From: Christopher Li <sparse@chrisli.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Dibyendu Majumdar <mobile@majumdar.org.uk>,
Linux-Sparse <linux-sparse@vger.kernel.org>
Subject: Re: [PATCH v2 6/8] transform (A & M) >> S to (A >> S) & (M >> S)
Date: Mon, 7 Aug 2017 21:50:56 -0400 [thread overview]
Message-ID: <CANeU7QnMbkx5txddPFBTcGq6Mcm5vcmum7sNqPFrU2W0micXBg@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFyw=CN=RoEAVMFXc6qk=Y-hbuDvgN=thmyZTj1tSRxkhQ@mail.gmail.com>
On Mon, Aug 7, 2017 at 9:00 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> But even in the absence of such further simplification, the smaller
> constant thing likely makes it worth it. Almost all architectures have
> an easier time with smaller constants, and doing
>
> (a >> 24) & 255;
>
> is often noticeably more efficient than
>
> (a & 0xff000000) >> 24;
>
> just because of the constant issue.
That totally make sense.
Thanks
Chris
next prev parent reply other threads:[~2017-08-08 1:50 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-28 12:40 Potential incorrect simplification Dibyendu Majumdar
2017-03-28 13:34 ` Luc Van Oostenryck
2017-03-28 13:58 ` Dibyendu Majumdar
2017-03-28 14:11 ` Luc Van Oostenryck
2017-03-28 14:19 ` Dibyendu Majumdar
2017-03-28 16:20 ` Linus Torvalds
2017-03-28 17:00 ` Luc Van Oostenryck
2017-03-28 18:02 ` Linus Torvalds
2017-03-28 20:27 ` Luc Van Oostenryck
2017-03-28 21:57 ` Linus Torvalds
2017-03-28 22:28 ` Luc Van Oostenryck
2017-03-28 22:22 ` Dibyendu Majumdar
2017-08-06 12:46 ` Christopher Li
2017-08-06 14:00 ` Luc Van Oostenryck
2017-08-06 14:24 ` Christopher Li
2017-08-06 14:54 ` Christopher Li
2017-08-06 15:07 ` Luc Van Oostenryck
2017-08-06 15:51 ` Christopher Li
2017-08-06 16:51 ` Luc Van Oostenryck
2017-08-06 18:35 ` Christopher Li
2017-08-06 19:51 ` Dibyendu Majumdar
2017-08-06 20:08 ` Luc Van Oostenryck
2017-08-06 19:52 ` Luc Van Oostenryck
2017-08-06 23:34 ` Christopher Li
2017-08-07 0:31 ` Luc Van Oostenryck
2017-08-07 0:38 ` Christopher Li
2017-08-06 15:52 ` Dibyendu Majumdar
2017-08-06 16:56 ` Luc Van Oostenryck
2017-08-06 17:04 ` Dibyendu Majumdar
2017-08-06 17:45 ` Luc Van Oostenryck
2017-08-06 17:58 ` Dibyendu Majumdar
2017-08-06 18:15 ` Luc Van Oostenryck
2017-08-06 18:18 ` Dibyendu Majumdar
2017-08-06 18:31 ` Luc Van Oostenryck
2017-08-07 19:11 ` [PATCH v2 0/8] fix loading of partially defined bitfield Luc Van Oostenryck
2017-08-07 19:11 ` [PATCH v2 1/8] Remove single-store shortcut Luc Van Oostenryck
2017-08-07 21:42 ` Linus Torvalds
2017-08-10 0:29 ` Christopher Li
2017-08-10 0:41 ` Luc Van Oostenryck
2017-08-10 0:53 ` Christopher Li
2017-08-10 11:01 ` Christopher Li
2017-08-10 12:26 ` Luc Van Oostenryck
2017-08-10 13:25 ` Christopher Li
2017-08-07 19:11 ` [PATCH v2 2/8] new helper: def_opcode() Luc Van Oostenryck
2017-08-07 19:12 ` [PATCH v2 3/8] reuse nbr_pseudo_users() Luc Van Oostenryck
2017-08-07 19:12 ` [PATCH v2 4/8] change the masking when loading bitfields Luc Van Oostenryck
2017-08-07 19:12 ` [PATCH v2 5/8] simplify ((A & M') | B ) & M when M' & M == 0 Luc Van Oostenryck
2017-08-07 19:12 ` [PATCH v2 6/8] transform (A & M) >> S to (A >> S) & (M >> S) Luc Van Oostenryck
2017-08-08 0:22 ` Christopher Li
2017-08-08 0:29 ` Luc Van Oostenryck
2017-08-08 1:48 ` Christopher Li
2017-08-08 1:00 ` Linus Torvalds
2017-08-08 1:38 ` Luc Van Oostenryck
2017-08-08 1:50 ` Christopher Li [this message]
2017-08-07 19:12 ` [PATCH v2 7/8] transform (A << S) >> S into A & (-1 " Luc Van Oostenryck
2017-08-07 21:54 ` Linus Torvalds
2017-08-07 22:08 ` Luc Van Oostenryck
2017-08-07 22:27 ` Luc Van Oostenryck
2017-08-07 19:12 ` [PATCH v2 8/8] fix: cast of OP_AND only valid if it's an OP_CAST Luc Van Oostenryck
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