User Guide

General-Purpose Programming 57
24592—Rev. 3.15—November 2009 AMD64 Technology
Compare Strings
• CMPS—Compare Strings
• CMPSB—Compare Strings by Byte
• CMPSW—Compare Strings by Word
• CMPSD—Compare Strings by Doubleword
• CMPSQ—Compare Strings by Quadword
The CMPSx instructions compare the values of two implicit operands of the same size located at
seg:[rSI] and ES:[rDI]. After the copy, both the rSI and rDI registers are auto-incremented (if the DF
flag is 0) or auto-decremented (if the DF flag is 1).
Scan String
• SCAS—Scan String
• SCASB—Scan String as Bytes
• SCASW—Scan String as Words
• SCASD—Scan String as Doubleword
• SCASQ—Scan String as Quadword
The SCASx instructions compare the values of a memory operands in ES:rDI to a value of the same
size in the AL/rAX register. Bits in rFLAGS are set to indicate the outcome of the comparison. After
the comparison, the rDI register is auto-incremented (if the DF flag is 0) or auto-decremented (if the
DF flag is 1).
Move String
• MOVS—Move String
• MOVSB—Move String Byte
• MOVSW—Move String Word
• MOVSD—Move String Doubleword
• MOVSQ—Move String Quadword
The MOVSx instructions copy an operand from the memory location seg:[rSI] to the memory location
ES:[rDI]. After the copy, both the rSI and rDI registers are auto-incremented (if the DF flag is 0) or
auto-decremented (if the DF flag is 1).
Load String
• LODS—Load String
• LODSB—Load String Byte
• LODSW—Load String Word
• LODSD—Load String Doubleword
• LODSQ—Load String Quadword