>> $ cat test.cc >> #include <x86intrin.h> >> >> #if _LP64 || __LP64__ >> typedef unsigned long my_u64; >> #else >> typedef unsigned long long my_u64; >> #endif > > The definition doesn't depend on ILP32 or LP64: > > ../gcc/config/i386/immintrin.h:_rdrand64_step (unsigned long long *__P) > > Looks like you want unsigned long long for Intel. If that doesn't work > for Neon then use the preprocessor to check for that, not for LP64. Thanks. Forgive my ignorance... 'unsigned long' is 64 bits, which is what that interface needs (if I am reading the docs correctly). It looks like 'unsigned long long' is 64-bits too (other wise, GCC would not be using it). Is it safe to cast a pointer of type 'unsigned long' to a pointer of 'unsigned long long' when using this particular function? Does UL and ULL provide the same alignment guarantees? Jeff
