Why does __builtin_popcountll in the Intel® HLS Compiler return unexpected value? - Why does __builtin_popcountll in the Intel® HLS Compiler return unexpected value? Description Due to a problem in the Intel® HLS Compiler Pro version 18.1 or earlier, you might see unexpected value by __builtin_popcountll(unsigned long long) and __builtin_popcountl(unsigned long) . You might also see ‘ Error: Cosim testbench elaboration failed. ’ with these built-in functions when compiling the Intel HLS Compiler Standard version 18.1 or earlier. Resolution To avoid this error, use __builtin_popcount(unsigned int) instead of the following functions: int __builtin_popcountll_workaround(unsigned long long v) { return __builtin_popcount((unsigned int)v) __builtin_popcount((unsigned int)(v>>32)) ; } This problem is scheduled to be fixed in a future release of the Intel® Quartus® Prime Pro/Standard Edition Software including the Intel HLS Compiler. Custom Fields values: ['novalue'] Troubleshooting 2205697241 False ['novalue'] ['FPGA Dev Tools Quartus® Prime Software Pro'] 19.3 18.0 ['Arria® V FPGAs and SoCs', 'Cyclone® V FPGAs and SoCs', 'Arria® 10 FPGAs and SoCs', 'Cyclone® 10 GX FPGA', 'MAX® 10 10 FPGAs', 'Stratix® 10 FPGAs and SoCs'] ['novalue'] ['novalue'] ['novalue']