Re: [boost] Request: RDTSC

From: Johan Råde (rade_at_[hidden])
Date: 2008-06-09 15:31:42

dherring_at_[hidden] wrote:
> The CPU timestamp counter is a high-resolution clock source useful for 
> profiling code or controlling tight timing loops.  AMD/Intel CPUs support 
> this via the RDTSC opcode, and other CPUs often provide similar 
> functionality.
> 
> Apparently MS compilers support an __rdtsc() intrinsic, but I couldn't 
> find one for gcc.

MSVS 8.0 and higher have the __rdtsc intrinsic.

Om earlier versions of MSVC you can use the following inline assembler:

inline uint64_t clockCycleCount()
{
        uint64_t ccc;
        __asm {
                cpuid		// serialize processor
                rdtsc		// read time stamp counter
                mov dword ptr [ccc + 0], eax
                mov dword ptr [ccc + 4], edx
        }
        return ccc;
}

I agree that a platform independent version would be useful.

--Johan Råde