有一段汇编请教

Question

text:000B8180 MOV R1, #0
.text:000B8184 STR R0, [SP,#12]
.text:000B8188 LDR R0, [SP,#12]
.text:000B818C STR R0, [SP,#16]
.text:000B8190 LDR R2, [SP,#16]
.text:000B8194 STR R2, [SP,#20]
.text:000B8198 LDR R3, [SP,#20]
.text:000B819C STR R3, [SP,#24]
.text:000B81A0 LDR R3, [SP,#24]
.text:000B81A4 STR R3, [SP,#28]
.text:000B81A8 STR R2, [SP,#40]
.text:000B81AC LDR R2, [SP,#40]
.text:000B81B0 STR R2, [SP,#44]
.text:000B81B4 LDR R2, [SP,#44]
.text:000B81B8 STR R2, [SP,#48]
.text:000B81BC LDR R2, [SP,#48]
.text:000B81C0 STR R2, [SP,#36]
.text:000B81C4 STR R1, [SP,#32]
.text:000B81C8 STR R0, [SP,#8]

这里为啥STR 和LDR 来回导呢？从寄存器到内存 然后从内存到寄存器，这是在干啥？