|
POOL16E 011011 |
rd |
rs |
Encoded Immediate |
0 |
|
6 |
3 |
3 |
3 |
1 |
ADDIUR2 rd, rs1, decoded_immediate_value |
microMIPS |
Add Immediate Unsigned Word Two Registers (16-bit instr size) |
Add Immediate Unsigned Word Two Registers (16-bit instr size)
To add a constant to a 32-bit integer.
GPR[rd] = GPR[rs] + sign_extend(decoded immediate)
The encoded immediate field is decoded to obtain the actual immediate value.
The decoded immediate value is sign-extended and then added to the 32-bit value in GPR rs, and the 32-bit arithmetic result is sign-extended and placed into GPR rd.
No Integer Overflow exception occurs under any circumstances.
Table 5.9 Encoded and Decoded Values of the Immediate Field
|
Encoded Value of Instr3..1 (Decimal) |
Encoded Value of Instr3..1 (Hex) |
Decoded Value of Immediate (Decimal) |
Decoded Value of Immediate (Hex) |
|
0 |
0x0 |
1 |
0x0001 |
|
1 |
0x1 |
4 |
0x0004 |
|
2 |
0x2 |
8 |
0x0008 |
|
3 |
0x3 |
12 |
0x000c |
|
4 |
0x4 |
16 |
0x0010 |
|
5 |
0x5 |
20 |
0x0014 |
|
6 |
0x6 |
24 |
0x0018 |
|
7 |
0x7 |
-1 |
0xffff |
The 3-bit register fields can only specify GPRs $2-$7, $16, $17.
If GPR rs does not contain a sign-extended 32-bit value (bits 63..31 equal), then the result of the operation is
UNPREDICTABLE.
if NotWordValue(GPR[rs]) then UNPREDICTABLE endif temp = GPR[rs] + sign_extend(decoded immediate) GPR[rd] = sign_extend(temp31..0)
None
The term "unsigned" in the instruction name is a misnomer; this operation is 32-bit modulo arithmetic that does not trap on overflow. This instruction is appropriate for unsigned arithmetic, such as address arithmetic, or integer arithmetic environments that ignore overflow, such as C language arithmetic.