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

[Richard Guenther <richard.guenther@gmail.com>]

On Fri, Jul 8, 2011 at 5:20 AM, Dimitrios Apostolou <jimis@gmx.net> wrote:
> Hello list,
>
> The attached patch does two things for df_get_call_refs():
> * First it uses HARD_REG_SETs for defs_generated and
> regs_invalidated_by_call, instead of bitmaps. Replacing in total more than
> 400K calls (for my testcase) to bitmap_bit_p() with the much faster
> TEST_HARD_REG_BIT, reduces the total instruction count from about 13M to
> 1.5M.
> * Second it produces the REFs in REGNO order, which is important to keep the
> collection_rec sorted most times, and avoid expensive calls to qsort().
> Thanks to Paolo Bonzini for idea and mentoring.
>
> The second part makes a big difference if accompanied with another patch in
> df_insn_refs_collect(). I'll post a followup patch, that is unfortunately
> unstable for some of my tests, so I'd appreciate any comments.

Did you check the impact on memory usage?  I suppose on targets
with not many hard registers it should even improve, but do we expect
memory usage to be worse in any case?

Thanks,
Richard.

>
> Thanks,
> Dimitris
>