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From: "rsandifo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/104387] New: aarch64: Redundant SXTH for “bag of bits” moves
Date: Fri, 04 Feb 2022 18:14:05 +0000	[thread overview]
Message-ID: <bug-104387-4@http.gcc.gnu.org/bugzilla/> (raw)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104387

            Bug ID: 104387
           Summary: aarch64: Redundant SXTH for “bag of bits” moves
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rsandifo at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64*-*-*

This PR is about another case in which we generate a redundant SXTH.
Specifically:

void f(short *x, short y)
{
  x[0] = y;
  x[1] = y;
}

generates:

        sxth    w1, w1
        strh    w1, [x0]
        strh    w1, [x0, 2]

even though the RTL makes it clear that the upper 16 bits of the
promoted “y” are unused.

This is related to PR64537, but I think it's worth keeping as a
separate PR since the fix isn't necessarily the same.

             reply	other threads:[~2022-02-04 18:14 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-04 18:14 rsandifo at gcc dot gnu.org [this message]
2022-02-04 21:25 ` [Bug rtl-optimization/104387] " pinskia at gcc dot gnu.org
2023-10-31 22:07 ` pinskia at gcc dot gnu.org
2023-10-31 22:09 ` pinskia at gcc dot gnu.org
2023-11-01  6:30 ` lis8215 at gmail dot com
2023-11-01 13:56 ` law at gcc dot gnu.org

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