Instruction cx programmer manual#

Exit the iteration if the prefix is REPE and ZF is 0 (the last comparison was not equal), or if the prefix is REPNE and ZF is one (the last comparison was equal).

If the repeat condition does not hold, exit the iteration and move to the next instruction.

Check the zero flag if the string operation is SCAS or CMPS.

Decrement CX or ECX by one no flags are modified.

If it is zero, exit the iteration, and move to the next instruction.

If the address-size attribute is 16 bits, use CX for the count register if the address-size attribute is 32 bits, use ECX for the count register.

The precise action for each iteration is as follows: To repeat a block of instructions, use the LOOP instruction or another looping construct.

The REP prefixes apply only to one string instruction at a time. Synonymous forms of REPE and REPNE are REPZ and REPNZ, respectively. 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. REP, REPE (repeat while equal), and REPNE (repeat while not equal) are prefix that are applied to string operation. IF (instruction is REPNZ or REPNE) AND (ZF=0) IF (instruction is REP/REPE/REPZ) AND (ZF=1) IF primitive operation is CMPB, CMPW, SCAB, or SCAW Move (E)CX dwords from to ES:Р”Р‡ind nonmatching bytes in ES: and Р”Р‡ind nonmatching words in ES: and Р”Р‡ind nonmatching dwords in ES: and Р”Р‡ind non-EAX dword starting at ES:Р”Р‡ind matching bytes in ES: and Р”Р‡ind matching words in ES: and Р”Р‡ind matching dwords in ES: and Р”В®LSE (* AddressSize = 32 *) use ECX for CountReg REP/REPE/REPZ/REPNE/REPNZ - Repeat Following String Operation Opcode

Instruction cx programmer manual#

80386 Programmer's Reference Manual - Opcode REP AngoLinuxР”РЃ0386 Programmer's Reference Manual - Opcode REP