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From: "simb611alt at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c/101985] New: vec_cpsgn parameter order
Date: Thu, 19 Aug 2021 18:36:48 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101985

            Bug ID: 101985
           Summary: vec_cpsgn parameter order
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: simb611alt at gmail dot com
  Target Milestone: ---

I have found an issue where the parameter order of the vec_cpsgn function on
POWER is reversed. Clang has recently fixed the same issue in their code wh=
ich
leaves only GCC using the reversed order.
XLC always used the order clang currently uses.

Patch link for clang -
https://github.com/llvm/llvm-project/commit/1af037f643fc5499f83d92e5aec1999=
50871d475

Link to POWER documentation -
http://cdn.openpowerfoundation.org/wp-content/uploads/resources/Intrinsics-=
Reference/content/VIPR.reference.vecfns.html

#include <stdio.h>
#include <altivec.h>

int main() {
    vector float a =3D {  1,  2, - 3, - 4};
    vector float b =3D {-10, 20, -30,  40};

    a =3D vec_cpsgn(a, b);
    printf("%f %f %f %f\n", a[0], a[1], a[2], a[3]);
    return 0;
}

Output for GCC 11.0.1:
-1.000000 2.000000 -3.000000 4.000000

Output for clang 12.0.1:
10.000000 20.000000 -30.000000 -40.000000

Output for xlc 16.1.1:
10.000000 20.000000 -30.000000 -40.000000=