[Bug tree-optimization/110068] New: missing min detection

[Bug tree-optimization/110068] New: missing min detection

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110068

            Bug ID: 110068
           Summary: missing min detection
           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
  Target Milestone: ---

Take:
```
#define min1(x,y) ((x) < (y) ? (x) : (y))
#define min2(x,y) ((x) <= (y) ? (x) : (y))
static inline unsigned
min3(unsigned x, unsigned y)
{
        return min1(x, y);
}
static inline unsigned
min4(unsigned x, unsigned y)
{
        return min3(x, y);
}
unsigned 
f1 (unsigned  x)
{
  return min1(x, 1U<<(sizeof(x)*8-1));
}
unsigned
f2 (unsigned  x)
{
  return min2(x, 1U<<(sizeof(x)*8-1));
}
unsigned
f3 (unsigned  x)
{
  return min3(x, 1U<<(sizeof(x)*8-1));
}
unsigned
f4 (unsigned  x)
{
  return min4(x, 1U<<(sizeof(x)*8-1));
}
```
f1,f2,f3, and f4 should all produce MIN_EXPRs but currently f1 does not.
I would have thought r11-1504-g2e0f4a18bc978  fixed this case but it does not.

[Bug tree-optimization/110068] missing min detection

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110068

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
here is another one:
```
unsigned
f5 (unsigned  x)
{
  bool t = x >= 1U<<(sizeof(x)*8-1);
  if (!t)
    ;
  else
    x = 1U<<(sizeof(x)*8-1);
  return x;
}
```

this time LLVM does not detect it either.

easy way to see that out is by using riscv and -march=rv32gc_zba_zbb_zbc_zbs.
You should get for all 5 functions:
        li      a5,-2147483648
        minu    a0,a0,a5
        ret

Or:
        lui     a1, 524288
        minu    a0, a0, a1
        ret

Both are execute the same in the end.

[Bug tree-optimization/110068] missing min detection

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110068

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot gnu.org
   Last reconfirmed|                            |2023-09-10
     Ever confirmed|0                           |1

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

I think I know how to fix this ...

minmax_from_comparison needs to pass the sign of what the exp0/exp1 are being
compared in.

Note I think we have other issues too ...