[llvm-bugs] [Bug 48406] New: Failure to optimize out abs when sign is known

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48406

            Bug ID: 48406
           Summary: Failure to optimize out abs when sign is known
           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 x)
{
  __builtin_assume(x <= 0);
  return abs(x);
}

This can be optimized to `return -x;`. This transformation is done by GCC (with
__builtin_assume replaced by `if (!(x <= 0)) __builtin_unreachable()`), but not
by LLVM.

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