/* quicksortA.s
 * quick sort in pentium assembly
 *
 * void quicksortA(int a[], int first, int last)
 *
 * NAME: David Bell
 * ebx = pivot
 * ecx = tmp1
 * edx = tmp2
 * eax = a
 * edi = i
 * esi = pivotpos
 */
.globl quicksortA
quicksortA:
	pushl %ebp		/* create stack frame */
	movl %esp, %ebp
	pushl %ebx		/* save callee-saved regs */
	pushl %esi
	pushl %edi

	movl 8(%ebp), %eax	/* move a to eax */
	movl 12(%ebp), %esi	/* move first to pivotpos */
	movl 12(%ebp), %edi	/* move first to i */
	movl (%eax,%edi,4), %ebx	/* move the first elt into pivot */
	
	cmpl 16(%ebp), %esi	/* if first >= last */
	jge end			/* if they're equal, end */	

ploop:
	incl %edi			/* i++ */
	
	cmpl 16(%ebp),%edi		/* if i > last */
	jg recend			/* if > recursively sort */

	cmpl  (%eax,%edi,4),%ebx	/* if pivot <= a[i] */
	jle ploop			/* skip switch */
	incl %esi			/* pivotpos++ */	
	movl (%eax,%esi,4),%ecx		/* tmp1 = a[pivotpos] */
	movl (%eax,%edi,4),%edx		/* tmp2 = a[i] */
	movl %ecx,(%eax,%edi,4)		/* a[i] = tmp1 */
	movl %edx,(%eax,%esi,4)		/* a[pivotpos] = tmp2 */
	jmp ploop			/* loop back */
	
	
recend:		
	movl 12(%ebp),%edi		/* set i = first */
	movl (%eax,%esi,4),%ecx		/* tmp1 = a[pivotpos] */
	movl (%eax,%edi,4),%edx		/* tmp2 = a[i] */
	movl %ecx,(%eax,%edi,4)		/* a[i] = tmp1 */
	movl %edx,(%eax,%esi,4)		/* a[pivotpos] = tmp2 */


	decl %esi
	pushl %esi
	pushl %edi
	pushl %eax
	call quicksortA
	pushl 16(%ebp)			/* push last */
	incl %esi
	incl %esi
	pushl %esi			/* push pivotpos+1 */
	pushl %eax			/* push a */
	call quicksortA
			
end:	
	popl %edi
	popl %esi
	popl %ebx
	leave
	ret