You can get the source code by using gcc -S filename
Note: ssort is an 8085 assembly code for selection sort, included for comparison purposes only.
Explanation for lab8.s (basic):
| Line | Work |
|---|---|
| Lines 1-3 | Definition |
| Line 5 | The .ascii directive places the characters in string into the object module at the current location |
| Line 10 | scl 2 means storage class 2(external storage class), and 32 refers to a function |
| Line 11 | main start |
| Line 17 | assigns the stack pointer to ebp register |
| Line 21 | main is called |
| Line 22 to 32 | We assign elements of the array to memory locations, based on offset from esp pointer |
It then moves to the for loops
| Line | Work |
|---|---|
| L2 | It simply compares if arr[j]>max. The jl (jump on less) command allows it to not enter the if section,as it then goes to L8 or else it goes to L9 |
| L8 | It sets index to -1 and max to arr[l-i-1] {first two lines of loop} before jumping to L3 (j loop) |
| L3 | Lines 58 to 62 perform the check if arr[j]>=max (by the subtract long, or subl command) and does a jump in that case to L5. Line 64-65 checks if index is -1, in which case L6 is called {L6's function described below}. Finally, L7 adds one to loop index (j++) |
| L5 | Does the two operations: {max=arr[j];index=j;} |
| L9 | Handles the end of program. It calls L10 repeatedly (boundary check done by jl command) to print the array and then returns |
| L4 | Handles increment for i (outer) loop |
| L6 | It handles the swap part {temp=arr[l-i-1];arr[l-i-1]=arr[index];arr[index]=temp;} |
Note2: add.s is much easier to understand. In lines 20-24, we first assign 2 and 3 to memory locations and then load them to registers (eax and edx). Addition is done with addl command, printf call is then made to output the value and then program exits.