Intel 253666-024US Manuel D’Utilisation
Vol. 2A 3-123
INSTRUCTION SET REFERENCE, A-M
CMP—Compare Two Operands
CMP—Compare Two Operands
Opcode
Instruction
64-Bit
Mode
Compat/
Leg Mode
Description
3C ib
CMP AL, imm8
Valid
Valid
Compare imm8 with AL.
3D iw
CMP AX, imm16
Valid
Valid
Compare imm16 with AX.
3D id
CMP EAX, imm32 Valid
Valid
Compare imm32 with EAX.
REX.W + 3D id
CMP RAX, imm32 Valid
N.E.
Compare imm32 sign-
extended to 64-bits with
RAX.
80 /7 ib
CMP r/m8, imm8 Valid
Valid
Compare imm8 with r/m8.
REX + 80 /7 ib
CMP r/m8
*
, imm8 Valid
N.E.
Compare imm8 with r/m8.
81 /7 iw
CMP r/m16,
imm16
Valid
Valid
Compare imm16 with
r/m16.
81 /7 id
CMP r/m32,
imm32
Valid
Valid
Compare imm32 with
r/m32.
REX.W + 81 /7 id
CMP r/m64,
imm32
Valid
N.E.
Compare imm32 sign-
extended to 64-bits with
r/m64.
83 /7 ib
CMP r/m16, imm8 Valid
Valid
Compare imm8 with r/m16.
83 /7 ib
CMP r/m32, imm8 Valid
Valid
Compare imm8 with r/m32.
REX.W + 83 /7 ib
CMP r/m64, imm8 Valid
N.E.
Compare imm8 with r/m64.
38 /r
CMP r/m8, r8
Valid
Valid
Compare r8 with r/m8.
REX + 38 /r
CMP r/m8
*
, r8
*
Valid
N.E.
Compare r8 with r/m8.
39 /r
CMP r/m16, r16
Valid
Valid
Compare r16 with r/m16.
39 /r
CMP r/m32, r32
Valid
Valid
Compare r32 with r/m32.
REX.W + 39 /r
CMP r/m64,r64
Valid
N.E.
Compare r64 with r/m64.
3A /r
CMP r8, r/m8
Valid
Valid
Compare r/m8 with r8.
REX + 3A /r
CMP r8
*
, r/m8
*
Valid
N.E.
Compare r/m8 with r8.
3B /r
CMP r16, r/m16
Valid
Valid
Compare r/m16 with r16.
3B /r
CMP r32, r/m32
Valid
Valid
Compare r/m32 with r32.
REX.W + 3B /r
CMP r64, r/m64
Valid
N.E.
Compare r/m64 with r64.
NOTES:
* 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.