as from cctools not recognizing tzcntl or lzcntl though my processor does

[dubiousjim]

As I explain at ​this StackOverflow post, if I compile this C function:

int function(unsigned u) {
  int r = __builtin_clz(u) + __builtin_ctz(u);
  return r;
}

in clang or gcc using -march=native, it will generate assembly containing the instructions lzcntl and tzcntl. Clang is fine to go ahead and assemble that into object code, and the result gives me the expected results. (My computer has a Haswell chip and has the BMI1 and LZCNT capabilities which include those two instructions.) However, the gcc build fails because the assembler it invokes, /opt/local/bin/as, reporting "Apple Inc version cctools-895, GNU assembler version 1.38", from the MacPorts port cctools @895_4+llvm50, doesn't know what to do with those instructions. It gives me "no such instruction" errors.

[raimue (Rainer Müller)]

Duplicate of #37846.

[dubiousjim]

Thanks, searched but didn't see that. So this problem has been around for 5 years!