> [3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109765
>> [4] https://gmplib.org/repo/gmp/rev/c5d0fcb06969
> It looks like that commit changes
>   adrp	x1, approx_tab
>   add	x1, x1, :lo12:approx_tab
> to
>   adrp	x1, :got:approx_tab
>   ldr	x1, [x1, #:got_lo12:approx_tab]
> and only when PIC is defined (via LEA_HI and LEA_LO m4 macros). I
> haven't double checked what assembly files actually look like after
> preprocessing, though.
> And something similar for __gmp_binvert_limb_table.
> But I have no clue about the arm64 abi. Is PIC defined in the failing
> build, or should it be?

I think it is set.

If I try with explicit ./configure --with-pic to be sure, it still

If I try with explicit ./configure --without-pic, I can't build gmp:
mpn/.libs/bdiv_q_1.o: relocation R_AARCH64_ADR_PREL_PG_HI21 against
symbol `__gmp_binvert_limb_table' which may bind externally can not be
used when making a shared object; recompile with -fPIC
mpn/.libs/bdiv_q_1.o: in function `__gmpn_bdiv_q_1':

with __gmp_binvert_limb_table being the symbol you and Jannik mentioned..

> Regards,
> /Niels

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