GCC 4.0 has a new optimization infrastructure, and future versions of GCC will realize even more performance improvements. Here’s an overview of what’s new and what’s to come.
Version 4.0.0 of the GNU Compiler Collection (GCC) was released in April 2004. More than three years in the making — the last major revision, 3.x, was released in 2001 — 4.0.0 was a substantial upgrade of one of the most ubiquitous software development tools around.
During the last year or so, the GCC development team has produced a series of maintenance releases and has continued to work on new features for 4.1. But besides the usual grind of adding enhancements and tweaking GCC’s extensive code base, the team’s also keeping an eye towards taking the elite GCC, the de facto standard compiler on Linux and many other free operating systems, to the “next level.” Even the best can get better.
The biggest advance in GCC 4.x is the inclusion of a new optimization framework dubbed Tree SSA. To understand that term and realize why it’s such an important improvement, you first need to understand a little bit about GCC’s internal infrastructure.
GCC (like most compilers) begins by parsing and analyzing your source code. At the end of this phase, GCC has a high-level internal representation of the program that clearly expresses the semantics of the input program. For example, if the input program was the succinct…
extern int f(double);
int g(int i) { return f(i); }
… the high-level representation for the return statement looks (conceptually) like Figure One. Since the representation in Figure One looks like (an…
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