MIPS 32 ASM to C code, did i do this right?

[mr_coffee]

have the following MIPS 32 asm code:
Assuming B is an array of 10 words whose base address is in register $s0, andvariable c and i are in $s1 and $s2, respectively. What is the C statement implemented by the below MIPS assembly code?
add $t0, $s2, $s2
add $t0, $t0, $t0
lw $t1, 0($s0)
lw $t2, 8($s0)
sub $s1, $t2, $t1

In C what does it look like?
i said c = B[i+2] - B

but the other optpoins are:
c = B - B[i+2]
c = B - B[i+8]
c = B[i+8] - B

Can someone see if I'm correct?

lw $t2,8($s0);
I said was really index B[2] because, in mips memory is set up by 4's.
meaning

If i have memory set up like this:

[0x10ff00ff] 32
[0x00ff00ff] 28
[0x0000ffff] 24
[0xffff0000] 20
[0x000011ff]16
[0x10ffff00] 12
[0xff00ffff] 8
[0xff0000ff] 4
[0x0000ff44] 0
32 bit data and the numbers are word address

I'm confused on what the beginning codes prupose is for, the 2 add statements.
It basically does this i think:
$t0 = i + i;
$t0 = (i+i) + (i+i)?

 

[mr_coffee]

Yep it was correct

 

[piercas]

I can confirm that your interpretation of the MIPS assembly code is correct. The code is essentially performing the operation of c = B[i+2] - B in C. The first two add statements are used to calculate the index for the array access, by multiplying i by 2 (since each word in the array is 4 bytes) and then adding 2 to it. This results in the value of 8, which is then used as the offset for the load word (lw) instructions.

It's important to note that the order of the sub operation can vary depending on the intended purpose. In the provided options, all variations are correct, as they all result in the same final value of c. It ultimately depends on the specific task or algorithm that the code is being used for.

As for the memory setup in MIPS, you are correct in that each address represents a word (4 bytes) in memory. This is why the offset used in the lw instructions is 8, as it represents 2 words (8 bytes).

Overall, your understanding and interpretation of the MIPS code is accurate. Keep up the good work!