x86 Instruction Set Reference

MOVSX

Move with Sign-Extension

Opcode	Mnemonic	Description
`0F BE /r`	`MOVSX r16,r/m8`	Move byte to word with sign-extension.
`0F BE /r`	`MOVSX r32,r/m8`	Move byte to doubleword, sign-extension.
`0F BF /r`	`MOVSX r32,r/m16`	Move word to doubleword, sign-extension.

Description
Copies the contents of the source operand (register or memory location) to the destination operand (register) and sign extends the value to 16 or 32 bits (see Figure 7-6 in the IA-32 Intel Architecture Software Developer's Manual, Volume 1). The size of the converted value depends on the operand-size attribute.

Operation
Destination = SignExtend(Source);

Flags affected
None.

Protected Mode Exceptions

`#GP(0)`	If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If the DS, ES, FS, or GS register contains a null segment selector.
`#GP(0)`	If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If the DS, ES, FS, or GS register contains a null segment selector.
`#SS(0)`	If a memory operand effective address is outside the SS segment limit.
`#PF(fault-code)`	If a page fault occurs.

Real-Address Mode Exceptions

`#GP`	If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
`#GP`	If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.

Virtual-8086 Mode Exceptions

`#GP(0)`	If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
`#GP(0)`	If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
`#SS(0)`	If a memory operand effective address is outside the SS segment limit.