Question

The following code should work at Linux. I want port the following code to Visual Studio 2008, but I am not very familiar with asm code. Could you help me?

#include <stdint.h>
static inline uint32_t log2(const uint32_t x) {
   uint32_t y;
   asm ( "\tbsr %1, %0\n"
     : "=r"(y)
     : "r" (x)
    );
    return y;
}

Answer 1

GCC uses the AT&T syntax. MSVC uses Intel syntax. That function would look something like this (compiles with MSVC 2010 /16.00.40219.01, but I see no reason why it would fail on 2008):

static inline uint32_t log2(const uint32_t x) {
  uint32_t y;
  __asm {
    bsr eax, x
    mov y, eax
  }
  return y;
}