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From: "law at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/109592] Failure to recognize shifts as sign/zero extension
Date: Tue, 30 May 2023 20:40:00 +0000	[thread overview]
Message-ID: <bug-109592-4-Y6DWz4udyB@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-109592-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109592

--- Comment #9 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Weird, I don't see the attachment either.  I'll extract & upload it again.

WRT costing.  fwprop and combine will both query the target rtx costs and will
reject when the target costing model indicates the change isn't actually
profitable.

As you'd noted before, combine will internally transform a sign/zero extension
into a pair of shifts.  The whole point of that internal canonicalization is to
expose cases where the shifts can combine with other nearby operations.  So
there's no significant risk to detecting and creating the extension form
earlier.

  parent reply	other threads:[~2023-05-30 20:40 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-04-22  0:12 [Bug rtl-optimization/109592] New: " law at gcc dot gnu.org
2023-04-24  2:46 ` [Bug rtl-optimization/109592] " wangfeng at eswincomputing dot com
2023-04-24  3:52 ` wangfeng at eswincomputing dot com
2023-04-24  7:02 ` rguenth at gcc dot gnu.org
2023-04-28 20:26 ` law at gcc dot gnu.org
2023-05-11  7:56 ` wangfeng at eswincomputing dot com
2023-05-11 14:33 ` law at gcc dot gnu.org
2023-05-29 16:35 ` law at gcc dot gnu.org
2023-05-30  6:17 ` wangfeng at eswincomputing dot com
2023-05-30 20:40 ` law at gcc dot gnu.org [this message]
2023-05-30 20:41 ` law at gcc dot gnu.org

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