[Bug tree-optimization/110405] New: missing nonzerobits on branch

[Bug tree-optimization/110405] New: missing nonzerobits on branch

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110405

            Bug ID: 110405
           Summary: missing nonzerobits on branch
           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:
```
void h(unsigned long);
void
f (unsigned long i)
{
  if ((i & 7) == 6)
    if(i & 1)
      h(0);
}
```

The call to h should be optimized away as we know on the branch (a&1) == 0 as
we know the nonzerobits of i is ~1 .

[Bug tree-optimization/110405] missing nonzerobits on branch

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110405

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=87104

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I forgot to mention I found this while looking into PR 87104 ...

[Bug tree-optimization/110405] missing nonzerobits on branch

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110405

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-11-12
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Another testcase:
```
void h(unsigned long);
void
f (unsigned long i)
{
  if ((i & 7) != 6) __builtin_unreachable();
  if(i & 1)
    h(0);
}
```

Note LLVM is able to optimize both cases.

Note for the above testcase we get for the range:
  # RANGE [irange] long unsigned int [6, 18446744073709551614]


Notice how the value/mask is not there even though we should be able to get it
from the IR.