Exploring Intel's PCLMULQDQ instruction

I find in Apple's header file cpuid.h:
/System/Library/Frameworks/Kernel.framework/Versions/A/Headers/i386/cpuid.h

...
 * The CPUID_FEATURE_XXX values define 64-bit values
 * returned in %ecx:%edx to a CPUID request with %eax of 1: 
...

#define _HBit(n)		(1ULL << ((n)+32))
...
#define CPUID_FEATURE_PCLMULQDQ _HBit(1)  /* PCLMULQDQ instruction */

See "Example 13-3." (pp 303)
For pclmulqdq  see pp 1069 (INSTRUCTION SET REFERENCE, M-Z)
Compare with mulq defined at pp 1007.

mulq	%rsi
pclmulqdq	%rsi
mulq puts answer in RDX:RAX

pclmulqdq takes its inputs and returns its results in registers with names such as "xmm1".

Try http://gcc.gnu.org/onlinedocs/gcc/X86-Built_002din-Functions.html
Search for "pclmulqdq".

It seems that my Mac is too old.