CPUID implementations in C++

by

Accessing raw CPUID information is actually very easy, here is a C++ class for that which works in Windows, Linux and OSX:

#ifndef CPUID_H
#define CPUID_H

#ifdef _WIN32
#include <limits.h>
#include <intrin.h>
typedef unsigned __int32  uint32_t;

#else
#include <stdint.h>
#endif

class CPUID {
  uint32_t regs[4];

public:
  explicit CPUID(unsigned i) {
#ifdef _WIN32
    __cpuid((int *)regs, (int)i);

#else
    asm volatile
      ("cpuid" : "=a" (regs[0]), "=b" (regs[1]), "=c" (regs[2]), "=d" (regs[3])
       : "a" (i), "c" (0));
    // ECX is set to zero for CPUID function 4
#endif
  }

  const uint32_t &EAX() const {return regs[0];}
  const uint32_t &EBX() const {return regs[1];}
  const uint32_t &ECX() const {return regs[2];}
  const uint32_t &EDX() const {return regs[3];}
};

#endif // CPUID_H

To use it just instantiate an instance of the class, load the CPUID instruction you are interested in and examine the registers. For example:

#include "CPUID.h"

#include <iostream>
#include <string>

using namespace std;

int main(int argc, char *argv[]) {
  CPUID cpuID(0); // Get CPU vendor

  string vendor;
  vendor += string((const char *)&cpuID.EBX(), 4);
  vendor += string((const char *)&cpuID.EDX(), 4);
  vendor += string((const char *)&cpuID.ECX(), 4);

  cout << "CPU vendor = " << vendor << endl;

  return 0;
}

This Wikipedia page tells you how to use CPUID: http://en.wikipedia.org/wiki/CPUID

EDIT: Added #include <intrin.h> for Windows, per comments.

More Related Contents:

  1. How do I achieve the theoretical maximum of 4 FLOPs per cycle?
  2. Why does this function push RAX to the stack as the first operation?
  3. Atomic double floating point or SSE/AVX vector load/store on x86_64
  4. How do I call “cpuid” in Linux?
  5. Unoptimized clang++ code generates unneeded “movl $0, -4(%rbp)” in a trivial main()
  6. C++ on x86-64: when are structs/classes passed and returned in registers?
  7. Most insanely fast way to convert 9 char digits into an int or unsigned int
  8. How to remove “noise” from GCC/clang assembly output?
  9. Why does clang produce inefficient asm with -O0 (for this simple floating point sum)?
  10. Why does C++ code for testing the Collatz conjecture run faster than hand-written assembly?
  11. How to get c code to execute hex machine code?
  12. How to check if a CPU supports the SSE3 instruction set?
  13. How can I measure CPU time and wall clock time on both Linux/Windows?
  14. __builtin_prefetch, How much does it read?
  15. Getting the high part of 64 bit integer multiplication
  16. Atomic operations, std::atomic and ordering of writes
  17. What do C and Assembler actually compile to? [closed]
  18. How to generate assembly code with clang in Intel syntax?
  19. std::pow produce different result in 32 bit and 64 bit application
  20. What does “rep; nop;” mean in x86 assembly? Is it the same as the “pause” instruction?
  21. Function to mangle/demangle functions
  22. Address of function is not actual code address
  23. Why do compilers insist on using a callee-saved register here?
  24. Calculate system time using rdtsc
  25. Address of labels (MSVC)
  26. How come INC instruction of x86 is not atomic? [duplicate]
  27. What are these seemingly-useless callq instructions in my x86 object files for?
  28. How is floating point conversion actually done in C++?(double to float or float to double)
  29. Why is this SIMD multiplication not faster than non-SIMD multiplication?
  30. How to force GCC to assume that a floating-point expression is non-negative?

Leave a Comment