[Bug tree-optimization/94783] New: Abs-equivalent pattern is not recognized as abs

[gabravier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94783

            Bug ID: 94783
           Summary: Abs-equivalent pattern is not recognized as abs
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

unsigned r(int v)
{
    const int mask = v >> (sizeof(int) * CHAR_BIT - 1);
    return (v + mask) ^ mask;
}

This can be optimized to `return abs(v)`. This transformation is done by LLVM,
not by GCC.

Comparison here : https://godbolt.org/z/4rduiJ