Retq instruction x86 vs x64

12 Sep 2012 Now let's use the disassemble command to show the assembly instructions for the pop %rbp 0x0000000100000f74 : retq End of assembler dump. As x86 moved from 16-bit to 32-bit to 64-bit, the registers were 27 Feb 2016 Let's look at the assembly instructions for this program: Simple Function: it only has 4 kinds of instructions in it, push , pop , mov , and retq . memory there is split up into 8 byte (64 bit) chunks that represent the current stack. 16 Feb 2016 So I've been doing a fair amount of x86-64 programming lately. . a function that is jumped to by PyObject_Malloc , a retq instruction will be hit. file format elf64-x86-64 Disassembly of section .text: 0000000000000000 : 0: f3 c3 repz retq So, repz is a prefix that repeats the following instruction until some register is 0. Also, it only So what on earth is gcc doing generating a repz retq?В длинном (64-разрядном) режиме вы возвращаете ( ret ), выбирая четвертый адрес из стека в %rip . В 32-битном режиме вы возвращаете ( ret ) x64 assembly code uses sixteen 64-bit registers. Additionally, the example, moving a quadword from %rax to %rbx results in the instruction movq %rax, %rbx. 1 Answer. In long (64-bit) mode, you return ( ret ) by popping a quadword address from the stack to %rip . In 32-bit mode, you return ( ret ) by popping a dword address from the stack to %eip . Some tools like objdump -d call the first one retq . After studying assembly code, here are my thoughts, let's look at a sample: fun: push %rbp mov %rsp,%rbp pop %rbp retq main: callq x86-64 (also known as just x64 and/or AMD64) is the 64-bit version of the x86/IA32 .. cleans up the stack, and use retq instruction to return control to the caller. 18 Feb 2017 This reference is intended to be precise opcode and instruction set reference (including x86-64). Its principal aim is exact definition of