work sheet for week 2: 
RISC-V assembly language programming

using this page
https://www.cp.eng.chula.ac.th/~prabhas//teaching/comparch/2024/Programming-RISC-V-assembly.htm

1)  run the following assembly programs in venus, observe the result.  Check that the result is correct.

1.1  move data from register to register
write your answer, what is the value in register x3 when program terminate?

  addi x2,x0,11
  add  x3,x2,x0

1.2  move data from register to/from memory
write your answer, what is the value in memory 0x104 when program terminate?

  addi x5,x0,0x11        # set x5 to 0x11
  sw x5, 0x100(x0)       # store at address 0x100
  lw x6, 0x100(x0)       # get from mem
  addi x6,x6,1          
  sw x6, 0x104(x0)       # store to mem 0x104

1.3  simple arithmetic, write the answer what is the value of memory at 0x100 when the program terminate?

  lw  x5, 0x104(x0)     # get b
  lw  x6, 0x108(x0)     # get c
  add x4, x5, x6
  sw  x4, 0x100(x0)     # store to a

1.4  accessing an array data

using offset,  base address points to the beginning of the array

   ax[20]    ax starts at 0x100  base address, size 20 bytes

   to get an element at ax[1], each element is 32-bit
   let x3 -index, x4 -base, x5 -effective address, x6 -value

   addi x3,x0,4         # offset to index 1, 4 bytes
   addi x4,x0,0x100     # base
   add  x5,x3,x4        # compute effective address
   lw   x6,0(x5)        # get from memory

write your answer, what is the value of the effective address?

1.5  loop

run the following program, what is the value of x3 when the program terminate?

   addi x3,x0,0    # i = 0
   addi x4,x0,10   # const 10
loop:
   bge  x3,x4, exit
   addi x3,x3,1
   j loop
exit:

2)  compiling high level language to assembly language

using "Compiler Explorer" (godbolt.org)
input language is C,
output language is "RISC_V rv32gc clang" 

compile and explain the output assembly code (no need to run)

2.1  simple one line program

int main(){
  int a;
  a = 11;
}

2.2  program with if..then

int main(){
  int a,b;
  if(a > 0){
    b = 22;
  }
}