assembly - MIPS: lw (load word) instruction -

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is lw $s0,8($0) same lw $s0,0($v0)?

i not see difference. think 8 represents offset, means need addres of $0 , add 2 (8/4) address.

edit:

my question lw instruction , mips register set. pretty difficult me understand how offset works...

they not same, although in circumstances behave alike. format of lw instruction follows:

lw regdest, offset(regsource)

where regdest , regsource mips registers, , offset immediate.

it means, load register regdest word contained in address resulting adding contents of register regsource , offset specified. resulting source address must word-aligned (i.e. multiple of 4)

therefore, lw $s0,8($0) means load in $s0 contents of word located @ address specified $0 plus 8. $0 register $zero contain constant zero, load word located in absolute address 8 $s0.

lw $s0,0($v0) means load in $s0 contents of word located @ address specified $v0. if $v0 contains value 8 both instructions have same effect. if $v0 not multiple of 4, instruction generate addressing trap.

usually lw pseudoinstruction in sense assembler may emmit more 1 instruction accomplish instruction. offset (displacement) has 16-bit signed value. if instruction has immediate more bits, assembler use temporary register ($at) hold contents of immediate , emmit equivalent instructions perform intended behavior. may see in action using dissassembler or mips monitor (also inspecting code mars simulator).


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