[llvm-bugs] [Bug 48984] New: Failure to optimize out low bits of result of left shift of constant

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48984

            Bug ID: 48984
           Summary: Failure to optimize out low bits of result of left
                    shift of constant
           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)
{
    return ((2 << a) & 1) == 0;
}

This can be optimized to `return 1;`. This transformation is done by GCC, but
by LLVM.

Godbolt comparison here: https://godbolt.org/z/dTfsbx
alive2 check here: https://alive2.llvm.org/ce/z/U3DMgJ

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