Intel Extensible Firmware Interface - Manual (Page 807)

EFI Byte Code Virtual Machine
Version 1.10 12/01/02 19-33
MOD
SYNTAX:
MOD[32|64] {@}R
1
, {@}R
2
{Index16|Immed16}
DESCRIPTION:
Perform a modulus on two signed 32-bit (MOD32) or 64-bit (MOD64) operands and store the
result to Operand 1.
OPERATION:
Operand 1 <= Operand 1 MOD Operand 2
Table 19-24. MOD Instruction Encoding
BYTE DESCRIPTION
Bit Description
7 0 = Immediate/index absent
1 = Immediate/index present
6 0 = 32-bit operation
1 = 64-bit operation
0
0..5 Opcode = 0x12
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 a signed value at address [R
2
+ Index16].
• If Operand 2 is direct, then the immediate data is considered a signed immediate value such that
Operand 2 = R
2
+ Immed16, and the value is sign extended to 32 or 64 bits accordingly.
• If Operand 2 = 0, then a divide-by-zero exception is generated.