[Bug middle-end/57748] [4.8/4.9 Regression] ICE when expanding assignment to unaligned zero-sized array

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57748

--- Comment #28 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
(In reply to Richard Biener from comment #19)
> Barking up wrong trees.  Hacky fix looks like:
> 
> Index: gcc/expr.c
> ===================================================================
> --- gcc/expr.c  (revision 202043)
> +++ gcc/expr.c  (working copy)
> @@ -4753,6 +4753,9 @@ expand_assignment (tree to, tree from, b
>         {
>           enum machine_mode address_mode;
>           rtx offset_rtx;
> +         rtx saved_to_rtx = to_rtx;
> +         if (misalignp)
> +           to_rtx = mem;
>  
>           if (!MEM_P (to_rtx))
>             {
> @@ -4785,6 +4788,11 @@ expand_assignment (tree to, tree from, b
>           to_rtx = offset_address (to_rtx, offset_rtx,
>                                    highest_pow2_factor_for_target (to,
>                                                                    offset));
> +         if (misalignp)
> +           {
> +             mem = to_rtx;
> +             to_rtx = saved_to_rtx;
> +           }
>         }
>  
>        /* No action is needed if the target is not a memory and the field
> 
> 

this patch generates wrong code too:

foo:
.LFB9:
        .cfi_startproc
        pushq   %rbx
        .cfi_def_cfa_offset 16
        .cfi_offset 3, -16
        movq    %rdi, %rbx
        subq    $16, %rsp
        .cfi_def_cfa_offset 32
        call    get_i
        movdqu  (%rbx), %xmm0
        cltq
        movq    .LC1(%rip), %xmm1
        psrldq  $8, %xmm0
        punpcklqdq      %xmm0, %xmm1
        movdqu  %xmm1, 16(%rbx,%rax,8)
        addq    $16, %rsp
        .cfi_def_cfa_offset 16
        popq    %rbx
        .cfi_def_cfa_offset 8
        ret
        .cfi_endproc

loads *s into xmm0, modifies low part,
writes back at s->b[0] and s->b[1].