Chapter 3: GCC Anatomy

When writing code, people don´t usually bother to think about the compiler or whatever lies inside, but instead just codes. However, everything that happens inside a compiler (for example, GCC) is interesting. Conformed of three main parts (which are Front End, Middle End, and Back End) the compiler aims towards performance thanks to everything that those parts make. The Front End, which is language specific, outputs to the front end, which is considered like a “neutral” zone, and finally the Back End works to produce specific architecture code.

Morgan Deters explains us the portability of GCC in the podcast; is one of the most widely used, for example, on Windows or Mac OS. It accepts many languages, such as C, C++, Java, Fortran, etc. The main output from the compiler is an object code for the aimed platform.

The compiler works with a simple input, a plain text, and the compiler has to understand what the plain text has and what everything inside it means, usually by parsing it into a tree-like representation. Whenever a variable is declared in the text file, the compiler should assign it to a variable and know how and when to access it. The compiler has to recognize the semantics of the language. Then, with all this information, produce an internal representation for the compiler to understand it easier. At the end, compiler programmers take a look at small details for low level optimizations, where simple instructions are refactored to either compacted versions or faster instructions.

Taking all this into consideration, I hope I can apply it to my course and the project we are currently working on. The part in semantic and lexical analysis sounds really interesting and I hope I can deepen that knowledge either by reading more about it or applying it practically (or why not, both).

References:

SER (2007) Episode 61: Internals of GCC, available on: http://www.se-radio.net/2007/07/episode-61-internals-of-gcc/

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