On Mon, Jan 26, 2015 at 04:06:11PM +0100, Richard Biener 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?
Does this work even without the other patch?
What do you think about Ilya's patch to set TREE_NO_WARNING in the unrolled
iterations where we had to keep the exit check?
> 2015-01-26 Richard Biener <rguent...@suse.de>
>
> PR tree-optimization/64277
> * tree-vrp.c (update_value_range): Intersect the range with
> old recorded SSA name range information.
Jakub
