[eckzow]

By my reading that implementation was assembled by humans, not the optimizer.

Although, there's certainly nothing magical that prevents the optimizer from generating such code. Here's something[1] I just threw together that (ab)uses constexpr to do just that.

On my machine, building with:

  $ clang++ -std=c++14 fizzbuzz.cpp -O2 -S

Gives code similar to:

  main:                                   # @main
          .cfi_startproc
  # BB#0:
          pushq   %rax
  .Ltmp0:
          .cfi_def_cfa_offset 16
          movl    $1, %edi
          movl    $_ZL6output, %esi
          movl    $413, %edx              # imm = 0x19D
          callq   write
          xorl    %eax, %eax
          popq    %rdx
          retq
  .Ltmp1:
          .size   main, .Ltmp1-main
          .cfi_endproc
  
          .type   _ZL6output,@object      # @_ZL6output
          .section        .rodata,"a",@progbits
  _ZL6output:
          .ascii  "1\n2\nFizz\n4\nBuzz\nFizz\n7\n8\nFizz\nBuzz\n11\nFizz\n13\n14\nFizzBuzz\n16\n17\nFizz\n19\nBuzz\nFizz\n22\n23\nFizz\nBuzz\n26\nFizz\n28\n29\nFizzBuzz\n31\n32\nFizz\n34\nBuzz\nFizz\n37\n38\nFizz\nBuzz\n41\nFizz\n43\n44\nFizzBuzz\n46\n47\nFizz\n49\nBuzz\nFizz\n52\n53\nFizz\nBuzz\n56\nFizz\n58\n59\nFizzBuzz\n61\n62\nFizz\n64\nBuzz\nFizz\n67\n68\nFizz\nBuzz\n71\nFizz\n73\n74\nFizzBuzz\n76\n77\nFizz\n79\nBuzz\nFizz\n82\n83\nFizz\nBuzz\n86\nFizz\n88\n89\nFizzBuzz\n91\n92\nFizz\n94\nBuzz\nFizz\n97\n98\nFizz\nBuzz\n"

Of course, having now written this I feel like I should retroactively fail my last interview.

[1] https://gist.github.com/anonymous/7818f902a374a953b274

[jevinskie]

This code snippet really made my night. I never thought of using constexpr to write a FizzBuzz that compiles to one of the most "optimal" solutions that I have ever seen. Awesome!