RFA PR middle-end/49465

[Richard Guenther]

On Thu, Jun 23, 2011 at 6:13 PM, Jeff Law <law@redhat.com> wrote:
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> At the core of this PR is a case where we were threading through a
> successor of a joiner block where there was already an edge from the
> threadable successor to the final target.  ie, the successor of the
> joiner ended with a conditional branch, after threading both arms
> reached the same location.
>
> For this case, we have to ensure that if the target block has PHIs that
> the PHI arguments are the same for both incoming edges so that when the
> two edges are combined into a single edge we don't lose information.
>
> We already check and reject cases where this is not true prior to
> registering the jump thread.  Unfortunately, the updating code tried to
> update the PHIs when no update is necessary or desirable.
>
> I don't have a small testcase for this bug.
>
> Bootstrapped and regression tested on x86_64-unknown-linux-gnu; also
> built and run cpu2006 C integer benchmarks which were failing with -O2
> - -fast-math.  Those benchmarks run correctly with this patch applied.
>
> OK for trunk?

Ok.

Thanks,
Richard.

> Jeff
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