Floating Point Arithmetic

Floating point operations in assembly are typically performed using the Floating Point Unit (FPU) or SIMD instructions like SSE (Streaming SIMD Extensions).

FPU Instructions

• fld: Load a floating-point value onto the FPU stack.
• fadd: Add two floating-point values.
• fsub: Subtract two floating-point values.
• fmul: Multiply two floating-point values.
• fdiv: Divide two floating-point values.
• fstp: Store and pop a floating-point value from the FPU stack.

Example: Simple Floating Point Calculation

This example demonstrates loading two floating-point values and performing arithmetic operations.

section .data
    num1 dq 5.5         ; First floating-point number
    num2 dq 2.2         ; Second floating-point number
    result dq 0.0       ; To store the result

section .text
    global _start

_start:
    fld qword [num1]    ; Load num1 onto the FPU stack
    fadd qword [num2]   ; Add num2 to the value on the FPU stack
    fstp qword [result] ; Store the result and pop the FPU stack

    mov rax, 60         ; System call: exit
    xor rdi, rdi        ; Exit code: 0
    syscall
    

Example: Using SIMD for Floating Point Arithmetic

SIMD instructions operate on multiple data points simultaneously.

section .data
    num1 dq 5.5, 6.5    ; Two floating-point numbers
    num2 dq 2.2, 3.2    ; Two more floating-point numbers
    result dq 0.0, 0.0  ; To store results

section .text
    global _start

_start:
    movaps xmm0, [num1] ; Load num1 into xmm0
    movaps xmm1, [num2] ; Load num2 into xmm1
    addps xmm0, xmm1    ; Perform parallel addition
    movaps [result], xmm0 ; Store the results

    mov rax, 60         ; System call: exit
    xor rdi, rdi        ; Exit code: 0
    syscall
    

Key Notes

• FPU operations use a stack-based model; plan your stack operations carefully.
• SIMD operations are faster for large datasets and are preferred in modern applications.
• Ensure proper alignment when working with SIMD registers to avoid runtime errors.