See also x86 assembly language for a quick tutorial for this processor family. The updated instruction set is also grouped according to architecture (i386, i486, i686) and more generally is referred to as x86 32 and x86 64 (also known as AMD64). (REP, REPE, REPNE, REPNZ, REPZ) RET: Return from procedure: Not a real instruction Documentation Home IA32 Assembly Language Reference Manual Chapter 2 InstructionSet Mapping Flag Instructions Clear Direction Flag (cld) IA32 Assembly Language Reference Manual.
Previous: Set Interrupt Flag (sti) In assemblyspeak, an operand that stands for itself (and not for an address where the interesting value lies) is an immediate.
Why was it not also recommended in the K8 manual? It turns out that among the other enhancements in the K10 family, the ret imm16 instruction is now fastpathed, when handling a repz ret, didnt recognize it, The Intel manual volume 2B (Intel 64 and IA32 Architectures Software Developer's Manual Volume 2B: Instruction Set Reference, NZ) says: The REPZ and REPNZ prefixes are synonymous forms of the REPE and REPNE prefixes, respectively.
) Advanced Micro Devices Publication No. Revision Date 3. 26 May 2018 AMD64 Technology AMD64 Architecture Programmers Manual Volume 3: GeneralPurpose and Instruction Set Summary 30 This chapter lists all the instructions in the Intel Architecture instruction set, divided into three Manual, Volume 3.
REPNEREPNZ Repeat while not equalRepeat while not zero Documentation Home x86 Assembly Language Reference Manual Chapter 3 Instruction Set Mapping GeneralPurpose Instructions String Instructions x86 Assembly Language Reference Manual Previous: Control Transfer Instructions When a fault occurs during the execution of a CMPS or SCAS instruction that is prefixed with REPE or REPNE, the EFLAGS value is restored to the state prior to the execution of the instruction.
Since the SCAS and CMPS instructions do not use EFLAGS as an input, the processor can resume the instruction after the page fault handler. I disassembled a file with OllyDbg and it had the following instruction: REPNE SCAS BYTE PTR ES: [EDI What does that exactly mean? x86 and amd64 instruction reference Derived from the May 2018 version of the Intel 64 and IA32 Architectures Software Developers Manual.
Last updated. 22 rows REP, REPE (repeat while equal), and REPNE (repeat while not equal) are prefix that are applied to string operation. Each prefix cause the string instruction that follows to be repeated the number of times indicated in the count register or (for REPE and REPNE) until the indicated condition in the zero flag is no longer met.