[llvm-bugs] [Bug 46472] New: Optimize some bit magic into a faster pattern when nand is not available

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46472

            Bug ID: 46472
           Summary: Optimize some bit magic into a faster pattern when
                    nand is not available
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: gabravier at gmail.com
                CC: llvm-bugs at lists.llvm.org

int f(int a, int b, int c)
{
    return (a & ~c) | (b & c);
}

Unless the target architecture has a nand intruction available (such as x86
with BMI) this can be optimized to `return ((b ^ a) & c) ^ a;`. This
transformation is done by GCC (though sadly it also does it when nand is
available), but not by LLVM

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