[llvm-bugs] [Bug 48516] New: Failure to optimize loop that does nothing and ends when result is used in comparison that is optimized out

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48516

            Bug ID: 48516
           Summary: Failure to optimize loop that does nothing and ends
                    when result is used in comparison that is optimized
                    out
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedb...@nondot.org
          Reporter: gabrav...@gmail.com
                CC: llvm-bugs@lists.llvm.org

void f(int *x, int *y)
{
    long res = 0;

    for (int i = 0; i < 100; i++)
        res += x[i] * y[i];

    if (res != 0)
        __builtin_abort();
    __builtin_unreachable();
}

This entire function can be optimized into `abort()`. This transformation is
done by GCC, but not by LLVM.

See also comparison here : https://godbolt.org/z/anzYMa

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