MOVSX sign-extends its source (second) operand to the length of
its destination (first) operand, and copies the result into the
destination operand. MOVZX does the same, but zero-extends
rather than sign-extending.
movsxw
386 and laterMove Data with Sign or Zero Extend
movsxw eax, ax | movsxw reg16, r/m16 | movsxw reg32, r/m16 | movsxw reg64, r/m16Loading...
Forms
Every form of movsxw the assembler accepts, from NASM's own instruction table.
The second column is the processor that introduced the form; a badge marks a form that needs
an extension, that is lockable, or that long mode dropped.
| Form | Since | Notes |
|---|---|---|
| movsxw eax, ax | 386 | |
| movsxw reg16, r/m16 | 386 | |
| movsxw reg32, r/m16 | 386 | |
| movsxw reg64, r/m16 | x86-64 | long |