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Re: Do not stream BINFO_VIRTUALs to ltrans unit
- From: Richard Guenther <richard dot guenther at gmail dot com>
- To: Jan Hubicka <hubicka at ucw dot cz>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Tue, 14 Jun 2011 12:04:59 +0200
- Subject: Re: Do not stream BINFO_VIRTUALs to ltrans unit
- References: <20110613125412.GC11211@kam.mff.cuni.cz>
On Mon, Jun 13, 2011 at 2:54 PM, Jan Hubicka <hubicka@ucw.cz> wrote:
> Hi,
> by accident I noticed that BINFO_VIRTUALs streaming is really expensive. It
> about doubles amount of IL and types streamed by Mozilla.
>
> One obvious optimization is to not stream into ltrans unit where it is
> too late to do any useful devirtualization anyway.
> Doing so reduces /tmp usage from 1.7GB to 1.1GB and proportionaly reduces
> streaming out time.
>
> Bootstrapped/regtested x86_64-linux.
> OK?
Ok.
Thanks,
Richard.
> Honza
> ? ? ? ?* lto-streamer-out.c (lto_output_ts_binfo_tree_pointers): Do not
> ? ? ? ?stream BINFO_VIRTUALS to ltrans units.
> Index: lto-streamer-out.c
> ===================================================================
> --- lto-streamer-out.c ?(revision 174985)
> +++ lto-streamer-out.c ?(working copy)
> @@ -1117,7 +1117,11 @@
>
> ? lto_output_tree_or_ref (ob, BINFO_OFFSET (expr), ref_p);
> ? lto_output_tree_or_ref (ob, BINFO_VTABLE (expr), ref_p);
> - ?lto_output_tree_or_ref (ob, BINFO_VIRTUALS (expr), ref_p);
> + ?/* BINFO_VIRTUALS is used to drive type based devirtualizatoin. ?It often links
> + ? ? together large portions of programs making it harder to partition. ?Becuase
> + ? ? devirtualization is interesting before inlining, only, there is no real
> + ? ? need to ship it into ltrans partition. ?*/
> + ?lto_output_tree_or_ref (ob, flag_wpa ? NULL : BINFO_VIRTUALS (expr), ref_p);
> ? lto_output_tree_or_ref (ob, BINFO_VPTR_FIELD (expr), ref_p);
>
> ? output_uleb128 (ob, VEC_length (tree, BINFO_BASE_ACCESSES (expr)));
>