Lab 01

This post is about Lab 1 for SPO600 course at Seneca College.

In this lab, I am going to use 6502 emulator to learn Assembly code and how to optimize the code.

The above code is given to the students, and we are required to change the code to do some required tasks such as changing color of the Bitmapped display, or optimizing code.


1. Calculate how long it takes for the code to execute, assuming a 1 MHz clock speed.













2. Also calculate the total memory usage for the program code plus any pointers or variables












3. Find one or more ways to decrease the time taken to fill the screen with a solid colour. Calculate the execution time of the fastest version of this program that you can create. Challenge: the fastest version is nearly twice as fast as the original version shown above!

Version 1. Just decreasing the number of loops by adding hard coding.















In this way, you can further reduce the cycles. However, there is a limit because `STA ($nn), Y` is very expensive. And also, `STA ($nn), Y` is colouring a pixel, so you cannot reduce the number of execution of this colouring process.

As you can see from the picture below, it is faster but the improvement is not huge:





















Version 2. Using cheaper code and reducing unnecessary loops, we can dramatically increase the speed.

















4. Change the code to fill the display with light blue instead of yellow.

        lda #$00         ;

  sta $40 ;

  lda #$02         ;

  sta $41 ; 

  lda #$e         ; Light Blue

  ldy #$00         ; 

 loop: sta ($40),y ; 

  iny         ; 

  bne loop         ;     

  inc $41 ; 

  ldx $41 ; 

  cpx #$06         ; 

  bne loop         ; 












5. Change the code to fill the display with a different colour on each page.

        lda #$00         ;

  sta $40 ;

  lda #$02         ;

  sta $41 ; 

  lda #$02         ; 

  ldy #$00         ; 

 loop: sta ($40),y ; 

  iny         ; 

  bne loop         ;     

  inc $41 ; 

  ldx $41 ; 

        lda $41            ; Change the Color for the next page

  cpx #$06         ; 

  bne loop         ; 











 6. Make each pixel a random colour.

        lda #$00         ;

  sta $40 ;

  lda #$02         ;

  sta $41 ; 

  lda #$02         ; 

  ldy #$00         ; 

 loop: sta ($40),y ; 

  iny         ; 

        lda $fe             ; set a random color for the next pixel

  bne loop         ;     

  inc $41 ; 

  ldx $41 ; 

  cpx #$06         ; 

  bne loop         ; 


















7. Review

First time when I saw lab 1 and the Assembly code, I seriously considered dropping course. It was overwhelming. However, after I studied the Assembly code for hours and finally understood how it works. And also it's really fun thinking about the cycles and how to reduce the cyles even if it is just a few cycles. This lab was very tough but interesting.

Comments

Post a Comment

popular posts in this blog

Project Stage 2 - part 2 : Clone-Pruning Analysis Pass

Intro In Project Stage 2, we are going to add a Pass to gcc compiler. Then, we will compile a code and see it generates a dump file that we added a pass for. Progress Let's start with adding a Pass to GCC compiler.  1. Open passes.def file in ~/project/gcc/gcc folder vi passes.def 2. You will See the codes as followings. Then, add a pass NEXT_PASS (pass_ctyler);  in line 444 440 NEXT_PASS (pass_cleanup_eh); 441 NEXT_PASS (pass_musttail); 442 NEXT_PASS (pass_lower_resx); 443 NEXT_PASS (pass_nrv); 444 NEXT_PASS (pass_ctyler); # Add your pass here # If you change the location, the order of compilation is changed; and it might have problem. # Since `pass_ctyler` is similar to `pass_nrv` I think it's safe to put here 445 NEXT_PASS (pass_gimple_isel); 446 NEXT_PASS (pass_harden_conditional_branches); 447 NEXT_PASS (pass_harden_compares); 448 NEXT_PASS (pass_warn_access, /*early=*/false); ...
Read more

Project Stage 2 part 4 - Testing clone-test-core.c file with Modified GCC file and making further modification

Intro  In the previous post, we modified to make it print function names; Now, we are going to test it with given clone-test-core.c file and also we will try to make further changes to display more information such as cloned function and gimple representation. Progress First, I tested the provided code without making any modifications, and the results are as follows: ;; Function sum_sample (sum_sample, funcdef_no=6, decl_uid=3859, cgraph_uid=7, symbol_order=6) === Function 1 Name '__builtin_cpu_supports' === === Function 2 Name '__builtin_cpu_init' === === Function 3 Name 'scale_samples.resolver' === === Function 4 Name 'scale_samples' === === Function 5 Name 'scale_samples.popcnt' === === Function 6 Name 'printf' === === Function 7 Name 'vol_createsample' === === Function 8 Name 'calloc' === === Function 9 Name 'main' === === Function 10 Name 'scale_samples' === === Function 11 Name 'sum_sample' =...
Read more

Project Stage 2 part 3 - Compile a program with revised GCC

  Intro In this post, we are going to use the GCC that we modified. Then, we will compile a code and see it generates a dump file by the pass we added. Progress 1. I will first test compiling my test program. Here is my simple C program. #include <stdio.h> int main() { int sum = 0; // For loop to add numbers from 1 to 5 for (int i = 1; i <= 5; i++) { sum += i; // Add i to sum // If statement to check if the number is even or odd if (i % 2 == 0) { printf("%d is even\n", i); } else { printf("%d is odd\n", i); } } printf("Sum of numbers from 1 to 5 is: %d\n", sum); return 0; } 2. I compiled the prgoram gcc -fdump-tree-all test.c -o test And this generated the following dump file as well as other dump files test.c.263t.ctyler 3. Check the content of the dump file. ===== Basic block count: 1 ===== ----- Statement count: 1 ----- sum_7 = 0; ----- Statement count...
Read more