Introduction to ARM64v8

👉 Overview

👀 What ?

The ARM64v8 is an advanced RISC machine architecture that's based on a 64-bit instruction set.

🧐 Why ?

Understanding ARM64v8 is important as it is widely used in mobile devices, embedded systems, and servers.

⛏️ How ?

To leverage ARM64v8, one needs to understand its architecture, instruction set, and how to write efficient code for it.

⏳ When ?

The ARM64v8 architecture has been in use since its introduction in 2011.

⚙️ Technical Explanations

The ARM64v8 architecture, also referred to as AArch64, is a 64-bit processing technology that was designed by ARM Holdings. The "64" in ARM64v8 refers to the architecture's 64-bit processing capabilities, which allow for a larger addressable memory space and improved performance in certain scenarios compared to its 32-bit counterpart.

The architecture is based on the principles of Reduced Instruction Set Computing (RISC). RISC architectures like ARM64v8 use a smaller number of simple instructions, as opposed to the complex instructions used by Complex Instruction Set Computing (CISC) architectures. This approach allows for higher performance and efficiency, as each instruction can be executed in a single clock cycle.

ARM64v8 is widely used across various types of devices, from mobile devices to embedded systems and servers. This is due to its efficiency and power-saving characteristics, which make it an excellent choice for environments where power consumption is a concern.

To effectively use the ARM64v8 architecture, it's essential to understand its instruction set and how to write efficient code for it. The instruction set is the collection of commands that a microprocessor can understand and execute. Writing efficient code for ARM64v8 involves techniques like optimizing memory access, taking advantage of the architecture's pipelining capabilities, and utilizing its specific features like the NEON vector processing instructions for parallel computing.

The ARM64v8 architecture has been in use since its introduction in 2011, and its adoption has been growing ever since, particularly in the area of mobile computing. As the Internet of Things (IoT) continues to expand, the importance of understanding and utilizing ARM64v8 architecture is likely to increase further.

Registers in the ARM64v8 architecture are small storage spaces within the processor that can hold data, addresses, conditions, and other types of information for quick processing. They are essential for the processor's operation.

In ARM64v8, there are 31 general-purpose registers, all 64-bits, named X0 to X30. There is also a zero constant register (XZR) that always returns zero when read. Registers X0 to X7 are typically used for passing arguments to function calls and for returning results. The other registers can be used for temporary storage.

There are also special registers like the stack pointer register (SP) which tracks the top of the stack, link register (LR) which holds the return address when a function is called, and the program counter register (PC) which holds the address of the currently executed instruction.

Understanding how these registers work and when to use them is crucial for writing efficient code for the ARM64v8 architecture.

To understand the ARM64v8 architecture and its usage, let's consider a simple example of a "Hello, World!" program written in ARM assembly language.

.section .data
hello:
    .asciz "Hello, World!\\n"

.section .text
.globl _start
_start:
    mov x0, 1
    ldr x1, =hello
    ldr x2, =13
    mov x8, 64
    svc 0
    mov x8, 93
    mov x0, 0
    svc 0

Here is what each line does:

• .section .data: This directive tells the assembler to place the following data into the data section of the object file.
• hello: .asciz "Hello, World!\\n": This defines a null-terminated string and labels it 'hello'.
• .section .text: This directive switches the section to the text section, where the code resides.
• .globl _start: This directive makes the _start symbol globally visible, which means it can be seen from other files.
• _start:: This is the entry point of the program.
• mov x0, 1: This instruction moves the value 1 (which represents the file descriptor for stdout) into register x0.
• ldr x1, =hello: This instruction loads the address of the string 'hello' into register x1.
• ldr x2, =13: This instruction loads the length of the string into register x2.
• mov x8, 64: This instruction moves the system call number for 'write' (64) into register x8.
• svc 0: This instruction triggers a system call.
• mov x8, 93: This instruction moves the system call number for 'exit' (93) into register x8.
• mov x0, 0: This instruction moves the exit status (0) into register x0.
• svc 0: This instruction makes the 'exit' system call, ending the program.

The above code is a basic example that demonstrates how we can use ARM64v8 architecture's instruction set to write a simple program. This example also shows how to utilize system calls, which are essential for performing various operations in any operating system.

🖇️ Références