From: Jeff Law <jeffreyalaw@gmail.com>
To: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] match.pd: Optimize __builtin_mul_overflow_p (x, cst, (utype)0) to x > ~(utype)0 / cst [PR30314]
Date: Wed, 1 Jun 2022 08:07:06 -0600 [thread overview]
Message-ID: <a5a091db-2a73-855a-6905-2a0f44b5e30b@gmail.com> (raw)
In-Reply-To: <Ypdv5qrjnk87DA8p@tucnak>
On 6/1/2022 7:55 AM, Jakub Jelinek via Gcc-patches wrote:
> Hi!
>
> A comparison with a constant is most likely always faster than
> .MUL_OVERFLOW from which we only check whether it overflowed and not the
> multiplication result, and even if not, it is simpler operation on GIMPLE
> and even if a target exists where such multiplications with overflow checking
> are cheaper than comparisons, because comparisons are so much more common
> than overflow checking multiplications, it would be nice if it simply
> arranged for comparisons to be emitted like those multiplications on its
> own...
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2022-06-01 Jakub Jelinek <jakub@redhat.com>
>
> PR middle-end/30314
> * match.pd (__builtin_mul_overflow_p (x, cst, (utype) 0) ->
> x > ~(utype)0 / cst): New simplification.
>
> * gcc.dg/tree-ssa/pr30314.c: New test.
OK
jeff
next prev parent reply other threads:[~2022-06-01 14:07 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-01 13:55 Jakub Jelinek
2022-06-01 14:07 ` Jeff Law [this message]
2022-06-02 8:36 ` Richard Biener
2022-06-02 9:18 ` Jakub Jelinek
2022-06-02 9:58 ` Richard Biener
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