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From: "jeevitha at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/110040] New: rs6000 port emits dead mfvsrd instruction
 for simple test case
Date: Tue, 30 May 2023 15:19:39 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 14.0
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X-Bugzilla-Who: jeevitha at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110040

            Bug ID: 110040
           Summary: rs6000 port emits dead mfvsrd instruction for simple
                    test case
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jeevitha at gcc dot gnu.org
  Target Milestone: ---

GCC Trunk generates a dead mfvsrd for the following test case.

[jeevitha@ltcden2-lp1 ~]$ cat bug.c=20
#include <altivec.h>

void
foo (signed long *dst, vector signed __int128 src)
{
  *dst =3D (signed long) src[0];
}

[jeevitha@ltcden2-lp1 ~]$ gcc bug.c  -O2 -mcpu=3Dpower9 -S -o bug.s
[jeevitha@ltcden2-lp1 ~]$ cat bug.s
        .file   "bug.c"
        .machine power9
        .abiversion 2
        .section        ".text"
        .align 2
        .p2align 4,,15
        .globl foo
        .type   foo, @function
foo:
.LFB0:
        .cfi_startproc
        mfvsrd 11,34   #dead instruction
        mfvsrld 10,34
        std 10,0(3)
        blr=