Previous posts on this topic:
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As my patch for Portable C compiler (PCC) was accepted, pcc can do __builtin_popcount() and I can use it to compile my pet projects written in C (bitfield, bitfield-eca, bitfield-io, bitfield-rule30).
I updated my ppa repository at Launchpad. Now it provides a recent (20170524 snapshot) version of pcc for a wide range of Ubuntu series.