18.9: Example Program, Absolute Value
- Page ID
- 58430
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This example is a simple assembly language program to find the absolute value of a floating-point value in order to demonstrate floating-point comparisons. Recall that if a value is negative, it must be made positive and if the value is already positive, nothing should be done.
; Floating-Point Absolute Value Example
section .data
; -----
; Define constants.
TRUE equ 1
FALSE equ 0
SUCCESS equ 0 ; successful operation
SYS_exit equ 60 ; call cdoe for terminate
; -----
; Define some test variables.
dZero dq 0.0
dNegOne dq -1.0
fltVal dq -8.25
; *********************************************************
section .text
global _start
_start:
; -----
; Perform absolute value function on flt1
movsd xmm0, qword [fltVal]
ucomisd xmm0, qword [dZero]
jae isPos
mulsd xmm0, qword [dNegOne]
movsd qword [fltVal], xmm0
isPos:
; -----
; Done, terminate program.
last:
mov rax, SYS_exit
mov rbx, EXIT_SUCCESS ; exit w/success
syscall
In this example, the final result for |fltVal| was saved to memory. Depending on the context, this may not be required.