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2.2.2.2 Computational instructions
Computational instructions perform arithmetic, logical, and shift operations on values in registers. Computational
instructions can be either in register (R-type) format, in which both operands are registers, or in immediate (I-type)
format, in which one operand is a 16-bit immediate.
Computational instructions are classified as:
(1) ALU immediate instructions
(2) Three-operand type instructions
(3) Shift instructions
(4) Multiply/divide instructions
To maintain data compatibility between the 64- and 32-bit modes, it is necessary to sign-extend 32-bit operands
correctly. If the sign extension is not correct, the 32-bit operation result is meaningless.
Instruction
Add Immediate
ADDI rt, rs, immediate
The 16-bit immediate is sign extended and then added to the contents of register rs to form a 32-bit
result. The result is stored into register rt. In the 64-bit mode, the operand must be sign extended.
An exception occurs on the generation of 2's complement overflow.
Add Immediate
ADDIU rt, rs, immediate
Unsigned
The 16-bit immediate is sign extended and then added to the contents of register rs to form a 32-bit
result. The result is stored into register rt. In the 64-bit mode, the operand must be sign extended. No
exception occurs on the generation of integer overflow.
Set On Less Than
SLTI rt, rs, immediate
Immediate
The 16-bit immediate is sign extended and then compared to the contents of register rt treating both
operands as signed integers. If rs is less than the immediate, the result is set to 1; otherwise, the
result is set to 0. The result is stored to register rt.
Set On Less Than
SLTIU rt, rs, immediate
Immediate Unsigned
The 16-bit immediate is sign extended and then compared to the contents of register rt treating both
operands as unsigned integers. If rs is less than the immediate, the result is set to 1; otherwise, the
result is set to 0. The result is stored to register rt.
And Immediate
ANDI rt, rs, immediate
The 16-bit immediate is zero extended and then ANDed with the contents of the register. The result is
stored into register rt.
Or Immediate
ORI rt, rs, immediate
The 16-bit immediate is zero extended and then ORed with the contents of the register. The result is
stored into register rt.
Exclusive Or Immediate
XORI rt, rs, immediate
The 16-bit immediate is zero extended and then Ex-ORed with the contents of the register. The result
is stored into register rt.
Load Upper Immediate
LUI rt, immediate
The 16-bit immediate is shifted left by 16 bits to set the lower 16 bits of word to 0. The result is stored
into register rt. In the 64-bit mode, the operand must be sign extended.
CHAPTER 2 V
Table 2-6. ALU Immediate Instruction
Format and Description
Preliminary User's Manual S15543EJ1V0UM
4120A
R
rs
op
rt
immediate
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