Re: [PATCH] Fix x86_64 ICE with -fpie -mcmodel=large (PR target/81766)

[Uros Bizjak <ubizjak at gmail dot com>]

On Fri, Sep 1, 2017 at 1:42 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> As mentioned in the PR, ix86_init_pic_reg for -mcmodel=large PIC creates
> invalid RTL.  Shrink wrapping managed to work around it by unconditionally
> running find_many_sub_basic_blocks that has been invoked even when the
> prologue or split prologue actually didn't contain anything, but that isn't
> done anymore.
>
> The problem is that we add a label into the sequence that we then insert on
> the single succ edge after ENTRY; but this insertion inserts the label after
> the NOTE_INSN_BLOCK_BEG, which is invalid, because labels should precede
> that.
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?
>
> 2017-09-01  Jakub Jelinek  <jakub@redhat.com>
>
>         PR target/81766
>         * config/i386/i386.c (ix86_init_large_pic_reg): Return label instead of void.
>         (ix86_init_pic_reg): Remember label from ix86_init_large_pic_reg, if non-NULL
>         and preceded by NOTE_INSN_BASIC_BLOCK, swap the note and label.
>
>         * gcc.target/i386/pr81766.c: New test.

OK.

Thanks,
Uros.

> --- gcc/config/i386/i386.c.jj   2017-08-07 18:50:10.000000000 +0200
> +++ gcc/config/i386/i386.c      2017-08-08 16:01:41.917136120 +0200
> @@ -8829,7 +8829,7 @@ ix86_use_pseudo_pic_reg (void)
>
>  /* Initialize large model PIC register.  */
>
> -static void
> +static rtx_code_label *
>  ix86_init_large_pic_reg (unsigned int tmp_regno)
>  {
>    rtx_code_label *label;
> @@ -8846,6 +8846,7 @@ ix86_init_large_pic_reg (unsigned int tm
>    emit_insn (gen_set_got_offset_rex64 (tmp_reg, label));
>    emit_insn (ix86_gen_add3 (pic_offset_table_rtx,
>                             pic_offset_table_rtx, tmp_reg));
> +  return label;
>  }
>
>  /* Create and initialize PIC register if required.  */
> @@ -8854,6 +8855,7 @@ ix86_init_pic_reg (void)
>  {
>    edge entry_edge;
>    rtx_insn *seq;
> +  rtx_code_label *label = NULL;
>
>    if (!ix86_use_pseudo_pic_reg ())
>      return;
> @@ -8863,7 +8865,7 @@ ix86_init_pic_reg (void)
>    if (TARGET_64BIT)
>      {
>        if (ix86_cmodel == CM_LARGE_PIC)
> -       ix86_init_large_pic_reg (R11_REG);
> +       label = ix86_init_large_pic_reg (R11_REG);
>        else
>         emit_insn (gen_set_got_rex64 (pic_offset_table_rtx));
>      }
> @@ -8887,6 +8889,22 @@ ix86_init_pic_reg (void)
>    entry_edge = single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun));
>    insert_insn_on_edge (seq, entry_edge);
>    commit_one_edge_insertion (entry_edge);
> +
> +  if (label)
> +    {
> +      basic_block bb = BLOCK_FOR_INSN (label);
> +      rtx_insn *bb_note = PREV_INSN (label);
> +      /* If the note preceding the label starts a basic block, and the
> +        label is a member of the same basic block, interchange the two.  */
> +      if (bb_note != NULL_RTX
> +         && NOTE_INSN_BASIC_BLOCK_P (bb_note)
> +         && bb != NULL
> +         && bb == BLOCK_FOR_INSN (bb_note))
> +       {
> +         reorder_insns_nobb (bb_note, bb_note, label);
> +         BB_HEAD (bb) = label;
> +       }
> +    }
>  }
>
>  /* Initialize a variable CUM of type CUMULATIVE_ARGS
> --- gcc/testsuite/gcc.target/i386/pr81766.c.jj  2017-08-08 16:10:04.299459808 +0200
> +++ gcc/testsuite/gcc.target/i386/pr81766.c     2017-08-08 16:09:28.000000000 +0200
> @@ -0,0 +1,9 @@
> +/* PR target/81766 */
> +/* { dg-do compile { target { pie && lp64 } } } */
> +/* { dg-options "-O2 -fpie -mcmodel=large" } */
> +
> +int
> +main ()
> +{
> +  return 0;
> +}
>
>         Jakub