Volume 3: General-Purpose and System Instructions - Stanford ...

AMD64 Technology 24594 Rev. 3.10 February 2005STOSSTOSBSTOSWSTOSDSTOSQStore StringCopies a byte, word, doubleword, or quadword from the AL, AX, EAX, or RAXregisters to the memory location pointed to by ES:rDI and increments or decrementsthe rDI register according to the state of the DF flag in the rFLAGS register.If the DF flag is 0, the instruction increments the pointer; otherwise, it decrements thepointer. It increments or decrements the pointer by 1, 2, 4, or 8, depending on the sizeof the value being copied.The forms of the STOSx instruction with an explicit operand use the operand only tospecify the type (size) of the value being copied.The no-operands forms specify the type (size) of the value being copied with themnemonic.The STOSx instructions support the REP prefixes. For details about the REP prefixes,see “Repeat Prefixes” on page 10. The STOSx instructions can also operate inside aLOOPcc instruction.Mnemonic Opcode DescriptionSTOS mem8STOS mem16STOS mem32STOS mem64STOSBSTOSWAAABABABAAABStore the contents of the AL register to ES:rDI, and thenincrement or decrement rDI.Store the contents of the AX register to ES:rDI, and thenincrement or decrement rDI.Store the contents of the EAX register to ES:rDI, and thenincrement or decrement rDI.Store the contents of the RAX register to ES:rDI, and thenincrement or decrement rDI.Store the contents of the AL register to ES:rDI, and thenincrement or decrement rDI.Store the contents of the AX register to ES:rDI, and thenincrement or decrement rDI.280 STOSx