//-------------------------------------------------------------------
//	repmovsl.cpp
//
//	This file shows the inline assembly language syntax needed 
//	for implementing a memory-to-memory copying operation with  
//	the Pentium processor's special 'move-string' instruction.
//
//	        compile using:  $ g++ -c -O repmovsl.cpp
//		examine using:  $ objdump -d repmovsl.o
//
//	Generic format of the 'asm' construct:
//		__asm__ __volatile__ ( 
//			  assembler instruction strings \
//			: output operands (optional) \
//			: input operands (optional) \
//			: clobbered registers (optional)
//			);
//
//	Reference: 
//	Rodriguez, Fischer and Smolski, "The Linux Kernel Primer,"
//	Pearson Education, Inc. (2006), pages 55-57 (but note that
//	we had to omit all semicolons inside the 'asm' construct). 
//
//	programmer: ALLAN CRUSE
//	written on: 12 NOV 2005
//-------------------------------------------------------------------

unsigned char *vram = (unsigned char*)0xA0000000; 
int 	hres = 1024, vres = 768;

void copy_page( int src, int dst )
{
	int		page_size = hres * vres;
	int		long_count = page_size / 4;
	unsigned long	*srcp = (unsigned long*)vram + long_count * src;
	unsigned long	*dstp = (unsigned long*)vram + long_count * dst;

	__asm__ __volatile__ (
		"movl %0, %%edi \n" \
		"movl %1, %%esi \n" \
		"movl %2, %%ecx \n" \
		"cld \n" \
		"rep movsl \n" 
		:
		: "m" (dstp), "m" (srcp), "m" (long_count) 
		: "ecx", "edi", "esi"
		);
}