Generating dumps with example.c

 I created a quick "Example.c" program to test out gcc file dumps. 



This program is very simple and takes two integers and returns the result, in this case the main function has 2 and 3 as arguments and will return 5. 

In this part of the project, I worked on generating and analyzing GCC dump files for a small C program to gain insight into the different stages of code transformation and optimization within the compiler. The process involved using the -fdump-tree-all option, which produces detailed output files at various stages, each reflecting a unique part of the compilation pipeline. Starting with a simple example.c file containing an add function and a main function, I ran GCC with -fdump-tree-all. This command generated a series of dump files named with suffixes like .original, .gimple, .cfg, and .optimized. Each of these files represents a part of the program as it progresses through the compiler's internal stages, from raw code to fully optimized machine-ready form. I found this step straightforward, but was a little overwhelmed with the amount of files it produced. The original file shows the unchanged original file to compare with future optimized versions. The gimple file contains the gimple intermediate representation which GCC uses for its optimizations. The code in gimple is much more simple but still has all of its functionality. This code is stripped down to basic operations so that the GCC compiler can optimize it best.




Next, the cfg files is the control flow graph to look at the programs flow structures like branches or loops. This is not the full code of my example program but more of a map to understand how the program goes from one code block to the next. It was hard for me to understand how this file actually worked as it is not typical code like a c++ program, but reviewing it helped me understand the actual structural changes that were made by the compiler. 


Lastly, the optimized file contains the fully optimized version after the final pass. This version has all of the improvements and adjustments from the compiler 





Analyzing the int add function for myself, I can see that int D.4875 and int_3 are temporary variables made my the compiler. _3 is used to store the result of the addition performed while in the basic blocks a_1(D) and b_2(D) are the parameters to be added together, they are marked with D to represent declared variables. <bb2> performs the addition while <bb3> will return the sum of the two parameters.
















Comments

Post a Comment

Popular posts from this blog

Early stages of project

 I initially set up and built the current version of GCC on the aarch64-3 server that is provided. I started the build and it took at least an hour to fully compile. I limited the enabled languages to strictly C and C++ as I am most comfortable in these languages and to reduce the complexity of the project. The two files that control compilation passes are passes.cc, and tree-pass.h /* Description of GIMPLE pass.  */ class gimple_opt_pass : public opt_pass { protected:   gimple_opt_pass (const pass_data& data, gcc::context *ctxt)     : opt_pass (data, ctxt)   {   } }; /* Description of RTL pass.  */ class rtl_opt_pass : public opt_pass { protected:   rtl_opt_pass (const pass_data& data, gcc::context *ctxt)     : opt_pass (data, ctxt)   {   } } I did some reading and research on gimple passes and learned that they help optimize code and makes transformation at a high level before going to lower representations.
Read more

Building GCC again on aarch64-002

 Unfortunately the server I used to build gcc originally was aarch64-003 but that was shut down so I have to go through the process again on 002. The build time on the aarch64-002 server took 1 hour and 55 minutes approximately, I initially used time in my build command but I accidentally missed the information so I had to use stat build.log and find the duration of the build time by subtracting the final modification from the birth of the build.log file. Access: 2024-11-29 14:20:41.788188929 -0500 Modify: 2024-11-29 13:53:09.328736193 -0500 Change: 2024-11-29 13:53:09.328736193 -0500  Birth: 2024-11-29 11:57:40.960613010 -0500
Read more

Project Stage 2: Testing

Image
 To test my custom pass I first extracted the spo600-test-clone files into my gcc-test-001 directory and simply compiled and ran the program with -fdump-tree-ctyler. I ran it on the vol1.c file, the contents of vol1.c are as following: [dpark39@aarch64-002 test-clone]$ cat vol1.c // vol1.c - fixed-point volume scaling algorithm // Chris Tyler 2017.11.29-2021.11.16 - Licensed under GPLv3. // For the Seneca College SPO600 Course #include <stdlib.h> #include <stdio.h> #include <stdint.h> #include <stdbool.h> #include "vol.h" int16_t scale_sample(int16_t sample, int volume) {         return ((((int32_t) sample) * ((int32_t) (32767 * volume / 100) <<1) ) >> 16); } int main() {         int             x;         int             ttl=0; // ---- Create in[] and out[] arrays         int16_t*    ...
Read more