[patch] Fix ICE during SCC hashing in LTO mode

[Richard Biener]

On Tue, Jun 30, 2015 at 12:10 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
> Hi,
>
> the attached Ada testcase triggers an internal error in LTO mode:
>
> eric@polaris:~/build/gcc/native> gcc/gnat1 -quiet lto17.adb -flto
> +===========================GNAT BUG DETECTED==============================+
> | 6.0.0 20150629 (experimental) [trunk revision 225111] (x86_64-suse-linux)
> GCC error:|
> | in hash_scc, at lto-streamer-out.c:1445
>
> This is the assertion verifying that you walk the same SCC using DFS after
> starting from another element of the SCC in hash_scc.  It fails here because
> this second DFS is not performed with the same THIS_REF_P parameter as the
> initial one, so there is no guaranteee that this will yield the same result
> because DFS_write_tree will behave differently.
>
> Fixed by passing the THIS_REF_P and REF_P parameters for FIRST to hash_scc.
>
> Tested on x86_64-suse-linux, OK for the mainline?

Ok (I suppose this also affects the GCC 5 branch?)

Thanks,
Richard.

>
> 2015-06-30  Eric Botcazou  <ebotcazou@adacore.com>
>
>         * lto-streamer-out.c (class DFS): Adjust hash_scc method.
>         (DFS::DFS): Pass this_ref_p and ref_p to hash_scc.
>         (hash_scc): Add this_ref_p and ref_p parameters and pass them
>         to the inner DFS walk.
>
>
> 2015-06-30  Eric Botcazou  <ebotcazou@adacore.com>
>
>         * gnat.dg/lto17.ad[sb]: New test.
>
>
> --
> Eric Botcazou