Re: [PATCH] Fix PR rtl-optimization/61278

[Richard Biener <richard dot guenther at gmail dot com>]

On Fri, May 23, 2014 at 9:23 AM, Zhenqiang Chen
<zhenqiang.chen@linaro.org> wrote:
> Hi,
>
> The patch fixes PR rtl-optimization/61278. Root cause for issue is
> that df_live does not exist at -O1.
>
> Bootstrap and no make check regression on X86-64.
>
> OK for trunk?

Why do you need to give up?  It seems you can simply avoid
marking the block as dirty (though df_get_live_in/out also hands you
back DF_LR_IN/OUT if !df_live).  So isn't the df_grow_bb_info the
"real" fix?

Note that df_get_live_in/out are functions tailored to IRA that
knows that they handle both df_live and df_lr dependent on
optimization level.  Is shrink-wrapping supposed to work with
both problems as well?

Thanks,
Richard.

> Thanks!
> -Zhenqiang
>
> ChangeLog:
> 2014-05-23  Zhenqiang Chen  <zhenqiang.chen@linaro.org>
>
>         PR rtl-optimization/61278
>         * shrink-wrap.c (move_insn_for_shrink_wrap): Check df_live.
>
> testsuite/ChangeLog:
> 2014-05-23  Zhenqiang Chen  <zhenqiang.chen@linaro.org>
>
>         * gcc.dg/lto/pr61278_0.c: New test.
>         * gcc.dg/lto/pr61278_1.c: New test.
>
> diff --git a/gcc/shrink-wrap.c b/gcc/shrink-wrap.c
> index f09cfe7..be17829 100644
> --- a/gcc/shrink-wrap.c
> +++ b/gcc/shrink-wrap.c
> @@ -204,8 +204,15 @@ move_insn_for_shrink_wrap (basic_block bb, rtx insn,
>    /* Create a new basic block on the edge.  */
>    if (EDGE_COUNT (next_block->preds) == 2)
>      {
> +      /* If DF_LIVE doesn't exist, i.e. at -O1, just give up.  */
> +      if (!df_live)
> +       return false;
> +
>        next_block = split_edge (live_edge);
>
> +      /* We create a new basic block.  Call df_grow_bb_info to make sure
> +        all data structures are allocated.  */
> +      df_grow_bb_info (df_live);
>        bitmap_copy (df_get_live_in (next_block), df_get_live_out (bb));
>        df_set_bb_dirty (next_block);
>
> diff --git a/gcc/testsuite/gcc.dg/lto/pr61278_0.c
> b/gcc/testsuite/gcc.dg/lto/pr61278_0.c
> new file mode 100644
> index 0000000..03a24ae
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/lto/pr61278_0.c
> @@ -0,0 +1,30 @@
> +/* { dg-lto-do link } */
> +/* { dg-lto-options { { -flto -O0 } } } */
> +/* { dg-extra-ld-options " -flto -O1 " } */
> +
> +static unsigned int
> +fn1 (int p1, int p2)
> +{
> +  return 0;
> +}
> +
> +char a, b, c;
> +
> +char
> +foo (char *p)
> +{
> +  int i;
> +  for (b = 1 ; b > 0; b++)
> +    {
> +      for (i = 0; i < 2; i++)
> +       ;
> +      for (a = 1; a > 0; a++)
> +       {
> +         char d[1] = { 0 };
> +         if (*p)
> +           break;
> +         c ^= fn1 (fn1 (fn1 (0, 0), 0), 0);
> +       }
> +    }
> +  return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/lto/pr61278_1.c
> b/gcc/testsuite/gcc.dg/lto/pr61278_1.c
> new file mode 100644
> index 0000000..b02c8ac
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/lto/pr61278_1.c
> @@ -0,0 +1,13 @@
> +/* { dg-lto-do link } */
> +/* { dg-lto-options { { -flto -O1 } } } */
> +
> +extern char foo (char *);
> +
> +char d;
> +
> +int
> +main ()
> +{
> +  foo (&d);
> +  return 0;
> +}