X86 scas instruction -544-

Here are the single byte x86 opcodes. This is literally a "byte-code" for the x86. CX is 0 or the instruction sets the Zero Flag to 0. This prefix is *only* valid for CMPS and SCAS instructions. Two Byte - 1 Byte Opcode and 1 Byte Operand Instructions or 2 Byte Opcode and 0 Bytes 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: CMPSW, SCAS, SCASB, SCASD and SCASW instructions CS, SS, DS, ES, FS and GS segment override Chapter 3 Instruction Set Mapping. This chapter provides a general mapping between the Solaris x86 assembly language mnemonics and the Intel or Advanced Micro Devices (AMD) mnemonics. Each prefix causes the associated string instruction to repeat until the count register (CX) or the zero flag (ZF) matches a tested condition. Examples rep movsb Repeat while equal: Copy the 8-bit byte from the DS:[(E)SI] to the ES:[(E)DI] register. repnz scasl Microprocessor - 8086 Instruction Sets. Advertisements. Previous Page. Next Page . The 8086 microprocessor supports 8 types of instructions ? SCAS/SCASB/SCASW ? Used to scan a string and compare its byte with a byte in AL or string word with a word in AX. The logic behind x86 string instructions. All the information from (1) squeezed into a table. let's make the distinction between string instructions (MOVS, LODS, STOS, CMPS, SCAS) and Im curious as to if the following x86 instructions movs, cmps, scas, stos, and lods truly get compiled as that instruction with an assembler..or do they get broken down into more then one instruction to equal those? 6.2 The 80x86 String Instructions All members of the 80x86 family support five different string instructions: MOVS x, CMPS x, SCAS x, LODS x, and STOS x 1. (x = B, W, or D for byte, word, or double word, respectively. This text will generally drop the x suffix when talking about these string instructions in a gen