On 30 July 2016 at 23:04, Jeffrey Walton wrote:
> I'm catching a compile error when using rdrand64_step on x86_64. If I
> change the typedef to use 'unsigned long long', then I catch a compile
> error under AArch64 when using NEON intrinsics.
>
> How should I clear the compile error in a way that does not lead to
> additional breaks?
>
> Thanks in advance.
>
> Jeff
>
> **********
>
> $ 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.
>
> int main(int argc, char* argv[])
> {
> my_u64 val;
> _rdrand64_step(&val);
>
> return 0;
> }
>
> $ gcc -mrdrnd test.cc -o test.exe
> test.cc: In function ‘int main(int, char**)’:
> test.cc:12:22: error: invalid conversion from ‘my_u64* {aka long
> unsigned int*}’ to ‘long long unsigned int*’ [-fpermissive]
> _rdrand64_step(&val);
> ^
> In file included from
> /usr/lib/gcc/x86_64-linux-gnu/4.9/include/x86intrin.h:46:0,
> from test.cc:1:
> /usr/lib/gcc/x86_64-linux-gnu/4.9/include/immintrin.h:166:1: note:
> initializing argument 1 of ‘int _rdrand64_step(long long unsigned
> int*)’
> _rdrand64_step (unsigned long long *__P)
> ^
>
> **********
>
> Intel's declaration is (http://software.intel.com/en-us/node/523864):
>
> extern int _rdrand64_step(unsigned __int64 *random_val);
But that's not what the GCC header says, as shown above.
> **********
>
> $ grep -R 'unsigned __int64' /usr/lib/gcc/x86_64-linux-gnu/4.9/include
> | grep typedef
> /usr/lib/gcc/x86_64-linux-gnu/4.9/include/cilk/common.h:
> typedef unsigned __int64 uint64_t;
To track down that definition shouldn't you be searching for __int64,
not "unsigned __int64"?
Searching for uint64_t will show where that's used, not how it's
defined. You already know how it's defined above, what you're missing
is how __int64 is defined. This doesn't help answer that:
> $ grep -R 'uint64_t' /usr/lib/gcc/x86_64-linux-gnu/4.9/include | grep typedef
> /usr/lib/gcc/x86_64-linux-gnu/4.9/include/stdint-gcc.h:typedef
> __UINT64_TYPE__ uint64_t;
> /usr/lib/gcc/x86_64-linux-gnu/4.9/include/cilk/common.h:
> typedef unsigned __int64 uint64_t;
However looking for how it's defined in the cilk headers isn't very
relevant, what matters is the declaration of _rdrand64_step in the
relevant header, which simply uses unsigned long long.
> The trail ends at __UINT64_TYPE__. I can't find what its defined as.
It's defined by the compiler:
https://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html
