|
POOL16A 000001 |
rs |
rt |
rd |
1 |
|
6 |
3 |
3 |
3 |
1 |
SUBU16 rd, rs, rt |
microMIPS |
Subtract Unsigned Word (16-bit instr size) |
Subtract Unsigned Word (16-bit instr size)
To subtract 32-bit integers
GPR[rd] = GPR[rs] - GPR[rt]
The 32-bit word value in GPR rt is subtracted from the 32-bit value in GPR rs and the 32-bit arithmetic result is signextended and placed into GPR rd.
No integer overflow exception occurs under any circumstances.
The 3-bit register fields can only specify GPRs $2-$7, $16, $17.
On 64-bit processors, if either GPR rt or GPR rs does not contain sign-extended 32-bit values (bits 63..31 equal), then the result of the operation is UNPREDICTABLE.
This instruction has been recoded for Release 6.
if NotWordValue(GPR[rs]) or NotWordValue(GPR[rt]) then UNPREDICTABLE endif temp = GPR[rs] - GPR[rt] GPR[rd] = sign_extend(temp)
None
The term "unsigned" in the instruction name is a misnomer; this operation is 32-bit modulo arithmetic that does not trap on overflow. It is appropriate for unsigned arithmetic, such as address arithmetic, or integer arithmetic environments that ignore overflow, such as C language arithmetic.