GCC is a widely used open source compiler system developed by the GNU Project. It compiles C, C++, Java, Fortran and other languages. GCC has undergone major changes to its structure since 2005, including the addition of GENERIC and GIMPLE intermediate representations between the front end and back end. The front end parses source code into ASTs, then GIMPLE trees are optimized through many passes in the middle end before being converted to RTL for the back end code generation.

1. GCC : GNU compilers collection Alberto Bustamante Reyes ( www.albertobustamante.com ) Author:

2. Brief introduction Compiler system developed by GNU Project

3. Distributed by FSF under GPL License

4. Written in C / C++

5. Default compiler for Unix and Mac OS X

6. Also ported to Windows (MinGW)

7. Brief introduction Originally developed for C language

8. Several front-ends added to support different languages: C / C++ (gcc / g++)

9. Java (gcj)

10. Objective-C / Objective-C++ (gobjc / gobjc++ )

11. Fortran (gfortran)

12. Structure Generic compiler: Front end

13. Back end GCC compiler: Front end

14. Middle end

15. Back end

16. Structure GCC Compiler (before 2005) Source code AST RTL RTL Object code FRONT END BACK END

17. Structure GCC Compiler (before 2005) Source code AST RTL RTL Object code FRONT END BACK END

18. Structure GCC Compiler (before 2005) Source code AST RTL RTL Object code FRONT END BACK END SSA Tree project: OPTIMIZATIONS

19. Structure GCC Compiler (after 2005) Source code AST GENERIC GIMPLE RTL FRONT END

20. Structure GCC Compiler (after 2005) Source code AST GENERIC GIMPLE RTL FRONT END Language dependent Language independent

21. Structure GCC Compiler (after 2005) Source code AST GENERIC GIMPLE RTL FRONT END Language dependent Language independent MIDDLE END

22. Structure: GENERIC & GIMPLE Why two kinds of trees? GIMPLE is a simplified subset of GENERIC GIMPLE GENERIC

23. Structure: GENERIC & GIMPLE GENERIC -> (Gimplifier) -> GIMPLE GIMPLIFIER if (foo ( a + b, c)) c = b ++ / a end if return c t1 = a +b t2 = foo (t1, c) If (t2 != 0 ) <L1, L2> L1: t3 = b b = b + 1 c = t3 / a goto L3 L2: L3: return c

24. Structure: GENERIC & GIMPLE Developed by SSA Tree Project

25. SSA Developed by IBM in 1980