On Tue, Nov 29, 2016 at 1:09 AM, Kyrill Tkachov
<kyrylo.tkac...@foss.arm.com> wrote:
> Hi all,
>
> This ICE only occurs on big-endian ILP32 -fpie code. The expansion code
> generates the invalid load:
> (insn 6 5 7 (set (reg/f:SI 76)
> (unspec:SI [
> (mem/u/c:SI (lo_sum:SI (nil)
> (symbol_ref:SI ("dbs") [flags 0x40] <var_decl
> 0x7f6e387c0ab0 dbs>)) [0 S4 A8])
> ] UNSPEC_GOTSMALLPIC28K))
> (expr_list:REG_EQUAL (symbol_ref:SI ("dbs") [flags 0x40] <var_decl
> 0x7f6e387c0ab0 dbs>)
> (nil)))
>
> to load the symbol. Note the (nil) argument to lo_sum.
> The buggy hunk meant to take the lowpart of the pic_offset_table_rtx
> register but it did so by explicitly
> constructing a subreg, for which the offset is wrong for big-endian. The
> right way is to use gen_lowpart which
> knows what exactly to do, with this patch we emit:
> (insn 6 5 7 (set (reg/f:SI 76)
> (unspec:SI [
> (mem/u/c:SI (lo_sum:SI (subreg:SI (reg:DI 73) 4)
> (symbol_ref:SI ("dbs") [flags 0x40] <var_decl
> 0x7ffb097e6ab0 dbs>)) [0 S4 A8])
> ] UNSPEC_GOTSMALLPIC28K))
> (expr_list:REG_EQUAL (symbol_ref:SI ("dbs") [flags 0x40] <var_decl
> 0x7ffb097e6ab0 dbs>)
> (nil)))
>
> and everything works fine.
>
> Bootstrapped and tested on aarch64-none-linux-gnu.
> Also tested on aarch64_be-none-elf.
> Ok for trunk?
Naveen posted the exact same patch:
https://gcc.gnu.org/ml/gcc-patches/2016-11/msg02305.html
Though with a slightly different testcase :).
Thanks,
Andrew
>
> Thanks,
> Kyrill
>
> 2016-11-29 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
>
> PR target/71112
> * config/aarch64/aarch64.c (aarch64_load_symref_appropriately,
> case SYMBOL_SMALL_GOT_28K): Use gen_lowpart rather than constructing
> subreg directly.
>
> 2016-11-29 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
>
> PR target/71112
> * gcc.c-torture/compile/pr71112.c: New test.
