Scas instruction x86 server

The repeat prefixes cause an instruction to be repeated for each element of a string. They can be used only with the string instructions: MOVS, CMPS, SCAS, LODS, STOS, INS, and OUTS. Use of the repeat prefixes with other IA-32 instructions is reserved and may cause unpredictable behavior • SCAS instruction flags are not retained while REP continues in single-step mode (see BOCHS SCAS demo). These two codes begin by setting the carry flag. 4 The REP instruction is handled specially by x86 CPUs, such that it completes even if the sequence is replaced in memory. 1.1 Intel® 64 and IA-32 Processors Covered in this Manual. 1.2 Overview of Volume 2A, 2B, 2C and 2D: Instruction Set Reference. 1.3 Notational Conventions. 1.3.1 Bit and Byte Order. SCAS :Cette instruction permet de comparer un octet, un mot ou un double mot avec la cellule memoire a l'adresse ES:[DI] et incremente/decremente le registre DI en fonction de la taille de l'operande cible et de l'etat du drapeau de direction. x86 assembly language includes instructions for a stack-based floating-point unit (FPU). The FPU was an optional separate coprocessor for the 8086 through the The x86 instruction set includes string load, store, move, scan and compare instructions (lods, stos, movs, scas and cmps) which perform • The x86 instruction set has been around for nearly 40 years and each new processor has had to maintain backward compatibility (support the old instruction set) Optimized With lea Instruction. x86 Convention: The return value of a function is expected in %eax / %rax. mov and add/sub Examples. This article describes how x86 and x86-64 instructions are encoded. An x86-64 instruction may be at most 15 bytes in length. It consists of the following components in the given order, where the prefixes are at the least-significant (lowest) address in memory: Legacy prefixes (1-4 bytes, optional). Intel 80x86 Instruction Set Summary. This document contains a description of all 80x86 instructions not including math coprocessor instructions. Each instruction is described briefly. All operand forms valid with each instruction are shown and some syntax examples are given. This reference is intended to be precise opcode and instruction set reference (including x86-64). Its principal aim is exact definition of instruction parameters Memory addressed by the ES:eDI or by RDI (only MOVS, CMPS, INS, STOS, and SCAS). In 64-bit mode, only 64-bit (RDI) and 32-bit (EDI) Happy Engineers Day :) - one-engineers-thoughts/x86-instructions.md at master · MaTriXy/one-engineers-thoughts. instruction SBB description Integer Subtraction with Borrow. instruction SCAS/SCASB/SCASW/SCASD description Scan String. 2.1 The x86 architecture instructions 2.1.1 Data movement instructions 2.1.2 Type Flat assembler is a fast assembly language compiler for the x86 architecture processors, which does multiple scas subtracts the destination string element from AL, AX, or EAX (depending on the size of string element)