[PATCH] Fix pr57637

[Richard Earnshaw]

On 27/06/13 10:02, Zhenqiang Chen wrote:
> Hi,
>
> Shrink-wrap optimization sinks some instructions for more
> opportunities. It uses DF_LR_BB_INFO (bb)->def to check whether BB
> clobbers SRC. But for ARM, gcc might generate cond_exec insns before
> shrink-wrapping. And DF_LR_BB_INFO (bb)->def does not include def info
> from cond_exec insns. So the check in function
> move_insn_for_shrink_wrap is not enough.
>
> The patch is to add more check bases on DF_LIVE_BB_INFO (bb)->gen if
> df-live is available.
>
> Bootstrap and no make check regression on x86-64 and Panda board.
>
> Is is OK for trunk?
>
> Thanks!
> -Zhenqiang
>
> ChangeLog:
> 2013-06-27  Zhenqiang Chen  <zhenqiang.chen@linaro.org>
>
>          PR target/57637
>          * function.c (move_insn_for_shrink_wrap): Check
> DF_LIVE_BB_INFO (bb)->gen.

First off, this isn't really my area, so all this might be off base. 
Did you really mean Richard Sandiford?

The code you're looking at here looks a bit odd.  We have

       live_out = df_get_live_out (bb);
       live_in = df_get_live_in (next_block);
       bb = next_block;

       /* Check whether BB uses DEST or clobbers DEST.  We need to add
	 INSN to BB if so.  Either way, DEST is no longer live on entry,
	 except for any part that overlaps SRC (next loop).  */
       bb_uses = &DF_LR_BB_INFO (bb)->use;
       bb_defs = &DF_LR_BB_INFO (bb)->def;

The setting of live_out and live in uses

   if (df_live)
     return DF_LIVE_OUT (bb);
   else
     return DF_LR_OUT (bb);

but for bb_uses and bb_defs, we unconditionally use the LR problem and 
never consider live.

That seems strange to me.

Perhaps a better fix would be to set bb_uses and bb_defs based on 
whether or not df_live was valid.  ie

       live_out = df_get_live_out (bb);
       live_in = df_get_live_in (next_block);
       bb = next_block;

       /* Check whether BB uses DEST or clobbers DEST.  We need to add
	 INSN to BB if so.  Either way, DEST is no longer live on entry,
	 except for any part that overlaps SRC (next loop).  */
       if (df_live)
         {
           bb_uses = &DF_LIVE_BB_INFO (bb)->use;
           bb_defs = &DF_LIVE_BB_INFO (bb)->def;
         }
       else
         {
           bb_uses = &DF_LR_BB_INFO (bb)->use;
           bb_defs = &DF_LR_BB_INFO (bb)->def;
         }

Richard (S), what are your thoughts?

R.

>
> diff --git a/gcc/function.c b/gcc/function.c
> index 3e33fc7..08ca4a1 100644
> --- a/gcc/function.c
> +++ b/gcc/function.c
> @@ -5508,7 +5508,8 @@ move_insn_for_shrink_wrap (basic_block bb, rtx insn,
>         bb_defs = &DF_LR_BB_INFO (bb)->def;
>         for (i = dregno; i < end_dregno; i++)
>          {
> -         if (REGNO_REG_SET_P (bb_uses, i) || REGNO_REG_SET_P (bb_defs, i))
> +         if (REGNO_REG_SET_P (bb_uses, i) || REGNO_REG_SET_P (bb_defs, i)
> +             || (df_live && REGNO_REG_SET_P (&DF_LIVE_BB_INFO (bb)->gen, i)))
>              next_block = NULL;
>            CLEAR_REGNO_REG_SET (live_out, i);
>            CLEAR_REGNO_REG_SET (live_in, i);
> @@ -5518,7 +5519,8 @@ move_insn_for_shrink_wrap (basic_block bb, rtx insn,
>           Either way, SRC is now live on entry.  */
>         for (i = sregno; i < end_sregno; i++)
>          {
> -         if (REGNO_REG_SET_P (bb_defs, i))
> +         if (REGNO_REG_SET_P (bb_defs, i)
> +             || (df_live && REGNO_REG_SET_P (&DF_LIVE_BB_INFO (bb)->gen, i)))
>              next_block = NULL;
>            SET_REGNO_REG_SET (live_out, i);
>            SET_REGNO_REG_SET (live_in, i);
>