How I can read this instruction directly:
unsigned int eax, ebx, ecx, edx;
unsigned int leaf, subleaf;
unsigned int intbuf[12];`
char *buffer;
int i,j,k,base,start,stop,length;
float freq_GHz;
float frequency;
subleaf=0;
base = 0;
for (leaf=0x80000002; leaf<0x80000005; leaf++) {
__asm__ __volatile__ ("cpuid" : \
"=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (leaf), "c" (subleaf));
intbuf[base] = eax;
intbuf[base+1] = ebx;
intbuf[base+2] = ecx;
intbuf[base+3] = edx;
base += 4;
}
I've been trying to read it like this but its not working:
for (leaf = 0x80000002; leaf < 0x80000005; leaf++) {
int regs[4];
__cpuid(regs, leaf);
intbuf[base] = (*regs),eax;
intbuf[base + 1] = (*regs),ebx;
intbuf[base + 2] = (*regs),ecx;
intbuf[base + 3] = (*regs),edx;
base += 4;
The regs
array that you pass to the __cpuid
call1 will, on return, have the values of the four registers, EAX
, EBX
, ECX
and EDX
, in order (i.e. in the array elements, regs[0]
thru regs[3]
). You access those elements using normal array operators, and there is no need for any temporary 'register' variables like your eax
.
Thus, your 'pure' C++ code would look something like this:
int intbuf[12];
int base = 0;
for (leaf = 0x80000002; leaf < 0x80000005; leaf++)
{
int regs[4];
__cpuid(regs, leaf);
intbuf[base] = regs[0]; // EAX
intbuf[base + 1] = regs[1]; // EBX
intbuf[base + 2] = regs[2]; // ECX
intbuf[base + 3] = regs[3]; // EDX
base += 4;
}
If you want to keep intbuf
as an array of unsigned int
, then you should add a cast to the assignments inside the loop, like:
//...
intbuf[base + 1] = static_cast<unsigned int>(regs[1]); // EBX
1 This answer is based on the operation of the MSVC implementation of the __cpuid
function; other compilers' versions may differ slightly but the general principle will likely remain the same.