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Re: [PATCH][2/2] Improve array-bound warnings and VRP
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Richard Biener <rguenther at suse dot de>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, Jakub Jelinek <jakub at redhat dot com>
- Date: Mon, 1 Feb 2016 17:05:45 -0800
- Subject: Re: [PATCH][2/2] Improve array-bound warnings and VRP
- Authentication-results: sourceware.org; auth=none
- References: <alpine dot LSU dot 2 dot 11 dot 1501261602400 dot 12482 at zhemvz dot fhfr dot qr>
On Mon, Jan 26, 2015 at 7:06 AM, Richard Biener <rguenther@suse.de> wrote:
>
> This is the 2nd thing I came up with after looking at PR64277.
> VRP does a poor job computing value-ranges of unrolled loop IVs
> thus a very simple thing to do is to factor in previous VRP results
> by intersecting what VRP2 computes with recorded SSA name range infos
> (that also makes errors in those more likely to pop up... :/).
>
> This reduces the number of array bound warnings I get from the testcase
> but doesn't fix it completely. It also ends up with saner value-ranges.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu (with one
> libstdc++ runtime failure which I am now checking if caused by the patch,
> and thus likely an existing latent issue with SSA name range info).
>
> Ok for trunk? Or should I delay this to GCC 6?
>
> Thanks,
> Richard.
>
> 2015-01-26 Richard Biener <rguenther@suse.de>
>
> PR tree-optimization/64277
> * tree-vrp.c (update_value_range): Intersect the range with
> old recorded SSA name range information.
>
This caused:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69606
H.J.