Or syntax, Description, Operation – Intel Extensible Firmware Interface User Manual
Page 824: Behaviors and restrictions
Extensible Firmware Interface Specification
19-50
12/01/02
Version 1.10
OR
SYNTAX:
OR[32|64] {@}R
1
, {@}R
2
{Index16|Immed16}
DESCRIPTION:
Performs a bit-wise OR of two 32-bit (OR32) or 64-bit (OR64) operands, and stores the result back
to Operand 1.
OPERATION:
Operand 1 <= Operand 1 OR Operand 2
Table 19-36. OR 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 = 0x15
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 OR32 and Operand 1 is direct, then the result is stored to Operand 1 register
with the upper 32 bits cleared.