For a function with prototype long decode2long x long y long

For a function with prototype:

long decode2(long x, long y, long z);

GCC generates the following assembly code:

1. decode2:

2.subq %rdx, %rsi

3. imultq %rsi, %rdi

4.movq %rsi, %rax

5. salq $63, %rax

6. sarq $63, %rax

7. xorq %rdi, %rax

8. ret

Parameters x, y, and z are passed in registers %rdi, %rsi, and %rdx. The code store the return value in register %rax.

Write C code for decode2 that will have an effect equivalent to the assembly code shown.

Please explain your reasoning.

I am just writting the equivalent line :

rsi - y, rdx- z , rdi - x and we are condering constant result to store the result value

subq %rdx, %rsi - this means rsi = rsi-rdx and so equivalent c code is y = y-z

imultq %rsi, %rdi - this means rdi = rdi*rsi so equivalent cdoe is x= x*y

movq %rsi, %rax this mean rax = rsi so equivalent c code is result = x

salq $63, %rax this means rax bits will shift 63 bits to left equivalent result >>> 63

sarq $63, %rax this means rax will shift 63 bits right

xorq %rdi, %rax this means rax= rax^rdi hence result = result ^ x