There are sixteen 64-bit registers in x86-64: %rax, %rbx, %rcx, %rdx, %rdi, %rsi, %rbp, %rsp, and %r8-r15. Of these, %rax, %rcx, %rdx, %rdi, %rsi, %rsp, and %r8-r11 are considered caller-save registers, …

With the 64 bit processors, Intel needed some way of identifying a 64 bit transfer versus a 32 bit or other transfer in the assembly language. At the same time Intel was introducing additional, general …

Jan 31, 2025 · The accumulator register (RAX / EAX / AX / AH / AL) plays a fundamental role in x86–64 assembly programming, it’s a key component in arithmetic operations, returning function values, and ...

If you specify one operand, it multiplies that by %rax, and splits the product across 2 registers. It puts the high-order 64 bits in %rdx and the low-order 64 bits in %rax.

Like C++ variables, registers are actually available in several sizes: rax is the 64-bit, "long" size register. It was added in 2003 during the transition to 64-bit processors. eax is the 32-bit, "int" size register. It …

Assembly generated by a compiler contains instructions as well as labels and directives.

This document is meant to summarise differences between x86-64 and i386 assembly assuming that you already know well the i386 gas syntax. I will try to keep this document up to date until official …

So the first big wall you will need to tackle is starting to learn assembly. It may be a little bit tough, but it is perfectly doable and a critical step for what comes after.

We will use the “gnu assembler (gas) syntax”, aka “AT&T syntax”. This different than “Intel Syntax” • x86 does have loads and stores. It has mov. Note that the amount of work per instruction varies widely …

Jul 7, 2017 · The registers starting with r as in rax, rbx, etc, are the 64-bit registers introduced with the AMD64 extension to the existing 32-bit x86 ISA. That ISA extension was subsequently adopted by …