[Bug tree-optimization/116475] New: autovect: may be optimized for min/max

[Bug tree-optimization/116475] New: autovect: may be optimized for min/max

[syq at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116475

            Bug ID: 116475
           Summary: autovect: may be optimized for min/max
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: syq at gcc dot gnu.org
  Target Milestone: ---

If we need get the minimal of 8 floats in an array.
We may have code like this

float min(float *x) {
        float ret = x[0];
        for (int i=0; i<8; i++) {       // from 0 in this line
                ret = ret<x[i] ? ret : x[i];
        }
        return ret;
}

While if we compile it with
   aarch64-linux-gnu-gcc -O3 -ffast-math -S xx.c
We get
        ldp     q0, q1, [x0]
        ld1r    {v31.4s}, [x0]      # <-- not needed
        fminnm  v31.4s, v1.4s, v31.4s  # <-- not needed
        fminnm  v0.4s, v31.4s, v0.4s
        fminnmv s0, v0.4s
        ret




And maybe we can also use
float min(float *x) {
        float ret = x[0];
        for (int i=1; i<8; i++) {             // from 1 in this line
                ret = ret<x[i] ? ret : x[i];
        }
        return ret;
}


It will be even worse
        ldr     q31, [x0, 4]
        ld1r    {v30.4s}, [x0]
        ldp     s0, s29, [x0, 20]
        fminnm  v31.4s, v31.4s, v30.4s
        ldr     s30, [x0, 28]
        fminnm  s0, s0, s29
        fminnmv s31, v31.4s
        fminnm  s31, s30, s31
        fminnm  s0, s0, s31
        ret

[Bug tree-optimization/116475] autovect: may be optimized for min/max

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116475

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |53947

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I thought I saw this before.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations

[Bug tree-optimization/116475] autovect: may be optimized for min/max

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116475

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

[Bug tree-optimization/116475] autovect: may be optimized for min/max

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116475

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Yep pr 102512

*** This bug has been marked as a duplicate of bug 102512 ***