CODEWITHSUNDEEP
assemblymips
just_a_newbie
just_a_newbie

Reputation: 375

In MIPS, what's the difference between signed addition, unsigned addition, signed subtraction and unsigned subtraction?

add rd, rs, rt
addu rd, rs, rt
sub rd, rs, rt
subu rd, rs, rt

In MIPS, what's the difference between signed addition, unsigned addition, signed subtraction and unsigned subtraction? If their results are the same, what's the point to classified as using signed and unsigned methods?

Upvotes: 4

Views: 3617

Answers (1)

Michael
Michael

Reputation: 58427

The u simply means that they don't trap on overflow.

Quoting from "MIPS32 Architecture For Programmers Volume II":

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.

Upvotes: 6

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