mips - MIPS 代码集之间有什么区别？

Question

两个代码有什么区别？

.data            |  .data
A:  .word   0:100|  A:  .word   0:100
                 |
.text            |  .text
li  $t1, 4       |  la  $t1, A
lw  $t0, A($t1)  | lw    $t0, 4($t1)

Answer 1

让我们逐行理解代码:

右:

    .data         # static variables are defined in .data block
A:  .word   0:100 # array 100 of integers each initialized to 0 

    .text         # MIPS code block
li  $t1, 4        # loading a 16 bit constant value 4 into register $t1

lw  $t0, A($t1)   # going to the memory at the address of A (address
                  # of first element of array) + $t1 (which contains
                  # value 4) and fetch it into register $t0

左:

    .data         # static variables are defined in .data block
A:  .word   0:100 # array 100 of integers each initialized to 0 

    .text         # MIPS code block
la  $t1, A        # load the address of first element of array 
                  # into register $t1

lw $t0, 4($t1)    # going to the memory at the address of $t1 + 4 
                  # and fetch it into register $t0

注释: MIPS 中的地址以字节为单位，整数 (.word) 为 4 个字节。因此，如果我们将数组的基地址(数组的基地址)增加4，就会得到数组第二个元素的地址。

因此: 两个代码是相同的。最后，数组第二个元素(index = 1)的内容将被加载到寄存器$t0中。