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EFI Byte Code Virtual Machine
Version 1.10 12/01/02 19-57
SHR
SYNTAX:
SHR[32|64] {@}R
1
, {@}R
2
{Index16|Immed16}
DESCRIPTION:
Right-shifts unsigned Operand 1 by Operand 2 bit positions and stores the result back to Operand 1.
The operand sizes may be either 32-bits (SHR32) or 64 bits (SHR64).
OPERATION:
Operand 1 <= Operand 1 >> Operand 2
Table 19-43. SHR Instruction Encoding
BYTE DESCRIPTION
Bit Description
7 0 = Operand 2 immediate/index absent
1 = Operand 2 immediate/index present
6 0 = 32-bit operation
1 = 64-bit operation
0
0..5 Opcode = 0x18
Bit Description
7 0 = Operand 2 direct
1 = Operand 2 indirect
4..6 Operand 2
3 0 = Operand 1 direct
1 = Operand 1 indirect
1
0..2 Operand 1
2..3 Optional 16-bit immediate data/index
BEHAVIORS AND RESTRICTIONS:
• If Operand 2 is indirect, then the immediate data is interpreted as an index, and the Operand 2
value is fetched from memory as an unsigned value at address [R
2
+ Index16].
• If Operand 2 is direct, then the immediate data is considered a signed immediate value and is
added to the Operand 2 register contents such that Operand 2 = R
2
+ Immed16.
• If the instruction is SHR32, and Operand 1 is direct, then the result is stored to the Operand 1
register with the upper 32 bits cleared.