Re: [df-scan.c] Optimise DF_REFs ordering in collection_rec, use HARD_REG_SETs instead of bitmaps

[Paolo Bonzini <bonzini at gnu dot org>]

On 07/08/2011 05:51 AM, Dimitrios Apostolou wrote:
> +	  /* first write DF_REF_BASE */

This is not necessary.  These uses are written to use_vec, while the 
uses from REG_EQUIV and REG_EQUAL are written to eq_use_vec (see 
df_ref_create_structure).

Also, anyway this wouldn't work because you would have to split the loop 
in two.  I'll attribute that to the time of day when you were writing 
the message. :)

> +        case REG_NON_LOCAL_GOTO:
> +          /* The frame ptr is used by a non-local goto.  */
> +          df_ref_record (DF_REF_BASE, collection_rec,
> +                         regno_reg_rtx[FRAME_POINTER_REGNUM],
> +                         NULL, bb, insn_info,
> +                         DF_REF_REG_USE, 0);
> +#if !HARD_FRAME_POINTER_IS_FRAME_POINTER
> +          df_ref_record (DF_REF_BASE, collection_rec,
> +                         regno_reg_rtx[HARD_FRAME_POINTER_REGNUM],
> +                         NULL, bb, insn_info,
> +                         DF_REF_REG_USE, 0);
> +#endif
> +          break;

Also note that you have to check which of FRAME_POINTER_REGNUM and 
HARD_FRAME_POINTER_REGNUM comes first here, if you want to ensure the 
DF_REF_BASE refs are created sorted.  But it's likely better to _not_ 
create them sorted and just replace qsort with an insertion sort, as 
discussed offlist.  It will cost a single swap in a pretty rare case.

Paolo