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INSTRUCTION FORMAT

Table 4-6. 32-Bit VSIB Addressing Forms of the SIB Byte

VR0/VR8

*8

11

000

C0

C1

C2

C3

C4

C5

C6

C7

VR1/VR9

 

 

001

C8

C9

CA

CB

CC

CD

CE

CF

VR2/VR10

 

 

010

D0

D1

D2

D3

D4

D5

D6

D7

VR3/VR11

 

 

011

D8

D9

DA

DB

DC

DD

DE

DF

VR4/VR12

 

 

100

E0

E1

E2

E3

E4

E5

E6

E7

VR5/VR13

 

 

101

E8

E9

EA

EB

EC

ED

EE

EF

VR6/VR14

 

 

110

F0

F1

F2

F3

F4

F5

F6

F7

VR7/VR15

 

 

111

F8

F9

FA

FB

FC

FD

FE

FF

 

 

 

 

 

 

 

 

 

 

 

 

NOTES:

1.If ModR/M.mod = 00b, then effective address is computed as [scaled vector index] + disp32. Otherwise the effective address is computed as [EBP/R13]+ disp, the displacement is either 8 bit or 32 bit

depending on the value of ModR/M.mod:

MOD

Effective Address

00b

[Scaled Vector Register] + Disp32

01b

[Scaled Vector Register] + Disp8 + [EBP/R13]

10b

[Scaled Vector Register] + Disp32 + [EBP/R13]

4.2.164-bit Mode VSIB Memory Addressing

In 64-bit mode VSIB memory addressing uses the VEX.B field and the base field of the SIB byte to encode one of the 16 general-purpose register as the base register. The VEX.X field and the index field of the SIB byte encode one of the 16 vector registers as the vector index register.

In 64-bit mode the top row of Table 4-6 base register should be interpreted as the full 64-bit of each register.

4.3VEX ENCODING SUPPORT FOR GPR INSTRUCTIONS

VEX prefix may be used to encode instructions that operate on neither YMM nor XMM registers. VEX-encoded general-purpose-register instructions have the following properties:

Instruction syntax support for three encodable operands.

Encoding support for instruction syntax of non-destructive source operand, destination operand encoded via VEX.vvvv, and destructive three-operand syntax.

Elimination of escape opcode byte (0FH), two-byte escape via a compact bit field representation within the VEX prefix.

Elimination of the need to use REX prefix to encode the extended half of generalpurpose register sets (R8-R15) for direct register access or memory addressing.

Flexible and more compact bit fields are provided in the VEX prefix to retain the full functionality provided by REX prefix. REX.W, REX.X, REX.B functionalities are provided in the three-byte VEX prefix only.

Ref. # 319433-011

4-13

INSTRUCTION FORMAT

VEX-encoded GPR instructions are encoded with VEX.L=0.

Any VEX-encoded GPR instruction with a 66H, F2H, or F3H prefix preceding VEX will #UD.

Any VEX-encoded GPR instruction with a REX prefix proceeding VEX will #UD. VEX-encoded GPR instructions are not supported in real and virtual 8086 modes.

§

4-14

Ref. # 319433-011

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