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From: "jens.seifert at de dot ibm.com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/95737] New: PPC: Unnecessary extsw after negative less
 than
Date: Thu, 18 Jun 2020 08:10:57 +0000
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X-Bugzilla-Version: 8.3.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95737

            Bug ID: 95737
           Summary: PPC: Unnecessary extsw after negative less than
           Product: gcc
           Version: 8.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jens.seifert at de dot ibm.com
  Target Milestone: ---

unsigned long long negativeLessThan(unsigned long long a, unsigned long lon=
g b)
{
   return -(a < b);
}

gcc -m64 -O2 -save-temps negativeLessThan.C

creates

_Z16negativeLessThanyy:
.LFB0:
        .cfi_startproc
        subfc 4,4,3
        subfe 3,3,3
        extsw 3,3
        blr

The extsw is not necessary.=