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Re: [PATCH] Fix 69845
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Richard Henderson <rth at redhat dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 23 Mar 2016 09:59:56 +0100
- Subject: Re: [PATCH] Fix 69845
- Authentication-results: sourceware.org; auth=none
- References: <56F1837D dot 1000508 at redhat dot com>
On Tue, Mar 22, 2016 at 6:40 PM, Richard Henderson <rth@redhat.com> wrote:
> In PR68142 you added a check for overflow + __INT_MIN__.
> I can't figure out why the check for __INT_MIN__, except
> that it seems specific to the test case you examined.
>
> And indeed, this test case shows how things go wrong
> with other distributed folding leading to overflow.
Huh, not sure what I was thinking .. but I remember being on
a hunt through various INT_MIN related overflow bugs when
running into this one.
> I added two tests, one signed, one unsigned. The second
> verifies that we do still fold for the defined-overflow case.
>
> Ok?
Ok.
Note that always when I find bugs in extract_muldiv and try
to decipher what it does I think we need to rip that out,
replacing it with some simple patterns and leaving the rest
to passes like reassoc. It's simply a beast that proved to
be a can of worms...
Thanks,
Richard.
>
> r~