MIPS Assembly/Pseudoinstructions

The MIPS instruction set is very small, so to do more complicated tasks we need to employ assembler macros called pseudoinstructions. List of Pseudoinstructions The following is a list of the standard MIPS instructions that are implemented as pseudoinstructions: abs blt bgt ble neg negu not bge li la move sge sgt Branch Pseudoinstructions Branch if less than (blt) The blt instruction compares 2 registers, treating them as signed integers, and takes a branch if one register is less than another. blt $8, $9, label translates to slt $1, $8, $9 bne $1, $0, label Other Pseudoinstructions Load Immediate (li) The li pseudo instruction loads an immediate value into a register. li $8, 0x3BF20 translates to lui $at, 0x0003 ori $8, $at, 0xBF20 Absolute Value (abs) The absolute value pseudo instruction loads the absolute value contained in one register into another register. abs $1, $2 translates to addu $1, $2, $0 bgez $2, 8 (offset=8 → skip 'sub' instruction) sub $1, $0, $2 Move (move) The move pseudo instruction moves the contents of the second register operand into the first register operand. move $1, $2 translates to add $1, $2, $0 Load Address (la) la $a0,address translates to lui $at, 4097 (0x1001 → upper 16 bits of $at). ori $a0,$at,disp where the immediate (“disp”) is the number of bytes between the first data location (always 0x 1001 0000) and the address of the first byte in the string. Set on greater than or equal (sge) The sge instruction compares 2 registers, treating them as signed integers, and sets a given register($1) if the value of the 1st register($8) >= the value of the 2nd register($9), else the given register($1) == 00. sge $1, $8, $9 translates to addiu $9, $9, -0x01 slt $1, $9, $8