Thread: Is this assembly?

Im currently correcting warnings on source code on Visual Studio.net 2003.

Im down to the last 4, but I dont know what it is. This is the warning:

Compiling...
d3d_render.cpp
3dc\win95\PENTIME.H(13) : warning C4068: unknown pragma
3dc\win95\PENTIME.H(18) : warning C4068: unknown pragma
3dc\win95\PENTIME.H(23) : warning C4068: unknown pragma
3dc\win95\PENTIME.H(36) : warning C4068: unknown pragma

And the code its refering to in pentime.h is:

Code:

//pentime.h
extern unsigned long int rdtsc_lo(void);
extern unsigned long int rdtsc_hi(void);
extern unsigned long int rdtsc_mid(void);

#define ProfileStart() \
{						   \
	int time = rdtsc_lo();
#define ProfileStop(x) \
	textprint("%s %d\n",x,rdtsc_lo()-time); \
}

#pragma aux rdtsc_lo = \
	"db 0fh, 31h"	\
	value [eax]		\
	modify [edx];

#pragma aux rdtsc_hi = \
	"db 0fh, 31h"	\
	value [edx]		\
	modify [eax];

#pragma aux rdtsc_mid = \
	"db 0fh, 31h"	\
	"shr eax, 10h" \
	"shl edx, 10h" \
	"add eax, edx" \
	value [eax]		\
	modify [edx];

So is this assembly and is it for Watcom compilers? And if so can I convert this to Visual Studio?

Thanks.

Yes, it's reading the time-stamp-counter (TSC).

If you are using Visual Studio 2005 or later, you should be able to use __rdtsc() for all of the above, and wrap it the follwoing way:

Code:

unsigned int rdtsc_lo()
{
   return (unsigned int)__rdtsc();
}

unsigned int rdtsc_hi()
{
    return (unsigned int)(__rdtsc() >> (__int64)32);
}

unsigned int rdtsc_mid()
{
   return (unsigned int)(__rdtsc() >> (__int64)16);
}

--
Mats

Ok, so you can use your own inline assembler for __rdtsc() then - there is an excample of this in WIkipedia:
http://en.wikipedia.org/wiki/RDTSC

--
Mats

Ok. I put the following in pentime.h:

Code:

__declspec(naked)unsigned __int64 __cdecl rdtsc_lo(void)
{
   __asm
   {
      rdtsc
      ret       ; return value at EDX:EAX
   }
}

which I assume replaces:

Code:

#pragma aux rdtsc_lo = \
	"db 0fh, 31h"	\
	value [eax]		\
	modify [edx];

Compiler gives no warning now, but what do those values in the original one mean? Like the "db 0fh, 32h"? Is what I put in replaces it correct? And where can I find out how to replace whats in here:

Code:

#pragma aux rdtsc_mid = \
	"db 0fh, 31h"	\
	"shr eax, 10h" \
	"shl edx, 10h" \
	"add eax, edx" \
	value [eax]		\
	modify [edx];

Sorry for dumbness, Ive never handled assembly before.

No, you need to ADD the __rdtsc() function as defined in the wiki article on top of the code I wrote.

The

Code:

db 0x0f, 0x31

is the rdtsc instruction - apparently Watcom compiler doesn't understand this particular assembler instruction, so the code had to be added manually.

The _lo, _hi, _mid functions are taking three different portions of the 64-bits that rdtsc returns: lo takes the low 32 bits, hi takes the high 32 bits, and mid takes 32 bits with 16 removed at the top and 16 at the bottom.

By the way, you shouldn't have to add "long" to the unsigned int - the long and regular int are both 32 bits in Visual Studio [even for 64-bit builds].

--
Mats

I believe mats wants you to do:
__declspec(naked) unsigned __int64 __cdecl __rdtsc(void)
Remember, rdtsc != __rdtsc (different names).

Considering the fact that any computer you are likely to deal with will be running a pentium or later at this point, why not look at the places that call this function, and see if you even need to worry about non pentium processors? a simple

Code:

unsigned char Pentium(void)
{
  return 1;
}

could suffice.

You may want to figure out what the PENTIUM_PROFILING does, because if you ever need to figure out where you are spending how much time, you may find it comes in handy.

But for getting it to work, I'd ignore it.

--
Mats