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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/112752] New: `~a - MIN<MIN<~a, ~b>, ~c>` is
 not optimized to `MAX<MAX<a,b>,c> - a`
Date: Tue, 28 Nov 2023 22:32:01 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: pinskia at gcc dot gnu.org
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112752

            Bug ID: 112752
           Summary: `~a - MIN<MIN<~a, ~b>, ~c>` is not optimized to
                    `MAX<MAX<a,b>,c> - a`
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
                CC: evstupac at gmail dot com, kirill.yukhin at intel dot c=
om,
                    pinskia at gcc dot gnu.org, rguenth at gcc dot gnu.org,
                    unassigned at gcc dot gnu.org
  Target Milestone: ---
            Target: x86_64-*-*

+++ This bug was initially created as a clone of Bug #52252 +++

This is an example of byte conversion from RGB (Red Green Blue) to CMYK (Cy=
an
Magenta Yellow blacK):
```
#define byte unsigned char
#define MIN(a, b) ((a) > (b)?(b):(a))

void convert_image(byte *in, byte *out, int size) {
    int i;
    for(i =3D 0; i < size; i++) {
        byte r =3D in[0];
        byte g =3D in[1];
        byte b =3D in[2];
        byte c, m, y, k, tmp;
        c =3D 255 - r;
        m =3D 255 - g;
        y =3D 255 - b;
        tmp =3D MIN(m, y);
        k =3D MIN(c, tmp);
        out[0] =3D c - k;
        out[1] =3D m - k;
        out[2] =3D y - k;
        out[3] =3D k;
        in +=3D 3;
        out +=3D 4;
    }
}
```

For the scalar (and vectorized versions) we should get instead:
```
#define byte unsigned char
#define MIN(a, b) ((a) > (b)?(b):(a))
#define MAX(a, b) ((a) < (b)?(b):(a))

void convert_image_1(byte *in, byte *out, int size) {
    int i;
    for(i =3D 0; i < size; i++) {
        byte r =3D in[0];
        byte g =3D in[1];
        byte b =3D in[2];
        byte c, m, y, k, tmp;
        tmp =3D MIN(r, g);
        k =3D MIN(b, tmp);
        out[0] =3D k - r;
        out[1] =3D k - g;
        out[2] =3D k - b;
        out[3] =3D 255 - k;
        in +=3D 3;
        out +=3D 4;
    }
}
```

See bug 52252 comment #10, 11, and 12 also.=