find max int in an array.

findMax.s

.pos 0x100

main:	irmovl bottom,  %esp     # initialize stack
	irmovl a,       %edi     # address of the first element of a
	irmovl alen,    %esi	  
	mrmovl (%esi),  %esi     # number of elements of a
	irmovl $0x1,    %eax
	subl   %eax,    %esi     # last index in a
					   # ready to call findmax: a --> edi, last --> esi
	call findmax
	halt


# Find position of the maximum element in an array.
.pos 0x200
findmax:
  pushl %edi                      # save *a
  pushl %esi                      # save n
  rrmovl %esi, %edx               # edx = n
  irmovl $4, %eax                 # eax = 4
  mull %eax, %edx                 # n * 4
  addl %edi, %edx                 # esi = *a + n
  mrmovl (%edx), %ecx             # ecx = max = a[n]
  pushl %ecx                      # save max = a[n]
  pushl %esi                      # save pos
  irmovl $0, %ecx
  addl %ecx, %esi                 # n <= 0? set result reg.
  jle end
loop:
  irmovl $1, %edx
  subl %edx, %esi                 # n--
  rrmovl %esi, %edx               # edx = n
  irmovl $4, %eax                 # 4 * n
  mull %edx, %eax
  addl %edi, %eax                 # eax = *a + n
  mrmovl (%eax), %edx             # edx = a[n] 
  mrmovl 4(%esp), %ecx             # ecx = max
  subl %edx, %ecx                 # ecx = max - x, set result reg
  jg check_loop                   # if max - x > 0, loop
  rmmovl %edx, 4(%esp)             # max = x
  rmmovl %esi, (%esp)            # pos = n
check_loop:
  irmovl $0, %edx
  subl %edx, %esi                 # n - 0 , set result reg
  jg loop
end:
  popl %eax                       # set return val to pos
  popl %esi                       # pop off max
  popl %esi                       # restore args
  popl %edi
  ret
	
#
# Array to sort
#
.pos 0x1000
a:	.long 30
      .long 9
      .long 21
      .long 13
      .long 6
	.long 26
	.long 35
	.long 32
	.long 15
	.long 17
alen:	.long 10

	#
# Stack (256 thirty-two bit words is more than enough here).
#
.pos 0x3000
top:	            .long 0x00000000, 0x100    # top of stack.
bottom:           .long 0x00000000          # bottom of stack.