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OPCODE MAP

0F3AH, respectively. Each entry in the opcode map of a VEX-encoded instruction is based on the value of the opcode byte, similar to non-VEX-encoded instructions.

A VEX prefix includes several bit fields that encode implied 66H, F2H, F3H prefix functionality (VEX.pp) and operand size/opcode information (VEX.L). See chapter 4 for details.

Opcode tables A2-A6 include both instructions with a VEX prefix and instructions without a VEX prefix. Many entries are only made once, but represent both the VEX and non-VEX forms of the instruction. If the VEX prefix is present all the operands are valid and the mnemonic is usually prefixed with a “v”. If the VEX prefix is not present the VEX.vvvv operand is not available and the prefix “v” is dropped from the mnemonic.

A few instructions exist only in VEX form and these are marked with a superscript “v”.

Operand size of VEX prefix instructions can be determined by the operand type code. 128-bit vectors are indicated by 'dq', 256-bit vectors are indicated by 'qq', and instructions with operands supporting either 128 or 256-bit, determined by VEX.L, are indicated by 'x'. For example, the entry "VMOVUPD Vx,Wx" indicates both VEX.L=0 and VEX.L=1 are supported.

B.2.5 Superscripts Utilized in Opcode Tables

Table B-1 contains notes on particular encodings. These notes are indicated in the following opcode maps by superscripts. Gray cells indicate instruction groupings.

 

Table B-1. Superscripts Utilized in Opcode Tables

Superscript

Meaning of Symbol

Symbol

 

 

 

1A

Bits 5, 4, and 3 of ModR/M byte used as an opcode extension (refer to Section

 

B.4, “Opcode Extensions For One-Byte And Two-byte Opcodes”).

 

 

1B

Use the 0F0B opcode (UD2 instruction) or the 0FB9H opcode when deliberately

 

trying to generate an invalid opcode exception (#UD).

 

 

1C

Some instructions use the same two-byte opcode. If the instruction has

 

variations, or the opcode represents different instructions, the ModR/M byte

 

will be used to differentiate the instruction. For the value of the ModR/M byte

 

needed to decode the instruction, see Table B-6.

 

 

i64

The instruction is invalid or not encodable in 64-bit mode. 40 through 4F

 

(single-byte INC and DEC) are REX prefix combinations when in 64-bit mode

 

(use FE/FF Grp 4 and 5 for INC and DEC).

 

 

o64

Instruction is only available when in 64-bit mode.

 

 

d64

When in 64-bit mode, instruction defaults to 64-bit operand size and cannot

 

encode 32-bit operand size.

 

 

B-8

Ref. # 319433-011

 

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