Re: patch to fix PR63906

[Andrew Pinski <pinskia at gmail dot com>]

On Mon, Nov 17, 2014 at 4:15 PM, Vladimir Makarov <vmakarov@redhat.com> wrote:
> The following patch fixes
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63906
>
> LRA rematerialization checks SP offsets at origin and rematerialization
> places when trying to rematerialize an insn.  But the offsets are not valid
> if sp elimination is prohibited (e.g. when alloca is used).  Value of
> frame_pointer_required is a flag of this.


Thanks for the fix, it works and glibc is no longer miscompiled.

Thanks,
Andrew

>
> The patch was bootstrapped on aarch64 and committed as rev. 217683.
>
> 2014-11-17  Vladimir Makarov  <vmakarov@redhat.com>
>
>         PR rtl-optimization/63906
>         * lra-remat.c (operand_to_remat): Check SP and
>         frame_pointer_required.
>
> Index: lra-remat.c
> ===================================================================
> --- lra-remat.c (revision 217658)
> +++ lra-remat.c (working copy)
> @@ -399,7 +399,13 @@ operand_to_remat (rtx_insn *insn)
>
>    /* First find a pseudo which can be rematerialized.  */
>    for (reg = id->regs; reg != NULL; reg = reg->next)
> -    if (reg->type == OP_OUT && ! reg->subreg_p
> +    /* True FRAME_POINTER_NEEDED might be because we can not follow
> +       changing sp offsets, e.g. alloca is used.  If the insn contains
> +       stack pointer in such case, we can not rematerialize it as we
> +       can not know sp offset at a rematerialization place.  */
> +    if (reg->regno == STACK_POINTER_REGNUM && frame_pointer_needed)
> +      return -1;
> +    else if (reg->type == OP_OUT && ! reg->subreg_p
>         && find_regno_note (insn, REG_UNUSED, reg->regno) == NULL)
>        {
>         /* We permits only one spilled reg.  */