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* [Bug tree-optimization/113383] New: `MAX(a,b) == 0` and `MAX(a,b) != 0` can be simplified (for unsigned types)
@ 2024-01-13 20:27 pinskia at gcc dot gnu.org
  0 siblings, 0 replies; only message in thread
From: pinskia at gcc dot gnu.org @ 2024-01-13 20:27 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113383

            Bug ID: 113383
           Summary: `MAX(a,b) == 0` and `MAX(a,b) != 0` can be simplified
                    (for unsigned types)
           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:
```
unsigned maxeq0(unsigned a, unsigned b)
{
        unsigned c = a > b ? a : b;
        return c == 0; // b == 0 && a == 0
}

unsigned maxeq0_1(unsigned a, unsigned b)
{
        return b == 0 && a == 0;
}

unsigned maxne0(unsigned a, unsigned b)
{
        unsigned c = a > b ? a : b;
        return c != 0; // b != 0 || a != 0
}

unsigned maxne0_1(unsigned a, unsigned b)
{
        return b != 0 || a != 0;
}

```
maxeq0 and maxeq0_1 are equivalent.
Likewise for maxne0 and maxne0_1.

LLVM is able to do this simplification.
Note this is only valid for unsigned MAX.

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2024-01-13 20:27 [Bug tree-optimization/113383] New: `MAX(a,b) == 0` and `MAX(a,b) != 0` can be simplified (for unsigned types) pinskia at gcc dot gnu.org

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