Specifications

Intel
®
64 and IA-32 Architectures Software Developer’s Manual Documentation Changes 172
Documentation Changes
Instruction Operand Encoding
...
RET—Return from Procedure
F2 A6 REPNE CMPS m8,
m8
A Valid Valid Find matching bytes in
ES:[(E)DI] and DS:[(E)SI].
F2 REX.W A6 REPNE CMPS m8,
m8
A Valid N.E. Find matching bytes in [RDI]
and [RSI].
F2 A7 REPNE CMPS m16,
m16
A Valid Valid Find matching words in
ES:[(E)DI] and DS:[(E)SI].
F2 A7 REPNE CMPS m32,
m32
A Valid Valid Find matching doublewords
in ES:[(E)DI] and DS:[(E)SI].
F2 REX.W A7 REPNE CMPS m64,
m64
A Valid N.E. Find matching doublewords
in [RDI] and [RSI].
F2 AE REPNE SCAS m8 A Valid Valid Find AL, starting at
ES:[(E)DI].
F2 REX.W AE REPNE SCAS m8 A Valid N.E. Find AL, starting at [RDI].
F2 AF REPNE SCAS m16 A Valid Valid Find AX, starting at
ES:[(E)DI].
F2 AF REPNE SCAS m32 A Valid Valid Find EAX, starting at
ES:[(E)DI].
F2 REX.W AF REPNE SCAS m64 A Valid N.E. Find RAX, starting at [RDI].
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.
Op/En Operand 1 Operand 2 Operand 3 Operand 4
ANA NA NA NA
Opcode* Instruction Op/
En
64-Bit
Mode
Compat/
Leg Mode
Description
C3 RET A Valid Valid Near return to calling
procedure.
CB RET A Valid Valid Far return to calling
procedure.
C2 iw RET imm16 B Valid Valid Near return to calling
procedure and pop imm16
bytes from stack.
CA iw RET imm16 B Valid Valid Far return to calling
procedure and pop imm16
bytes from stack.
Opcode Instruction Op/
En
64-Bit
Mode
Compat/
Leg Mode
Description