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MOVSX_MOVSXD
MOVSX / MOVSXD — Move with Sign-Extension
| Opcode | Instruction | Op/ En | 64-Bit Mode | Compat/ Leg Mode | Description |
| 0F BE /r | MOVSX r16, r/m8 | Valid | Move byte to word with sign-extension. | ||
| 0F BE /r | MOVSX r32, r/m8 | Valid | Move byte to doubleword with sign- extension. | ||
| REX + 0F BE /r | MOVSX r64, r/m8* | N.E. | Move byte to quadword with sign-extension. | ||
| 0F BF /r | MOVSX r32, r/m16 | Valid | Move word to doubleword, with sign- extension. | ||
| REX.W + 0F BF /r | MOVSX r64, r/m16 | N.E. | Move word to quadword with sign-extension. | ||
| REX.W** + 63 /r | MOVSXD r64, r/m32 | N.E. | Move doubleword to quadword with sign- extension. |
* In 64-bit mode, r/m8 can not be encoded to access the following byte registers if a REX prefix is used: AH, BH, CH, DH. ** The use of MOVSXD without REX.W in 64-bit mode is discouraged. Regular MOV should be used instead of using MOVSXD without REX.W.
| Op/En | Operand 1 | Operand 2 | Operand 3 | Operand 4 |
| RM | ModRM:reg (w) | ModRM:r/m (r) | NA | NA |
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 Intel® 64 and IA-32 Architectures Software Devel- oper’s Manual, Volume 1). The size of the converted value depends on the operand-size attribute.
In 64-bit mode, the instruction’s default operation size is 32 bits. Use of the REX.R prefix permits access to addi- tional registers (R8-R15). Use of the REX.W prefix promotes operation to 64 bits. See the summary chart at the beginning of this section for encoding data and limits.
DEST ← SignExtend(SRC);None.
\#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.
\#AC(0) If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.
\#UD If the LOCK prefix is used.
\#GP If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
\#SS If a memory operand effective address is outside the SS segment limit.
\#UD If the LOCK prefix is used.
\#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.
\#PF(fault-code) If a page fault occurs.
\#UD If the LOCK prefix is used.
Same exceptions as in protected mode.
\#SS(0) If a memory address referencing the SS segment is in a non-canonical form.
\#GP(0) If the memory address is in a non-canonical form.
\#PF(fault-code) If a page fault occurs.
\#AC(0) If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.
\#UD If the LOCK prefix is used.
Source: Intel Architecture Software Developer's Manual (July 2017)