[llvm-bugs] [Bug 48769] New: Failure to optimize __builtin_mul_overflow pattern

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48769

            Bug ID: 48769
           Summary: Failure to optimize __builtin_mul_overflow pattern
           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 f1(unsigned x, unsigned y)
{
    unsigned int r = x * y;
    return x && ((int)r / (int)x) != (int)y;
}

This can be optimized to :

int f2(unsigned x, unsigned y)
{
    int res;
    return __builtin_mul_overflow((int)x, (int)y, &res);
}

This optimization is done by GCC, but not by LLVM.

See also comparison here : https://godbolt.org/z/f9Yv9c

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