SLTIU

SLTIU, short for Set on Less Than Immediate Unsigned, is a MIPS instruction of the I-type format. It compares the value in a source register to a 16-bit immediate constant treated as unsigned and writes 1 to the destination register if the source is less than the immediate; otherwise it writes 0.

Encoding and operation: SLTIU uses the I-type encoding with opcode 0x0B (binary 001011). The fields are rs (bits 25–21), rt (bits 20–16), and a 16-bit immediate (bits 15–0). The 16-bit immediate is zero-extended to 32 bits for the unsigned comparison. In assembly, the syntax is sltiu rt, rs, immediate.

Assembly example: sltiu $t0, $t1, 100. This sets $t0 to 1 if the value in $t1 is less than 100 when both are interpreted as unsigned 32-bit integers; otherwise, it sets $t0 to 0.

Usage and scope: SLTIU is used for unsigned comparisons against a constant, such as implementing conditional logic or loop bounds where values are treated as unsigned. It is distinct from SLTI (signed comparison) and from SLT/SLTU (two-register comparisons). The immediate variant provides a convenient way to compare a register value against a fixed boundary without needing an additional register to hold the constant.

See also: MIPS instruction set, SLTI, SLT, SLTU, addi.