From: kenner@vlsi1.ultra.nyu.edu (Richard Kenner)
To: richard.guenther@gmail.com
Cc: ebotcazou@adacore.com, gcc-patches@gcc.gnu.org, rguenther@suse.de
Subject: Re: [PATCH] Remove bogus TYPE_IS_SIZETYPE special-casing in extract_muldiv_1
Date: Sat, 03 Sep 2011 21:27:00 -0000 [thread overview]
Message-ID: <11109032127.AA29336@vlsi1.ultra.nyu.edu> (raw)
In-Reply-To: <CAFiYyc3c0fT2KvM2JjaJFuvZV3nzGnKQU7rFV6v9f9D2c8_ufQ@mail.gmail.com>
> So what's your opinion on the "bug" that triggered the patch in question?\
> Namely extract_muldiv_1 folding
>
> (((10240 - (sizetype) first) + 1) * 8) /[cl] 8
>
> to
>
> ((sizetype) first * 0x0fffffffffffffff8 + 81928) /[cl] 8
>
> to
>
> ((sizetype) first * 2305843009213693951 + 10241)
I think this optimization "works" if you sign-extend the constant when
you do division by 8.
next prev parent reply other threads:[~2011-09-03 21:27 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-31 9:14 Richard Guenther
2011-09-02 8:37 ` Eric Botcazou
2011-09-02 9:05 ` Richard Guenther
2011-09-02 13:26 ` Eric Botcazou
2011-09-02 13:33 ` Richard Guenther
2011-09-03 9:23 ` Eric Botcazou
2011-09-03 11:57 ` Richard Guenther
2011-09-03 15:08 ` Eric Botcazou
2011-09-03 19:09 ` Richard Guenther
2011-09-03 19:47 ` Richard Kenner
2011-09-03 20:37 ` Richard Guenther
2011-09-03 20:39 ` Richard Guenther
2011-09-03 21:20 ` Richard Kenner
2011-09-03 21:20 ` Richard Kenner
2011-09-03 21:27 ` Richard Kenner [this message]
2011-09-05 7:33 ` Richard Guenther
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