What is GCC
GNU C Compiler --> GNU Compiler Collection
GCC is the cornerstone of development in both the open source and closed source worlds. It's the enabler of architectures and operating systems. When a new processor appears, its success depends on a version of GCC that will support it (a back end that can generate code for it). GCC is also the enabler of Linux®. Linux as an operating system is widely successful because it is run on so many different architectures. Once again, a port of GCC to the target environment enables Linux to be ported and run on it. Without trying to put too fine a point on it, GCC paves the way for Linux and embedded development.
GCC principle
Compilers are constructed in a pipeline architecture made up of several stages that communicate different forms of data. The front end of a compiler is language specific and includes a parser for the given language that results in parsed trees and the intermediate representation (the Register Transfer Language, or RTL). The back end is then responsible for using this language-independent representation and product instructions for the particular target architecture. To do this, the optimizer uses the RTL to create fast or more compact code (or both, when possible). The optimized RTL is then fed to the code generator, which produces target code.
GCC4 is coming
But GCC can't just sit still. New processor architectures continue to appear, and new research finds better ways to optimize and generate code. So GCC moves forward and has now matured into its fourth major release. The most inmportant changes are the introduction of a new optimization framework (Tree SSA) and support for autovectorization.
Prior to GCC 4, the intermediate representation used was called Register Transfer Language (RTL). RTL is a low-level representation very close to assembly language (inspired by LISP S-expressions). The problem with RTL is that the optimizations it enables are those close to the target. Optimizations that require higher-level information about the program may not be possible, because their expression is lost in RTL. Tree SSA is designed to be both language independent and target independent while supporting improved analysis and richer optimizations.
Benifit of GCC4
Software compiled with GCC 4 will be generally more compact and faster, meaning software industry goodness all around.
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