From: Jakub Jelinek <jakub@redhat.com>
To: Richard Biener <richard.guenther@gmail.com>
Cc: Krister Walfridsson <krister.walfridsson@gmail.com>,
Andrew MacLeod <amacleod@redhat.com>,
gcc@gcc.gnu.org
Subject: Re: CLZ when CLZ_DEFINED_VALUE_AT_ZERO is false
Date: Fri, 1 Sep 2023 10:27:07 +0200 [thread overview]
Message-ID: <ZPGgW/hot/i0Umzf@tucnak> (raw)
In-Reply-To: <CAFiYyc3sNxK0SRokoNK6pM_Tozt4ch+kN0ddQu13=Q_wSO3C+A@mail.gmail.com>
On Fri, Sep 01, 2023 at 10:13:40AM +0200, Richard Biener via Gcc wrote:
> The value of .CLZ (0) is undefined then. I belive your analysis is correct in
> that both 63 - _35 might overflow and that dom3 (thus ranger) mis-computes
> the range for _35. I wonder why we don't elide _36 ? _31 : 1 with that info
> (possibly no range-op for .CLZ?), of course it would be wrong to do so.
>
> Can you open a bugreport please?
Seems similar to https://gcc.gnu.org/pipermail/gcc-patches/2023-February/thread.html#612214
except that case is at RTL level.
But arguably, I think at least at GIMPLE level we should just emit here
GIMPLE_COND + separate bb around it rather than COND_EXPR.
Jakub
next prev parent reply other threads:[~2023-09-01 8:27 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-31 13:56 Krister Walfridsson
2023-09-01 8:13 ` Richard Biener
2023-09-01 8:27 ` Jakub Jelinek [this message]
2023-09-03 23:30 ` Krister Walfridsson
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